Abstract
BACKGROUND: Beta-blockers are first-line clinical drugs for the treatment of chronic heart failure (CHF). In the guidelines for cardiac rehabilitation, patients with heart failure who do or do not receive beta-blocker therapy have different reference thresholds for maximal oxygen uptake (VO(2max)). It has been reported that left atrial (LA) strain can be used to predict VO(2max) in patients with heart failure, which can be used to assess exercise capacity. However, most existing studies included patients who did not receive beta-blocker therapy, which could have a heterogeneous influence on the conclusions. For the vast majority of CHF patients receiving beta-blockers, the exact relationship between LA strain parameters and exercise capacity is unclear. METHODS: This cross-sectional study enrolled 73 patients with CHF who received beta-blockers. All patients underwent a thorough resting echocardiogram and a cardiopulmonary exercise test to obtain VO(2max), which was used to reflect exercise capacity. RESULTS: LA reservoir strain, LA maximum volume index (LAVI(max)), LA minimum volume index (LAVI(min)) (P < 0.0001) and LA booster strain (P < 0.01) were all significantly correlated with VO(2max), and LA conduit strain was significantly correlated with VO(2max) (P < 0.05) after adjusting for sex, age, and body mass index. LA reservoir strain, LAVI(max), LAVI(min) (P < 0.001), and LA booster strain (P < 0.05) were significantly correlated with VO(2max) after adjusting for left ventricular ejection fraction, the ratio of transmitral E velocity to tissue Doppler mitral annulus e' velocity (E/e'), and tricuspid annular plane systolic excursion. LA reservoir strain with a cutoff value of 24.9% had a sensitivity of 74% and specificity of 63% for the identification of patients with VO(2max) < 16 mL/kg/min. CONCLUSION: Among CHF patients receiving beta-blocker therapy, resting LA strain is linearly correlated with exercise capacity. LA reservoir strain is a robust independent predictor of reduced exercise capacity among all resting echocardiography parameters. CLINICAL TRIAL REGISTRATION: This study is a part of the Baduanjin-Eight-Silken-Movement with Self-efficacy Building for Patients with Chronic Heart Failure (BESMILE-HF) trial NCT03180320 (ClinicalTrials.gov, registration date: 08/06/2017).