The preserved autonomic functions may provide the asymptomatic clinical status in heart failure despite advanced left ventricular systolic dysfunction

Abstract

Autonomic dysfunction is an important marker of prognosis in congestive heart failure (CHF) and may determine the symptoms and progression of CHF. The aim of our study was to investigate whether preserved autonomic function assessed by heart rate variability (HRV) analyses is related to absence of CHF symptoms despite prominently reduced systolic function. The study had a cross-sectional observational design. Fifty patients with left ventricular ejection fraction (EF) below 40% were enrolled. The patients were divided into two groups according to their CHF symptomatic status as Group 1 (NYHA functional class I, asymptomatic group) and Group 2 (NYHA functional class ≥ II, symptomatic group). Plasma C-reactive protein (CRP), N-terminal proB-type natriuretic peptide (NT-proBNP) levels, echocardiographic parameters and HRV indices were measured while the patients were clinically stable in each group. Possible factors associated with the development of CHF symptoms were assessed by using multiple regression analysis. Baseline clinical characteristics and left ventricular EF were similar in the two groups. Serum CRP (15 ± 21 vs 7 ± 18 mg/L, p=0.011) and NT-proBNP levels (1935 ± 1088 vs 1249 ± 1083 pg/mL, p=0.020) were significantly higher in symptomatic group. The HRV parameters (SDNN: 78 ± 57 vs 122 ± 42 ms, p=0.001; SDANN: 65 ± 55 vs 84 ± 38 ms, p=0.024; SDNNi: 36 ± 41 vs 70 ± 46 ms, p<0.001; triangular index [Ti]: 17 ± 12 vs 32 ± 14, p<0.001) were also significantly depressed in symptomatic group. When multiple regression analysis was performed, only HRV indices of autonomic function were significantly associated with the asymptomatic status (SDNN, OR: 1.016, 95%CI: 1.002-1.031, p=0.028; SDNNi, OR: 1.030, 95%CI: 1.008-1.052, p=0.006; TI, OR: 1.088, 95%CI: 1.019-1.161, p=0.011). Preserved autonomic functions were shown to be associated with absence of CHF symptoms independently of angiotensin converting enzyme inhibitor/angiotensin receptor blocker's treatment and BNP levels and may be protective against the development of CHF symptoms despite advanced left ventricular systolic dysfunction.