Diagnostic characteristics and prognoses of primary-care patients referred for clinical exercise testing: a prospective observational study

BACKGROUND: Evaluation of angina symptoms in primary care often includes clinical exercise testing. We sought to identify clinical characteristics that predicted the outcome of exercise testing and to describe the occurrence of cardiovascular events during follow-up. METHODS: This study followed patients referred to exercise testing for suspected coronary disease by general practitioners in the County of Jämtland, Sweden (enrolment, 25 months from February 2010). Patient characteristics were registered by pre-test questionnaire. Exercise tests were performed with a bicycle ergometer, a 12-lead electrocardiogram, and validated scales for scoring angina symptoms. Exercise tests were classified as positive (ST-segment depression >1 mm and chest pain indicative of angina), non-conclusive (ST depression or chest pain), or negative. Odds ratios (ORs) for exercise-test outcome were calculated with a bivariate logistic model adjusted for age, sex, systolic blood pressure, and previous cardiovascular events. Cardiovascular events (unstable angina, myocardial infarctions, decisions on revascularization, cardiovascular death, and recurrent angina in primary care) were recorded within six months. A probability cut-off of 10% was used to detect cardiovascular events in relation to the predicted test outcome. RESULTS: We enrolled 865 patients (mean age 63.5 years, 50.6% men); 6.4% of patients had a positive test, 75.5% were negative, 16.4% were non-conclusive, and 1.7% were not assessable. Positive or non-conclusive test results were predicted by exertional chest pain (OR 2.46, 95% confidence interval (CI) 1.69-3.59), a pathologic ST-T segment on resting electrocardiogram (OR 2.29, 95% CI 1.44-3.63), angina according to the patient (OR 1.70, 95% CI 1.13-2.55), and medication for dyslipidaemia (OR 1.51, 95% CI 1.02-2.23). During follow-up, cardiovascular events occurred in 8% of all patients and 4% were referred to revascularization. Cardiovascular events occurred in 52.7%, 18.3%, and 2% of patients with positive, non-conclusive, or negative tests, respectively. The model predicted 67/69 patients with a cardiovascular event. CONCLUSIONS: Clinical characteristics can be used to predict exercise test outcome. Primary care patients with a negative exercise test have a very low risk of cardiovascular events, within six months. A predictive model based on clinical characteristics can be used to refine the identification of low-risk patients.