HEART RATE VARIABILITY IN PATIENTS WITH OBSTRUCTIVE SLEEP APNOEA SYNDROME

Abstract

Purpose of the study. To assess 24-hours heart rate variability in patients with obstructive sleep apnea syndrome. Materials and Methods. The 143 eligible patients with OSA were enrolled into the main group in this study. Twenty healthy subjects with increased body weight and without significant chronic pathologies were included into the control group. The mean age and gender characteristics of the groups were similar. Each patient underwent a clinical evaluation during the consultation (with measurement of body mass, height, circumference of the neck, waist and hips), biological tests, cardio-respiratory monitoring and Holter ECG monitoring. Results and discussion. The average daily HR, HRmax and HRmin the main group was higher in comparison with the control group, but the sechanges had no significant differences (p  0,05). The heart rate analysis at night in patients with OSAS revealed the presence of periodic episodes of severe bradycardia (up to 28 beats/min) with subsequent episodes of tachycardia and normalization of heart rhythm. Episodes of bradycardia/tachycardia duringsleep inpatientswith OSAScould beexplaned as the response of the autonomic nervous system to periods of apnea/hypopnea. It was found that most indicators in patients of the main group and control group differed statistically significant in the HRV analysis. Thus, SDNN and RMSSD in patients from main group were lower than the corresponding values in the control group (p = 0,022, p = 0,038, respectively). During the day the value of pNN50 did not differ significantly between the groups, but at night this parameter decreased but was lower by 40% from the control value (p = 0,007). The maximum values during the day for SDNN and pNN50 in the main group were resisted at night in comparison with the control group. There was a pathological increase in the spectral parameters (VLF, LF, LFN) during the day and at night in patients with OSAS, which indicated persistent hypersympathicotonia during daytime and nighttime. During the correlation analysis, a direct correlation was established between AHI, BMI and neck circumference (r = 0,73, p = 0,007; r = 0,71, p=0,003, respectively). When compared with the spectral indices of HRV, an inverse correlation was established between the indices SDNNnight, and AHI (r = –0,71, p = 0,024), a positive correlation between LFnight and AHI (r = 0,70, p = 0,011) and the negative correlation between AHI and RMSSDnight (r = –0,63, p = 0,013). Conclusions. It was shown that all patients with OSAS have Imbalance between branches of the automatic nervous system which manifest as an pathological increase of activity of sympathetic branch in the day, and at night as well. A significant correlations between AHI and BMI (r = 0,73, p = 0,007), neck circumference (r = 0,71, p = 0,003), and SDNNnight (r =–0,71, p = 0,024), LFnight (r = 0,70, p = 0,011), RMSSDnight (r =-0,63, p = 0,013)) were established.

Keywords

• heart rate variability
• obstructive sleep apnoea syndrome
• obesity