Abstract 3723: Can an Abnormal Exercise Test be Counted as a Cardiovascular Disease Risk-equivalent?
Introduction. Poor functional capacity, abnormal heart rate responses, and electrocardiographic (ECG) abnormalities during exercise testing (ET) independently predict mortality. The incremental effect of these 3 factors on total mortality was compared in patients with and without known cardiovascular disease (CVD) to determine if an abnormal exercise test could serve as a CVD risk-equivalent.
Methods. Patients referred for ET during 1986–1991 were included. Functional capacity < 74% predicted by age and gender, heart rate reserve (HRR) of < 68 beats per minute, or a horizontal or downsloping ST depression of ≥1 mm were considered abnormal. Cox proportional hazards regression was used to determine all-cause mortality (adjusted for age, sex, and beta blocker use) based on the number of ET abnormalities (0, 1, 2, or all 3). Complete follow-up was available for 14 years.
Results. Among 10,897 patients, CVD history was established in 20.9% (n=2277). In patients without CVD, there was an increased risk of mortality with poor functional capacity (adjusted hazard ratio [HR] 1.86; 95% CI, 1.57–2.21), poor HRR (HR 1.54; 95% CI, 1.30–1.83) and abnormal exercise ECG (HR 1.50; 95% CI, 1.28–1.76). Subjects without CVD having at least two abnormal ET results had similar mortality to those with CVD but no abnormal ET results (see Table⇓). Further adjustment for traditional risk factors did not affect the results.
Conclusions. There is an incremental increase in risk of mortality with increasing number of abnormal ET results. Comparison between the two groups suggests that the presence of 2 or more ET abnormalities constitutes a “CVD mortality risk-equivalent”.