Left ventricular end-diastolic volume predicts exercise capacity in patients with a normal ejection fraction

Background: Exercise capacity is a powerful predictor of all-cause mortality. The duration of exercise with treadmill stress testing is an important prognostic marker in both healthy subjects and patients with cardiovascular disease. Left ventricular (LV) structure is known to adapt to sustained changes in level of physical activity. Hypothesis: Poor exercise capacity in patients with a preserved LV ejection fraction (LVEF) should be reflected in smaller LV dimensions, and a normal exercise capacity should be associated with larger LV dimensions, irrespective of comorbidities. Methods: This hypothesis was first tested in a cross-sectional analysis of 201 patients with normal chamber dimensions and preserved LVEF who underwent a clinically indicated treadmill stress echocardiogram using the Bruce protocol (derivation cohort). The best LV dimensional predictor of exercise capacity was then tested in 1285 patients who had a Bruce-protocol treadmill exercise stress test and a separate transthoracic echocardiogram (validation cohort). Results: In the derivation cohort, there was a strong positive relationship between exercise duration and LV end-diastolic volume deciles (r² = 0.85; P < 0.001). Regression analyses of several LV dimensional parameters revealed that the body surface area–based LV end-diastolic volume index was best suited to predict exercise capacity (P < 0.0001). In a large validation cohort, LV end-diastolic volume was confirmed to predict exercise capacity (P < 0.0001). Conclusions: Among patients referred for outpatient stress echocardiography who have a preserved LVEF and no evidence of myocardial ischemia, we found a strong positive association between LV volume and exercise capacity.