Impact of Cardiac Power Output on Exercise Capacity and Clinical Outcome in Patients With Chronic Heart Failure

Abstract

Less data are available regarding the impact of cardiac power output on exercise capacity or clinical outcome in patients with chronic heart failure (CHF). The study enrolled 280 consecutive patients with CHF referred for cardiopulmonary exercise testing and right-sided heart catheterization between 2013 and 2018. The primary outcome was composite of heart failure hospitalization or death. Cardiac power output was calculated as (mean arterial pressure × CO) ÷ 451. Patients with low cardiac power output (<0.53 W, n = 99) were older and had a higher brain natriuretic peptide level than patients with high cardiac power output (≥0.53W, n = 181). Cardiac power output was correlated with peak oxygen consumption (peak V̇O₂), peak workload achievement, and ventilatory efficiency (V̇_E/V̇CO₂ slope) in cardiopulmonary exercise testing, whereas each of cardiac output or mean arterial pressure was not. There were 48 patients with events over a median follow-up period of 3.5 (interquartile range 1.0 to 6.0) years. Patients with low cardiac power output had about a 2-fold higher risk of events than those with a high cardiac power output (hazard ratio 1.97, 95% confidence interval 1.12 to 3.48). In the multivariable Cox regression, a 0.1-W decrease in cardiac power output was associated with 19% increased adverse events (hazard ratio 0.81, 95% confidence interval 0.67 to 0.99). In conclusion, cardiac power output was associated with reduced exercise capacity and poor clinical outcome, suggesting that cardiac power output is useful for risk stratification in patients with CHF. Further study is required to identify therapies targeting cardiac power output to improve the exercise capacity or clinical outcome in patients with CHF.

Keywords: cardiac power output; cardiopulmonary exercise testing; chronic heart failure; exercise intolerance; outcome.