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1.  Sympathovagal Imbalance Contributes to Prehypertension Status and Cardiovascular Risks Attributed by Insulin Resistance, Inflammation, Dyslipidemia and Oxidative Stress in First Degree Relatives of Type 2 Diabetics 
PLoS ONE  2013;8(11):e78072.
Background
Though cardiovascular (CV) risks are reported in first-degree relatives (FDR) of type 2 diabetics, the pathophysiological mechanisms contributing to these risks are not known. We investigated the association of sympathovagal imbalance (SVI) with CV risks in these subjects.
Subjects and Methods
Body mass index (BMI), basal heart rate (BHR), blood pressure (BP), rate-pressure product (RPP), spectral indices of heart rate variability (HRV), autonomic function tests, insulin resistance (HOMA-IR), lipid profile, inflammatory markers, oxidative stress (OS) marker, rennin, thyroid profile and serum electrolytes were measured and analyzed in subjects of study group (FDR of type 2 diabetics, n = 72) and control group (subjects with no family history of diabetes, n = 104).
Results
BMI, BP, BHR, HOMA-IR, lipid profile, inflammatory and OS markers, renin, LF-HF (ratio of low-frequency to high-frequency power of HRV, a sensitive marker of SVI) were significantly increased (p<0.0001) in study group compared to the control group. SVI in study group was due to concomitant sympathetic activation and vagal inhibition. There was significant correlation and independent contribution of markers of insulin resistance, dyslipidemia, inflammation and OS to LF-HF ratio. Multiple-regression analysis demonstrated an independent contribution of LF-HF ratio to prehypertension status (standardized beta 0.415, p<0.001) and bivariate logistic-regression showed significant prediction (OR 2.40, CI 1.128–5.326, p = 0.002) of LF-HF ratio of HRV to increased RPP, the marker of CV risk, in study group.
Conclusion
SVI in FDR of type 2 diabetics occurs due to sympathetic activation and vagal withdrawal. The SVI contributes to prehypertension status and CV risks caused by insulin resistance, dyslipidemia, inflammation and oxidative stress in FDR of type 2 diabetics.
doi:10.1371/journal.pone.0078072
PMCID: PMC3827034  PMID: 24265679
2.  Association of Sympathovagal Imbalance with Cardiovascular Risks in Overt Hypothyroidism 
Background:
Cardiovascular morbidities have been reported in hypothyroidism.
Aims:
The objective of this study is to investigate the link of sympathovagal imbalance (SVI) to cardiovascular risks (CVRs) and the plausible mechanisms of CVR in hypothyroidism.
Materials and Methods:
Age-matched 104 females (50 controls, 54 hypothyroids) were recruited and their body mass index (BMI), cardiovascular parameters, autonomic function tests by spectral analysis of heart rate variability (HRV), heart rate response to standing, deep breathing and blood pressure response to isometric handgrip were studied. Thyroid profile, lipid profile, immunological and inflammatory markers were estimated and their association with low-frequency to the high-frequency ratio (LF-HF) of HRV, the marker of SVI was assessed by multivariate regression.
Results:
Increased diastolic pressure, decreased HRV, increased LF-HF, dyslipidemia and increased high-sensitive C-reactive protein (hsCRP) were observed in hypothyroid patients and all these parameters had significant correlation with LF-HF. BMI had no significant association with LF-HF. Atherogenic index (β 1.144, P = 0.001) and hsCRP (b 0.578, P = 0.009) had independent contribution to LF-HF. LF-HF could significantly predict hypertension status (odds ratio 2.05, confidence interval 1.110-5.352, P = 0.008) in hypothyroid subjects.
Conclusions:
SVI due to sympathetic activation and vagal withdrawal occurs in hypothyroidism. Dyslipidemia and low-grade inflammation, but not obesity contribute to SVI and SVI contributes to cardiovascular risks.
doi:10.4103/1947-2714.118921
PMCID: PMC3818829  PMID: 24251274
Autonomic imbalance; Body mass index; Cardiovascular risks; Dyslipidemia; High-sensitive C-reactive protein; Hypothyroidism; Sympathovagal imbalance
3.  A comparative study of the effects of asan, pranayama and asan-pranayama training on neurological and neuromuscular functions of Pondicherry police trainees 
International Journal of Yoga  2013;6(2):96-103.
Background:
Though neurological benefits of yoga training have been reported, lacunae still exists in understanding neurophysiological effects of such training. Hence, the present study was conducted to find the effect of yogasanas and pranayams on neurological and neuromuscular functions in healthy human volunteers and also determined differential effects of training in asan, pranayama and their combination.
Materials and Methods:
Eighty male trainees from Pondicherry Police Training School were randomly divided into asan, pranayama, and asan-pranayama groups who received a training of 4 days a week for 6 months and a control group. Electroencephalogram (EEG), nerve conduction (NC), electromyogram (EMG), visual evoked potentials (VEP), and auditory reaction time (ART) were recorded before and after the study period. NC, EMG, and VEP data were obtained from 28 subjects; EEG data from 48 subjects; and RT from 67 subjects. Intergroup differences were assessed by AVOVA/Kruskal–Wallis and intragroup differences by Student's t-test.
Results and Discussion:
Police trainees showed beneficial effects of yoga training, although they were undergoing intensive police training and the yoga training was relatively less intense. Alpha, theta, and total power of EEG increased as a result of asan training. A shortening of visual reaction time and a decrease in red-green discriminatory reaction time signifies an improved and faster processing of visual input. They also showed a decrease in resting EMG voltage, signifying better muscular relaxation following pranayama training. Beta, theta and total power of EEG increased. ART and red-green discriminatory reaction times decreased in the trainees, signifying a more alert state as well as improved central neural processing. A combination of asan and pranayama training for 6 months produced an improvement in motor and sensory nerve conduction. Total power of EEG, alpha and theta power as well as delta % increased, while reaction time decreased signifying an alert and yet relaxed state of the neuromuscular system.
Summary and Conclusion:
The present study has shown that 6 months training in asan, pranayama as well as their combination is effective in improving physiological functions of police trainees. They showed beneficial effects of yoga training, although they were undergoing intensive police training and the yoga training was relatively less intense. Hence, we recommend that yoga training be introduced in police training curricula.
doi:10.4103/0973-6131.113398
PMCID: PMC3734645  PMID: 23930027
Asan-pranayama; neurophysiology; police trainees; yoga training
4.  Body mass index contributes to sympathovagal imbalance in prehypertensives 
Background
The present study was conducted to assess the nature of sympathovagal imbalance (SVI) in prehypertensives by short-term analysis of heart rate variability (HRV) to understand the alteration in autonomic modulation and the contribution of BMI to SVI in the genesis of prehypertension.
Methods
Body mass index (BMI), basal heart rate (BHR), blood pressure (BP), rate pressure product (RPP) and HRV indices such as total power (TP), low-frequency power (LF), normalized LF (LFnu), high-frequency power (HF), normalized HF (HFnu), LF-HF ratio, mean heart rate (mean RR), square root of the mean squared differences of successive normal to normal intervals (RMSSD), standard deviation of normal to normal RR interval (SDNN), the number of interval differences of successive NN intervals greater than 50 ms (NN50) and the proportion derived by dividing NN50 by the total number of NN intervals (pNN50) were assessed in three groups of subjects: normotensives having normal BMI (Group 1), prehypertensives having normal BMI (Group 2) and prehypertensives having higher BMI (Group 3). SVI was assessed from LF-HF ratio and correlated with BMI, BHR, BP and RPP in all the groups by Pearson correlation. The contribution of BMI to SVI was assessed by multiple regression analysis.
Results
LF and LFnu were significantly increased and HF and HFnu were significantly decreased in prehypertensive subjects in comparison to normotensive subjects and the magnitude of these changes was more prominent in subjects with higher BMI compared to that of normal BMI. LF-HF ratio, the sensitive indicator of sympathovagal balance had significant correlation with BMI (P = 0.000) and diastolic blood pressure (DBP) (P = 0.002) in prehypertensives. BMI was found to be an independent contributing factor to SVI (P = 0.001) in prehypertensives.
Conclusions
It was concluded that autonomic imbalance in prehypertensives manifested in the form of increased sympathetic activity and vagal inhibition. In prehypertensives with higher BMI, vagal withdrawal was predominant than sympathetic overactivity. Magnitude of SVI (alteration in LF-HF ratio) was linked to changes in BMI and DBP. BMI had an independent influence on LF-HF ratio. It was advised that life-style modifications such as yoga and exercise would enable achieve the sympathovagal balance and blood pressure homeostasis in prehypertensives.
doi:10.1186/1471-2261-12-54
PMCID: PMC3441642  PMID: 22812583
Prehypertension; Heart rate variability; Body mass index; Sympathovagal imbalance; LF-HF ratio

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