PERIOPERATIVE MYOCARDIAL-ISCHEMIA IN PATIENTS UNDERGOING NONCARDIAC SURGERY .1. INCIDENCE AND SEVERITY DURING THE 4 DAY PERIOPERATIVE PERIOD

To determine the incidence and characteristics of perioperative myocardial ischemia, the electrocardiographic (ECG) changes consistent with ischemia during the 4 day perioperative period were documented and characterized in 100 patients with or at risk for coronary artery disease undergoing noncardiac surgery. Using continuous two channel ECG monitoring (leads CC5 and CM5), the frequency and severity of ECG ischemic episodes defined by ST segment depression greater-than-or-equal-to 1 mm or elevation greater-than-or-equal-to 2 mm during the preoperative (up to 2 days), intraoperative and early postoperative (first 2 days) periods were compared. Preoperatively, 28 patients (28%) exhibited 105 episodes of ischemia; intraoperatively, 27 patients exhibited 39 episodes and postoperatively, 42 patients exhibited 187 episodes. There was no difference between the pre- and intraoperative episode characteristics. However, postoperative ischemic episodes were the most severe. The mean ST change was 1.5, 2 and 2.6 mm for pre-, intra- and postoperative episodes, respectively (p < 0.0001 postoperative versus pre- or intraoperative); duration of ischemic episodes was 69, 45 and 207 min, respectively (p < 0.005 postoperative versus preoperative, p < 0.001 versus intraoperative) and area under the ST curve was 88, 74 and 383 mm.min (p < 0.009 postoperative versus preoperative, p < 0.005 versus intraoperative). Ninety-four percent of all postoperative ischemic episodes were silent; 80% of all episodes occurred without acute change (+/- 20% of control) in heart rate and 77% of intraoperative episodes occurred without acute change in blood pressure. However, postoperative heart rate was chronically higher (mean 92 versus 76 beats/min preoperative and 71 beats/min intraoperative, p less-than-or-equal-to 0.001). Patients with coronary artery disease versus those with risk factors alone were equally likely to develop ischemia during any period (chi-2 = 0.21, df = 2, p = 0.60); 11 of the 13 adverse cardiac outcomes were preceded by postoperative ischemia. It is concluded that in noncardiac surgical patients with or at risk for coronary artery disease 1) preoperative ischemia is relatively common, occurring equally in patients with documented and potential coronary artery disease; 2) anesthesia and surgery are not associated with an increased incidence or severity of ischemia; 3) ischemia is most frequent and most severe during the postoperative period; and 4) postoperative ischemia is silent, may be related to chronically elevated heart rate and appears to be associated with adverse cardiac outcome.