Preoperative Stress Test and Postoperative MI in Patients Requiring Lower Extremity Bypass for Critical Limb Ischemia

Patients with critical limb ischemia (CLI) often require lower extremity bypass surgery for limb salvage. A myocardial infarction (MI) is a major postoperative risk. Our objective is to assess the utility of preoperative stress test in determining patient outcomes.

This is a retrospective study utilizing the national Vascular Quality Initiative database. We collected data from 2013-2018 on all patients undergoing lower extremity bypass for CLI and assessed whether or not they had a preoperative stress test. Rates of an MI were then compared between groups of patients who either did not receive a stress test, had a normal stress test or a positive stress test. An MI was distinguished as troponin only and electrocardiogram (EKG)/clinical. Our secondary end point was in-hospital mortality. Univariate and multivariate analysis with the stress test as a covariate was used to determine significance.

During this time period, 29,937 bypasses were performed on 27,219 patients. The average age was 67.5 years (±11.09), 66.3% were men, and 17.3% were African American. Risk factors included hypertension (89.5%), diabetes (55.9%), congestive heart failure (20%), coronary artery disease (32.5%), coronary artery bypass graft (22.2%), and percutaneous coronary intervention (21%). 19,108 patients (64.1%) did not undergo the stress test before bypass, 6,830 (22.9%) had a normal stress test, and 2,898 (9.7%) had a positive stress test. Overall rate of an MI was 4%, with 2% being troponin only and 2% EKG/clinical. The positive stress test had a higher rate of troponin only (2.85%) as well as EKG/clinical (3.37%) MI. For every 10 year increase in age, the odds of having a postoperative MI increased by 27% (P < 0.0001). Overall in-hospital mortality was 1.4%. Patients with positive stress tests had a 2.6% mortality compared with normal/not performed at 1.3%. Of the patients who died, 21.5% had an EKG/clinical MI. Of those patients, 50% did not have a stress test, 12% had normal stress tests, and 23% had positive stress tests. When comparing rates of patients who died or had an MI, there was no difference between patients who had no or a normal stress test (7.29%) versus those who had a positive stress test (7.58%), (P = 0.11).

A positive stress test before lower extremity bypass is a significant predictor of a postoperative MI. However, mortality increase was minimal in patients with a positive stress test. Therefore, the stress test result should not delay care for patients needing urgent revascularization.