Changes in heart rate variability in chronic uremic patients during ultrafiltration and hemodialysis

Background. The analysis of heart rate variability (HRV) is a useful tool t o evaluate cardiac autonomic modulation, which is frequently impaired in ch ronic uremia. Aims: The aim of this study was to evaluate HRV in chronic ur emics and to separately investigate the acute changes induced by volume dep letion and solute removal during a hemodialysis session. Methods: Fourteen uremic patients (8 males and 6 females, aged 50 +/- 15 years) on maintenanc e hemodialysis and 14 sex- and age-matched healthy controls were studied. B oth groups underwent ambulatory electrocardiogram monitoring to evaluate th e HRV time and frequency domain indices. The hemodialysis session was perfo rmed by 1 h of highrate isolated ultrafiltration followed by 3 h of bicarbo nate diffusive procedure. Results: In uremic patients, the overall variabil ity in the frequency [low-frequency power (LF): 505 +/- 473, vs. 1,446 +/- 654; high-frequency power (HF): 133 +/- 162 vs. 512 +/- 417; p < 0.001] and time domain indices (standard deviation of normal R-R intervals: 101.9 +/- 33.3 vs. 181.7 +/- 44.1 ms; p < 0.001) was markedly reduced compared to co ntrols, whereas mean heart rate (83 +/- 12.4 vs. 60.9 +/- 8.8 bpm; p < 0.00 1) and LF/HF ratio (5.8 +/- 3.5 vs. 2.2 +/- 0.8; p < 0.001) were increased. Isolated ultrafiltration produced a marked further decrease in HRV indices , but the subsequent diffusive hemodialysis procedure, with a low ultrafilt ration rate, made HRV increase again. Conclusions: Chronic uremics showed a bnormal autonomic modulation with sympathetic-vagal imbalance. The unbalanc ed hypersympathetic response to body fluid depletion is related to the ultr afiltration rate. Low interdialytic weight gain and a low ultrafiltration r ate, associated with adequate hemodialysis, should be the preferable strate gy for uremic patients with autonomic dysfunction. Copyright (C) 2001 S. Ka rger AG, Basel.