716-1 Long-term Prognostic Significance of Exercise-Induced Silent Myocardial ischemia in Apparently Healthy Volunteers

Abstract

Silent myocardial ischemia (SI) defined by concordant ST segment depressian on ECG and a planar thallium (TL) perfusion defect during maximal treadmill testing was a potent independent predictor of future coronary events (CE) over a mean follow-up of 4.7 years in 407 asymptomatic volunteers aged 40–96 years (mean = 60) from the Baltimore Longitudinal Study of Aging (Circulation 1990;81:428). To determine the longer term prognostic significance of SI in this population. we examined the incidence and predictors of CE over a mean follow-up of 9.2 years. A total of 61 CE developed (32 cases of new angina pectoris, 17 non-fatal myocardial infarctions, 12 cardiac deaths). Events occurred in 15% of subjects with both negative ECG and TL responses, 30% of those with either a positive ECG or TL result. and 48% of those in whom both tests were positive (p < 0.001). By proportional hazards analysis. older age (relative risk [RR] = 2.3 per 15 year incrementl. male gender (RR = 2.2), hypertension (RR = 2.5), shorter exercise duration (RR = 0.91 per minute). and a concordant positive ECG and TL response (RR = 2.5) were significant independent predictors of CE, Hard CE, i.e. myocardial infarction orcardiac death, were predicted by older age (RR = 3,1), male gender (RR = 2.8), current smoking (RR = 3,0), plasma cholesterol (RR = 1.01 per mg/dl), fasting plasma glucose (RR = 1,01 per mg/dl) and a concordant positive ECG and TL (RR = 3.4). Thus, at a mean follow-up of over 9 years, exercise-induced SI remains a potent predictor of future CE in apparently healthy volunteers. independent of conventional risk factors.