Exercise testing in asymptomatic patients after revascularization: are outcomes altered?

BACKGROUND: Although exercise echocardiography (ExE) of asymptomatic patients early (2 years after percutaneous coronary intervention [PCI] or 5 years after coronary bypass graft surgery [CABG]) after revascularization is considered inappropriate, the appropriateness of later testing is indeterminate. Treatment responses to positive test results in either setting have uncertain outcome implications. We sought to identify whether predictors of increased risk by ExE could lead to interventions that change outcome in asymptomatic patients with previous coronary revascularization.

METHODS: Exercise echocardiography was performed in 2105 asymptomatic patients (mean [SD] age, 64 [10] years; 310 [15%] were women; 845 [40%] had a history of myocardial infarction; 1143 [54%] had undergone PCI and 962 [46%] had undergone CABG 4.1 [4.7] years prior to the ExE). Ischemia was identified as a new or worsening wall motion abnormality. Patients were followed for a mean (SD) period of 5.7 (3.0) years for cardiac mortality. The association of ischemia during ExE with survival was assessed using Cox proportional hazard models, and an interaction with revascularization was sought.

RESULTS: Of 262 patients with ischemia (13%), only 88 (34%) underwent subsequent revascularization. Mortality (97 patients [4.6%]) was associated with ischemia (hazard ratio, 2.10; 95% CI, 1.05-4.19; P=.04) in groups tested both early (P=.03) and late (≥2 years after PCI or ≥ 5 years after CABG) (P=.001). However, the main predictors of outcome were clinical and stress testing findings rather than echocardiographic features. Subgroup analysis showed that asymptomatic patients without diabetes mellitus, with normal ejection fraction (≥50%), and normal exercise capacity (>6 METs [metabolic equivalent for task]) were unlikely to have a positive test result or events. Even high-risk patients did not seem to benefit from repeated revascularization.

CONCLUSIONS: Asymptomatic patients who undergo ExE after coronary revascularization may be identified as being at high risk but do not seem to have more favorable outcomes with repeated revascularization. From a health economic standpoint, appropriateness of such testing must be carefully reviewed.