The relationship between red cell distribution width and cardiac autonomic function in heart failure.

Background: Both increases in red cell distribution width (RDW) levels and autonomic dysfunction are considered to be correlated with worsening heart failure. However, the relation of RDW levels to autonomic function remains uncertain. We aimed to investigate the association of RDW levels in heart failure with autonomic function, evaluated by heart rate variability (HRV) and heart rate turbulence (HRT), and prognosis.

Methods: We studied 222 hospitalized patients with stable heart failure before discharge, and Holter recordings (HRV and HRT) were performed. Additionally, RDW levels were measured, and high RDW was defined as over 14.5%. We then divided the patients into two groups based on RDW levels: high RDW group (>14.5%, n = 92) and low RDW group (≤14.5%, n = 130). The relation of RDW to autonomic function and prognosis was assessed.

Results: In the high RDW group, severely impaired HRV and HRT were found compared to the low RDW group. In the linear regression analysis after the adjustment of multiple confounders, RDW levels were correlated with a low-frequency (LF) to high-frequency (HF) ratio and very low-frequency (VLF) power (LF to HF ratio, β = -0.146,  = .027, and VLF power, β = -0.137,  = .041, respectively). During the observation period (median 1400 days), cardiac events (re-hospitalization of heart failure, cardiac death or sudden death) were found in 73 (32.8%) patients. The Kaplan-Meier analysis demonstrated that the high RDW group had a higher rate of cardiac events compared to the low RDW group (45.6% vs 23.8%, log-rank  < .001).

Conclusion: High RDW levels were correlated with autonomic dysfunction, resulting in poor clinical outcomes.