Independent Prognostic Significance of Ischemic ST-Segment Response Limited to Recovery From Treadmill Exercise in Asymptomatic Subjects

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Abstract
Background—Although exercise-induced ST depression is an independent predictor of future coronary events in asymptomatic populations, the predictive value of ST depression beginning after exercise cessation is unknown. Methods and Results—We analyzed the treadmill exercise tests of 825 healthy volunteers who were 22 to 89 years of age from the Baltimore Longitudinal Study of Aging. All subjects were free from coronary heart disease by history, physical examination, and resting ECG. From 825 participants, 611 (group 0) had no ischemic ST-segment changes during or after treadmill exercise, while 214 subjects developed ≥1-mm flat or downsloping ST depression: 151 (group 1) had ST changes starting during exercise, and 63 (group 2) had changes limited to recovery. Groups 1 and 2 were similar in age, sex, smoking status, hypertension prevalence, fasting plasma glucose, and serum cholesterol (CHOL). However, both groups were older and had higher CHOL and prevalence of hypertension than group 0. Treadmill exercise duration, peak oxygen consumption, and maximal heart rate were similar between groups 1 and 2 but were lower than in group 0 (each PP=0.001). By survival analysis, the risk of coronary events was similar in groups 1 and 2 but significantly higher than in group 0 (PP=0.00001), CHOL (OR=1.02 per 1 mg, P=0.0001), and presence of ST-segment depression (OR=2.59, P=0.007 and OR=2.38, P=0.04 for groups 1 and 2, respectively) were independent predictors of events. Conclusions—Thus, ischemic ST-segment changes developing during recovery from treadmill exercise in apparently healthy individuals have adverse prognostic significance similar to those appearing during exercise.

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