Cardiac resynchronization therapy improves exercise heart rate recovery in patients with heart failure

AIMS: Heart rate (HR) recovery (HRR), defined as the rate of decline in the HR immediately following the cessation of exercise, is influenced by autonomic function. Heart rate recovery in heart failure (HF) has been shown to correlate with severity of HF. Cardiac resynchronization therapy (CRT) improves cardiac autonomic functions in HF. We aimed to evaluate the effects of CRT on cardiac autonomic function assessed by HRR. METHODS AND RESULTS: Forty-eight patients [62.3 ± 10.7 years; 37 men; left ventricular (LV) ejection fraction 24.8 ± 4.1%] with HF were enrolled. A treadmill exercise testing was conducted in all patients by using a modified Naughton protocol before and 6 months after CRT. Heart rate recovery indices were calculated by subtracting first, second, and third minute HR from the maximal HR and designated as HRR1, HRR2, and HRR3, respectively. Standard echocardiography was performed before and 6 months after CRT. Left ventricular reverse remodelling (LVRM) was quantified as the percentage of decline in the LV end-systolic volume after CRT. Mean HRR1 (13.0 ± 5.9 vs. 17.9 ± 8.9 b.p.m., P = 0.001), HRR2 (20.5 ± 9.3 vs. 23.8 ± 11.3 b.p.m., P = 0.001), and HRR3 (25.7 ± 11.1 vs. 29.2 ± 12.0 b.p.m., P = 0.001) values improved 6 months after CRT. Pearson's analyses revealed a good positive correlation between LVRM and ΔHRR1 (r = 0.642, P = 0.001) and a moderate correlation between reduction LVRM and ΔHRR2 (r = 0.591, P = 0.033) and ΔHRR3 (r = 0.436, P = 0.001). CONCLUSION: Cardiac resynchronization therapy favourably alters the cardiac autonomic functions. Heart rate recovery indices improved after CRT and the degree of improvement in HRR indices correlated with LVRM.