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MI risk prediction after noncardiac surgery simplified



– The risk of perioperative MI or death associated with noncardiac surgery is vanishingly low in patients free of diabetes, hypertension, and smoking, Tanya Wilcox, MD, reported at the annual meeting of the American College of Cardiology.

How small is the risk? A mere 1 in 1,000, according to her analysis of more than 3.8 million major noncardiac surgeries in the American College of Surgeons National Surgical Quality Improvement Program database for 2009-2015, according to Dr. Wilcox of New York University.

Physicians are frequently asked by surgeons to clear patients for noncardiac surgery in terms of cardiovascular risk. Because current risk scores are complex, aren’t amenable to rapid bedside calculations, and may entail cardiac stress testing, Dr. Wilcox decided it was worth assessing the impact of three straightforward cardiovascular risk factors – current smoking and treatment for hypertension or diabetes – on 30-day postoperative MI-free survival. For this purpose she turned to the National Surgical Quality Improvement Program database, a validated, risk-adjusted, outcomes-based program to measure and improve the quality of surgical care utilizing data from 250 U.S. surgical centers.

Of the 3,817,113 patients who underwent major noncardiac surgery, 1,586,020 (42%) of them had none of the three cardiovascular risk factors of interest, 1,541,846 (40%) had one, 643,424 (17%) had two, and 45,823, or 1.2%, had all three. The patients’ mean age was 57, 75% were white, and 57% were women. About half of all patients underwent various operations within the realm of general surgery; next most frequent were orthopedic procedures, accounting for 18% of total noncardiac surgery. Of note, only 23% of patients with zero risk factors were American Society of Anesthesiologists Class 3-5, compared with 51% of those with one cardiovascular risk factor, 76% with two, and 71% with all three.

The incidence of acute MI or death within 30 days of noncardiac surgery climbed in stepwise fashion according to a patient’s risk factor burden. In a multivariate analysis adjusted for age, race, and gender, patients with any one of the cardiovascular risk factors had a 30-day risk of acute MI or death that was 1.52 times greater than those with no risk factors, patients with two risk factors were at 2.4-fold increased risk, and those with all three were at 3.63-fold greater risk than those with none. The degree of increased risk associated with any single risk factor ranged from 1.47-fold for hypertension to 1.94-fold for smoking.

“Further study is needed to determine whether aggressive risk factor modifications in the form of blood pressure control, glycemic control, and smoking cessation could reduce the incidence of postoperative MI,” Dr. Wilcox observed.

She reported having no financial conflicts regarding her study.

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