Circadian Variation Of Heart Rate Variability Research Articles

Circadian variation of heart rate variability during different sleep stages

Introduction Heart rate (HR) and heart rate variability (HRV) have been shown to be influenced by the circadian system during wakefulness and to be affected by sleep. The aim of the present study was to assess the effects of sleep stages on the circadian variation of HRV. Materials and methods Fifteen healthy subjects (12 men, 3 women in follicular phase; mean age ± SD: 24.6 ± 4.5 years) entered the laboratory for an 8-h baseline nocturnal sleep episode during which sleep disorders were ruled out. Upon awakening, they underwent a 72-h ultradian sleep–wake cycle (USW) procedure consisting of 60-min wake episodes in dim light ( 10 lux) alternating with 60-min nap opportunities in darkness. HR was monitored, high and low frequencies (HF, LF), and the LF:HF ratio were calculated as indexes of HRV. Core body temperature (CBT) and polysomnographic sleep recordings were collected throughout the experiment.Circadian phase was determined based on CBT min (0°) and HRV data was analyzed based on circadian phase and its corresponding sleep stage using non-linear mixed models. Results A significant circadian rhythm was observed for HR during each sleep stage (P = 0.002); for HF power during each sleep stage (P = 0.05) except REM sleep; for LF power during each sleep stage (P = 0.02) except slow wave sleep (SWS) and REM sleep; and for the LF:HF ratio only during wake epochs during naps and REM sleep (P = 0.003).During stage 2 sleep and SWS, HR minimum occurred at the beginning of the night, advanced relative to the CBT minimum (P ⩽ 0.03).During REM sleep, HR was maximal around the time of habitual awakening (10:13 ± 0:42).The acrophase of HF and LF power rhythms measured during sleep was aligned with CBT min.There was a trend for the HF power acrophase during SWS to be advanced relative to the CBT min (P = 0.07).The acrophase of the LF:HF ratio during REM sleep occurred in the early morning, significantly advanced compared to that of wake episodes (P 0.001). Conclusion A significant circadian rhythm in parasympathetic cardiac modulation was observed during non-REM sleep with an acrophase around 02:00.Sympathovagal cardiac balance also followed a circadian pattern during REM sleep, with maximal sympathetic cardiac dominance occurring in the early morning.The temporal relationship between sleep stage-specific circadian rhythms in HRV and the diurnal distribution of adverse cardiovascular events lends support to the theory that autonomic balance modulates cardiovascular risks throughout the day. Acknowledgements Research was supported by the Canadian Institutes of Health Research (CIHR). P. Boudreau was supported by Institut de recherche Robert-Sauve en sante et en securite du travail (IRSST).

Circadian Variation in Heart‐Rate Variability in Localization‐related Epilepsy

Case-control studies of sudden unexpected death in epilepsy (SUDEP) have reported that SUDEP is more likely to occur during sleep and thus presumably during night hours. The circadian variation of heart-rate variability (HRV) might be of relevance to this risk. We examined night versus daytime HRV in patients with newly diagnosed and refractory localization-related epilepsy, assessing the effects of drug treatment and epilepsy surgery on the night/daytime HRV ratio. We used spectral analysis to assess HRV and calculated the night-time (00.00-05.00)/daytime (07.30-21.30) ratio of HRV in 14 patients with newly diagnosed localization-related epilepsy before and during carbamazepine (CBZ) treatment and in 21 patients with temporal lobe epilepsy before and after epilepsy surgery. Both groups were compared with age- and sex-matched controls. No significant differences were found from controls in the night/daytime ratios of HRV whether compared before or after initiation of treatment with CBZ in newly diagnosed epilepsy patients. When patients were used as their own controls, night/daytime ratios of standard deviation of RR intervals (p = 0.04) and total power (p = 0.04) were significantly lower during treatment than before. Compared with those of controls, the night/daytime ratios were lower in epilepsy surgery patients before surgery [low-frequency power (p = 0.04); high-frequency power (p = 0.04)]. Night/daytime ratios did not change significantly after surgery. The HRV of the patients was more affected during night-time when the risk of SUDEP seems to be highest in such patients.

Diminished circadian rhythm of heart rate variability after aortic surgery appears to be independent of myocardial ischemia.

Impaired heart rate variability (HRV) has been described postoperatively. Diminished HRV may be related to myocardial ischemia and potentially causes circulatory instability. Cardiac ischemic events and a compromised cardiovascular function are not uncommon after aortic surgery. Circadian variation of HRV seems to be a prognostically more important parameter than HRV itself with respect to the development of cardiac dysfunction. We therefore investigated whether the diurnal rhythm of HRV is simultaneously altered postoperatively and the potential contribution of myocardial ischemia. After approval by the hospital ethics committee and having obtained informed consent, we studied 11 consecutive male patients undergoing elective aortic surgery. Patients were monitored with a Holter-ECG perioperatively. Spectral HRV measures (total, low, and high frequency power) were determined and night/day ratios calculated. Ischemic ECG changes were recorded and serum was sampled for troponin T analysis. A remarkable decline in circadian variation accompanied the decrease in all HRV parameters postoperatively. Five patients showed ECG changes suggestive of myocardial ischemia and two had increased levels of troponin T. These two patients showed greatly diminished HRV postoperatively with a similarly reduced circadian rhythm. We have demonstrated that the circadian rhythm of HRV is not preserved after aortic surgery. Diminished diurnal variability seems to be a general manifestation and myocardial ischemia may just be one contributing factor. An altered biorhythm in combination with stress related changes in the neuroendocrine system after surgery most likely have a more significant influence on the circadian rhythm of HRV.

Diminished Circadian Variation in Heart Rate Variability before Surgery in Patients Developing Postoperative Atrial Fibrillation

Objective - To evaluate the role of the autonomic nervous system for the development of atrial fibrillation (AF) after coronary artery bypass surgery. Design - Eighty patients without a previous history of AF were included. The sympathetic and parasympathetic activity were evaluated by the analysis of heart rate variability (HRV) in the frequency domain from 24-h Holter recordings and by measuring neuropeptides (neuropeptide Y, chromogranin A, chromogranin B, and pancreatic polypeptide (PP)) and catecholamines, obtained pre- and postoperatively. Results - Preoperatively, patients (36.3%) developing AF postoperatively showed a statistically significant less circadian variation in the HRV variables, the high-frequency (HF) component ( p = 0.013) and the low-frequency (LF)/HF ratio ( p = 0.007), than patients remaining in sinus rhythm. The HF component and PP, both reflecting parasympathetic activity, and all other variables in the frequency domain, decreased significantly after surgery in both patient groups ( p < 0.0001). Although catecholamines increased significantly postoperatively in both patient groups, neither catecholamines nor neuropeptides expressing sympathetic activity, differed between the two groups. PP was, however, significantly higher in patients with postoperative AF than in those with sinus rhythm post-operatively on day 1. Conclusion - The diminished circadian variation in HRV before surgery and the indirect signs of a higher parasympathetic activity in patients developing postoperative AF compared with patients remaining in sinus rhythm, may indicate a propensity for AF.

Heart rate variability in diabetic and non-diabetic renal transplant patients.

Heart rate variability (HRV) has been used to investigate the autonomic modulation of heart rate. Diminished HRV has been observed in diabetic autonomic neuropathy, a condition associated with increased mortality. Uraemia is associated with impaired autonomic function, but reports on the effects of uraemia on HRV are scarce. HRV and its circadian variation were studied in 12 diabetic and 11 non-diabetic renal transplantation and in 12 control patients. HRV in time and frequency domains was determined from 24-hour ECG recordings. In the diabetic group, all time domain and frequency domain measures of HRV were markedly reduced (P < 0.05), when compared with the control group, and the circadian variation of HRV was absent. The mean (SD) amplitudes (ms) in the frequency bands were: high frequency: 3 (1), 6 (3) and 15 (3); low frequency: 9 (7), 16 (10) and 25 (8); very low frequency: 14 (8), 23 (12) and 30 (11) in the diabetic and non-diabetic uraemic and in the control patients, respectively. In non-diabetic uraemic patients, a tendency to reduced HRV was observed, but no statistical differences in HRV measures were found when compared with the control group. The severe impairment of HRV in patients with end-stage diabetic nephropathy is probably due to autonomic neuropathy and partly also to the co-existing heart diseases. It may be a contributing risk factor for ventricular arrhythmias and sudden death in these patients. Uraemia alone causes similar but less severe changes in HRV.