Silent myocardial ischemia is not predictive of myocardial infarction in peripheral vascular surgery patients

Continuous ambulatory ECG (CAECG) monitoring has been advocated as an effective low-cost preoperative method for detecting silent myocardial ischemia in patients undergoing peripheral vascular surgery. In addition, silent ischemic events are associated with an increased incidence of postoperative myocardial infarctions. Ninety-six patients (mean age 73 years) admitted for elective aortic (24) or infrainguinal (72) operations over a 2-year period underwent 24-hour two- or three-lead CAECG monitoring. Results were reviewed by a single cardiologist blinded to the study. The criterion for ischemia was ST segment depressions of 1 mm or greater for 40 seconds or more 60 msec after the J point. Postoperative myocardial infarction was determined by ECG changes and/or elevated serum creatinine phosphokinase with positive MB isoenzymes. Risk factors included hypertension (71%), history of coronary artery disease (66%), smoking (61%), and diabetes mellitus (47%). Nine out of 96 patients (9.4%) had a positive CAECG test for silent myocardial ischemia. Only one patient (11.1%) developed postoperative myocardial infarction and there were no deaths in this group. The incidence of postoperative myocardial infarction in the nonischemic group was 16.1% (14/87). However, the mortality in this group was 6.9% (6/87). New and malignant arrhythmias requiring preoperative medical intervention were observed in seven patients (7.4%): two cases of ventricular tachycardia and five cases of atrial flutter/fibrillation. Contrary to previous reports, CAECG monitoring for silent ischemia was not a significant predictor of postoperative myocardial infarction or mortality in our patient population. However, we continue to recommend the preoperative use of CAECG monitoring as a diagnostic tool for unsuspected malignant arrhythmias.Presented at the Seventeenth Annual Meeting of the Peripheral Vascular Surgery Society, Chicago, Ill., June 7, 1992.