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 > or =1 mm; 11:2 (n=66), flat or downsloping ST depression > or =0.5 mm and <1 mm; 11:4 (n=124), ST-J depression > or =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 > or =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 > or =1 mm independently predicted future CE in this asymptomatic population. Neither slowly rising ST depression nor horizontal ST depression <1 mm was prognostic.