Unstable angina pectoris. Factors influencing operative risk.

Experience was reviewed with 471 consecutive patients who had coronary artery bypass (CAB) operation alone. The hospital mortality rate was 2% in 341 patients operated on for treatment of stable angina pectoris. There were ten deaths (7.7%) in the 130 patients who underwent CAB for treatment of unstable angina. In this series, age greater than 70 years, poor left ventricular function, distal coronary arteries unfavorable for grafting and the presence of main left coronary artery disease were factors associated with increased operative mortality. In 78 patients with unstable angina who had none of these increased risk factors, the mortality rate was 1.3%. Hospital mortality was 33% in patients older than 70 years and 29% in patients with poor left ventricular function and/or distal vessels unfavorable for grafting. In 23 of the 130 patients, the only increased risk factor present was severe stenosis of the main left coronary artery and one of them (4.3%) died. Thus, when elderly patients and patients with poor left ventricular function or poor distal vessels were excluded, the hospital mortality rate associated with CAB in patients with unstable angina was low (2.0%, 2/101 patients) and equal to that for operation in patients with stable angina pectoris.