Risk Factors Associated with Perioperative Myocardial Infarction in Major Open Vascular Surgery

Abstract

Background: Among patients undergoing noncardiac surgery, major vascular surgery is associated with a high risk of perioperative myocardial infarction (MI). Currently, there are no perioperative MI risk calculators accounting for intraoperative and postoperative risk factors in vascular surgery patients. We aimed to investigate specific risk factors for perioperative MI after major open vascular surgery to determine which patients are at highest risk of MI and the association of perioperative MI with perioperative transfusion.

Methods: This statewide, retrospective cohort study analyzed risk factors for perioperative MI in major open vascular surgery between July 2012 and December 2015 using the Michigan Surgical Quality Collaborative, a multicenter quality collaborative. Patients were identified using current procedure terminology codes including open abdominal aortic aneurysm repairs (oAAA), aortobifemoral bypasses (AFB), and lower extremity bypasses (LEB). Rates of myocardial infarction were described for each procedure. A priori, preoperative, intraoperative, and postoperative variables were evaluated using univariate and multivariable statistics after adjusting for intraoperative factors including anesthesia type, intraoperative blood loss, intraoperative transfusion, and intraoperative vasopressor medications.

Results: A total of 3,689 patients underwent major open vascular surgery, including 375 oAAA, 392 AFB, and 2,922 LEB procedures. The overall incidence of MI was 2.4%, varying from 1.8% for aortobifemoral bypass, 2.4% for lower extremity bypass, and 3.7% for open abdominal aortic aneurysm repair. Although preoperative risk factors for myocardial infarction included age, American Society of Anesthesiologists score, diabetes, coronary artery disease, congestive heart failure, use of beta blocker, lower preoperative hematocrit, and surgical priority (urgent/emergent cases), after adjusting for intraoperative risk factors, all preoperative risk factors were not significant with the exception of surgical priority. After adjusting for intraoperative factors, only surgical priority (odds ratio [OR] = 1.70, 95% confidence interval [CI] [1.01-2.85], P < 0.001) and postoperative transfusion (OR = 2.65, 95% CI [1.59-4.44], P < 0.001) was associated with myocardial infarction, and higher nadir hematocrit was inversely associated with myocardial infarction (OR = 0.89, 95% CI [0.85-0.94], P < 0.001).

Conclusions: Among vascular surgery patients undergoing major open vascular surgery, surgical priority was the only preoperative risk factors independently associated with MI, and only postoperative variables such as nadir hematocrit and postoperative transfusion were associated with MI. This suggests minimizing intraoperative blood loss and prioritizing early intraoperative transfusion may be the potential targets for process improvement.