Should clopidogrel be discontinued prior to open vascular procedures?

The continued use of perioperative clopidogrel is appropriate

Surgeons have always worried about bleeding risks for procedures we do. Complex vascular procedures are further complicated by the myriad of available antiplatelet agents designed to reduce ischemic events from cardiovascular disease burden at the expense of potential bleeding complications if antiplatelet medications are continued. Rather than relying on anecdotal reports by historical vignettes, let’s look at the evidence.

There probably is no other drug available in our vascular toolbox which has been studied more in the last 20 years than clopidogrel. Multiple randomized and double blinded studies such as CASPAR¹ and CHARISMA² have amplified what was known since the early CAPRIE trial in the 1990’s and that is that clopidogrel is safe when used as a single medication or as a dual agent with aspirin (duel antiplatelet therapy [DAPT]).

But not all our patients need DAPT. There is no level 1 evidence demonstrating the need for any antiplatelet therapy in the primary prevention of cardiovascular events for patients deemed at low or moderate risk of cardiovascular disease from a large meta-analysis review of six primary prevention trials encompassing over 95,000 patients.³

If our patients do present with vascular disease, current ACCP guidelines recommend single-agent antiplatelet medication (either ASA or clopidogrel) for symptomatic peripheral arterial disease (PAD) whether planning LE revascularization with bypass or via endovascular means with grade 1A evidence.⁴ This works fine for single-focus vascular disease and each antiplatelet agent have proponents but either works well.

That’s great, but what about all those sick cardiac patients we see the most of? First, CHARISMA subgroup analysis of patients with preexisting coronary and/or cerebrovascular disease demonstrate a 7.1% risk reduction in MI, cerebrovascular events, and cardiac ischemic deaths when continuing DAPT over aspirin alone, and similar risk reduction is found in PAD patients for endpoints of MI and ischemic cardiovascular events. Second, there was no significant difference in severe, fatal, or moderate bleeding in those receiving DAPT vs. aspirin alone with only minor bleeding increased using DAPT. Third, real-life practice echoes multiple trial experiences such as the Vascular Study Group of New England study group confirmed in reviewing 16 centers and 66 surgeons with more than 10,000 patients. Approximately 39% underwent major aortic or lower extremity bypass operations.

No statistical difference could be found for reoperation (P = .74), transfusion (P = .1) or operative type between DAPT or aspirin use alone.⁵ This is rediscovered once again by Saadeh and Sfeir in their prospective study of 647 major arterial procedures over 7 years finding no significant difference in reoperation for bleeding or bleeding mortality between DAPT vs. aspirin alone.⁶

So can we stop bashing clopidogrel as an evil agent of bleeding as Dr. Dalsing wishes to do? After all, he has been on record as stating, “I don’t know if our bleeding risk is worse or better … something we have to do to keep our grafts going.” Evidence tells us the benefits for continuing DAPT as seen in risk reduction in primary cardiovascular outcomes far outweigh the risk of minor bleeding associated with continued use.

Let the science dictate practice. Patients with low or moderate risk for cardiovascular disease need no antiplatelet medication unless undergoing PAD treatment where a single agent, either aspirin or clopidogrel alone, is sufficient. In those patients having a large cardiovascular burden of disease, combination of aspirin and clopidogrel improves survival benefit and reduces ischemic events without a significant risk of reoperation, transfusion, or bleeding-related mortality. As many of our patients require DAPT for drug eluting coronary stents, withholding clopidogrel preoperatively increases overall risk beyond acceptable limits. Improving surgical skills and paying attention to hemostasis during the operation will allow naysayers to achieve improved patient survival without fear of bleeding when continuing best medical therapy such as DAPT.

Gary Lemmon, MD, is professor of vascular surgery at Indiana University, Indianapolis, and chief, vascular surgery, Indianapolis VA Medical Center. He reported no relevant conflicts.

References

1. J Vasc Surg. 2010;52:825-33

2. Eur Heart J. 2009;30:192-201

3. Lancet. 2009;373:1849-604. Chest. 2012;141:e669s-90s

5. J Vasc Surg. 2011;54: 779-84

6. J Vasc Surg. 2013;58: 1586-92

The continued use of perioperative clopidogrel is debatable!

There are cases in which clopidogrel should not be discontinued for a needed vascular intervention. Delaying operation or maintaining clopidogrel during operation if your patient required a recent coronary stent is warranted unless you are willing to accept an acute coronary thrombosis.

However, in other cases, for example infrainguinal grafts, the risk of potential increased bleeding when adding clopidogrel to aspirin may outweigh potential improvements in graft patency. This is especially true of below-knee vein bypass grafts where data do not support improved patency. However, in the CASPAR trial, prosthetic graft patency did appear to be beneficial, but only in subgroup analysis.¹

It is true that severe bleeding was not increased (intracranial hemorrhage, or hemodynamic compromise: 1 vs 2.7%, P = NS) but moderate bleeding (transfusion required: 0.7 vs 3.7%, P = .012) and mild bleeding (5.4 vs 12.1%, P = .004) was increased when this agent was used especially in vein graft surgery. This risk of bleeding was present even when clopidogrel was begun 2 or more days after surgery.¹

To complicate this decision, a Cochrane review did not consider subgroup analysis as statistically valid and so the authors considered infrainguinal graft patency as not improved with clopidogrel but bleeding risk was increased. One might even question the use of acetylsalicylic acid (ASA) for vein graft bypasses based on the results of this metanalysis.2 Carotid endarterectomy is a common vascular surgery procedure in which antiplatelet use has been evaluated in the real-world situation and with large cohorts. As is always the case when dealing with patient issues, the addition of one agent does not tell the entire story and patient demographics can have a significant influence on the outcome. A report from the Vascular Quality Initiative (VQI) database controlled for patient differences by propensity matching with more than 4,500 patients in each of the two groups; ASA vs. ASA + clopidogrel; demonstrated that major bleeding, defined as return to the OR for bleeding, was statistically more common with dual therapy (1.3% vs. 0.7%, P = .004).³

The addition of clopidogrel did statistically decrease the risk of ipsilateral TIA or stroke (0.8% vs. 1.2%, P = .02) but not the risk of death (0.2% vs. 0.3%, P = .3) or postoperative MI (1% vs. 0.8%, P = .4). Reoperation for bleeding is not inconsequential since in patients requiring this intervention, there is a significantly worse outcome in regard to stroke (3.7% vs. 0.8%, P = .001), MI (6.2% vs. 0.8%, P = .001), and death (2.5% vs. 0.2%,P = .001). Further drill down involving propensity score–matched analysis stratified by symptom status (asymptomatic vs. symptomatic) was quite interesting in that in only asymptomatic patients did the addition of clopidogrel actually demonstrate a statistically significant reduction in TIA or stroke, any stroke, or composite stroke/death. Symptomatic patients taking dual therapy demonstrated a slight reduction in TIA or stroke (1.4% vs. 1.7%, P = .6), any stroke (1.1% vs. 1.2%, P = .9) and composite stroke/death (1.2% vs. 1.5%, P = .5) but in no instance was statistical significance reached. The use of protamine did help to decrease the risk of bleeding.

Regarding the use of dual therapy during open aortic operations, an earlier report of the VQI database demonstrated no significant difference in bleeding risk statistically, but if one delves deeper the data indicate something different. In the majority of cases, vascular surgeons do not feel comfortable preforming this extensive dissection on dual therapy. Of the cases reported, 1,074 were preformed either free of either drug or only on ASA while 42 were on dual therapy and only 12 on clopidogrel only. In fact, in the conclusions, the authors note that they do not believe that conclusions regarding clopidogrel use in patient undergoing open abdominal aortic aneurysm repair can be drawn based on their results since the potential for a type II error was too great.⁴

It may be that our current level of sophistication is not sufficiently mature to determine the actual effect that clopidogrel is having on our patients. Clopidogrel, a thienopyridine, inhibits platelet activation by blocking the ADP-binding site for the P2Y12 receptor. Over 85% of ingested drug is metabolized into inactive metabolites while 15% is metabolized by the liver via a two-step oxidative process into the active thiol metabolite. Inter-individual variability in the antiplatelet response to thienopyridines is noted and partially caused by genetic mutations in the CP isoenzymes. Platelet reactivity testing is possible but most of the work has been conducted for those patients requiring coronary artery revascularization. Results of tailoring intervention to maximize therapeutic benefit and decrease the risk of bleeding have been inconsistent but, in some studies, appear to be promising.⁵ This approach may ultimately be found superior to determining how effective clopidogrel actually is in a particular case with some insight into the bleeding risk as well. With this determination, whether or not to hold clopidogrel perioperatively can be made with some science behind the decision.

Clearly, a blanket statement that the risk of bleeding should be accepted or ignored because of the demonstrated benefits of clopidogrel in patients requiring vascular surgery is not accurate. In some cases, there is no clear benefit, so eliminating the bleeding risk may well be the appropriate decision. The astute vascular surgeon understands the details of the written word in order to make an educated decision and understands that new information such as determining platelet reactivity may provide more clarity to such decisions in the future.

Michael C. Dalsing, MD, is chief of vascular surgery at Indiana University, Indianapolis. He reported no relevant conflicts.

References

1. J Vasc Surg. 2010;52:825-33

2. Cochrane Database Syst Rev. 2015, Issue 2. Art. No.: CD000535

3. J Vasc Surg. 2016;63:1262-70

4.J Vasc Surg. 2011;54:779-84

5. Vascul Pharmacol. 2016;77:19-27

The continued use of perioperative clopidogrel is appropriate

Surgeons have always worried about bleeding risks for procedures we do. Complex vascular procedures are further complicated by the myriad of available antiplatelet agents designed to reduce ischemic events from cardiovascular disease burden at the expense of potential bleeding complications if antiplatelet medications are continued. Rather than relying on anecdotal reports by historical vignettes, let’s look at the evidence.

There probably is no other drug available in our vascular toolbox which has been studied more in the last 20 years than clopidogrel. Multiple randomized and double blinded studies such as CASPAR¹ and CHARISMA² have amplified what was known since the early CAPRIE trial in the 1990’s and that is that clopidogrel is safe when used as a single medication or as a dual agent with aspirin (duel antiplatelet therapy [DAPT]).

But not all our patients need DAPT. There is no level 1 evidence demonstrating the need for any antiplatelet therapy in the primary prevention of cardiovascular events for patients deemed at low or moderate risk of cardiovascular disease from a large meta-analysis review of six primary prevention trials encompassing over 95,000 patients.³

If our patients do present with vascular disease, current ACCP guidelines recommend single-agent antiplatelet medication (either ASA or clopidogrel) for symptomatic peripheral arterial disease (PAD) whether planning LE revascularization with bypass or via endovascular means with grade 1A evidence.⁴ This works fine for single-focus vascular disease and each antiplatelet agent have proponents but either works well.

That’s great, but what about all those sick cardiac patients we see the most of? First, CHARISMA subgroup analysis of patients with preexisting coronary and/or cerebrovascular disease demonstrate a 7.1% risk reduction in MI, cerebrovascular events, and cardiac ischemic deaths when continuing DAPT over aspirin alone, and similar risk reduction is found in PAD patients for endpoints of MI and ischemic cardiovascular events. Second, there was no significant difference in severe, fatal, or moderate bleeding in those receiving DAPT vs. aspirin alone with only minor bleeding increased using DAPT. Third, real-life practice echoes multiple trial experiences such as the Vascular Study Group of New England study group confirmed in reviewing 16 centers and 66 surgeons with more than 10,000 patients. Approximately 39% underwent major aortic or lower extremity bypass operations.

No statistical difference could be found for reoperation (P = .74), transfusion (P = .1) or operative type between DAPT or aspirin use alone.⁵ This is rediscovered once again by Saadeh and Sfeir in their prospective study of 647 major arterial procedures over 7 years finding no significant difference in reoperation for bleeding or bleeding mortality between DAPT vs. aspirin alone.⁶

So can we stop bashing clopidogrel as an evil agent of bleeding as Dr. Dalsing wishes to do? After all, he has been on record as stating, “I don’t know if our bleeding risk is worse or better … something we have to do to keep our grafts going.” Evidence tells us the benefits for continuing DAPT as seen in risk reduction in primary cardiovascular outcomes far outweigh the risk of minor bleeding associated with continued use.

Let the science dictate practice. Patients with low or moderate risk for cardiovascular disease need no antiplatelet medication unless undergoing PAD treatment where a single agent, either aspirin or clopidogrel alone, is sufficient. In those patients having a large cardiovascular burden of disease, combination of aspirin and clopidogrel improves survival benefit and reduces ischemic events without a significant risk of reoperation, transfusion, or bleeding-related mortality. As many of our patients require DAPT for drug eluting coronary stents, withholding clopidogrel preoperatively increases overall risk beyond acceptable limits. Improving surgical skills and paying attention to hemostasis during the operation will allow naysayers to achieve improved patient survival without fear of bleeding when continuing best medical therapy such as DAPT.

Gary Lemmon, MD, is professor of vascular surgery at Indiana University, Indianapolis, and chief, vascular surgery, Indianapolis VA Medical Center. He reported no relevant conflicts.

References

1. J Vasc Surg. 2010;52:825-33

2. Eur Heart J. 2009;30:192-201

3. Lancet. 2009;373:1849-604. Chest. 2012;141:e669s-90s

5. J Vasc Surg. 2011;54: 779-84

6. J Vasc Surg. 2013;58: 1586-92

The continued use of perioperative clopidogrel is debatable!

There are cases in which clopidogrel should not be discontinued for a needed vascular intervention. Delaying operation or maintaining clopidogrel during operation if your patient required a recent coronary stent is warranted unless you are willing to accept an acute coronary thrombosis.

However, in other cases, for example infrainguinal grafts, the risk of potential increased bleeding when adding clopidogrel to aspirin may outweigh potential improvements in graft patency. This is especially true of below-knee vein bypass grafts where data do not support improved patency. However, in the CASPAR trial, prosthetic graft patency did appear to be beneficial, but only in subgroup analysis.¹

It is true that severe bleeding was not increased (intracranial hemorrhage, or hemodynamic compromise: 1 vs 2.7%, P = NS) but moderate bleeding (transfusion required: 0.7 vs 3.7%, P = .012) and mild bleeding (5.4 vs 12.1%, P = .004) was increased when this agent was used especially in vein graft surgery. This risk of bleeding was present even when clopidogrel was begun 2 or more days after surgery.¹

To complicate this decision, a Cochrane review did not consider subgroup analysis as statistically valid and so the authors considered infrainguinal graft patency as not improved with clopidogrel but bleeding risk was increased. One might even question the use of acetylsalicylic acid (ASA) for vein graft bypasses based on the results of this metanalysis.2 Carotid endarterectomy is a common vascular surgery procedure in which antiplatelet use has been evaluated in the real-world situation and with large cohorts. As is always the case when dealing with patient issues, the addition of one agent does not tell the entire story and patient demographics can have a significant influence on the outcome. A report from the Vascular Quality Initiative (VQI) database controlled for patient differences by propensity matching with more than 4,500 patients in each of the two groups; ASA vs. ASA + clopidogrel; demonstrated that major bleeding, defined as return to the OR for bleeding, was statistically more common with dual therapy (1.3% vs. 0.7%, P = .004).³

The addition of clopidogrel did statistically decrease the risk of ipsilateral TIA or stroke (0.8% vs. 1.2%, P = .02) but not the risk of death (0.2% vs. 0.3%, P = .3) or postoperative MI (1% vs. 0.8%, P = .4). Reoperation for bleeding is not inconsequential since in patients requiring this intervention, there is a significantly worse outcome in regard to stroke (3.7% vs. 0.8%, P = .001), MI (6.2% vs. 0.8%, P = .001), and death (2.5% vs. 0.2%,P = .001). Further drill down involving propensity score–matched analysis stratified by symptom status (asymptomatic vs. symptomatic) was quite interesting in that in only asymptomatic patients did the addition of clopidogrel actually demonstrate a statistically significant reduction in TIA or stroke, any stroke, or composite stroke/death. Symptomatic patients taking dual therapy demonstrated a slight reduction in TIA or stroke (1.4% vs. 1.7%, P = .6), any stroke (1.1% vs. 1.2%, P = .9) and composite stroke/death (1.2% vs. 1.5%, P = .5) but in no instance was statistical significance reached. The use of protamine did help to decrease the risk of bleeding.

Regarding the use of dual therapy during open aortic operations, an earlier report of the VQI database demonstrated no significant difference in bleeding risk statistically, but if one delves deeper the data indicate something different. In the majority of cases, vascular surgeons do not feel comfortable preforming this extensive dissection on dual therapy. Of the cases reported, 1,074 were preformed either free of either drug or only on ASA while 42 were on dual therapy and only 12 on clopidogrel only. In fact, in the conclusions, the authors note that they do not believe that conclusions regarding clopidogrel use in patient undergoing open abdominal aortic aneurysm repair can be drawn based on their results since the potential for a type II error was too great.⁴

It may be that our current level of sophistication is not sufficiently mature to determine the actual effect that clopidogrel is having on our patients. Clopidogrel, a thienopyridine, inhibits platelet activation by blocking the ADP-binding site for the P2Y12 receptor. Over 85% of ingested drug is metabolized into inactive metabolites while 15% is metabolized by the liver via a two-step oxidative process into the active thiol metabolite. Inter-individual variability in the antiplatelet response to thienopyridines is noted and partially caused by genetic mutations in the CP isoenzymes. Platelet reactivity testing is possible but most of the work has been conducted for those patients requiring coronary artery revascularization. Results of tailoring intervention to maximize therapeutic benefit and decrease the risk of bleeding have been inconsistent but, in some studies, appear to be promising.⁵ This approach may ultimately be found superior to determining how effective clopidogrel actually is in a particular case with some insight into the bleeding risk as well. With this determination, whether or not to hold clopidogrel perioperatively can be made with some science behind the decision.

Clearly, a blanket statement that the risk of bleeding should be accepted or ignored because of the demonstrated benefits of clopidogrel in patients requiring vascular surgery is not accurate. In some cases, there is no clear benefit, so eliminating the bleeding risk may well be the appropriate decision. The astute vascular surgeon understands the details of the written word in order to make an educated decision and understands that new information such as determining platelet reactivity may provide more clarity to such decisions in the future.

Michael C. Dalsing, MD, is chief of vascular surgery at Indiana University, Indianapolis. He reported no relevant conflicts.

References

1. J Vasc Surg. 2010;52:825-33

2. Cochrane Database Syst Rev. 2015, Issue 2. Art. No.: CD000535

3. J Vasc Surg. 2016;63:1262-70

4.J Vasc Surg. 2011;54:779-84

5. Vascul Pharmacol. 2016;77:19-27

The continued use of perioperative clopidogrel is appropriate

Surgeons have always worried about bleeding risks for procedures we do. Complex vascular procedures are further complicated by the myriad of available antiplatelet agents designed to reduce ischemic events from cardiovascular disease burden at the expense of potential bleeding complications if antiplatelet medications are continued. Rather than relying on anecdotal reports by historical vignettes, let’s look at the evidence.

There probably is no other drug available in our vascular toolbox which has been studied more in the last 20 years than clopidogrel. Multiple randomized and double blinded studies such as CASPAR¹ and CHARISMA² have amplified what was known since the early CAPRIE trial in the 1990’s and that is that clopidogrel is safe when used as a single medication or as a dual agent with aspirin (duel antiplatelet therapy [DAPT]).

But not all our patients need DAPT. There is no level 1 evidence demonstrating the need for any antiplatelet therapy in the primary prevention of cardiovascular events for patients deemed at low or moderate risk of cardiovascular disease from a large meta-analysis review of six primary prevention trials encompassing over 95,000 patients.³

If our patients do present with vascular disease, current ACCP guidelines recommend single-agent antiplatelet medication (either ASA or clopidogrel) for symptomatic peripheral arterial disease (PAD) whether planning LE revascularization with bypass or via endovascular means with grade 1A evidence.⁴ This works fine for single-focus vascular disease and each antiplatelet agent have proponents but either works well.

That’s great, but what about all those sick cardiac patients we see the most of? First, CHARISMA subgroup analysis of patients with preexisting coronary and/or cerebrovascular disease demonstrate a 7.1% risk reduction in MI, cerebrovascular events, and cardiac ischemic deaths when continuing DAPT over aspirin alone, and similar risk reduction is found in PAD patients for endpoints of MI and ischemic cardiovascular events. Second, there was no significant difference in severe, fatal, or moderate bleeding in those receiving DAPT vs. aspirin alone with only minor bleeding increased using DAPT. Third, real-life practice echoes multiple trial experiences such as the Vascular Study Group of New England study group confirmed in reviewing 16 centers and 66 surgeons with more than 10,000 patients. Approximately 39% underwent major aortic or lower extremity bypass operations.

No statistical difference could be found for reoperation (P = .74), transfusion (P = .1) or operative type between DAPT or aspirin use alone.⁵ This is rediscovered once again by Saadeh and Sfeir in their prospective study of 647 major arterial procedures over 7 years finding no significant difference in reoperation for bleeding or bleeding mortality between DAPT vs. aspirin alone.⁶

So can we stop bashing clopidogrel as an evil agent of bleeding as Dr. Dalsing wishes to do? After all, he has been on record as stating, “I don’t know if our bleeding risk is worse or better … something we have to do to keep our grafts going.” Evidence tells us the benefits for continuing DAPT as seen in risk reduction in primary cardiovascular outcomes far outweigh the risk of minor bleeding associated with continued use.

Let the science dictate practice. Patients with low or moderate risk for cardiovascular disease need no antiplatelet medication unless undergoing PAD treatment where a single agent, either aspirin or clopidogrel alone, is sufficient. In those patients having a large cardiovascular burden of disease, combination of aspirin and clopidogrel improves survival benefit and reduces ischemic events without a significant risk of reoperation, transfusion, or bleeding-related mortality. As many of our patients require DAPT for drug eluting coronary stents, withholding clopidogrel preoperatively increases overall risk beyond acceptable limits. Improving surgical skills and paying attention to hemostasis during the operation will allow naysayers to achieve improved patient survival without fear of bleeding when continuing best medical therapy such as DAPT.

Gary Lemmon, MD, is professor of vascular surgery at Indiana University, Indianapolis, and chief, vascular surgery, Indianapolis VA Medical Center. He reported no relevant conflicts.

References

1. J Vasc Surg. 2010;52:825-33

2. Eur Heart J. 2009;30:192-201

3. Lancet. 2009;373:1849-604. Chest. 2012;141:e669s-90s

5. J Vasc Surg. 2011;54: 779-84

6. J Vasc Surg. 2013;58: 1586-92

The continued use of perioperative clopidogrel is debatable!

There are cases in which clopidogrel should not be discontinued for a needed vascular intervention. Delaying operation or maintaining clopidogrel during operation if your patient required a recent coronary stent is warranted unless you are willing to accept an acute coronary thrombosis.

However, in other cases, for example infrainguinal grafts, the risk of potential increased bleeding when adding clopidogrel to aspirin may outweigh potential improvements in graft patency. This is especially true of below-knee vein bypass grafts where data do not support improved patency. However, in the CASPAR trial, prosthetic graft patency did appear to be beneficial, but only in subgroup analysis.¹

It is true that severe bleeding was not increased (intracranial hemorrhage, or hemodynamic compromise: 1 vs 2.7%, P = NS) but moderate bleeding (transfusion required: 0.7 vs 3.7%, P = .012) and mild bleeding (5.4 vs 12.1%, P = .004) was increased when this agent was used especially in vein graft surgery. This risk of bleeding was present even when clopidogrel was begun 2 or more days after surgery.¹

To complicate this decision, a Cochrane review did not consider subgroup analysis as statistically valid and so the authors considered infrainguinal graft patency as not improved with clopidogrel but bleeding risk was increased. One might even question the use of acetylsalicylic acid (ASA) for vein graft bypasses based on the results of this metanalysis.2 Carotid endarterectomy is a common vascular surgery procedure in which antiplatelet use has been evaluated in the real-world situation and with large cohorts. As is always the case when dealing with patient issues, the addition of one agent does not tell the entire story and patient demographics can have a significant influence on the outcome. A report from the Vascular Quality Initiative (VQI) database controlled for patient differences by propensity matching with more than 4,500 patients in each of the two groups; ASA vs. ASA + clopidogrel; demonstrated that major bleeding, defined as return to the OR for bleeding, was statistically more common with dual therapy (1.3% vs. 0.7%, P = .004).³

The addition of clopidogrel did statistically decrease the risk of ipsilateral TIA or stroke (0.8% vs. 1.2%, P = .02) but not the risk of death (0.2% vs. 0.3%, P = .3) or postoperative MI (1% vs. 0.8%, P = .4). Reoperation for bleeding is not inconsequential since in patients requiring this intervention, there is a significantly worse outcome in regard to stroke (3.7% vs. 0.8%, P = .001), MI (6.2% vs. 0.8%, P = .001), and death (2.5% vs. 0.2%,P = .001). Further drill down involving propensity score–matched analysis stratified by symptom status (asymptomatic vs. symptomatic) was quite interesting in that in only asymptomatic patients did the addition of clopidogrel actually demonstrate a statistically significant reduction in TIA or stroke, any stroke, or composite stroke/death. Symptomatic patients taking dual therapy demonstrated a slight reduction in TIA or stroke (1.4% vs. 1.7%, P = .6), any stroke (1.1% vs. 1.2%, P = .9) and composite stroke/death (1.2% vs. 1.5%, P = .5) but in no instance was statistical significance reached. The use of protamine did help to decrease the risk of bleeding.

Regarding the use of dual therapy during open aortic operations, an earlier report of the VQI database demonstrated no significant difference in bleeding risk statistically, but if one delves deeper the data indicate something different. In the majority of cases, vascular surgeons do not feel comfortable preforming this extensive dissection on dual therapy. Of the cases reported, 1,074 were preformed either free of either drug or only on ASA while 42 were on dual therapy and only 12 on clopidogrel only. In fact, in the conclusions, the authors note that they do not believe that conclusions regarding clopidogrel use in patient undergoing open abdominal aortic aneurysm repair can be drawn based on their results since the potential for a type II error was too great.⁴

It may be that our current level of sophistication is not sufficiently mature to determine the actual effect that clopidogrel is having on our patients. Clopidogrel, a thienopyridine, inhibits platelet activation by blocking the ADP-binding site for the P2Y12 receptor. Over 85% of ingested drug is metabolized into inactive metabolites while 15% is metabolized by the liver via a two-step oxidative process into the active thiol metabolite. Inter-individual variability in the antiplatelet response to thienopyridines is noted and partially caused by genetic mutations in the CP isoenzymes. Platelet reactivity testing is possible but most of the work has been conducted for those patients requiring coronary artery revascularization. Results of tailoring intervention to maximize therapeutic benefit and decrease the risk of bleeding have been inconsistent but, in some studies, appear to be promising.⁵ This approach may ultimately be found superior to determining how effective clopidogrel actually is in a particular case with some insight into the bleeding risk as well. With this determination, whether or not to hold clopidogrel perioperatively can be made with some science behind the decision.

Clearly, a blanket statement that the risk of bleeding should be accepted or ignored because of the demonstrated benefits of clopidogrel in patients requiring vascular surgery is not accurate. In some cases, there is no clear benefit, so eliminating the bleeding risk may well be the appropriate decision. The astute vascular surgeon understands the details of the written word in order to make an educated decision and understands that new information such as determining platelet reactivity may provide more clarity to such decisions in the future.

Michael C. Dalsing, MD, is chief of vascular surgery at Indiana University, Indianapolis. He reported no relevant conflicts.

References

1. J Vasc Surg. 2010;52:825-33

2. Cochrane Database Syst Rev. 2015, Issue 2. Art. No.: CD000535

3. J Vasc Surg. 2016;63:1262-70

4.J Vasc Surg. 2011;54:779-84

5. Vascul Pharmacol. 2016;77:19-27