Detection and significance of myocardial ischemia in stable patients after recovery from an acute coronary event. Multicenter Myocardial Ischemia Research Group

OBJECTIVE: To determine the clinical significance of silent and symptomatic myocardial ischemia detected by noninvasive testing in stable postcoronary patients. DESIGN: Cohort study with a mean 23-month follow-up. SETTING: Ambulatory outpatients after recent hospitalization for an acute coronary event. PATIENTS: Nine hundred thirty-six patients (76% male; mean age, 58 years) who were clinically stable 1 to 6 months after hospitalization for acute myocardial infarction or unstable angina. INTERVENTIONS: Noninvasive testing involved rest, ambulatory, and exercise electrocardiograms and stress thallium-201 scintigraphy. MAIN OUTCOME MEASURES: Cox regression analysis was used to evaluate the risk (hazard ratio) of first recurrent primary events (cardiac death, nonfatal infarction, or unstable angina) or restricted events (cardiac death or nonfatal infarction) associated with ischemic noninvasive test results. RESULTS: ST segment depression on the rest electrocardiogram was the only noninvasive test variable that identified a significantly increased risk (P = .05) for first recurrent primary events (hazard ratio; 95% confidence limits): rest electrocardiogram ST depression (1.5; 1.00, 2.25); ambulatory electrocardiogram ST depression (0.86; 0.49, 1.51); exercise electrocardiogram ST depression (1.13; 0.82, 1.56); and stress thallium-201 reversible defects (1.3; 0.96, 1.74). Test results were similar for first recurrent restricted events, and in patients with and without angina. Significantly increased risk (P < .05) was noted when exercise-induced ST depression occurred in patients who also had reduced exercise duration (hazard ratio, 3.4) or when reversible thallium-201 defects occurred in patients who also had increased lung uptake (hazard ratio, 2.8). Each high-risk subset made up less than 3% of the population and contained less than 6% of patients with first primary events. CONCLUSION: Detection of silent or symptomatic myocardial ischemia by non-invasive testing in stable patients 1 to 6 months after an acute coronary event is not useful in identifying patients at increased risk for subsequent coronary events.