Prognostic Role of Cardiac Power in a Large Cohort of Patients with Normal Ejection Fraction Referred for Dobutamine Stress Echocardiography

Background: Cardiac power reflects cardiac performance in terms of energy transferred by the left ventricle to the aorta per unit time. Peak stress cardiac power has been shown to predict outcomes in patients with reduced left ventricular ejection fraction (LVEF) and, more recently, in patients with normal LVEF referred for exercise stress echocardiography. The aim of this study was to evaluate the prognostic significance of cardiac power in patients with normal LVEF referred for dobutamine stress echocardiography. Methods: Data were studied from 15,576 patients with LVEF ≥ 50% and no significant valvular or right ventricular dysfunction who underwent dobutamine stress echocardiography. Cardiac power at rest and peak stress and power reserve (peak stress minus rest power) were calculated and normalized to left ventricular mass. Outcome end points were all-cause mortality and new-onset heart failure (HF). Results: The mean age was 66 ± 13 years, and 49% patients were women. Resting and peak stress power/mass were 0.7 ± 0.2 and 1.6 ± 0.6 W/100 g left ventricular myocardium, respectively. During follow-up (median, 3.3 years; interquartile range, 0.7-7.3 years), 2,278 patients died and 2,137 developed HF. After adjusting for age, sex, comorbidities, and stress test results, lower peak stress power/mass was independently associated with mortality (adjusted hazard ratio, highest vs lowest quartile, 0.84; 95% CI, 0.74-0.95; P = .004) and HF at follow-up (adjusted hazard ratio, 0.67; 95% CI, 0.59-0.76; P < .0001). Power reserve showed similar associations with outcomes. Conclusions: Assessment of cardiac power during dobutamine stress echocardiography in patients with normal LVEF provides valuable prognostic information regarding risk for mortality and future HF, in addition to stress test results. It is an important research tool to study cardiac performance, and the development of risk scores incorporating this novel index could be considered after further validation in prospective studies.