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Acute aortic syndrome is often a life-threatening emergency, but because the presenting symptoms are nonspecific, it can be difficult to diagnose. Advances in computed tomography (CT)i have made the diagnosis of acute aortic syndromes easier and faster.
This article discusses the role of CT in patients with acute aortic syndrome. We review the imaging features and common indications for treating the various causes of acute aortic syndrome, and we discuss the possibly wider future role of CT for evaluating acute chest pain.
ACUTE AORTIC SYNDROME PRESENTS WITH CHEST PAIN
Acute aortic syndrome is defined as chest pain due to an aortic condition such as acute aortic dissection, intramural hematoma, penetrating atherosclerotic ulcer, or unstable thoracic aneurysm (see below).1
Risk factors2 are listed in Table1. Most patients have a history of hypertension; however, the blood pressure may be low at the time of presentation if the aorta has ruptured.
Of 464 patients included in the International Registry of Acute Aortic Dissection (IRAD),3 85% had acute symptoms. The pain was more often described as sharp than as the classic tearing pain. More than 70% of patients had hypertension.3 Half of patients younger than 40 years had Marfan syndrome4;a young patient with Marfan features who presents with acute chest pain should be strongly suspected of having aortic dissection. A bicuspid aortic valve or a history of aortic surgery should also raise the suspicion of acute aortic dissection.4
Acute chest pain is nonspecific
Figure 1. Diagnostic strategy for acute aortic syndrome.Acute chest pain is a nonspecific symptom: besides esophageal disease, it can be due to pneumonia, pulmonary embolism, pneumothorax, or acute coronary syndrome, and these must be ruled out on the basis of the history, physical findings, cardiac enzyme levels, electrocardiographic findings, and chest radiographic findings (Figure 1).
Furthermore, other possible manifestations of acute aortic syndrome are also nonspecific, eg, unexplained syncope, stroke, acute onset of congestive heart failure, pulse differentials (weaker pulses in one or more extremities), and malperfusion syndromes of the extremities or viscera.
Although aortic disease can sometimes cause acute coronary syndrome, keep in mind that acute coronary syndrome is more than 100 times more common than acute aortic dissection.3
IMAGING STUDIES FOR ACUTE AORTIC SYNDROME
Contrast-enhanced, cardiac-gated multidetector CT is nearly 100% sensitive and specific for evaluating acute aortic syndrome (Table 2).5
Transthoracic echocardiography is limited for evaluating acute aortic syndromes. However, transesophageal echocardiography is about 95% sensitive and specific for diagnosing acute aortic dissection, and intramural hematoma, and associated valvular regurgitation if the personnel who perform and interpret the test are highly experienced (although this level of expertise is not always available in the emergency department).5
CT has been improved
Several recent advances have contributed to CT’s very high sensitivity and specificity for diagnosing aortic disease.
Multiple detectors. Today’s CT machines have up to 64 rows of detectors, and this enables them to generate multiple simultaneous images with a slice thickness of less than 1 mm. Multidetector CT is also extremely fast: spiral imaging of the thorax can be done in a single breath-hold, which eliminates respiratory motion artifact.
Figure 2. Left, an axial image from a contrast-enhanced, nongated CT study with 3-mm slices of the aortic root from a patient with acute aortic syndrome demonstrates cardiac motion artifact mimicking an acute aortic dissection (arrows, left panel). Right, contrast-enhanced, cardiac-gated CT with 0.75-mm slices of the aortic root reveals no dissection, although the aortic root is dilated.
Cardiac synchronization of the image acquisition (cardiac gating) should be performed whenever the heart, coronary vessels, pulmonary veins, or aortic root needs to be evaluated; without cardiac gating, motion of the aortic root wall during the cardiac cycle causes artifacts in more than 90% of CT studies,5–7 precluding adequate evaluation of these structures (Figure 2). In cardiac gating, CT is synchronized with electrocardiography, “freezing” the action at specific phases of the cardiac cycle, typically during diastole when heart motion is limited. Two types of cardiac synchronization are available: retrospective gating and prospective triggering.
In retrospective gating (“spiral” or “helical” scanning), the x-ray source stays on throughout the cardiac cycle, but only the data from the desired part of the cardiac cycle are used to construct images. With this method, one can refine the images and remove motion abnormalities caused by irregular heartbeats. This acquisition technique is currently the most frequently used.
In prospective triggering (“step and shoot”), the x-ray source is turned on only during diastole or another prespecified part of the cardiac cycle. An advantage is that the patient is exposed to less radiation. A disadvantage is that, afterward, one has very little ability to correct any motion artifacts that occurred due to changes in heart rate or dysrhythmias.
Other improvements that have increased the sensitivity and specificity of CT for evaluating acute aortic syndrome are the ability to generate images in multiple planes (multiplanar reformation) on dedicated computer workstations.
INTRAVENOUS CONTRAST IMPROVES IMAGING STUDIES
Intravenous contrast is necessary for CT to achieve its high accuracy for diagnosing aortic disease. However, it should be noted that in a CT study without contrast enhancement, an acute intramural hematoma is easily recognized by the higher Hounsfield-unit value of the blood products in the wall in comparison with the flowing blood in the lumen.
Check renal function
Before doing an intravenous contrast study, the serum creatinine level should be checked as a measure of renal function. Generally, if the serum creatinine concentration is less than 2.0 mg/dL and if the patient is hydrated and does not have diabetes, iodinated intravenous contrast can be given safely. If the patient’s serum creatinine level is between 1.5 and 2.0 mg/dL or if he or she is dehydrated or has diabetes, isosmolar iodinated contrast (iodixanol [Visipaque]) may be used.
An alternative that can be used for some patients with contrast allergy is gadolinium chelate, a paramagnetic compound normally used in magnetic resonance imaging. However, it is less radiopaque and much more expensive than iodinated contrast. It should be noted that the US Food and Drug Administration has recently warned that gadolinium contrast is associated with a systemic fibrosing disorder (nephrogenic systemic fibrosis) in patients with poor renal function (usually but not only in patients on dialysis).8 Because of this risk, gadolinium contrast should generally be used only in patients with good renal function who have had a prior serious adverse reaction to iodinated contrast.
Insert a large-gauge intravenous line
Proper intravenous access is needed for contrast injection. To opacify the aorta properly, the contrast must be injected rapidly (3.0 mL/second) using a power injector.
We recommend at least an 18-gauge peripheral intravenous catheter in the forearm or a large-bore central line (an introducer or Hickman catheter). Smaller-gauge intravenous lines (often located in smaller veins such as in the wrist) and most central lines placed without radiographic or surgical assistance (eg, triple-lumen central catheters) cannot safely handle such a rapid rate without infiltration or embolization. Some peripherally inserted central catheters are designed to handle high injection rates and are typically labeled with the injection rate.
USE OF CT IN SPECIFIC ACUTE AORTIC SYNDROMES
Acute aortic dissection
Aortic dissection occurs when a tear in the intimal layer allows blood to enter and accumulate in the medial layer of the aorta, giving rise to a true lumen and a false lumen separated by an intimomedial flap. Dissection is considered to be acute if symptoms have been present for less than 2 weeks.9
Aortic dissections are often complex and can spiral around the aorta. The relationship of the intimomedial flap to the coronary arteries, aortic-arch branch vessels, and visceral branch vessels can be described on contrast enhanced, cardiac-gated CT scans. The true lumen is often smaller and more opacified with contrast than the false lumen; intimal calcification often surrounds the true lumen. Slender areas of low attenuation (“cobwebs”) are occasionally seen in the false lumen. The false lumen also has beaked edges where it meets the true lumen, which usually appears rounder.2,10 The radiologist should state where the dissection begins and ends, determine if target vessel ischemia is evident, and assess for concomitant aneurysmal dilatation of the aorta. Contrast-enhanced, cardiac-gated multidetector CT of the aorta is necessary to properly evaluate the aortic root.
Figure 3. The DeBakey and Stanford systems.
The Stanford system. Two systems exist for classifying the location of aortic dissections: the DeBakey system and the Stanford system (Figure 3). The Stanford system is more clinically useful and uses the following classification:
Figure 4. Coronal reformatted image (left) and oblique reformatted image (right) from contrast-enhanced, cardiac-gated computed tomography in a patient with acute aortic syndrome show a type A aortic dissection involving the aortic root, extending around the aortic valve, and aneurysmal dilatation of the aortic root.Type A dissections involve the ascending aorta and aortic arch, with or without involvement of the descending aorta (Figure 4, Figure 5)
Figure 5. Oblique reformatted images from contrast-enhanced, cardiac-gated CT before (left) and after (right) surgical aortic root repair with aortic valve replacement in a patient who initially presented with acute aortic syndrome and had a type A acute aortic dissection with aneurysmal dilatation of the aortic root.Type B dissections involve the descending aorta beginning distal to the left subclavian artery (Figure 6).11
Figure 6. A coronal reformatted image (left) and an axial image (right) from contrast-enhanced, cardiac-gated CT in a patient who presented with acute aortic syndrome show a type B aortic dissection extending from the aortic arch (distal to the arch vessels) into the abdomen. Hemorrhage from recent rupture is seen in the left and right hemithorax and in the mediastinum (arrow).
Type A acute aortic dissection generally should be surgically repaired immediately to avoid fatal complications such as extension into the pericardium, pleural space, coronary arteries, or aortic valvular ring. It can also cause stroke, visceral ischemia, or circulatory failure.2,11 Without surgery, 20% of patients with type A acute aortic dissection die within 24 hours, 30% within 48 hours, 40% within 1 week, and 50% within 1 month.2 The initial target is the tear in the ascending aorta: typically the aortic root or the ascending aorta or both are replaced and the aortic valve is repaired if indicated (Figure 5). Further aortic repair can often be delayed or may not be needed if the disease does not progress with medical management.
Without surgery, type B acute aortic dissection has a 30-day mortality rate of 10%.2 Patients who develop renal failure, ischemic leg symptoms, or visceral ischemic symptoms with acute aortic syndrome should undergo imaging of the chest, abdomen, and pelvis. Type B acute aortic dissection without end-organ ischemia is typically managed with antihypertensive drugs. Except in patients with Marfan syndrome, only a small minority of type B dissections progress to type A dissections.Urgent aortic repair, often with an endovascular stent graft, is needed if imaging shows visceral vessel occlusion or ischemia, acute vessel thrombosis, or progression of aneurysmal dilatation.
Aortic intramural hematoma
Intramural hematomas are believed to be caused by a spontaneous hemorrhage of the vaso vasorum into the medial layer. They appear as crescent-shaped areas of increased attenuation with eccentric aortic wall-thickening and displacement of intimal calcifications. Hematomas do not enhance after contrast administration, and unlike dissections, they usually do not spiral around the aorta.
Figure 7. Coronal reformatted image (left) and axial image (middle) from contrast-enhanced, cardiac-gated CT in a patient with an acute type A intramural hematoma and a penetrating ulcer. Note the eccentric increased attenuation in the lateral aspect of the aortic arch representing the hematoma (arrow, middle panel) and the contrast-filled outpouching laterally representing the penetrating ulcer. Follow-up imaging several months later (right) shows that the intramural hematoma resolved although the penetrating ulcer persisted (arrow, right panel).Intramural hematomas can also be classified according to the Stanford system. Type A intramural hematomas (Figure 7) have traditionally been urgently treated with surgery because they can progress to dissection, aortic rupture, or pericardial, pleural, or mediastinal hemorrhage. Recent evidence suggests that some patients with a limited type A intramural hematoma may be managed with aggressive medical therapy with frequent serial imaging to monitor progression of disease.2,12
Type B intramural hematomas are typically managed with medical therapy and often regress with time, although they can progress to dissection or aneurysmal formation.
Unstable thoracic aneurysm
Thoracic aneurysms are considered unstable if they are enlarging rapidly, show signs of imminent rupture, or have already ruptured (typically ,the rupture is contained if the patient survives for imaging).
An aortic aneurysm is defined as a permanent dilation at least 150% of normal size, or larger than 5 cm if in the thoracic aorta or larger than 3 cm if in the abdominal aorta. True aneurysms involve all three layers of the aorta and tend to be fusiform; pseudoaneurysms tend to be saccular and often arise after trauma, surgery, or infection. Dilations are more likely to rupture if they grow at least 1 cm per year or measure 6.0 cm or more (if in the ascending aorta) or 7.2 cm (if in the descending thoracic aorta).13
How big the aortic diameter needs to be before invasive treatment—surgery or an endovascular procedure—is indicated depends on the characteristics of the individual patient, and an experienced surgeon should be involved in the decision. Patients are typically treated when a dilation in the ascending aorta reaches 5.5 cm or when one in the descending aorta reaches 6.0 cm; patients with Marfan syndrome should undergo invasive treatment for aneurysms with smaller diameters.14,15
CT signs of imminent rupture include a high-attenuating crescent in the wall of the aorta, discontinuous calcification in a circumferentially calcified aorta, an aorta that conforms to the neighboring vertebral body (“draped” aorta), and an eccentric nipple shape to the aorta.16,17
Figure 8. Axial image from contrast-enhanced,cardiac-gated CT in a patient with acute aortic syndrome and hypotension demonstrates aneurysmal dilatation of the descending thoracic aorta with a contained aortic rupture anterolaterally (arrow). A layering left hemithorax is also visible (star). The patient underwent urgent endovascular stent repair.CT signs of rupture include hemothorax (usually in the left hemithorax) and stranding of the periaortic fat (Figure 8).
Penetrating atherosclerotic ulcer
Figure 9. Coronal reformatted image (left) and axial image (right) from contrast-enhanced, cardiac-gated CT in a patient with acute aortic syndrome demonstrate a focal contrast-filled outpouching of the distal thoracic aorta consistent with a penetrating atherosclerotic ulcer (arrows).When an atherosclerotic ulcer penetrates the aortic intima and extends into the media, it can lead to dissection, an intramural hematoma, aneurysm, or aortic rupture. Many penetrating aortic ulcers are focal lesions of the descending thoracic aorta. On contrast-enhanced, cardiac-gated CT they appear as contrast-filled irregular outpouchings of the aortic wall (Figure 9).18,19
Typical patients are elderly, and many have coexisting atherosclerotic atheromata and aneurysmal disease. Some experts contend that most saccular aneurysms are caused by penetrating atherosclerotic ulcers.19
Surgery to stabilize disease is recommended for a penetrating ulcer that causes acute aortic syndrome, or in patients with hemodynamic instability, aortic rupture, distal embolization, or a rapidly enlarging aorta. For a penetrating ulcer that is found incidentally in a patient without acute aortic syndrome, medical management of risk factors is recommended, with annual follow-up to see if it enlarges.
FUTURE USES OF IMAGING IN PATIENTS WITH ACUTE CHEST PAIN
Multidetector CT systems are undergoing rapid technical advances, including the recently released dual x-ray source multidetector CT scanners and the expected multidetector CTs with 128 to 256 detector rows. These and other developments will improve temporal resolution and decrease radiation exposure. Calcium artifacts—which hinder the evaluation of coronary arteries that contain atherosclerotic calcifications—will be reduced, thereby improving the accuracy of diagnosing acute coronary disease. As clinical knowledge increases based on the experience gained from the new technology, indications for imaging may expand.
CT of the chest performed for aortic disease provides information about other organ systems that may be considered when evaluating the cause of chest pain.20
Evaluating pulmonary artery embolism
Although current contrast-enhanced, cardiac-gated CT of the aorta is not ideal for assessing the pulmonary arteries, it can almost always rule out central pulmonary artery thromboemboli and evaluate the more distal pulmonary arteries in a more limited way.
‘Triple rule-out’ CT
Several institutions now use CT (typically with 64-row scanners) to simultaneously evaluate patients for coronary artery disease, acute aortic syndrome, and pulmonary embolism—or “triple rule-out CT.” The study can be performed with dual intravenous contrast bolus techniques with nongated contrast-enhanced CT of the pulmonary arteries, rapidly followed by cardiac-gated, contrast-enhanced CT of the aorta. The pulmonary arteries can be evaluated on the initial nongated study, and the aorta (including the aortic root) and the coronary arteries are evaluated on the cardiac-gated portion. The timing of the contrast bolus for optimal opacification of the pulmonary arteries and the coronary arteries has yet to be determined.
The usefulness of assessing all three vascular beds with a single study is currently still unclear and the protocol is currently not routinely performed at Cleveland Clinic. Its sensitivity, specificity, and cost-benefit ratio are also unclear and must be determined in prospective clinical trials, which are currently under way.21
References
Vilacosta I, Roman JA. Acute aortic syndrome. Heart 2001; 85:365–368.
Nienaber CA, Eagle KA. Aortic dissection: new frontiers in diagnosis and management: Part I: From etiology to diagnostic strategies. Circulation 2003; 108:628–635.
Hagan PG, Nienaber CA, Isselbacher EM, et al. The International Registry of Acute Aortic Dissection (IRAD): new insights into an old disease. JAMA 2000; 283:897–903.
Januzzi JL, Isselbacher EM, Fattori R, et al; International Registry of Aortic Dissection (IRAD). Characterizing the young patient with aortic dissection: results from the International Registry of Aortic Dissection (IRAD). J Am Coll Cardiol 2004; 43:665–669.
Manghat NE, Morgan-Hughes GJ, Roobottom CA. Multi-detector row computed tomography: imaging in acute aortic syndrome. Clin Radiol 2005; 60:1256–1267.
Roos JE, Willmann JK, Weishaupt D, Lachat M, Marincek B, Hilfiker PR. Thoracic aorta: motion artifact reduction with retrospective and prospective electrocardiography-assisted multi-detector row CT. Radiology 2002; 222:271–277.
Cademartiri F, Pavone P. Advantages of retrospective ECG-gating in cardio-thoracic imaging with 16-row multislice computed tomography. Acta Biomed 2003; 74:126–130.
US Food and Drug Administration. Public Health Advisory: Gadolinium-containing Contrast Agents for Magnetic Resonance Imaging (MRI): Omniscan, OptiMARK, Magnevist, ProHance, and MultiHance. US Food and Drug Administration; June 8, 2006, updated May 23, 2007. http://www.fda.gov/cder/drug/advisory/gadolinium_agents.htm.
Hirst AE Jr, Johns VJ Jr, Kime SW Jr. Dissecting aneurysm of the aorta: a review of 505 cases. Medicine (Baltimore) 1958; 37:217–279.
Batra P, Bigoni B, Manning J, et al. Pitfalls in the diagnosis of thoracic aortic dissection at CT angiography. Radiographics 2000; 20:309–320.
Daily PO, Trueblood HW, Stinson EB, Wuerflein RD, Shumway NE. Management of acute aortic dissections. Ann Thorac Surg 1970; 10:237–247.
Yamada T, Tada S, Harada J. Aortic dissection without intimal rupture: diagnosis with MR imaging and CT. Radiology 1988; 168:347–352.
Svensson LG, Khitin L. Aortic cross-sectional area/height ratio timing of aortic surgery in asymptomatic patients with Marfan syndrome. J Thorac Cardiovasc Surg 2002; 123:360–361.
Svensson LG, Kim KH, Lytle BW, Cosgrove DM. Relationship of aortic cross-sectional area to height ratio and the risk of aortic dissection in patients with bicuspid aortic valves. J Thorac Cardiovasc Surg 2003; 126:892–893.
Bhalla S, West OC. CT of nontraumatic thoracic aortic emergencies. Semin Ultrasound CT MR 2005; 26:281–304.
Castaner E, Andreu M, Gallardo X, Mata JM, Cabezuelo MA, Pallardo Y. CT in nontraumatic acute thoracic aortic disease: typical and atypical features and complications. Radiographics 2003; 23:S93–S110.
Quint LE, Williams DM, Francis IR, et al. Ulcer-like lesions of the aorta: imaging features and natural history. Radiology 2001; 218:719–723.
Stillman AE, Oudkerk M, Ackerman M, et al. Use of multidetector computed tomography for the assessment of acute chest pain: a consensus statement of the North American Society of Cardiac Imaging and the European Society of Cardiac Radiology. Int J Cardiovasc Imaging 2007; 23:415–427.
Savino G, Herzog C, Costello P, Schoepf UJ. 64 slice cardiovascular CT in the emergency department: concepts and first experiences. Radiol Med (Torino) 2006; 111:481–496.
Acute aortic syndrome is often a life-threatening emergency, but because the presenting symptoms are nonspecific, it can be difficult to diagnose. Advances in computed tomography (CT)i have made the diagnosis of acute aortic syndromes easier and faster.
This article discusses the role of CT in patients with acute aortic syndrome. We review the imaging features and common indications for treating the various causes of acute aortic syndrome, and we discuss the possibly wider future role of CT for evaluating acute chest pain.
ACUTE AORTIC SYNDROME PRESENTS WITH CHEST PAIN
Acute aortic syndrome is defined as chest pain due to an aortic condition such as acute aortic dissection, intramural hematoma, penetrating atherosclerotic ulcer, or unstable thoracic aneurysm (see below).1
Risk factors2 are listed in Table1. Most patients have a history of hypertension; however, the blood pressure may be low at the time of presentation if the aorta has ruptured.
Of 464 patients included in the International Registry of Acute Aortic Dissection (IRAD),3 85% had acute symptoms. The pain was more often described as sharp than as the classic tearing pain. More than 70% of patients had hypertension.3 Half of patients younger than 40 years had Marfan syndrome4;a young patient with Marfan features who presents with acute chest pain should be strongly suspected of having aortic dissection. A bicuspid aortic valve or a history of aortic surgery should also raise the suspicion of acute aortic dissection.4
Acute chest pain is nonspecific
Figure 1. Diagnostic strategy for acute aortic syndrome.Acute chest pain is a nonspecific symptom: besides esophageal disease, it can be due to pneumonia, pulmonary embolism, pneumothorax, or acute coronary syndrome, and these must be ruled out on the basis of the history, physical findings, cardiac enzyme levels, electrocardiographic findings, and chest radiographic findings (Figure 1).
Furthermore, other possible manifestations of acute aortic syndrome are also nonspecific, eg, unexplained syncope, stroke, acute onset of congestive heart failure, pulse differentials (weaker pulses in one or more extremities), and malperfusion syndromes of the extremities or viscera.
Although aortic disease can sometimes cause acute coronary syndrome, keep in mind that acute coronary syndrome is more than 100 times more common than acute aortic dissection.3
IMAGING STUDIES FOR ACUTE AORTIC SYNDROME
Contrast-enhanced, cardiac-gated multidetector CT is nearly 100% sensitive and specific for evaluating acute aortic syndrome (Table 2).5
Transthoracic echocardiography is limited for evaluating acute aortic syndromes. However, transesophageal echocardiography is about 95% sensitive and specific for diagnosing acute aortic dissection, and intramural hematoma, and associated valvular regurgitation if the personnel who perform and interpret the test are highly experienced (although this level of expertise is not always available in the emergency department).5
CT has been improved
Several recent advances have contributed to CT’s very high sensitivity and specificity for diagnosing aortic disease.
Multiple detectors. Today’s CT machines have up to 64 rows of detectors, and this enables them to generate multiple simultaneous images with a slice thickness of less than 1 mm. Multidetector CT is also extremely fast: spiral imaging of the thorax can be done in a single breath-hold, which eliminates respiratory motion artifact.
Figure 2. Left, an axial image from a contrast-enhanced, nongated CT study with 3-mm slices of the aortic root from a patient with acute aortic syndrome demonstrates cardiac motion artifact mimicking an acute aortic dissection (arrows, left panel). Right, contrast-enhanced, cardiac-gated CT with 0.75-mm slices of the aortic root reveals no dissection, although the aortic root is dilated.
Cardiac synchronization of the image acquisition (cardiac gating) should be performed whenever the heart, coronary vessels, pulmonary veins, or aortic root needs to be evaluated; without cardiac gating, motion of the aortic root wall during the cardiac cycle causes artifacts in more than 90% of CT studies,5–7 precluding adequate evaluation of these structures (Figure 2). In cardiac gating, CT is synchronized with electrocardiography, “freezing” the action at specific phases of the cardiac cycle, typically during diastole when heart motion is limited. Two types of cardiac synchronization are available: retrospective gating and prospective triggering.
In retrospective gating (“spiral” or “helical” scanning), the x-ray source stays on throughout the cardiac cycle, but only the data from the desired part of the cardiac cycle are used to construct images. With this method, one can refine the images and remove motion abnormalities caused by irregular heartbeats. This acquisition technique is currently the most frequently used.
In prospective triggering (“step and shoot”), the x-ray source is turned on only during diastole or another prespecified part of the cardiac cycle. An advantage is that the patient is exposed to less radiation. A disadvantage is that, afterward, one has very little ability to correct any motion artifacts that occurred due to changes in heart rate or dysrhythmias.
Other improvements that have increased the sensitivity and specificity of CT for evaluating acute aortic syndrome are the ability to generate images in multiple planes (multiplanar reformation) on dedicated computer workstations.
INTRAVENOUS CONTRAST IMPROVES IMAGING STUDIES
Intravenous contrast is necessary for CT to achieve its high accuracy for diagnosing aortic disease. However, it should be noted that in a CT study without contrast enhancement, an acute intramural hematoma is easily recognized by the higher Hounsfield-unit value of the blood products in the wall in comparison with the flowing blood in the lumen.
Check renal function
Before doing an intravenous contrast study, the serum creatinine level should be checked as a measure of renal function. Generally, if the serum creatinine concentration is less than 2.0 mg/dL and if the patient is hydrated and does not have diabetes, iodinated intravenous contrast can be given safely. If the patient’s serum creatinine level is between 1.5 and 2.0 mg/dL or if he or she is dehydrated or has diabetes, isosmolar iodinated contrast (iodixanol [Visipaque]) may be used.
An alternative that can be used for some patients with contrast allergy is gadolinium chelate, a paramagnetic compound normally used in magnetic resonance imaging. However, it is less radiopaque and much more expensive than iodinated contrast. It should be noted that the US Food and Drug Administration has recently warned that gadolinium contrast is associated with a systemic fibrosing disorder (nephrogenic systemic fibrosis) in patients with poor renal function (usually but not only in patients on dialysis).8 Because of this risk, gadolinium contrast should generally be used only in patients with good renal function who have had a prior serious adverse reaction to iodinated contrast.
Insert a large-gauge intravenous line
Proper intravenous access is needed for contrast injection. To opacify the aorta properly, the contrast must be injected rapidly (3.0 mL/second) using a power injector.
We recommend at least an 18-gauge peripheral intravenous catheter in the forearm or a large-bore central line (an introducer or Hickman catheter). Smaller-gauge intravenous lines (often located in smaller veins such as in the wrist) and most central lines placed without radiographic or surgical assistance (eg, triple-lumen central catheters) cannot safely handle such a rapid rate without infiltration or embolization. Some peripherally inserted central catheters are designed to handle high injection rates and are typically labeled with the injection rate.
USE OF CT IN SPECIFIC ACUTE AORTIC SYNDROMES
Acute aortic dissection
Aortic dissection occurs when a tear in the intimal layer allows blood to enter and accumulate in the medial layer of the aorta, giving rise to a true lumen and a false lumen separated by an intimomedial flap. Dissection is considered to be acute if symptoms have been present for less than 2 weeks.9
Aortic dissections are often complex and can spiral around the aorta. The relationship of the intimomedial flap to the coronary arteries, aortic-arch branch vessels, and visceral branch vessels can be described on contrast enhanced, cardiac-gated CT scans. The true lumen is often smaller and more opacified with contrast than the false lumen; intimal calcification often surrounds the true lumen. Slender areas of low attenuation (“cobwebs”) are occasionally seen in the false lumen. The false lumen also has beaked edges where it meets the true lumen, which usually appears rounder.2,10 The radiologist should state where the dissection begins and ends, determine if target vessel ischemia is evident, and assess for concomitant aneurysmal dilatation of the aorta. Contrast-enhanced, cardiac-gated multidetector CT of the aorta is necessary to properly evaluate the aortic root.
Figure 3. The DeBakey and Stanford systems.
The Stanford system. Two systems exist for classifying the location of aortic dissections: the DeBakey system and the Stanford system (Figure 3). The Stanford system is more clinically useful and uses the following classification:
Figure 4. Coronal reformatted image (left) and oblique reformatted image (right) from contrast-enhanced, cardiac-gated computed tomography in a patient with acute aortic syndrome show a type A aortic dissection involving the aortic root, extending around the aortic valve, and aneurysmal dilatation of the aortic root.Type A dissections involve the ascending aorta and aortic arch, with or without involvement of the descending aorta (Figure 4, Figure 5)
Figure 5. Oblique reformatted images from contrast-enhanced, cardiac-gated CT before (left) and after (right) surgical aortic root repair with aortic valve replacement in a patient who initially presented with acute aortic syndrome and had a type A acute aortic dissection with aneurysmal dilatation of the aortic root.Type B dissections involve the descending aorta beginning distal to the left subclavian artery (Figure 6).11
Figure 6. A coronal reformatted image (left) and an axial image (right) from contrast-enhanced, cardiac-gated CT in a patient who presented with acute aortic syndrome show a type B aortic dissection extending from the aortic arch (distal to the arch vessels) into the abdomen. Hemorrhage from recent rupture is seen in the left and right hemithorax and in the mediastinum (arrow).
Type A acute aortic dissection generally should be surgically repaired immediately to avoid fatal complications such as extension into the pericardium, pleural space, coronary arteries, or aortic valvular ring. It can also cause stroke, visceral ischemia, or circulatory failure.2,11 Without surgery, 20% of patients with type A acute aortic dissection die within 24 hours, 30% within 48 hours, 40% within 1 week, and 50% within 1 month.2 The initial target is the tear in the ascending aorta: typically the aortic root or the ascending aorta or both are replaced and the aortic valve is repaired if indicated (Figure 5). Further aortic repair can often be delayed or may not be needed if the disease does not progress with medical management.
Without surgery, type B acute aortic dissection has a 30-day mortality rate of 10%.2 Patients who develop renal failure, ischemic leg symptoms, or visceral ischemic symptoms with acute aortic syndrome should undergo imaging of the chest, abdomen, and pelvis. Type B acute aortic dissection without end-organ ischemia is typically managed with antihypertensive drugs. Except in patients with Marfan syndrome, only a small minority of type B dissections progress to type A dissections.Urgent aortic repair, often with an endovascular stent graft, is needed if imaging shows visceral vessel occlusion or ischemia, acute vessel thrombosis, or progression of aneurysmal dilatation.
Aortic intramural hematoma
Intramural hematomas are believed to be caused by a spontaneous hemorrhage of the vaso vasorum into the medial layer. They appear as crescent-shaped areas of increased attenuation with eccentric aortic wall-thickening and displacement of intimal calcifications. Hematomas do not enhance after contrast administration, and unlike dissections, they usually do not spiral around the aorta.
Figure 7. Coronal reformatted image (left) and axial image (middle) from contrast-enhanced, cardiac-gated CT in a patient with an acute type A intramural hematoma and a penetrating ulcer. Note the eccentric increased attenuation in the lateral aspect of the aortic arch representing the hematoma (arrow, middle panel) and the contrast-filled outpouching laterally representing the penetrating ulcer. Follow-up imaging several months later (right) shows that the intramural hematoma resolved although the penetrating ulcer persisted (arrow, right panel).Intramural hematomas can also be classified according to the Stanford system. Type A intramural hematomas (Figure 7) have traditionally been urgently treated with surgery because they can progress to dissection, aortic rupture, or pericardial, pleural, or mediastinal hemorrhage. Recent evidence suggests that some patients with a limited type A intramural hematoma may be managed with aggressive medical therapy with frequent serial imaging to monitor progression of disease.2,12
Type B intramural hematomas are typically managed with medical therapy and often regress with time, although they can progress to dissection or aneurysmal formation.
Unstable thoracic aneurysm
Thoracic aneurysms are considered unstable if they are enlarging rapidly, show signs of imminent rupture, or have already ruptured (typically ,the rupture is contained if the patient survives for imaging).
An aortic aneurysm is defined as a permanent dilation at least 150% of normal size, or larger than 5 cm if in the thoracic aorta or larger than 3 cm if in the abdominal aorta. True aneurysms involve all three layers of the aorta and tend to be fusiform; pseudoaneurysms tend to be saccular and often arise after trauma, surgery, or infection. Dilations are more likely to rupture if they grow at least 1 cm per year or measure 6.0 cm or more (if in the ascending aorta) or 7.2 cm (if in the descending thoracic aorta).13
How big the aortic diameter needs to be before invasive treatment—surgery or an endovascular procedure—is indicated depends on the characteristics of the individual patient, and an experienced surgeon should be involved in the decision. Patients are typically treated when a dilation in the ascending aorta reaches 5.5 cm or when one in the descending aorta reaches 6.0 cm; patients with Marfan syndrome should undergo invasive treatment for aneurysms with smaller diameters.14,15
CT signs of imminent rupture include a high-attenuating crescent in the wall of the aorta, discontinuous calcification in a circumferentially calcified aorta, an aorta that conforms to the neighboring vertebral body (“draped” aorta), and an eccentric nipple shape to the aorta.16,17
Figure 8. Axial image from contrast-enhanced,cardiac-gated CT in a patient with acute aortic syndrome and hypotension demonstrates aneurysmal dilatation of the descending thoracic aorta with a contained aortic rupture anterolaterally (arrow). A layering left hemithorax is also visible (star). The patient underwent urgent endovascular stent repair.CT signs of rupture include hemothorax (usually in the left hemithorax) and stranding of the periaortic fat (Figure 8).
Penetrating atherosclerotic ulcer
Figure 9. Coronal reformatted image (left) and axial image (right) from contrast-enhanced, cardiac-gated CT in a patient with acute aortic syndrome demonstrate a focal contrast-filled outpouching of the distal thoracic aorta consistent with a penetrating atherosclerotic ulcer (arrows).When an atherosclerotic ulcer penetrates the aortic intima and extends into the media, it can lead to dissection, an intramural hematoma, aneurysm, or aortic rupture. Many penetrating aortic ulcers are focal lesions of the descending thoracic aorta. On contrast-enhanced, cardiac-gated CT they appear as contrast-filled irregular outpouchings of the aortic wall (Figure 9).18,19
Typical patients are elderly, and many have coexisting atherosclerotic atheromata and aneurysmal disease. Some experts contend that most saccular aneurysms are caused by penetrating atherosclerotic ulcers.19
Surgery to stabilize disease is recommended for a penetrating ulcer that causes acute aortic syndrome, or in patients with hemodynamic instability, aortic rupture, distal embolization, or a rapidly enlarging aorta. For a penetrating ulcer that is found incidentally in a patient without acute aortic syndrome, medical management of risk factors is recommended, with annual follow-up to see if it enlarges.
FUTURE USES OF IMAGING IN PATIENTS WITH ACUTE CHEST PAIN
Multidetector CT systems are undergoing rapid technical advances, including the recently released dual x-ray source multidetector CT scanners and the expected multidetector CTs with 128 to 256 detector rows. These and other developments will improve temporal resolution and decrease radiation exposure. Calcium artifacts—which hinder the evaluation of coronary arteries that contain atherosclerotic calcifications—will be reduced, thereby improving the accuracy of diagnosing acute coronary disease. As clinical knowledge increases based on the experience gained from the new technology, indications for imaging may expand.
CT of the chest performed for aortic disease provides information about other organ systems that may be considered when evaluating the cause of chest pain.20
Evaluating pulmonary artery embolism
Although current contrast-enhanced, cardiac-gated CT of the aorta is not ideal for assessing the pulmonary arteries, it can almost always rule out central pulmonary artery thromboemboli and evaluate the more distal pulmonary arteries in a more limited way.
‘Triple rule-out’ CT
Several institutions now use CT (typically with 64-row scanners) to simultaneously evaluate patients for coronary artery disease, acute aortic syndrome, and pulmonary embolism—or “triple rule-out CT.” The study can be performed with dual intravenous contrast bolus techniques with nongated contrast-enhanced CT of the pulmonary arteries, rapidly followed by cardiac-gated, contrast-enhanced CT of the aorta. The pulmonary arteries can be evaluated on the initial nongated study, and the aorta (including the aortic root) and the coronary arteries are evaluated on the cardiac-gated portion. The timing of the contrast bolus for optimal opacification of the pulmonary arteries and the coronary arteries has yet to be determined.
The usefulness of assessing all three vascular beds with a single study is currently still unclear and the protocol is currently not routinely performed at Cleveland Clinic. Its sensitivity, specificity, and cost-benefit ratio are also unclear and must be determined in prospective clinical trials, which are currently under way.21
Acute aortic syndrome is often a life-threatening emergency, but because the presenting symptoms are nonspecific, it can be difficult to diagnose. Advances in computed tomography (CT)i have made the diagnosis of acute aortic syndromes easier and faster.
This article discusses the role of CT in patients with acute aortic syndrome. We review the imaging features and common indications for treating the various causes of acute aortic syndrome, and we discuss the possibly wider future role of CT for evaluating acute chest pain.
ACUTE AORTIC SYNDROME PRESENTS WITH CHEST PAIN
Acute aortic syndrome is defined as chest pain due to an aortic condition such as acute aortic dissection, intramural hematoma, penetrating atherosclerotic ulcer, or unstable thoracic aneurysm (see below).1
Risk factors2 are listed in Table1. Most patients have a history of hypertension; however, the blood pressure may be low at the time of presentation if the aorta has ruptured.
Of 464 patients included in the International Registry of Acute Aortic Dissection (IRAD),3 85% had acute symptoms. The pain was more often described as sharp than as the classic tearing pain. More than 70% of patients had hypertension.3 Half of patients younger than 40 years had Marfan syndrome4;a young patient with Marfan features who presents with acute chest pain should be strongly suspected of having aortic dissection. A bicuspid aortic valve or a history of aortic surgery should also raise the suspicion of acute aortic dissection.4
Acute chest pain is nonspecific
Figure 1. Diagnostic strategy for acute aortic syndrome.Acute chest pain is a nonspecific symptom: besides esophageal disease, it can be due to pneumonia, pulmonary embolism, pneumothorax, or acute coronary syndrome, and these must be ruled out on the basis of the history, physical findings, cardiac enzyme levels, electrocardiographic findings, and chest radiographic findings (Figure 1).
Furthermore, other possible manifestations of acute aortic syndrome are also nonspecific, eg, unexplained syncope, stroke, acute onset of congestive heart failure, pulse differentials (weaker pulses in one or more extremities), and malperfusion syndromes of the extremities or viscera.
Although aortic disease can sometimes cause acute coronary syndrome, keep in mind that acute coronary syndrome is more than 100 times more common than acute aortic dissection.3
IMAGING STUDIES FOR ACUTE AORTIC SYNDROME
Contrast-enhanced, cardiac-gated multidetector CT is nearly 100% sensitive and specific for evaluating acute aortic syndrome (Table 2).5
Transthoracic echocardiography is limited for evaluating acute aortic syndromes. However, transesophageal echocardiography is about 95% sensitive and specific for diagnosing acute aortic dissection, and intramural hematoma, and associated valvular regurgitation if the personnel who perform and interpret the test are highly experienced (although this level of expertise is not always available in the emergency department).5
CT has been improved
Several recent advances have contributed to CT’s very high sensitivity and specificity for diagnosing aortic disease.
Multiple detectors. Today’s CT machines have up to 64 rows of detectors, and this enables them to generate multiple simultaneous images with a slice thickness of less than 1 mm. Multidetector CT is also extremely fast: spiral imaging of the thorax can be done in a single breath-hold, which eliminates respiratory motion artifact.
Figure 2. Left, an axial image from a contrast-enhanced, nongated CT study with 3-mm slices of the aortic root from a patient with acute aortic syndrome demonstrates cardiac motion artifact mimicking an acute aortic dissection (arrows, left panel). Right, contrast-enhanced, cardiac-gated CT with 0.75-mm slices of the aortic root reveals no dissection, although the aortic root is dilated.
Cardiac synchronization of the image acquisition (cardiac gating) should be performed whenever the heart, coronary vessels, pulmonary veins, or aortic root needs to be evaluated; without cardiac gating, motion of the aortic root wall during the cardiac cycle causes artifacts in more than 90% of CT studies,5–7 precluding adequate evaluation of these structures (Figure 2). In cardiac gating, CT is synchronized with electrocardiography, “freezing” the action at specific phases of the cardiac cycle, typically during diastole when heart motion is limited. Two types of cardiac synchronization are available: retrospective gating and prospective triggering.
In retrospective gating (“spiral” or “helical” scanning), the x-ray source stays on throughout the cardiac cycle, but only the data from the desired part of the cardiac cycle are used to construct images. With this method, one can refine the images and remove motion abnormalities caused by irregular heartbeats. This acquisition technique is currently the most frequently used.
In prospective triggering (“step and shoot”), the x-ray source is turned on only during diastole or another prespecified part of the cardiac cycle. An advantage is that the patient is exposed to less radiation. A disadvantage is that, afterward, one has very little ability to correct any motion artifacts that occurred due to changes in heart rate or dysrhythmias.
Other improvements that have increased the sensitivity and specificity of CT for evaluating acute aortic syndrome are the ability to generate images in multiple planes (multiplanar reformation) on dedicated computer workstations.
INTRAVENOUS CONTRAST IMPROVES IMAGING STUDIES
Intravenous contrast is necessary for CT to achieve its high accuracy for diagnosing aortic disease. However, it should be noted that in a CT study without contrast enhancement, an acute intramural hematoma is easily recognized by the higher Hounsfield-unit value of the blood products in the wall in comparison with the flowing blood in the lumen.
Check renal function
Before doing an intravenous contrast study, the serum creatinine level should be checked as a measure of renal function. Generally, if the serum creatinine concentration is less than 2.0 mg/dL and if the patient is hydrated and does not have diabetes, iodinated intravenous contrast can be given safely. If the patient’s serum creatinine level is between 1.5 and 2.0 mg/dL or if he or she is dehydrated or has diabetes, isosmolar iodinated contrast (iodixanol [Visipaque]) may be used.
An alternative that can be used for some patients with contrast allergy is gadolinium chelate, a paramagnetic compound normally used in magnetic resonance imaging. However, it is less radiopaque and much more expensive than iodinated contrast. It should be noted that the US Food and Drug Administration has recently warned that gadolinium contrast is associated with a systemic fibrosing disorder (nephrogenic systemic fibrosis) in patients with poor renal function (usually but not only in patients on dialysis).8 Because of this risk, gadolinium contrast should generally be used only in patients with good renal function who have had a prior serious adverse reaction to iodinated contrast.
Insert a large-gauge intravenous line
Proper intravenous access is needed for contrast injection. To opacify the aorta properly, the contrast must be injected rapidly (3.0 mL/second) using a power injector.
We recommend at least an 18-gauge peripheral intravenous catheter in the forearm or a large-bore central line (an introducer or Hickman catheter). Smaller-gauge intravenous lines (often located in smaller veins such as in the wrist) and most central lines placed without radiographic or surgical assistance (eg, triple-lumen central catheters) cannot safely handle such a rapid rate without infiltration or embolization. Some peripherally inserted central catheters are designed to handle high injection rates and are typically labeled with the injection rate.
USE OF CT IN SPECIFIC ACUTE AORTIC SYNDROMES
Acute aortic dissection
Aortic dissection occurs when a tear in the intimal layer allows blood to enter and accumulate in the medial layer of the aorta, giving rise to a true lumen and a false lumen separated by an intimomedial flap. Dissection is considered to be acute if symptoms have been present for less than 2 weeks.9
Aortic dissections are often complex and can spiral around the aorta. The relationship of the intimomedial flap to the coronary arteries, aortic-arch branch vessels, and visceral branch vessels can be described on contrast enhanced, cardiac-gated CT scans. The true lumen is often smaller and more opacified with contrast than the false lumen; intimal calcification often surrounds the true lumen. Slender areas of low attenuation (“cobwebs”) are occasionally seen in the false lumen. The false lumen also has beaked edges where it meets the true lumen, which usually appears rounder.2,10 The radiologist should state where the dissection begins and ends, determine if target vessel ischemia is evident, and assess for concomitant aneurysmal dilatation of the aorta. Contrast-enhanced, cardiac-gated multidetector CT of the aorta is necessary to properly evaluate the aortic root.
Figure 3. The DeBakey and Stanford systems.
The Stanford system. Two systems exist for classifying the location of aortic dissections: the DeBakey system and the Stanford system (Figure 3). The Stanford system is more clinically useful and uses the following classification:
Figure 4. Coronal reformatted image (left) and oblique reformatted image (right) from contrast-enhanced, cardiac-gated computed tomography in a patient with acute aortic syndrome show a type A aortic dissection involving the aortic root, extending around the aortic valve, and aneurysmal dilatation of the aortic root.Type A dissections involve the ascending aorta and aortic arch, with or without involvement of the descending aorta (Figure 4, Figure 5)
Figure 5. Oblique reformatted images from contrast-enhanced, cardiac-gated CT before (left) and after (right) surgical aortic root repair with aortic valve replacement in a patient who initially presented with acute aortic syndrome and had a type A acute aortic dissection with aneurysmal dilatation of the aortic root.Type B dissections involve the descending aorta beginning distal to the left subclavian artery (Figure 6).11
Figure 6. A coronal reformatted image (left) and an axial image (right) from contrast-enhanced, cardiac-gated CT in a patient who presented with acute aortic syndrome show a type B aortic dissection extending from the aortic arch (distal to the arch vessels) into the abdomen. Hemorrhage from recent rupture is seen in the left and right hemithorax and in the mediastinum (arrow).
Type A acute aortic dissection generally should be surgically repaired immediately to avoid fatal complications such as extension into the pericardium, pleural space, coronary arteries, or aortic valvular ring. It can also cause stroke, visceral ischemia, or circulatory failure.2,11 Without surgery, 20% of patients with type A acute aortic dissection die within 24 hours, 30% within 48 hours, 40% within 1 week, and 50% within 1 month.2 The initial target is the tear in the ascending aorta: typically the aortic root or the ascending aorta or both are replaced and the aortic valve is repaired if indicated (Figure 5). Further aortic repair can often be delayed or may not be needed if the disease does not progress with medical management.
Without surgery, type B acute aortic dissection has a 30-day mortality rate of 10%.2 Patients who develop renal failure, ischemic leg symptoms, or visceral ischemic symptoms with acute aortic syndrome should undergo imaging of the chest, abdomen, and pelvis. Type B acute aortic dissection without end-organ ischemia is typically managed with antihypertensive drugs. Except in patients with Marfan syndrome, only a small minority of type B dissections progress to type A dissections.Urgent aortic repair, often with an endovascular stent graft, is needed if imaging shows visceral vessel occlusion or ischemia, acute vessel thrombosis, or progression of aneurysmal dilatation.
Aortic intramural hematoma
Intramural hematomas are believed to be caused by a spontaneous hemorrhage of the vaso vasorum into the medial layer. They appear as crescent-shaped areas of increased attenuation with eccentric aortic wall-thickening and displacement of intimal calcifications. Hematomas do not enhance after contrast administration, and unlike dissections, they usually do not spiral around the aorta.
Figure 7. Coronal reformatted image (left) and axial image (middle) from contrast-enhanced, cardiac-gated CT in a patient with an acute type A intramural hematoma and a penetrating ulcer. Note the eccentric increased attenuation in the lateral aspect of the aortic arch representing the hematoma (arrow, middle panel) and the contrast-filled outpouching laterally representing the penetrating ulcer. Follow-up imaging several months later (right) shows that the intramural hematoma resolved although the penetrating ulcer persisted (arrow, right panel).Intramural hematomas can also be classified according to the Stanford system. Type A intramural hematomas (Figure 7) have traditionally been urgently treated with surgery because they can progress to dissection, aortic rupture, or pericardial, pleural, or mediastinal hemorrhage. Recent evidence suggests that some patients with a limited type A intramural hematoma may be managed with aggressive medical therapy with frequent serial imaging to monitor progression of disease.2,12
Type B intramural hematomas are typically managed with medical therapy and often regress with time, although they can progress to dissection or aneurysmal formation.
Unstable thoracic aneurysm
Thoracic aneurysms are considered unstable if they are enlarging rapidly, show signs of imminent rupture, or have already ruptured (typically ,the rupture is contained if the patient survives for imaging).
An aortic aneurysm is defined as a permanent dilation at least 150% of normal size, or larger than 5 cm if in the thoracic aorta or larger than 3 cm if in the abdominal aorta. True aneurysms involve all three layers of the aorta and tend to be fusiform; pseudoaneurysms tend to be saccular and often arise after trauma, surgery, or infection. Dilations are more likely to rupture if they grow at least 1 cm per year or measure 6.0 cm or more (if in the ascending aorta) or 7.2 cm (if in the descending thoracic aorta).13
How big the aortic diameter needs to be before invasive treatment—surgery or an endovascular procedure—is indicated depends on the characteristics of the individual patient, and an experienced surgeon should be involved in the decision. Patients are typically treated when a dilation in the ascending aorta reaches 5.5 cm or when one in the descending aorta reaches 6.0 cm; patients with Marfan syndrome should undergo invasive treatment for aneurysms with smaller diameters.14,15
CT signs of imminent rupture include a high-attenuating crescent in the wall of the aorta, discontinuous calcification in a circumferentially calcified aorta, an aorta that conforms to the neighboring vertebral body (“draped” aorta), and an eccentric nipple shape to the aorta.16,17
Figure 8. Axial image from contrast-enhanced,cardiac-gated CT in a patient with acute aortic syndrome and hypotension demonstrates aneurysmal dilatation of the descending thoracic aorta with a contained aortic rupture anterolaterally (arrow). A layering left hemithorax is also visible (star). The patient underwent urgent endovascular stent repair.CT signs of rupture include hemothorax (usually in the left hemithorax) and stranding of the periaortic fat (Figure 8).
Penetrating atherosclerotic ulcer
Figure 9. Coronal reformatted image (left) and axial image (right) from contrast-enhanced, cardiac-gated CT in a patient with acute aortic syndrome demonstrate a focal contrast-filled outpouching of the distal thoracic aorta consistent with a penetrating atherosclerotic ulcer (arrows).When an atherosclerotic ulcer penetrates the aortic intima and extends into the media, it can lead to dissection, an intramural hematoma, aneurysm, or aortic rupture. Many penetrating aortic ulcers are focal lesions of the descending thoracic aorta. On contrast-enhanced, cardiac-gated CT they appear as contrast-filled irregular outpouchings of the aortic wall (Figure 9).18,19
Typical patients are elderly, and many have coexisting atherosclerotic atheromata and aneurysmal disease. Some experts contend that most saccular aneurysms are caused by penetrating atherosclerotic ulcers.19
Surgery to stabilize disease is recommended for a penetrating ulcer that causes acute aortic syndrome, or in patients with hemodynamic instability, aortic rupture, distal embolization, or a rapidly enlarging aorta. For a penetrating ulcer that is found incidentally in a patient without acute aortic syndrome, medical management of risk factors is recommended, with annual follow-up to see if it enlarges.
FUTURE USES OF IMAGING IN PATIENTS WITH ACUTE CHEST PAIN
Multidetector CT systems are undergoing rapid technical advances, including the recently released dual x-ray source multidetector CT scanners and the expected multidetector CTs with 128 to 256 detector rows. These and other developments will improve temporal resolution and decrease radiation exposure. Calcium artifacts—which hinder the evaluation of coronary arteries that contain atherosclerotic calcifications—will be reduced, thereby improving the accuracy of diagnosing acute coronary disease. As clinical knowledge increases based on the experience gained from the new technology, indications for imaging may expand.
CT of the chest performed for aortic disease provides information about other organ systems that may be considered when evaluating the cause of chest pain.20
Evaluating pulmonary artery embolism
Although current contrast-enhanced, cardiac-gated CT of the aorta is not ideal for assessing the pulmonary arteries, it can almost always rule out central pulmonary artery thromboemboli and evaluate the more distal pulmonary arteries in a more limited way.
‘Triple rule-out’ CT
Several institutions now use CT (typically with 64-row scanners) to simultaneously evaluate patients for coronary artery disease, acute aortic syndrome, and pulmonary embolism—or “triple rule-out CT.” The study can be performed with dual intravenous contrast bolus techniques with nongated contrast-enhanced CT of the pulmonary arteries, rapidly followed by cardiac-gated, contrast-enhanced CT of the aorta. The pulmonary arteries can be evaluated on the initial nongated study, and the aorta (including the aortic root) and the coronary arteries are evaluated on the cardiac-gated portion. The timing of the contrast bolus for optimal opacification of the pulmonary arteries and the coronary arteries has yet to be determined.
The usefulness of assessing all three vascular beds with a single study is currently still unclear and the protocol is currently not routinely performed at Cleveland Clinic. Its sensitivity, specificity, and cost-benefit ratio are also unclear and must be determined in prospective clinical trials, which are currently under way.21
References
Vilacosta I, Roman JA. Acute aortic syndrome. Heart 2001; 85:365–368.
Nienaber CA, Eagle KA. Aortic dissection: new frontiers in diagnosis and management: Part I: From etiology to diagnostic strategies. Circulation 2003; 108:628–635.
Hagan PG, Nienaber CA, Isselbacher EM, et al. The International Registry of Acute Aortic Dissection (IRAD): new insights into an old disease. JAMA 2000; 283:897–903.
Januzzi JL, Isselbacher EM, Fattori R, et al; International Registry of Aortic Dissection (IRAD). Characterizing the young patient with aortic dissection: results from the International Registry of Aortic Dissection (IRAD). J Am Coll Cardiol 2004; 43:665–669.
Manghat NE, Morgan-Hughes GJ, Roobottom CA. Multi-detector row computed tomography: imaging in acute aortic syndrome. Clin Radiol 2005; 60:1256–1267.
Roos JE, Willmann JK, Weishaupt D, Lachat M, Marincek B, Hilfiker PR. Thoracic aorta: motion artifact reduction with retrospective and prospective electrocardiography-assisted multi-detector row CT. Radiology 2002; 222:271–277.
Cademartiri F, Pavone P. Advantages of retrospective ECG-gating in cardio-thoracic imaging with 16-row multislice computed tomography. Acta Biomed 2003; 74:126–130.
US Food and Drug Administration. Public Health Advisory: Gadolinium-containing Contrast Agents for Magnetic Resonance Imaging (MRI): Omniscan, OptiMARK, Magnevist, ProHance, and MultiHance. US Food and Drug Administration; June 8, 2006, updated May 23, 2007. http://www.fda.gov/cder/drug/advisory/gadolinium_agents.htm.
Hirst AE Jr, Johns VJ Jr, Kime SW Jr. Dissecting aneurysm of the aorta: a review of 505 cases. Medicine (Baltimore) 1958; 37:217–279.
Batra P, Bigoni B, Manning J, et al. Pitfalls in the diagnosis of thoracic aortic dissection at CT angiography. Radiographics 2000; 20:309–320.
Daily PO, Trueblood HW, Stinson EB, Wuerflein RD, Shumway NE. Management of acute aortic dissections. Ann Thorac Surg 1970; 10:237–247.
Yamada T, Tada S, Harada J. Aortic dissection without intimal rupture: diagnosis with MR imaging and CT. Radiology 1988; 168:347–352.
Svensson LG, Khitin L. Aortic cross-sectional area/height ratio timing of aortic surgery in asymptomatic patients with Marfan syndrome. J Thorac Cardiovasc Surg 2002; 123:360–361.
Svensson LG, Kim KH, Lytle BW, Cosgrove DM. Relationship of aortic cross-sectional area to height ratio and the risk of aortic dissection in patients with bicuspid aortic valves. J Thorac Cardiovasc Surg 2003; 126:892–893.
Bhalla S, West OC. CT of nontraumatic thoracic aortic emergencies. Semin Ultrasound CT MR 2005; 26:281–304.
Castaner E, Andreu M, Gallardo X, Mata JM, Cabezuelo MA, Pallardo Y. CT in nontraumatic acute thoracic aortic disease: typical and atypical features and complications. Radiographics 2003; 23:S93–S110.
Quint LE, Williams DM, Francis IR, et al. Ulcer-like lesions of the aorta: imaging features and natural history. Radiology 2001; 218:719–723.
Stillman AE, Oudkerk M, Ackerman M, et al. Use of multidetector computed tomography for the assessment of acute chest pain: a consensus statement of the North American Society of Cardiac Imaging and the European Society of Cardiac Radiology. Int J Cardiovasc Imaging 2007; 23:415–427.
Savino G, Herzog C, Costello P, Schoepf UJ. 64 slice cardiovascular CT in the emergency department: concepts and first experiences. Radiol Med (Torino) 2006; 111:481–496.
References
Vilacosta I, Roman JA. Acute aortic syndrome. Heart 2001; 85:365–368.
Nienaber CA, Eagle KA. Aortic dissection: new frontiers in diagnosis and management: Part I: From etiology to diagnostic strategies. Circulation 2003; 108:628–635.
Hagan PG, Nienaber CA, Isselbacher EM, et al. The International Registry of Acute Aortic Dissection (IRAD): new insights into an old disease. JAMA 2000; 283:897–903.
Januzzi JL, Isselbacher EM, Fattori R, et al; International Registry of Aortic Dissection (IRAD). Characterizing the young patient with aortic dissection: results from the International Registry of Aortic Dissection (IRAD). J Am Coll Cardiol 2004; 43:665–669.
Manghat NE, Morgan-Hughes GJ, Roobottom CA. Multi-detector row computed tomography: imaging in acute aortic syndrome. Clin Radiol 2005; 60:1256–1267.
Roos JE, Willmann JK, Weishaupt D, Lachat M, Marincek B, Hilfiker PR. Thoracic aorta: motion artifact reduction with retrospective and prospective electrocardiography-assisted multi-detector row CT. Radiology 2002; 222:271–277.
Cademartiri F, Pavone P. Advantages of retrospective ECG-gating in cardio-thoracic imaging with 16-row multislice computed tomography. Acta Biomed 2003; 74:126–130.
US Food and Drug Administration. Public Health Advisory: Gadolinium-containing Contrast Agents for Magnetic Resonance Imaging (MRI): Omniscan, OptiMARK, Magnevist, ProHance, and MultiHance. US Food and Drug Administration; June 8, 2006, updated May 23, 2007. http://www.fda.gov/cder/drug/advisory/gadolinium_agents.htm.
Hirst AE Jr, Johns VJ Jr, Kime SW Jr. Dissecting aneurysm of the aorta: a review of 505 cases. Medicine (Baltimore) 1958; 37:217–279.
Batra P, Bigoni B, Manning J, et al. Pitfalls in the diagnosis of thoracic aortic dissection at CT angiography. Radiographics 2000; 20:309–320.
Daily PO, Trueblood HW, Stinson EB, Wuerflein RD, Shumway NE. Management of acute aortic dissections. Ann Thorac Surg 1970; 10:237–247.
Yamada T, Tada S, Harada J. Aortic dissection without intimal rupture: diagnosis with MR imaging and CT. Radiology 1988; 168:347–352.
Svensson LG, Khitin L. Aortic cross-sectional area/height ratio timing of aortic surgery in asymptomatic patients with Marfan syndrome. J Thorac Cardiovasc Surg 2002; 123:360–361.
Svensson LG, Kim KH, Lytle BW, Cosgrove DM. Relationship of aortic cross-sectional area to height ratio and the risk of aortic dissection in patients with bicuspid aortic valves. J Thorac Cardiovasc Surg 2003; 126:892–893.
Bhalla S, West OC. CT of nontraumatic thoracic aortic emergencies. Semin Ultrasound CT MR 2005; 26:281–304.
Castaner E, Andreu M, Gallardo X, Mata JM, Cabezuelo MA, Pallardo Y. CT in nontraumatic acute thoracic aortic disease: typical and atypical features and complications. Radiographics 2003; 23:S93–S110.
Quint LE, Williams DM, Francis IR, et al. Ulcer-like lesions of the aorta: imaging features and natural history. Radiology 2001; 218:719–723.
Stillman AE, Oudkerk M, Ackerman M, et al. Use of multidetector computed tomography for the assessment of acute chest pain: a consensus statement of the North American Society of Cardiac Imaging and the European Society of Cardiac Radiology. Int J Cardiovasc Imaging 2007; 23:415–427.
Savino G, Herzog C, Costello P, Schoepf UJ. 64 slice cardiovascular CT in the emergency department: concepts and first experiences. Radiol Med (Torino) 2006; 111:481–496.
Acute aortic syndrome typically presents with chest pain in patients with a history of hypertension. In young patients with aortic dissection, one should consider Marfan syndrome and other connective tissue abnormalities.
Cardiac gating is essential to avoid cardiac motion artifacts when evaluating the aortic root with contrast-enhanced multidetector CT.
Urgent surgical repair is often necessary, especially for acute aortic dissection and intramural hematoma in the ascending aorta and aortic arch, unstable or ruptured thoracic aneurysm, and symptomatic penetrating atherosclerotic ulcers.
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“The time has come,” the Walrus said, “To talk of many things: Of shoes—and ships—and sealing-wax— Of cabbages—and kings— And why the sea is boiling hot And whether pigs have wings.” —Lewis Carroll, The Walrus and the Carpenter (from Through the Looking-Glass and What Alice Found There, 1872).
Lewis Carroll's poem of 1872 is a useful starting point for identifying issues resulting from confusion over the variously described acute aortic syndromes—and, for oysters, the dangers of listening to walruses.
In cases of aortic dissection (splitting or separation of the layers of the aortic wall), it is important to establish the type (ie, the location and extent) and class (ie, the structure) of the dissection, because these distinctions determine the treatment.1 Similarly, in cases of painful or leaking degenerative aneurysms, we need to know the location of the aneurysm and whether the presenting pain is from compression of surrounding tissue, particularly of the vertebral bodies, or from leakage.
The location and extent of an aortic dissection can be classified in three ways (see Figure 3 in Smith and Schoenhagen’s excellent review of the use of computed tomography [CT] in acute aortic syndromes in this issue of the Cleveland Clinic Journal of Medicine2):
The DeBakey system (type I, II, or III)
The Stanford system (type A or B)
Distal or proximal to the left subclavian artery.
Of note, the DeBakey system does not include tears in the arch that extend distally without ascending involvement. The original Stanford system included arch tears with distal extension in type B; hence, type B excluded all patients without ascending involvement.
The importance of the extent of dissection is that most patients with Stanford type A or DeBakey type I or II dissections should undergo immediate surgery, as most of them would die without it. Surgery is also indicated for arch tears (non-DeBakey, original Stanford type B).
Because these classifications are somewhat confusing, the simplest approach is to note whether the dissection extends proximal or distal to the left subclavian artery, because proximal dissections need surgery and distal ones are first managed medically.
The classes of dissection also have bearing on treatment.1 These are:
Class I—classic aortic dissection in the media with two lumens separated by a “flap” or septum
Class II—intramural hematoma in the aortic wall from dissection in which the intimal tear cannot be imaged (these are nearly always found duringsurgery or autopsy)
Class III—localized confined intimal tears without extensive undermining of the intima or flap formation. These are often seen with Marfan syndrome and can rupture or cause tamponade, as can any type of proximal dissection. The typical appearance is of a bulging bubble in the aortic wall.
Class IV—penetrating atherosclerotic ulcers with localized dissections or wall hematomas, often with calcium at the base of a mushroom-shaped area of extraluminal contrast. Of note, the plane of dissection is often between the media and adventitia.
Class V—iatrogenic or posttraumatic dissection.
All class I to class IV tears of the proximal aorta require surgery, whereas distal class IV and V tears may require either open or endovascular surgical intervention. Surgery is also indicated for patients with distal dissections who have severe narrowing of the true lumen, distal ischemia, uncontrolled pain, severe hypertension, or evidence of leaking, particularly with class IV tears.
In distal dissections that are subacute (2–6 week sold), the Investigation of Stent grafts in Patients With Type B Aortic Dissection (INSTEAD) trial found that inserting a stent prophylactically provided no benefit. Further-more, there is no proof that stenting is beneficial if the aortic dissection is chronic, ie, more than 6 weeks old.1,3–5
WHICH SHOE FITS?
There is no ideal procedure to detect dissection, although the trend is towards CT angiography, as Smith and Schoenhagen report.2 Although some investigators have optimistically estimated CT’s sensitivity and specificity as 100%, cardiovascular surgeons are well aware of both false-positive and false-negative CT studies. Thus, for emergency repairs of proximal dissections, transesophageal echocardiography should be done after intubation and before opening a patient’s chest if time allows. Magnetic resonance imaging, CT, and transesophageal echocardiography may all miss class III tears, but these are frequently evidenced by eccentric “bubbles”or “ballooning.”1
SHIPS
Patients with either acute aortic dissection or severe pain associated with degenerative aneurysms need to be “shipped” promptly to a tertiary medical center after diagnosis, since larger volumes of procedures appear to be associated with better outcomes.
SEALING WAX
Using current surgical methods, the aortic valve can be preserved during aortic dissection repair unless the valve is bicuspid or the patient has Marfan syndrome.1,3,4,6–8
Sealing wax in the form of biological glues, rather than for letters, is a new innovation. A caveat remains, however: we have seen patients who have required reoperation for false aneurysms or infection. Hence, glues should be used with caution.
CABBAGES
A dilemma is whether patients should undergo coronary catheterization (or CT angiography—a separate question) and subsequent coronary artery bypass grafting (CABG), if needed, at the time of aortic dissection repair. The problem is that approximately one-third of patients have coronary artery disease that may require CABG, but the delay for catheterization increases the risk of rupture or tamponade before surgery.
Indeed, 40% of patients with proximal dissections die immediately, and 1% to 3% die in the hour before surgery. The short-term (in-hospital and 30-day) mortality rates range from 3.4% (Cleveland Clinic 2006 data) to 25%, and of the survivors only about 50% area live 5 years after surgery.
Though dismal, the prognosis is improving. In 162 patients with aortic dissection and Marfan syndrome or connective tissue disorders who underwent surgery at Cleveland Clinic in the years 1978–2003, the 5-year survival rate in those with aortic dissection was 75% and the 10-year rate was 55%.7 In those without dissection, the 10-year survival rate was approximately 90% (P < .001).
KINGS
Noted personalities who have had aortic dissection include King George II of England (who died in 1760), Lucille Ball, Conway Twitty, Jan Larson, and most recently John Ritter. None of these famous people survived their aortic dissections. Indeed, dissection and diseases of the aorta or its branches cause between 43,000 and 47,000 deaths annually,9 more than from breast cancer, murders, or motor vehicle accidents. The main reason for these dismal statistics is that the disease is often misdiagnosed at the time of presentation.
BOILING SEA
Careful studies from Olmsted County, Minnesota,10 have shown a tripling of the incidence of aortic disease, particularly in women, even though the rate of deaths from coronary artery disease has been decreasing. Furthermore, Olsson et al11 report that the incidence of aortic dissection in men in Sweden increased to approximately16 per 100,000 per year from 1987 to 2002, a 52% increase. The aging of the population must play a large role, but other factors may exist that are not well understood or defined and require further research.
PIGS HAVE WINGS
Will it be possible to overcome this rising problem? The answer is a definite yes. The results of aortic surgery have never been better. Many new innovations are available, such as aortic root preservation and endovascular stenting procedures. It may be possible to slow the growth of or prevent some aneurysms and aortic dissections, particularly with beta-blockers and, potentially, with losartan (Cozaar) for Marfan syndrome patients.
One of the keys to preventing aortic catastrophes and aortic dissection is to repair aortic aneurysms. The threshold for surgery, however, depends on a surgeon’s experience and results, the underlying pathology, and the aortic size.
We observed that 12.5% of dissections in patients with bicuspid valves and 15% of those in patients with Marfan syndrome were in aortas smaller than 5.0 cm in diameter, that aortic dissection occurred at smaller diameters in shorter patients, and that the risk of dissection increased exponentially with the size of the aorta. Subsequently, we found that a better measure of risk is the maximal aortic cross-sectional area in cm2 divided by the patient’s height in meters; if this ratio exceeds 10, then surgery is recommended.12
Results of surgery are good in experienced hands. In patients who undergo surgical repair of bicuspid aortic valves with or without concurrent repair of the ascending aorta (mostly in patients with an aortic cross-section-to-height ratio > 10), the perioperative mortality rate is about 1.0% for both groups, and at 10 years about 98% of patients are free from re-operation on the aorta and more than 90% are free from re-operation on the aortic valve.8 This is important because these are typically young patients who would do better without biological replacement valves (which are not very durable) or mechanical valves (which necessitate lifelong anticoagulation). Results are also good in surgery of the aortic arch and even better in patients with tricuspid aortic valves.4,6,8
Increasingly, in patients at high risk, we are inserting thoracic, abdominal, and thoracoabdominal stent grafts, with excellent early results. An even newer innovation is to replace the aortic valve in high-risk patients via a transcatheter balloon-expandable valve stent inserted through the groin or left ventricular apex.
These treatment innovations have been big strides, but aortic disease continues to increase. Indeed, our volume of thoracic aortic surgery at Cleveland Clinic increased from 190 procedures in 1999 to 717 in 2006. Early detection—before acute emergency surgery is required, with its concomitant high risk of death—is the key to successful surgical outcome and long-term survival.
References
Svensson LG, Labib SB, Eisenhauer AC, Butterly JR. Intimal tear without hematoma: an important variant of aortic dissection that can elude current imaging techniques. Circulation 1999; 99:1331–1336.
Smith AD, Schoenhagen P. CT imaging for acute aortic syndrome. Cleve Clin J Med 2008; 75:7–24.
Svensson LG, Nadolny EM, Kimmel WA. Multimodal protocol influence on stroke and neurocognitive deficit prevention after ascending/arch aortic operations. Ann Thorac Surg 2002; 74:2040–2046.
Svensson LG, Kim KH, Blackstone EH, et al. Elephant trunk procedure: newer indications and uses. Ann Thorac Surg 2004; 78:109–116.
Greenberg RK, Haddad F, Svensson L, et al. Hybrid approaches to thoracic aortic aneurysms: the role of endovascular elephant trunk completion. Circulation 2005; 112:2619–2626.
Svensson LG. Sizing for modified David’s reimplantation procedure. Ann Thorac Surg 2003; 76:1751–1753.
Svensson LG, Blackstone EH, Feng J, et al. Are Marfan syndrome and marfanoid patients distinguishable on long-term follow-up? Ann Thorac Surg 2007; 83:1067–1074.
Svensson LG, Blackstone EH, Cosgrove DM 3rd. Surgical options in young adults with aortic valve disease. Curr Probl Cardiol 2003; 28:417–480.
Svensson LG, Rodriguez ER. Aortic organ disease epidemic, and why do balloons pop? Circulation 2005; 112:1082–1084.
Clouse WD, Hallett JW Jr, Schaff HV, Gayari MM, Ilstrup DM, Melton LJ 3rd. Improved prognosis of thoracic aortic aneurysms: a population-based study. JAMA 1998; 280:1926–1929.
Olsson C, Thelin S, Ståhle E, Ekbom A, Granath F. Thoracic aortic aneurysm and dissection: increasing prevalence and improved outcomes reported in a nationwide population-based study of more than 14,000 cases from 1987 to 2002. Circulation 2006; 114:2611–2618.
Svensson LG, Kim KH, Lytle BW, Cosgrove DM. Relationship of aortic cross-sectional area to height ratio and the risk of aortic dissection inpatients with bicuspid aortic valves. J Thorac Cardiovasc Surg 2003;126:892–893.
Lars G. Svensson, MD, PhD Director, Aortic Surgery, and Marfan Syndrome and Connective Tissue Disorder Clinic, Department of Thoracic and Cardiovascular Surgery, Cleveland Clinic
Address: Lars Svensson, MD, PhD, Department of Thoracic and Cardiovascular Surgery, F24, Cleveland Clinic, 9500 Euclid Avenue,Cleveland, OH 44195. [email protected]
Lars G. Svensson, MD, PhD Director, Aortic Surgery, and Marfan Syndrome and Connective Tissue Disorder Clinic, Department of Thoracic and Cardiovascular Surgery, Cleveland Clinic
Address: Lars Svensson, MD, PhD, Department of Thoracic and Cardiovascular Surgery, F24, Cleveland Clinic, 9500 Euclid Avenue,Cleveland, OH 44195. [email protected]
Author and Disclosure Information
Lars G. Svensson, MD, PhD Director, Aortic Surgery, and Marfan Syndrome and Connective Tissue Disorder Clinic, Department of Thoracic and Cardiovascular Surgery, Cleveland Clinic
Address: Lars Svensson, MD, PhD, Department of Thoracic and Cardiovascular Surgery, F24, Cleveland Clinic, 9500 Euclid Avenue,Cleveland, OH 44195. [email protected]
“The time has come,” the Walrus said, “To talk of many things: Of shoes—and ships—and sealing-wax— Of cabbages—and kings— And why the sea is boiling hot And whether pigs have wings.” —Lewis Carroll, The Walrus and the Carpenter (from Through the Looking-Glass and What Alice Found There, 1872).
Lewis Carroll's poem of 1872 is a useful starting point for identifying issues resulting from confusion over the variously described acute aortic syndromes—and, for oysters, the dangers of listening to walruses.
In cases of aortic dissection (splitting or separation of the layers of the aortic wall), it is important to establish the type (ie, the location and extent) and class (ie, the structure) of the dissection, because these distinctions determine the treatment.1 Similarly, in cases of painful or leaking degenerative aneurysms, we need to know the location of the aneurysm and whether the presenting pain is from compression of surrounding tissue, particularly of the vertebral bodies, or from leakage.
The location and extent of an aortic dissection can be classified in three ways (see Figure 3 in Smith and Schoenhagen’s excellent review of the use of computed tomography [CT] in acute aortic syndromes in this issue of the Cleveland Clinic Journal of Medicine2):
The DeBakey system (type I, II, or III)
The Stanford system (type A or B)
Distal or proximal to the left subclavian artery.
Of note, the DeBakey system does not include tears in the arch that extend distally without ascending involvement. The original Stanford system included arch tears with distal extension in type B; hence, type B excluded all patients without ascending involvement.
The importance of the extent of dissection is that most patients with Stanford type A or DeBakey type I or II dissections should undergo immediate surgery, as most of them would die without it. Surgery is also indicated for arch tears (non-DeBakey, original Stanford type B).
Because these classifications are somewhat confusing, the simplest approach is to note whether the dissection extends proximal or distal to the left subclavian artery, because proximal dissections need surgery and distal ones are first managed medically.
The classes of dissection also have bearing on treatment.1 These are:
Class I—classic aortic dissection in the media with two lumens separated by a “flap” or septum
Class II—intramural hematoma in the aortic wall from dissection in which the intimal tear cannot be imaged (these are nearly always found duringsurgery or autopsy)
Class III—localized confined intimal tears without extensive undermining of the intima or flap formation. These are often seen with Marfan syndrome and can rupture or cause tamponade, as can any type of proximal dissection. The typical appearance is of a bulging bubble in the aortic wall.
Class IV—penetrating atherosclerotic ulcers with localized dissections or wall hematomas, often with calcium at the base of a mushroom-shaped area of extraluminal contrast. Of note, the plane of dissection is often between the media and adventitia.
Class V—iatrogenic or posttraumatic dissection.
All class I to class IV tears of the proximal aorta require surgery, whereas distal class IV and V tears may require either open or endovascular surgical intervention. Surgery is also indicated for patients with distal dissections who have severe narrowing of the true lumen, distal ischemia, uncontrolled pain, severe hypertension, or evidence of leaking, particularly with class IV tears.
In distal dissections that are subacute (2–6 week sold), the Investigation of Stent grafts in Patients With Type B Aortic Dissection (INSTEAD) trial found that inserting a stent prophylactically provided no benefit. Further-more, there is no proof that stenting is beneficial if the aortic dissection is chronic, ie, more than 6 weeks old.1,3–5
WHICH SHOE FITS?
There is no ideal procedure to detect dissection, although the trend is towards CT angiography, as Smith and Schoenhagen report.2 Although some investigators have optimistically estimated CT’s sensitivity and specificity as 100%, cardiovascular surgeons are well aware of both false-positive and false-negative CT studies. Thus, for emergency repairs of proximal dissections, transesophageal echocardiography should be done after intubation and before opening a patient’s chest if time allows. Magnetic resonance imaging, CT, and transesophageal echocardiography may all miss class III tears, but these are frequently evidenced by eccentric “bubbles”or “ballooning.”1
SHIPS
Patients with either acute aortic dissection or severe pain associated with degenerative aneurysms need to be “shipped” promptly to a tertiary medical center after diagnosis, since larger volumes of procedures appear to be associated with better outcomes.
SEALING WAX
Using current surgical methods, the aortic valve can be preserved during aortic dissection repair unless the valve is bicuspid or the patient has Marfan syndrome.1,3,4,6–8
Sealing wax in the form of biological glues, rather than for letters, is a new innovation. A caveat remains, however: we have seen patients who have required reoperation for false aneurysms or infection. Hence, glues should be used with caution.
CABBAGES
A dilemma is whether patients should undergo coronary catheterization (or CT angiography—a separate question) and subsequent coronary artery bypass grafting (CABG), if needed, at the time of aortic dissection repair. The problem is that approximately one-third of patients have coronary artery disease that may require CABG, but the delay for catheterization increases the risk of rupture or tamponade before surgery.
Indeed, 40% of patients with proximal dissections die immediately, and 1% to 3% die in the hour before surgery. The short-term (in-hospital and 30-day) mortality rates range from 3.4% (Cleveland Clinic 2006 data) to 25%, and of the survivors only about 50% area live 5 years after surgery.
Though dismal, the prognosis is improving. In 162 patients with aortic dissection and Marfan syndrome or connective tissue disorders who underwent surgery at Cleveland Clinic in the years 1978–2003, the 5-year survival rate in those with aortic dissection was 75% and the 10-year rate was 55%.7 In those without dissection, the 10-year survival rate was approximately 90% (P < .001).
KINGS
Noted personalities who have had aortic dissection include King George II of England (who died in 1760), Lucille Ball, Conway Twitty, Jan Larson, and most recently John Ritter. None of these famous people survived their aortic dissections. Indeed, dissection and diseases of the aorta or its branches cause between 43,000 and 47,000 deaths annually,9 more than from breast cancer, murders, or motor vehicle accidents. The main reason for these dismal statistics is that the disease is often misdiagnosed at the time of presentation.
BOILING SEA
Careful studies from Olmsted County, Minnesota,10 have shown a tripling of the incidence of aortic disease, particularly in women, even though the rate of deaths from coronary artery disease has been decreasing. Furthermore, Olsson et al11 report that the incidence of aortic dissection in men in Sweden increased to approximately16 per 100,000 per year from 1987 to 2002, a 52% increase. The aging of the population must play a large role, but other factors may exist that are not well understood or defined and require further research.
PIGS HAVE WINGS
Will it be possible to overcome this rising problem? The answer is a definite yes. The results of aortic surgery have never been better. Many new innovations are available, such as aortic root preservation and endovascular stenting procedures. It may be possible to slow the growth of or prevent some aneurysms and aortic dissections, particularly with beta-blockers and, potentially, with losartan (Cozaar) for Marfan syndrome patients.
One of the keys to preventing aortic catastrophes and aortic dissection is to repair aortic aneurysms. The threshold for surgery, however, depends on a surgeon’s experience and results, the underlying pathology, and the aortic size.
We observed that 12.5% of dissections in patients with bicuspid valves and 15% of those in patients with Marfan syndrome were in aortas smaller than 5.0 cm in diameter, that aortic dissection occurred at smaller diameters in shorter patients, and that the risk of dissection increased exponentially with the size of the aorta. Subsequently, we found that a better measure of risk is the maximal aortic cross-sectional area in cm2 divided by the patient’s height in meters; if this ratio exceeds 10, then surgery is recommended.12
Results of surgery are good in experienced hands. In patients who undergo surgical repair of bicuspid aortic valves with or without concurrent repair of the ascending aorta (mostly in patients with an aortic cross-section-to-height ratio > 10), the perioperative mortality rate is about 1.0% for both groups, and at 10 years about 98% of patients are free from re-operation on the aorta and more than 90% are free from re-operation on the aortic valve.8 This is important because these are typically young patients who would do better without biological replacement valves (which are not very durable) or mechanical valves (which necessitate lifelong anticoagulation). Results are also good in surgery of the aortic arch and even better in patients with tricuspid aortic valves.4,6,8
Increasingly, in patients at high risk, we are inserting thoracic, abdominal, and thoracoabdominal stent grafts, with excellent early results. An even newer innovation is to replace the aortic valve in high-risk patients via a transcatheter balloon-expandable valve stent inserted through the groin or left ventricular apex.
These treatment innovations have been big strides, but aortic disease continues to increase. Indeed, our volume of thoracic aortic surgery at Cleveland Clinic increased from 190 procedures in 1999 to 717 in 2006. Early detection—before acute emergency surgery is required, with its concomitant high risk of death—is the key to successful surgical outcome and long-term survival.
“The time has come,” the Walrus said, “To talk of many things: Of shoes—and ships—and sealing-wax— Of cabbages—and kings— And why the sea is boiling hot And whether pigs have wings.” —Lewis Carroll, The Walrus and the Carpenter (from Through the Looking-Glass and What Alice Found There, 1872).
Lewis Carroll's poem of 1872 is a useful starting point for identifying issues resulting from confusion over the variously described acute aortic syndromes—and, for oysters, the dangers of listening to walruses.
In cases of aortic dissection (splitting or separation of the layers of the aortic wall), it is important to establish the type (ie, the location and extent) and class (ie, the structure) of the dissection, because these distinctions determine the treatment.1 Similarly, in cases of painful or leaking degenerative aneurysms, we need to know the location of the aneurysm and whether the presenting pain is from compression of surrounding tissue, particularly of the vertebral bodies, or from leakage.
The location and extent of an aortic dissection can be classified in three ways (see Figure 3 in Smith and Schoenhagen’s excellent review of the use of computed tomography [CT] in acute aortic syndromes in this issue of the Cleveland Clinic Journal of Medicine2):
The DeBakey system (type I, II, or III)
The Stanford system (type A or B)
Distal or proximal to the left subclavian artery.
Of note, the DeBakey system does not include tears in the arch that extend distally without ascending involvement. The original Stanford system included arch tears with distal extension in type B; hence, type B excluded all patients without ascending involvement.
The importance of the extent of dissection is that most patients with Stanford type A or DeBakey type I or II dissections should undergo immediate surgery, as most of them would die without it. Surgery is also indicated for arch tears (non-DeBakey, original Stanford type B).
Because these classifications are somewhat confusing, the simplest approach is to note whether the dissection extends proximal or distal to the left subclavian artery, because proximal dissections need surgery and distal ones are first managed medically.
The classes of dissection also have bearing on treatment.1 These are:
Class I—classic aortic dissection in the media with two lumens separated by a “flap” or septum
Class II—intramural hematoma in the aortic wall from dissection in which the intimal tear cannot be imaged (these are nearly always found duringsurgery or autopsy)
Class III—localized confined intimal tears without extensive undermining of the intima or flap formation. These are often seen with Marfan syndrome and can rupture or cause tamponade, as can any type of proximal dissection. The typical appearance is of a bulging bubble in the aortic wall.
Class IV—penetrating atherosclerotic ulcers with localized dissections or wall hematomas, often with calcium at the base of a mushroom-shaped area of extraluminal contrast. Of note, the plane of dissection is often between the media and adventitia.
Class V—iatrogenic or posttraumatic dissection.
All class I to class IV tears of the proximal aorta require surgery, whereas distal class IV and V tears may require either open or endovascular surgical intervention. Surgery is also indicated for patients with distal dissections who have severe narrowing of the true lumen, distal ischemia, uncontrolled pain, severe hypertension, or evidence of leaking, particularly with class IV tears.
In distal dissections that are subacute (2–6 week sold), the Investigation of Stent grafts in Patients With Type B Aortic Dissection (INSTEAD) trial found that inserting a stent prophylactically provided no benefit. Further-more, there is no proof that stenting is beneficial if the aortic dissection is chronic, ie, more than 6 weeks old.1,3–5
WHICH SHOE FITS?
There is no ideal procedure to detect dissection, although the trend is towards CT angiography, as Smith and Schoenhagen report.2 Although some investigators have optimistically estimated CT’s sensitivity and specificity as 100%, cardiovascular surgeons are well aware of both false-positive and false-negative CT studies. Thus, for emergency repairs of proximal dissections, transesophageal echocardiography should be done after intubation and before opening a patient’s chest if time allows. Magnetic resonance imaging, CT, and transesophageal echocardiography may all miss class III tears, but these are frequently evidenced by eccentric “bubbles”or “ballooning.”1
SHIPS
Patients with either acute aortic dissection or severe pain associated with degenerative aneurysms need to be “shipped” promptly to a tertiary medical center after diagnosis, since larger volumes of procedures appear to be associated with better outcomes.
SEALING WAX
Using current surgical methods, the aortic valve can be preserved during aortic dissection repair unless the valve is bicuspid or the patient has Marfan syndrome.1,3,4,6–8
Sealing wax in the form of biological glues, rather than for letters, is a new innovation. A caveat remains, however: we have seen patients who have required reoperation for false aneurysms or infection. Hence, glues should be used with caution.
CABBAGES
A dilemma is whether patients should undergo coronary catheterization (or CT angiography—a separate question) and subsequent coronary artery bypass grafting (CABG), if needed, at the time of aortic dissection repair. The problem is that approximately one-third of patients have coronary artery disease that may require CABG, but the delay for catheterization increases the risk of rupture or tamponade before surgery.
Indeed, 40% of patients with proximal dissections die immediately, and 1% to 3% die in the hour before surgery. The short-term (in-hospital and 30-day) mortality rates range from 3.4% (Cleveland Clinic 2006 data) to 25%, and of the survivors only about 50% area live 5 years after surgery.
Though dismal, the prognosis is improving. In 162 patients with aortic dissection and Marfan syndrome or connective tissue disorders who underwent surgery at Cleveland Clinic in the years 1978–2003, the 5-year survival rate in those with aortic dissection was 75% and the 10-year rate was 55%.7 In those without dissection, the 10-year survival rate was approximately 90% (P < .001).
KINGS
Noted personalities who have had aortic dissection include King George II of England (who died in 1760), Lucille Ball, Conway Twitty, Jan Larson, and most recently John Ritter. None of these famous people survived their aortic dissections. Indeed, dissection and diseases of the aorta or its branches cause between 43,000 and 47,000 deaths annually,9 more than from breast cancer, murders, or motor vehicle accidents. The main reason for these dismal statistics is that the disease is often misdiagnosed at the time of presentation.
BOILING SEA
Careful studies from Olmsted County, Minnesota,10 have shown a tripling of the incidence of aortic disease, particularly in women, even though the rate of deaths from coronary artery disease has been decreasing. Furthermore, Olsson et al11 report that the incidence of aortic dissection in men in Sweden increased to approximately16 per 100,000 per year from 1987 to 2002, a 52% increase. The aging of the population must play a large role, but other factors may exist that are not well understood or defined and require further research.
PIGS HAVE WINGS
Will it be possible to overcome this rising problem? The answer is a definite yes. The results of aortic surgery have never been better. Many new innovations are available, such as aortic root preservation and endovascular stenting procedures. It may be possible to slow the growth of or prevent some aneurysms and aortic dissections, particularly with beta-blockers and, potentially, with losartan (Cozaar) for Marfan syndrome patients.
One of the keys to preventing aortic catastrophes and aortic dissection is to repair aortic aneurysms. The threshold for surgery, however, depends on a surgeon’s experience and results, the underlying pathology, and the aortic size.
We observed that 12.5% of dissections in patients with bicuspid valves and 15% of those in patients with Marfan syndrome were in aortas smaller than 5.0 cm in diameter, that aortic dissection occurred at smaller diameters in shorter patients, and that the risk of dissection increased exponentially with the size of the aorta. Subsequently, we found that a better measure of risk is the maximal aortic cross-sectional area in cm2 divided by the patient’s height in meters; if this ratio exceeds 10, then surgery is recommended.12
Results of surgery are good in experienced hands. In patients who undergo surgical repair of bicuspid aortic valves with or without concurrent repair of the ascending aorta (mostly in patients with an aortic cross-section-to-height ratio > 10), the perioperative mortality rate is about 1.0% for both groups, and at 10 years about 98% of patients are free from re-operation on the aorta and more than 90% are free from re-operation on the aortic valve.8 This is important because these are typically young patients who would do better without biological replacement valves (which are not very durable) or mechanical valves (which necessitate lifelong anticoagulation). Results are also good in surgery of the aortic arch and even better in patients with tricuspid aortic valves.4,6,8
Increasingly, in patients at high risk, we are inserting thoracic, abdominal, and thoracoabdominal stent grafts, with excellent early results. An even newer innovation is to replace the aortic valve in high-risk patients via a transcatheter balloon-expandable valve stent inserted through the groin or left ventricular apex.
These treatment innovations have been big strides, but aortic disease continues to increase. Indeed, our volume of thoracic aortic surgery at Cleveland Clinic increased from 190 procedures in 1999 to 717 in 2006. Early detection—before acute emergency surgery is required, with its concomitant high risk of death—is the key to successful surgical outcome and long-term survival.
References
Svensson LG, Labib SB, Eisenhauer AC, Butterly JR. Intimal tear without hematoma: an important variant of aortic dissection that can elude current imaging techniques. Circulation 1999; 99:1331–1336.
Smith AD, Schoenhagen P. CT imaging for acute aortic syndrome. Cleve Clin J Med 2008; 75:7–24.
Svensson LG, Nadolny EM, Kimmel WA. Multimodal protocol influence on stroke and neurocognitive deficit prevention after ascending/arch aortic operations. Ann Thorac Surg 2002; 74:2040–2046.
Svensson LG, Kim KH, Blackstone EH, et al. Elephant trunk procedure: newer indications and uses. Ann Thorac Surg 2004; 78:109–116.
Greenberg RK, Haddad F, Svensson L, et al. Hybrid approaches to thoracic aortic aneurysms: the role of endovascular elephant trunk completion. Circulation 2005; 112:2619–2626.
Svensson LG. Sizing for modified David’s reimplantation procedure. Ann Thorac Surg 2003; 76:1751–1753.
Svensson LG, Blackstone EH, Feng J, et al. Are Marfan syndrome and marfanoid patients distinguishable on long-term follow-up? Ann Thorac Surg 2007; 83:1067–1074.
Svensson LG, Blackstone EH, Cosgrove DM 3rd. Surgical options in young adults with aortic valve disease. Curr Probl Cardiol 2003; 28:417–480.
Svensson LG, Rodriguez ER. Aortic organ disease epidemic, and why do balloons pop? Circulation 2005; 112:1082–1084.
Clouse WD, Hallett JW Jr, Schaff HV, Gayari MM, Ilstrup DM, Melton LJ 3rd. Improved prognosis of thoracic aortic aneurysms: a population-based study. JAMA 1998; 280:1926–1929.
Olsson C, Thelin S, Ståhle E, Ekbom A, Granath F. Thoracic aortic aneurysm and dissection: increasing prevalence and improved outcomes reported in a nationwide population-based study of more than 14,000 cases from 1987 to 2002. Circulation 2006; 114:2611–2618.
Svensson LG, Kim KH, Lytle BW, Cosgrove DM. Relationship of aortic cross-sectional area to height ratio and the risk of aortic dissection inpatients with bicuspid aortic valves. J Thorac Cardiovasc Surg 2003;126:892–893.
References
Svensson LG, Labib SB, Eisenhauer AC, Butterly JR. Intimal tear without hematoma: an important variant of aortic dissection that can elude current imaging techniques. Circulation 1999; 99:1331–1336.
Smith AD, Schoenhagen P. CT imaging for acute aortic syndrome. Cleve Clin J Med 2008; 75:7–24.
Svensson LG, Nadolny EM, Kimmel WA. Multimodal protocol influence on stroke and neurocognitive deficit prevention after ascending/arch aortic operations. Ann Thorac Surg 2002; 74:2040–2046.
Svensson LG, Kim KH, Blackstone EH, et al. Elephant trunk procedure: newer indications and uses. Ann Thorac Surg 2004; 78:109–116.
Greenberg RK, Haddad F, Svensson L, et al. Hybrid approaches to thoracic aortic aneurysms: the role of endovascular elephant trunk completion. Circulation 2005; 112:2619–2626.
Svensson LG. Sizing for modified David’s reimplantation procedure. Ann Thorac Surg 2003; 76:1751–1753.
Svensson LG, Blackstone EH, Feng J, et al. Are Marfan syndrome and marfanoid patients distinguishable on long-term follow-up? Ann Thorac Surg 2007; 83:1067–1074.
Svensson LG, Blackstone EH, Cosgrove DM 3rd. Surgical options in young adults with aortic valve disease. Curr Probl Cardiol 2003; 28:417–480.
Svensson LG, Rodriguez ER. Aortic organ disease epidemic, and why do balloons pop? Circulation 2005; 112:1082–1084.
Clouse WD, Hallett JW Jr, Schaff HV, Gayari MM, Ilstrup DM, Melton LJ 3rd. Improved prognosis of thoracic aortic aneurysms: a population-based study. JAMA 1998; 280:1926–1929.
Olsson C, Thelin S, Ståhle E, Ekbom A, Granath F. Thoracic aortic aneurysm and dissection: increasing prevalence and improved outcomes reported in a nationwide population-based study of more than 14,000 cases from 1987 to 2002. Circulation 2006; 114:2611–2618.
Svensson LG, Kim KH, Lytle BW, Cosgrove DM. Relationship of aortic cross-sectional area to height ratio and the risk of aortic dissection inpatients with bicuspid aortic valves. J Thorac Cardiovasc Surg 2003;126:892–893.
Carolyn F. Nemec, MD Women’s Health Center, Cleveland Clinic, Willoughby Hills, OH
Jay Listinsky, MD, PhD Breast Imaging, University Hospitals, Cleveland, OH
Alice Rim, MD Head, Section of Breast Imaging, Cleveland Clinic
Address: Carolyn F. Nemec, MD, Cleveland Clinic Willoughby Hills, 2550 SOM Center Road, N Building, Suite 100, Willoughby Hills, OH 44094; e-mail: [email protected]
Carolyn F. Nemec, MD Women’s Health Center, Cleveland Clinic, Willoughby Hills, OH
Jay Listinsky, MD, PhD Breast Imaging, University Hospitals, Cleveland, OH
Alice Rim, MD Head, Section of Breast Imaging, Cleveland Clinic
Address: Carolyn F. Nemec, MD, Cleveland Clinic Willoughby Hills, 2550 SOM Center Road, N Building, Suite 100, Willoughby Hills, OH 44094; e-mail: [email protected]
Author and Disclosure Information
Carolyn F. Nemec, MD Women’s Health Center, Cleveland Clinic, Willoughby Hills, OH
Jay Listinsky, MD, PhD Breast Imaging, University Hospitals, Cleveland, OH
Alice Rim, MD Head, Section of Breast Imaging, Cleveland Clinic
Address: Carolyn F. Nemec, MD, Cleveland Clinic Willoughby Hills, 2550 SOM Center Road, N Building, Suite 100, Willoughby Hills, OH 44094; e-mail: [email protected]
Sherif B. Mossad, MD Department of Infectious Diseases, Cleveland Clinic; Associate Professor of Medicine, Cleveland Clinic Lerner College of Medicine of Case Western Reserve University, Cleveland, OH
Address: Sherif B. Mossad, MD, Department of Infectious Diseases, S32, Cleveland Clinic, 9500 Euclid Avenue, Cleveland OH, 44195; e-mail: [email protected]
Dr. Mossad is the site principal investigator for a study sponsored by Roche, manufacturer of oseltamivir.
Sherif B. Mossad, MD Department of Infectious Diseases, Cleveland Clinic; Associate Professor of Medicine, Cleveland Clinic Lerner College of Medicine of Case Western Reserve University, Cleveland, OH
Address: Sherif B. Mossad, MD, Department of Infectious Diseases, S32, Cleveland Clinic, 9500 Euclid Avenue, Cleveland OH, 44195; e-mail: [email protected]
Dr. Mossad is the site principal investigator for a study sponsored by Roche, manufacturer of oseltamivir.
Author and Disclosure Information
Sherif B. Mossad, MD Department of Infectious Diseases, Cleveland Clinic; Associate Professor of Medicine, Cleveland Clinic Lerner College of Medicine of Case Western Reserve University, Cleveland, OH
Address: Sherif B. Mossad, MD, Department of Infectious Diseases, S32, Cleveland Clinic, 9500 Euclid Avenue, Cleveland OH, 44195; e-mail: [email protected]
Dr. Mossad is the site principal investigator for a study sponsored by Roche, manufacturer of oseltamivir.
Deepa Kabirdas, MD Department of Internal Medicine, Cleveland Clinic Florida, Weston, FL
Bianca Afonso, MD Department of Internal Medicine, Cleveland Clinic Florida, Weston, FL
Hernan Avella, MD Department of Internal Medicine, Cleveland Clinic Florida, Weston, FL
Aarti Kanwar, MD Department of Internal Medicine, Cleveland Clinic Florida, Weston, FL
Mariana Berho, MD Chairman, Department of Pathology, Cleveland Clinic Florida, Weston, FL
Eduardo Oliveira, MD Chairman, Division of Medicine; Medical Director, Intensive Care Unit; Departments of Pulmonary and Critical Care Medicine, Cleveland Clinic Florida, Weston, FL
Deepa Kabirdas, MD Department of Internal Medicine, Cleveland Clinic Florida, Weston, FL
Bianca Afonso, MD Department of Internal Medicine, Cleveland Clinic Florida, Weston, FL
Hernan Avella, MD Department of Internal Medicine, Cleveland Clinic Florida, Weston, FL
Aarti Kanwar, MD Department of Internal Medicine, Cleveland Clinic Florida, Weston, FL
Mariana Berho, MD Chairman, Department of Pathology, Cleveland Clinic Florida, Weston, FL
Eduardo Oliveira, MD Chairman, Division of Medicine; Medical Director, Intensive Care Unit; Departments of Pulmonary and Critical Care Medicine, Cleveland Clinic Florida, Weston, FL
Deepa Kabirdas, MD Department of Internal Medicine, Cleveland Clinic Florida, Weston, FL
Bianca Afonso, MD Department of Internal Medicine, Cleveland Clinic Florida, Weston, FL
Hernan Avella, MD Department of Internal Medicine, Cleveland Clinic Florida, Weston, FL
Aarti Kanwar, MD Department of Internal Medicine, Cleveland Clinic Florida, Weston, FL
Mariana Berho, MD Chairman, Department of Pathology, Cleveland Clinic Florida, Weston, FL
Eduardo Oliveira, MD Chairman, Division of Medicine; Medical Director, Intensive Care Unit; Departments of Pulmonary and Critical Care Medicine, Cleveland Clinic Florida, Weston, FL
James K. Stoller, MD, MS Professor of Medicine, Cleveland Clinic Lerner College of Medicine of Case Western Reserve University; Vice Chairman, Division of Medicine, Cleveland Clinic; Head, Section of Respiratory Therapy, Department of Pulmonary, Allergy, and Critical Care Medicine, Cleveland Clinic
Leonard Fromer, MD Assistant Clinical Professor, Family Medicine, David Geffen School of Medicine, The University of California at Los Angeles
Mark Brantly, MD Professor of Medicine, Molecular Genetics and Microbiology, Division of Pulmonary and Critical Care Medicine and Department of Biometry, University of Florida College of Medicine; Director, University of Florida Alpha-1 Antitrypsin Genetics Laboratory, University of Florida College of Medicine, Gainesville
James Stocks, MD Professor of Medicine, Director of the Pulmonary Function and Sleep Laboratories, University of Texas at Tyler
Charlie Strange, MD Professor, Pulmonary and Critical Care Medicine, Medical University of South Carolina, Charleston
Address: James K. Stoller, MD, MS, Department of Pulmonary, Allergy, and Critical Care Medicine, A90, Cleveland Clinic, 9500 Euclid Avenue, Cleveland, OH 44195; e-mail [email protected]
Dr. Stoller has indicated that he has been a consultant for Talecris and Baxter corporations.
Dr. Brantly has indicated that he has received honoraria from Talecris. Dr. Strange has indicated that he has been a consultant for Talecris, GTC Biotherapeutics, and Arriva.
James K. Stoller, MD, MS Professor of Medicine, Cleveland Clinic Lerner College of Medicine of Case Western Reserve University; Vice Chairman, Division of Medicine, Cleveland Clinic; Head, Section of Respiratory Therapy, Department of Pulmonary, Allergy, and Critical Care Medicine, Cleveland Clinic
Leonard Fromer, MD Assistant Clinical Professor, Family Medicine, David Geffen School of Medicine, The University of California at Los Angeles
Mark Brantly, MD Professor of Medicine, Molecular Genetics and Microbiology, Division of Pulmonary and Critical Care Medicine and Department of Biometry, University of Florida College of Medicine; Director, University of Florida Alpha-1 Antitrypsin Genetics Laboratory, University of Florida College of Medicine, Gainesville
James Stocks, MD Professor of Medicine, Director of the Pulmonary Function and Sleep Laboratories, University of Texas at Tyler
Charlie Strange, MD Professor, Pulmonary and Critical Care Medicine, Medical University of South Carolina, Charleston
Address: James K. Stoller, MD, MS, Department of Pulmonary, Allergy, and Critical Care Medicine, A90, Cleveland Clinic, 9500 Euclid Avenue, Cleveland, OH 44195; e-mail [email protected]
Dr. Stoller has indicated that he has been a consultant for Talecris and Baxter corporations.
Dr. Brantly has indicated that he has received honoraria from Talecris. Dr. Strange has indicated that he has been a consultant for Talecris, GTC Biotherapeutics, and Arriva.
Author and Disclosure Information
James K. Stoller, MD, MS Professor of Medicine, Cleveland Clinic Lerner College of Medicine of Case Western Reserve University; Vice Chairman, Division of Medicine, Cleveland Clinic; Head, Section of Respiratory Therapy, Department of Pulmonary, Allergy, and Critical Care Medicine, Cleveland Clinic
Leonard Fromer, MD Assistant Clinical Professor, Family Medicine, David Geffen School of Medicine, The University of California at Los Angeles
Mark Brantly, MD Professor of Medicine, Molecular Genetics and Microbiology, Division of Pulmonary and Critical Care Medicine and Department of Biometry, University of Florida College of Medicine; Director, University of Florida Alpha-1 Antitrypsin Genetics Laboratory, University of Florida College of Medicine, Gainesville
James Stocks, MD Professor of Medicine, Director of the Pulmonary Function and Sleep Laboratories, University of Texas at Tyler
Charlie Strange, MD Professor, Pulmonary and Critical Care Medicine, Medical University of South Carolina, Charleston
Address: James K. Stoller, MD, MS, Department of Pulmonary, Allergy, and Critical Care Medicine, A90, Cleveland Clinic, 9500 Euclid Avenue, Cleveland, OH 44195; e-mail [email protected]
Dr. Stoller has indicated that he has been a consultant for Talecris and Baxter corporations.
Dr. Brantly has indicated that he has received honoraria from Talecris. Dr. Strange has indicated that he has been a consultant for Talecris, GTC Biotherapeutics, and Arriva.
