Effect of Yoga Based Cardiac Rehabilitation on Blood Pressure Variability and Baroreflex Sensitivity: RCT in Patients Post MI.

To assess the effects of 12 weeks Yoga based Cardiac Rehabilitation program on Blood Pressure Variability and Baroreflex Sensitivity in Eighty patients post myocardial infarction. Randomized controlled trial with two parallel groups. A tertiary care institution in India. The Yoga group received 13 hospital-based structured yoga sessions in adjunct to the standard care. Control Group participants received enhanced standard care involving three brief educational sessions on importance of diet and physical activity. Beat to beat arterial pressure variability and baroreflex sensitivity was determined non-invasively. Baseline measurement was done at 3 weeks post Myocardial Infarction. The measurements were repeated at 13th week and at 26th week post MI. There was no significant difference between the groups in time domain indices of SBP variability. At 26th week post MI, after normalization the Low Frequency power increased in the yoga group as compared to the decrease in the standard care group (p = 0.02). Though the High Frequency power increased in both the groups, the magnitude of increase was higher in the standard care group (p = 0.005). However, the total power increased significantly in yoga group with a concurrent decrease in standard care group (p = < 0.001). The SBP All BRS was significantly different between the groups with an increase in the yoga group and a decline in standard care group (p = 0.003) at 13th week. A short-term Yoga based cardiac rehabilitation has additive effects in improving baroreflex sensitivity and dampening blood pressure variability post myocardial infarction in patients under optimal medication.The main trial is registered in Clinical Trials Registry-India (CTRI) (Ref. No: CTRI/2012/02/002408). In addition, CTRI has also been registered for the sub-study. (Ref. No: CTRI/2017/09/009925).

Yoga Practitioners Exhibit Higher Parasympathetic Activity and Baroreflex Sensitivity and Better Adaptability to 40 mm Hg Lower-Body Negative Pressure.

Yoga has been shown to improve autonomic conditioning in humans, as evidenced by the enhancement of parasym-pathetic activity and baroreflex sensitivity. Therefore, we hypothesized that the experience of yoga may result in adaptation to acute hemodynamic changes. To decipher the long-term effects of yoga on cardiovascular variability, yoga practitioners were compared to yoga-naïve subjects during exposure to -40 mm Hg lower-body negative pressure (LBNP). A comparative study was conducted on 40 yoganaïve subjects and 40 yoga practitioners with an average age of 31.08 ± 7.31 years and 29.93 ± 7.57 years, respectively. Heart rate variability, blood pressure variability, baroreflex sensitivity, and correlation between systolic blood pressure and RR interval were evaluated at rest and during LBNP. In yoga practitioners, the heart rate was lower in supine rest (p = 0.011) and during LBNP (p = 0.043); the pNN50 measure of heart rate variability was higher in supine rest (p = 0.011) and during LBNP (p = 0.034). The yoga practitioners' standard deviation of successive beat-to-beat blood pressure intervals of systolic blood pressure variability was lower in supine rest (p = 0.034) and during LBNP (p = 0.007), with higher sequence baroreflex sensitivity (p = 0.019) and ~ high-frequency baroreflex sensitivity. Mean systolic blood pressure and RR interval were inversely correlated in the yoga group (r = -0.317, p = 0.049). The yoga practitioners exhibited higher parasympathetic activity and baroreflex sensitivity with lower systolic blood pressure variability, indicating better adaptability to LBNP compared to the yoga-naïve group. Our findings indicate that the yoga module was helpful in conditions of hypovolemia in healthy subjects; it is proposed to be beneficial in clinical conditions associated with sympathetic dominance, impaired barore-flex sensitivity, and orthostatic intolerance.

Cortex senses environmental temperature earlier than the hypothalamus in awake rats.

Simultaneous and direct recording of temperature from the body, hypothalamus, and cortex in animals exposed to acute thermal challenges lack evidence. This study was conducted to assess the usual concept, that brain temperature is rather stable when animals are exposed to different ambient temperatures. In this study, we report the characteristic changes in the body, hypothalamic, and cortical temperature, when the rats were acutely exposed to cold (6 °C) and hot (36 °C) ambient temperature. The results of our study show that the body temperature is robustly regulated while hypothalamic and cortical temperatures vary on challenges to ambient cold (6 °C) and warm (36 °C) exposure in awake rats. The onset of response was observed quickest in the cortex, indicating that the cortical thermal sensing may relay intracranial thermal input to the hypothalamus for the regulation of body temperature within narrow limits. The present findings contradict earlier evidence, which stated that the brain does not participate in thermal sensing.

Effect of slow breathing on autonomic tone & baroreflex sensitivity in yoga practitioners.

BACKGROUND & OBJECTIVES: Slow breathing increases parasympathetic activity and baroreflex sensitivity (BRS) in healthy individuals, also similarly observed in yoga practitioners. Pranayama which is an important component of yoga when practiced at a slow pace was at a respiratory frequency of around 0.1 Hz (6 breaths/min). Therefore, it was hypothesized that yoga practitioners might have adapted to slow breathing. This study was aimed to decipher the role of yoga on cardiovascular variability during slow breathing (0.1 Hz) in yoga practitioners. METHODS: A cross-sectional study was undertaken in naïve-to-yoga individuals (n=40) and yoga practitioners (n=40) with an average age of 31.08 ± 7.31 and 29.93 ± 7.57 yr, respectively. The analysis of heart rate variability, blood pressure variability (BPV) and BRS during spontaneous and slow breathing was compared between the two groups. RESULTS: During slow breathing, the heart rate (P<0.01) was lower, respiratory rate interval (P<0.05) and pNN50 per cent (P=0.01) were higher, mean systolic BP (SBP) (P<0.05) and SDSD (Standard deviation of successive beat to beat systolic blood pressure differences) (P<0.01) of SBP variability were lower with sequence BRS (P<0.001) and α low frequency (P<0.01) and α high frequency (P<0.001) of spectral BRS were higher in yoga practitioners. INTERPRETATION & CONCLUSIONS: The present study indicated higher parasympathetic activity and BRS with lower SBP variability at rest and during slow breathing in yoga practitioners compared to naive group. Findings indicate that the short-term practice of slow breathing complements the augmented parasympathetic activity and BRS in the yoga group.

Effect of Yoga-Based Cardiac Rehabilitation on Heart Rate Variability: Randomized Controlled Trial in Patients Post-MI.

Autonomic dysfunction is an independent predictor of cardiovascular and all-cause mortality after myocardial infarction (MI). We tested the effects of a 12-week yoga-based cardiac rehabilitation program on heart rate variability (HRV) in 80 patients post-MI. This randomized controlled trial with two parallel groups was carried out in a tertiary care institution in India. The yoga group received 13 hospital-based structured yoga sessions as an adjunct to standard care. Control group participants received enhanced standard care involving three brief educational sessions with a leaflet on the importance of diet and physical activity. HRV was measured in all participants with lead II electrocardiogram (ECG) signals. One yoga group patient's data were excluded due to ECG abnormalities. Baseline measurement was done 3 weeks post-MI, and postintervention assessment took place at the 13th week. HRV frequency and time domain indices were analyzed. There were no significant between-group differences in the HRV time domain indices. Frequency domain indices showed significant between-group differences in HF power (absolute) (yoga vs. control: 114.42 [-794.80-7,993.78] vs. -38.14 [-4,843.50-1,617.87], p = 0.005) and total power (nu) (yoga vs. control: 44.96 [21.94] vs. -19.55 [15.42], p = 0.01) with higher HF power and total power (nu) in the yoga group. It should be noted that these results cannot be generalized to high risk patients. Respiratory frequency control to check for influence of respiratory rate on RR interval was not evaluated. This short-term yoga-based cardiac rehabilitation program had additive effects in shifting sympathovagal balance toward parasympathetic predominance while increasing overall HRV in optimally medicated post-MI patients.

Acute effects on cardiovascular oscillations during controlled slow yogic breathing.

BACKGROUND & OBJECTIVES: Breathing exercises are believed to modulate the cardiovascular oscillations in the body. To assess the validity of the assumption and understand the underlying mechanism, the key autonomic regulatory parameters such as heart rate variability (HRV), blood pressure variability (BPV) and baroreflex sensitivity (BRS) were recorded during controlled slow yogic breathing. Alternate nostril breathing (ANB) was selected as the yogic manoeuvre. METHODS: Twelve healthy volunteers (age 30±3.8 yr) participated in the study. ANB was performed at a breathing frequency of 5 breaths per minute (bpm). In each participant, the electrocardiogram, respiratory movements, beat-to-beat BP and end-tidal carbon dioxide were recorded for five minutes each: before, during and after ANB. The records were analyzed for HRV, BPV and BRS. RESULTS: During ANB, HRV analysis showed significant increase in the standard deviation of all NN intervals, low-frequency (LF) component, LF/HF (low frequency/high frequency) ratio and significant decrease in the HF component. BPV analysis showed a significant increase in total power in systolic BPV (SBPV), diastolic BPV (DBPV) and mean BPV. BRS analysis showed a significant increase in the total number of sequences in SBPV and DBPV and significant augmentation of α-LF and reduction in α-HF. The power spectrum showed a dominant peak in HRV at 0.08 Hz (LF component) similar to the respiratory frequency. The acute short-term change in circulatory control system declined immediately after the cessation of slow yogic breathing (ANB) and remained elevated in post-ANB stage as compared to the pre-ANB. INTERPRETATION & CONCLUSIONS: Significant increase in cardiovascular oscillations and baroreflex recruitments during-ANB suggested a dynamic interaction between respiratory and cardiovascular system. Enhanced phasic relationship with some delay indicated the complexity of the system. It indicated that respiratory and cardiovascular oscillations were coupled through multiple regulatory mechanisms, such as mechanical coupling, baroreflex and central cardiovascular control.