DETECTION AND SIGNIFICANCE OF MYOCARDIAL-ISCHEMIA IN STABLE PATIENTS AFTER RECOVERY FROM AN ACUTE CORONARY EVENT

Objective.-To determine the clinical significance of silent and sympto matic myocardial ischemia detected by noninvasive testing in stable po stcoronary patients. Design.-Cohort study with a mean 23-month follow- up. Setting.-Ambulatory outpatients after recent hospitalization for a n acute coronary event. Patients.-Nine hundred thirty-six patients (76 % male; mean age, 58 years) who were clinically stable 1 to 6 months a fter hospitalization for acute myocardial infarction or unstable angin a. Interventions.-Noninvasive testing involved rest, ambulatory, and e xercise electrocardiograms and stress thallium-201 scintigraphy. Main Outcome Measures.-Cox regression analysis was used to evaluate the ris k (hazard ratio) of first recurrent primary events (cardiac death, non fatal infarction, or unstable angina) or restricted events (cardiac de ath 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 rat io; 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); an d stress thallium-201 reversible defects (1.3; 0.96, 1.74). Test resul ts were similar for first recurrent restricted events, and in patients with and without angina. Significantly increased risk (P<.05) was not ed when exercise-induced ST depression occurred in patients who also h ad reduced exercise duration (hazard ratio, 3.4) or when reversible th allium-201 defects occurred in patients who also had increased lung up take (hazard ratio, 2.8). Each high-risk subset made up less than 3% o f the population and contained less than 6% of patients with first pri mary events. Conclusion.-Detection of silent or symptomatic myocardial ischemia by noninvasive testing in stable patients 1 to 6 months afte r an acute coronary event is not useful in identifying patients at inc reased risk for subsequent coronary events.