Abstract
Background: Submaximal stress testing, <85% maximum predicted heart rate (MPHR) may be non diagnostic and high exercise capacity (≥10 metabolic equivalents, METS) is a predictor of favorable prognosis. The purpose of this study was to evaluate the prognostic value of submaximal and high exercise capacity stress echocardiography (EXSE). Methods: We evaluated 1781 patients (55 ± 13 years; 59% male) undergoing EXSE divided into 811 with submaximal (<85% MPHR) and 970 with high exercise capacity (≥10 METS). Resting left ventricular ejection fraction and wall motion was assessed. The left ventricle was divided into 16 segments and scored on a 5-point scale of wall motion. Abnormal EXSE was defined as stress-induced ischemia (wall-motion score of ≥1 grade). Follow-up (3.3 ± 1.5 years) for non-fatal myocardial infarction (n = 40) and cardiac death (n = 52) were obtained. Results: By univariate analysis, exercise work load (p<0.0001), ejection fraction (p<0.0001) and number of new ischemic wall motion abnormalities (p<0.0001) were significant predictors of cardiac events. Cumulative survival was significantly worse in patients with abnormal vs. normal EXSE in submaximal (4.5%/year vs. 1.4%/year, p<0.0001) and high exercise capacity groups (1.1%/year vs. 0.2%/year, p=0.001) (Graph). Multivariate logistic regression analysis identified number of new ischemic wall motion abnormalities as the best predictor of cardiac events (p<0.05) in both groups. Conclusions: Despite normal EXSE, inability to achieve 85% MPHR conferred a higher, intermediate event rate of 3.0%/year. The ability to achieve nine minutes (≥10 METS) on EXSE conferred a benign prognosis (1.0%/year) regardless of EXSE results. In either group (submaximal or high exercise capacity), EXSE results (absence or presence ischemia) were useful in further, effectively risk stratifying patients.
Published Version
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