Long-term results of coronary artery bypass surgery for unstable angina: incidence of mortality,myocardial infarction,and angina resumption

To determine if routine treadmill testing would be helpful in identifying patients at high risk for subsequent events, the first 81 patients to undergo coronary artery bypass0 surgery for unstable angina pectoris at Stanford University Medical Center were reevaluated at four intervals after surgery. Evaluations, including assessment of angina pectoris and a treadmill test, were done at mean times of 18,40, and 72 months after surgery. At a mean time of 90 months postoperatively, angina status was determined in survivors. The prevalence of angina rose from 19% during the first year to 53% during the fourth and fifth postoperative years. Cardiac deaths and myocardial infarctions were frequent during the first postoperative year, and were more frequent in patients with three-vessel disease and those with one or more severely narrowed coronary arteries which were not bypassed. Cardiac events were rare between 12 and 36 months after operation; clinical and treadmill variables did not predict these events. During the fourth and subsequent postoperative years, the incidence of cardiac events increased. While the presence of stable angina pectoris was the clinical variable most useful prognostically, treadmill testing added additional independent prognostic information (p<0.0001). During the intervals between visits 1 and 2, and visits 2 and 3, cardiac events were ten times more frequent in persons with a maximal heart rate of 130 beats/min or less on the treadmill at 18 and 40 months. We conclude that the prevalence of angina increased steadily during the first 5 postoperative years. Myocardial infarction and cardiac death rates were high during the first postoperative year, low during the second and third postoperative years, and then began to rise thereafter. The early events were more frequent in persons with three-vessel disease and one or more severely narrowed coronary arteries which were unbypassed. The late events were more frequent in persons with a maximal heart rate of 130 beats/min or less on treadmill exercise testing. No other clinical or treadmill variables added additional independent prognostic information.