Exercise echocardiography for the prognostic stratification of patients with low pretest probability of coronary artery disease

PURPOSE: The aim of this study was to determine whether exercise echocardiography provides incremental data for risk stratification of patients with a low pretest probability of coronary artery disease. PATIENTS AND METHODS: The study included patients referred for exercise echocardiography whose probability of coronary artery disease was 25% or less. We calculated an exercise wall motion score index (on a 1-5 scale), an indicator of the extent and severity of exercise-induced abnormalities. The primary outcomes of the study were subsequent cardiac events (cardiac death and nonfatal myocardial infarction). RESULTS: We studied 571 men and 1047 women; their mean (± SD) age was 55 ± 13 years. During a median follow-up of 3 years, there were 19 cardiac events (6 cardiac deaths and 13 nonfatal myocardial infarctions); an additional 37 patients underwent coronary revascularization. In a multivariate analysis of clinical, exercise electrocardiographic, and echocardiographic parameters, exercise wall motion score index (hazard ratio [HR] = 2.1 per 0.5 units; 95% confidence interval [CI]: 1.3 to 3.4), and age (HR = 2.0 per decade; 95% CI: 1.2-2.8) were independently associated with the risk of cardiac events. Although exercise echocardiographic variables contributed significantly (P = 0.01) to a model of the risk of adverse events, only 9 (47%) of the 19 patients with cardiac events were identified by an abnormal exercise echocardiogram. CONCLUSION: Among patients with low pretest probability of coronary artery disease by clinical criteria, exercise echocardiography identifies some, but not all, patients at risk of future events. Because of the low event rate, routine application of exercise echocardiography in a patient with a low pretest probability does not appear to be cost-effective and therefore cannot be recommended.