Severe exercise-induced ischemia does not identify high risk patients with normal left ventricular function and one- or two-vessel coronary artery disease

Mayo Clinic, Rochester, Minnesota 55905.

OBJECTIVES. This study was conducted to determine whether severe exercise-induced ischemia identifies high risk patients with a normal left ventricular ejection fraction and one- or two-vessel coronary artery disease. BACKGROUND. Severe ischemia during exercise radionuclide angiography has been shown to identify high risk patients among certain other patient subsets. METHODS. Four hundred twenty patients with left ventricular ejection fraction > or = 50% and one- or two-vessel disease underwent exercise radionuclide angiography within 3 months of coronary angiography. Patients were treated initially with revascularization (n = 140) or medical therapy (n = 280) at the discretion of their physicians. Patients treated with revascularization were more likely to have angina by history, a positive exercise electrocardiogram, a lower exercise ejection fraction, two-vessel disease and proximal left anterior descending coronary artery disease. Two hundred sixty-four of the 280 patients given medical therapy who had complete follow-up data formed the study group. Outcome was compared between patients with (n = 56) and without (n = 208) severe exercise-induced ischemia, defined by previously published criteria (work load < or = 600 kg-m/min, ST segment depression > or = 1 mm and decrease in ejection fraction with exercise). RESULTS. During follow-up, there were 30 initial cardiac events (12 cardiac deaths and 18 nonfatal myocardial infarctions). There was no difference in the 5-year event-free survival rate: 91% in patients with and 87% in patients without severe ischemia (p = 0.89). There was no association between event-free survival and severe ischemia (chi 2 = 1.41, p = 0.24). The study had approximately 80% power at alpha = 0.05 to detect a 25% decrease in event-free survival in the group with severe ischemia. In addition, there was no association between severe ischemia and outcome if late revascularization was included as an event or if the total mortality rate (overall survival) was analyzed. CONCLUSIONS. Severe exercise-induced ischemia fails to identify a high risk subgroup among patients with normal left ventricular function and one- or two-vessel disease who are treated initially with medical therapy.

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