Analysis of Heart Rate Asymmetry During Sleep Stages

It is one of the hot spots in recent years to explore changes in the sleep stage by assessing autonomic nervous activity. In recent years, heart rate asymmetry (HRA) is often used to measure the activity of autonomic nerves. However, the relationship between HRA and sleep stage is not clear. We performed Porta’s index (PI), Guzik’s index (GI), slope index (SI) and area index (AI) analyses on RR intervals per 30-s for understanding the HRA during sleep. Two measurement protocols were set: 1) the HRA values were calculated; 2) the degrees of heart rate deviation from symmetry were estimated. Results showed that PI significantly decreased from N1 and N2 to N3 (p<0.01), and it is increased the highest in REM than other stages (p<0.05). The asymmetry of HRA were significantly lower in N3 (PI and AI p’s<0.05; GI and SI p’s<0.01), and it increased in REM (PI p<0.05; GI, SI and AI p’s<0.0001). The results suggested that HRA has the potential to be used in sleep stage monitoring.

The effect of passive lower limb training on heart rate asymmetry

Objective: Heart rate asymmetry (HRA) is an approach for quantitatively assessing the uneven distribution of heart rate accelerations and decelerations for sinus rhythm. We aimed to investigate whether automatic regulation led to HRA alternation during passive lower limb training. Methods: Thirty healthy participants were recruited in this study. The protocol included a baseline (Pre-E) and three passive lower limb training trials (E1, E2 and E3) with a randomized order. Several variance-based HRA variables were established. Heart rate variability (HRV) parameters, i.e., mean RR, SDNN, RMSSD, LF (n.u.), HF (n.u.) and VLF (ms2), and HRA variables, i.e., SD1a, SD1d, SD2a, SD2d, SDNNa and SDNNd, were calculated by using 5-min RR time series, as well as the normalized HRA variables, i.e., C1a, C1d, C2a, C2d, Ca and Cd. Results: Our results showed that the performance of HRA was distinguished. The normalized HRA was observed with significant changes in E1, E2 and E3 compared to Pre -E. Moreover, parts of non-normalized HRA variables correlated with HRV parameters, which indicated that HRA might benefit in assessing cardiovascular modulation in passive lower limb training. Conclusions: In summary, this study suggested that passive training led to significant HRA alternation and the application of HRA gave us the possibility for autonomic assessment.

Heart Rate Asymmetry Analysis During Head-Up Tilt Test in Healthy Men

The purpose of this study is to assess the cardiovascular system response to orthostatic stress in a group of 133 healthy men using heart rate asymmetry (HRA) methods. HRA is a feature of variability in human heart rate which is dependent upon external and internal body conditions. The initial phases of head-up tilt test (HUTT), namely, supine and tilt, were chosen as the external body affecting factors. Various calculation methods of HRA, such as Porta’s index (PI), Guzik’s index (GI), and its variance based components, were used to assess the heart rate variability (HRV) and its asymmetry. We compared 5-min ECG recordings from both supine and tilt phases of HUT test. Short-term HRA was observed in 54.1% of men in supine phase and 65.4% of men in tilt phase. The study revealed significant increase of GI (from 0.50 to 0.52, p &lt; 0.001) in the tilt phase as well as significant changes in HRV descriptors between HUTT phases. Our results showed that the variability of human heart rate and its asymmetry are sensitive to orthostatic stress. The study of short-term HRA is a potential additional tool to increase sensitivity in conditions where HUTT is a diagnostic tool, such as vasovagal syncope.

Rationale, design and methods planned in a prospective study concerning the circadian rhythm of heart rate asymmetry in healthy subjects

Heart rate asymmetry (HRA) is a physiological phenomenon caused by an unequal (asymmetric) contribution of heart rate decelerations and accelerations to the variability (variance) and microstructure of the heart rhythm of sinus origin. HRA has been studied in healthy people and patients with heart failure, diabetes, obstructive sleep apnoea, ischaemic heart disease, and survivors of myocardial infarction. HRA is a particular form of the heart rate variability (HRV) phenomenon related to the changes in the duration of cardiac cycles of sinus origin. HRV is influenced by physical activity, age, gender or time of day. It has been reported that HRA expression differs between day and night. However, its circadian rhythm has not been analysed so far. Moreover, the differences in HRA expression related to gender, level of physical activity or age have not been investigated either. With this study, we aim to explore the circadian rhythm of the HRA features, as well as the relation of the HRA expression to gender, physical activity, sleep pattern and body composition in a group of at least 100 healthy adults of both sexes aged between 19 and 60. This study might provide reference values for HRA as well as confirming or dismissing the existence of circadian rhythm of this physiological phenomenon.

The effect of passive lower limb training on heart rate asymmetry

Background: Heart rate asymmetry (HRA) is an approach for quantitatively assessing the uneven distribution points of RR intervals of sinus rhythm. We aimed to investigate whether the automatic regulation lead to HRA alternation during passive lower limb training. Methods : Several variance-based HRA variables derived from Poincaré plot were established. Thirty healthy participants were recruited in this study. The protocol included baseline (Pre-E) and three passive lower limb training trials (E1, E2 and E3) with a randomized order. Heart rate variability (HRV) frequency-domain parameters (LF (n.u.), HF (n.u.) and VLF (ms 2 )) and HRA variables (SD1a, SD1d, SD2a, SD2d, SDNNa and SDNNd) were calculated by using 5-min RR time series. Results : Our results showed that the performance of HRA distinguished. The HRA was observed with significant changes in E1, E2 and E3 compared to Pre -E. Moreover, HRA variables correlated with HRV parameters in all trials, which indicated that HRA might benefit in assessing autonomic alteration in passive lower limb trainings. Conclusions: In summary, this study suggested that passive training led to significant HRA alternation and the application of HRA gave us the possibility for autonomic assessment.

Short-term recovery of heart rate variability and its relationship with blood pressure after different intensity treadmill exercise

Background : Heart rate variability (HRV) provides an opportunity to capture the tiny but early signs that may predict the future cardiovascular risk in healthy individuals and further, helps understand how well the cardiovascular autonomic system works. Aims of this study were to elucidate short-term recovery of HRV and its relationship with blood pressure recovery after different intensity treadmill exercise. Methods : Fifteen healthy participants performed four different conditions (REST; speed 6km/h; speed 8km/h; speed 10km/h), systolic and diastolic blood pressure per 30s (SBP, DBP) and 5-mins consecutive heart beats intervals were measured after each trial. Autonomic nervous regulation was evaluated using HRV time-frequency domain indices and heart rate asymmetry (HRA) indices. Each index was calculated using 5 mins electrocardiogram (ECG) series and consecutive 30-s windows in 5 mins. Results : the vagally related indices (RMSSD, pNN50 and HF) decreased and the indices representing overall variability (SDNN, LF) had different trends as intensity increasing. The sympathetic-vagal balance parameter LF/HF increased, too. HRV indices had strong correlations with DBP but weak with SBP. Meanwhile, heart rate asymmetry vanished after each trial. Conclusions : The findings suggested a vagal withdrawal as soon as the end of treadmill exercise. It could be concluded that sympathetic modulation was stronger as intensity increasing. During recovery period, DBP was mediated by vagal activation and sympathetic withdrawal. The diminished asymmetry in Poincaré plot was the result of sympathetic acceleration and vagal reduction.