Determinants of cardiac autonomic dysfunction in ESRD

Background and objectives: Cardiovascular events are common in patients with ESRD. Whether sympathetic overactivity or vagal withdrawal contribute to cardiovascular events is unclear. We determined the general prevalence and clinical correlates of heart rate variability in patients on hemodialysis. Design, setting, participants, & measurements: We collected baseline information on demographics, clinical conditions, laboratory values, medications, physical performance, left ventricular mass (LVM), and 24-hour Holter monitoring on 239 subjects enrolled in the Frequent Hemodialysis Network Daily Trial. Results: The mean R-R interval was 812 ± 217 ms. The SD of R-R intervals was 79.1 ± 40.3 ms. Spectral power analyses showed low-frequency (sympathetic modulation of heart rate) and high-frequency power (HF; vagal modulation of heart rate) to be 106.0 (interquartile range, 48.0 to 204 ms²) and 42.4 ms² (interquartile range, 29.4 to 56.3 ms²), respectively. LVM was inversely correlated with log HF (-0.02 [-0.0035; -0.0043]) and the R-R interval (-1.00 [-1.96; -0.032]). Physical performance was associated with mean R-R intervals (1.98 [0.09; 3.87]) and SD of R-R intervals (0.58 [0.049; 1.10]). After adjustment for age, race, ESRD vintage, diabetes, and physical performance, the relationship between log HF and LVM (per 10 g) remained significant (-0.025 [-0.042; -0.0085]). Conclusions: Holter findings in patients on hemodialysis are characterized by sympathetic overactivity and vagal withdrawal and are associated with higher LVM and impaired physical performance. Understanding the spectrum of autonomic heart rate modulation and its determinants could help to guide preventive and therapeutic strategies.