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Silent myocardial ischemia is not predictive of myocardial infarction in peripheral vascular surgery patients
J D Kirwin1, E Ascer, M Gennaro
1Division of Vascular Surgery, Maimonides Medical Center, State University of New York, New York.
Insights
Continuous ambulatory ECG monitoring did not predict heart attacks in vascular surgery patients. However, it effectively identified dangerous arrhythmias, warranting continued preoperative use for arrhythmia detection.
Area of Science:
- Cardiology
- Vascular Surgery
- Diagnostic Monitoring
Background:
- Silent myocardial ischemia is linked to increased postoperative myocardial infarction.
- Continuous ambulatory ECG (CAECG) monitoring is a proposed method for detecting silent ischemia preoperatively.
Purpose of the Study:
- To evaluate CAECG monitoring as a predictor of postoperative myocardial infarction and mortality in patients undergoing major vascular surgery.
- To assess the incidence of silent myocardial ischemia and new malignant arrhythmias detected by CAECG.
Main Methods:
- 96 patients undergoing elective aortic or infrainguinal surgery had 24-hour CAECG monitoring.
- Ischemia defined by ST segment depression; postoperative myocardial infarction by ECG and cardiac enzyme changes.
- Results reviewed by a blinded cardiologist.
Main Results:
- 9.4% of patients showed silent myocardial ischemia on CAECG.
- CAECG monitoring was not a significant predictor of postoperative myocardial infarction or mortality.
- 7.4% of patients had new malignant arrhythmias requiring intervention.
Conclusions:
- CAECG monitoring did not predict postoperative myocardial infarction or mortality in this cohort.
- Preoperative CAECG monitoring is recommended for detecting unsuspected malignant arrhythmias.
- Further research may be needed to clarify the role of ischemia detection in this population.
Abstract:
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.