Perioperative myocardial ischemia: Its relation to anatomic pattern of coronary artery stenosis

Background: Recently, the frequency of intraoperative myocardial ischemic episodes in patients with steal-prone coronary anatomy, compared with other groups of patients undergoing coronary artery surgery (CABG), has been characterized. Because the relationship between anatomic distribution of coronary stenosis and myocardial ischemic episodes over the entire perioperative period has not been well defined, the authors sought to examine this relationship in 100 adult patients undergoing CABG surgery. Methods: Continuous electrocardiographic (ECG) monitoring was performed in the pre-, intra-, and postoperative periods, quantifying the frequency (episodes/hour of monitoring [epis/h]) and duration (minutes/hour of monitoring [min/h]) of ECG ischemic episodes defined as a reversible ST segment shift ≥ 1 mm at J + 60 ms of ≥ 1 min duration. Based on preoperative coronary angiography, patients were categorized into the following groups: group 1 (n = 40), steal- prone coronary anatomy (occluded major coronary artery and ≥ 50% stenosis of the artery supplying the collateral vessels); group 2 (n = 17), left main or equivalent coronary stenosis (≥ 50% stenosis of left main coronary artery or ≥ 70% proximal stenosis of the left anterior descending and circumflex coronary arteries); and group 3 (n = 43), coronary artery stenosis ≥ 70% not fitting the preceding categories. Results: Compared with group 3, patients in group 1 had more frequent and longer ECG ischemic events preoperatively, and were nearly two times more likely (relative risk 1.82, 95% confidence interval 1.07-3.10) to develop an ischemic event during this period. There were no differences in the relative risk, frequency, or duration of an ischemic episode between groups 1 and 3 during the intraoperative and postoperative periods, or between groups 1 and 2 or groups 2 and 3 during any perioperative period. In group 2 patients, the frequency of ischemic epis/h was less intra- compared with preoperatively, while, in group 3, the ischemic epis/h decreased postoperatively compared with the intraoperative period. The duration of ischemic episodes (min/h) in group 3, however, increased postoperatively compared with the pre- and intraoperative periods, while, in group 2, the duration of ischemic episodes (min/h) was less intraoperatively compared with the preoperative period. Ninety-seven percent of preoperative ECG ischemic episodes occurred without symptoms. Postoperative myocardial infarction occurred in three patients in group 3, two in group 2, and one in group 1. There were no perioperative deaths. Conclusion: These data indicate that, compared with patients with non-left main or equivalent coronary stenosis, those with steal-prone coronary anatomy have more frequent and longer ECG ischemic episodes preoperatively. The data also indicate that there are no other differences in the risk, frequency, or duration of ischemic episodes between groups perioperatively. Thus, different distributions of coronary artery stenosis may be associated with changes in the perioperative characteristics of ECG ischemic episodes.