Does Perioperative Myocardial Ischemia Lead to Postoperative Myocardial Infarction?

TLDR

To determine whether perioperative myocardial ischemia (ST segment depression ≥0.1 mV) predicts postoperative myocardial infarction (PMI) during 1,023 elective CABG procedures. Observers recorded ECG, hemodynamic, and other events from OR arrival to cardiopulmonary bypass onset, while preoperative characteristics, surgical quality, and duration of ischemic arrest were quantified as potential risk factors. ECG ischemia occurred in 36.9 % of patients—nearly half before anesthesia—and was linked to a nearly threefold increase in PMI (6.9 % vs 2.5 %) independent of timing; it correlated with tachycardia but not blood pressure, the anesthesiologist with the highest tachycardia/ischemia rates had the highest PMI, and suboptimal surgical quality and prolonged ischemic arrest also raised PMI risk, underscoring perioperative ischemia as a common, independent risk factor for PMI unrelated to preoperative characteristics.

Abstract

To determine if a relationship exists between perioperative myocardial ischemia (ST segment depression greater than or equal to 0.1 mV) and postoperative myocardial infarction (PMI), nonparticipating observers recorded all ECG, hemodynamic, and other events between arrival of patients in the operating room and onset of cardiopulmonary bypass during 1,023 elective coronary artery bypass operations (CABG). The roles of preoperative patient characteristics, quality of the operation limited by disease as rated by the surgeon and duration of ischemic cardiac arrest as risk factors for PMI also were quantified. ECG ischemia occurred in 36.9% of all patients, with almost half the episodes occurring before induction of anesthesia. PMI was almost three times as frequent in patients with ischemia (6.9% vs. 2.5%) and was independent of when ischemia occurred. Ischemia was related significantly to tachycardia but not hypertension nor hypotension and was frequent in the absence of any hemodynamic abnormalities. The anesthesiologist whose patients had the highest rate of tachycardia and ischemia had the highest rate of PMI. Although neither single nor multiple preoperative patient characteristics related to PMI, suboptimal quality of operation and prolonged ischemic cardiac arrest increased the likelihood of PMI independent of the occurrence of myocardial ischemia. The authors conclude that perioperative myocardial ischemia is common in patients undergoing CABG, occurs randomly as well as in response to hemodynamic abnormalities, and is one of three independent risk factors the authors identified as related to PMI. PMI is unrelated to preoperative patient characteristics such as ejection fraction and left main coronary artery disease, and its frequency will relate primarily to perioperative management rather than patient selection.