Role of nondiagnostic exercise-induced ST-segment abnormalities in predicting future coronary events in asymptomatic volunteers

Abstract

Background - Whether exercise-induced ST-segment depression <1 mm is an independent predictor of future coronary events (CEs) in asymptomatic subjects is unknown. Methods and Results - We performed maximal treadmill exercise tests on 1083 volunteers from the Baltimore Longitudinal Study of Aging who were free from clinical coronary heart disease. Exercise ST-segment changes were stratified by Minnesota code criteria: 11:1 (n = 213), flat or downsloping ST depression ≥1 mm; 11:2 (n = 66), flat or downsloping ST depression ≥0.5 mm and <1 mm; 11:4 (n = 124), ST-J depression ≥1 mm with slowly rising ST segments; and 11:5 (n = 69), minor ST depression (<0.5 mm) before exercise that worsened to flat or downsloping ST depression ≥1 mm during or after exercise. Risk of CE was compared with subjects with normal exercise ECG (n = 611). Over a mean follow-up of 7.9 years, 76 subjects developed CEs (angina pectoris, myocardial infarction, or coronary death). On univariate analysis, age (relative risk [RR] = 1.07/year, P<0.0001), male sex (RR = 1.98, P = 0.009), plasma cholesterol (RR = 1.02/mg per dL, P<0.0001), hypertension (RR = 2.23, P = 0.002), duration of exercise (RR = 0.71/min, P = 0.0001), and systolic blood pressure at peak effort (RR = 1.02/mm Hg, P = 0.002) were associated with CE. By Cox proportional hazards analysis, age (RR = 1.06/year, P<0.0001), male sex (RR = 2.76, P = 0.0002), plasma cholesterol (RR = 1.02 per 1 mg/dL, P<0.0001), duration of exercise (RR = 0.87/min, P = 0.004), and ST-segment changes coded as either 11:1 (RR = 2.70, P = 0.0005) or 11:5 (RR = 2.73, P = 0.04) were independent predictors of CE. Conclusions - Both a classic ischemic ST-segment exercise response and intensification of minor preexercise ST-segment depression to levels ≥1 mm independently predicted future CE in this asymptomatic population. Neither slowly rising ST depression nor horizontal ST depression <1 mm was prognostic.