Baroreflex sensitivity is impaired in survivors of mild COVID-19 at 3-6 months of clinical recovery; association with carotid artery stiffness

The association between the stiffening of barosensitive regions of central arteries and the derangements in baroreflex functions remains unexplored in COVID-19 survivors. Fifty-seven survivors of mild COVID-19 (defined as presence of upper respiratory tract symptoms and/or fever without shortness of breath or hypoxia; SpO2 > 93%), with an age range of 22-66 years (27 females) participated at 3-6 months of recovering from the acute phase of RT-PCR positive COVID-19. Healthy volunteers whose baroreflex sensitivity (BRS) and arterial stiffness data were acquired prior to the onset of the pandemic constituted the control group. BRS was found to be significantly lower in the COVID survivor group for the systolic blood pressure-based sequences (BRSSBP ) [9.78 (7.16-17.74) ms/mmHg vs 16.5 (11.25-23.78) ms/mmHg; p = 0.0253]. The COVID survivor group showed significantly higher carotid β stiffness index [7.16 (5.75-8.18) vs 5.64 (4.34-6.96); (p = 0.0004)], and pulse wave velocity β (PWVβ ) [5.67 (4.96-6.32) m/s vs 5.12 (4.37-5.41) m/s; p = 0.0002]. BRS quantified by both the sequence and spectral methods showed an inverse correlation with PWVβ in the male survivors. Impairment of BRS in the male survivors of mild COVID-19 at 3-6 months of clinical recovery shows association with carotid artery stiffness.

Vasoconstriction during non-hypotensive hypovolemia is not associated with activation of baroreflex: A causality-based approach

Non-hypotensive hypovolemia simulated with oscillatory lower body negative pressure in the range of -10 to -20 mmHg is associated with vasoconstriction {increase in total peripheral vascular resistance (TPVR)}. Due to the mechanical stiffening of vessels, there is a disjuncture of mechano-neural coupling at the level of arterial baroreceptors which has not been investigated. The study was designed to quantify both the cardiac and vascular arms of the baroreflex using an approach based on Wiener-Granger causality (WGC) - partial directed coherence (PDC). Thirty-three healthy human volunteers were recruited and continuous heart rate and blood pressure {systolic (SBP), diastolic (DBP), and mean (MBP)} were recorded. The measurements were taken in resting state, at -10 mmHg (level 1) and -15 mmHg (level 2). Spectral causality - PDC was estimated from the MVAR model in the low-frequency band using the GMAC MatLab toolbox. PDC from SBP and MBP to RR interval and TPVR was calculated. The PDC from MBP to RR interval showed no significant change at -10 mmHg and -15 mmHg. No significant change in PDC from MBP to TPVR at -10 mmHg and -15 mmHg was observed. Similar results were obtained for PDC estimation using SBP as input. However, a significant increase in TPVR from baseline at both levels of oscillatory LBNP (p-value <0.001). No statistically significant change in PDC from blood pressure to RR interval and blood pressure to TPVR implies that vasoconstriction is not associated with activation of the arterial baroreflex in ≤-15 mmHg LBNP. Thereby, indicating the role of cardiopulmonary reflexes during the low level of LBNP simulated non-hypotensive hypovolemia.

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).

Temporal Analysis of Sequential Changes in Heart Rate Variability During Non-hypotensive Hypovolemia

INTRODUCTION

Haemorrhage is associated with changes in the cardiac autonomic drive which begins during early stages of mild haemorrhage. The knowledge of chronology of the autonomic changes at smaller timescale during the period of haemorrhage can help identify the primary autonomic parameter which signals the institution of cardiovascular reflex mechanisms.

AIM

To evaluate the heart rate variability in 2-min sequential segments with one minute overlap during and after the period of mild haemorrhage (450 ml) using blood donation as a model of acute blood loss.

METHODS

47 male blood donors who had volunteered for blood donation were recruited for the study. Continuous lead II ECG was recorded before the start of the blood donation (5 min), during the period of the blood donation (~ 5-7 min) and after blood donation (5 min). The parasympathetic and sympathetic drive to heart was estimated by measures of heart rate variability in time and frequency domain.

RESULTS

A significant decrease in the parameters assessing parasympathetic drive i.e., normalised High frequency (HFn) and NN50 (Number of pairs of adjacent NN intervals differing by more than 50 ms) and pNN50 (NN50 divided by the total number of all NN Intervals) was observed during blood donation at 3-5 min, as compared to baseline. An increase in parameters associated with sympathetic drive i.e., normalised low frequency (LFn) was observed only in the post donation period at 2-3 min. A significant rise in LF/HF ratio which is a marker of sympatho vagal balance was observed at 4-5 min during blood donation when compared to baseline.

CONCLUSION

The initial cardiac autonomic change during mild haemorrhage is withdrawal of parasympathetic drive, followed by an increase in sympathetic tone which occurs much later.

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.

Predictive value of intraoperative D-wave and m-MEP neurophysiological monitoring in patients with preoperative motor deficits in immediate and late postoperative period

Background:

Presence of preoperative motor deficits in patients poses a distinct challenge in monitoring the integrity of corticospinal tracts during spinal surgeries. The inconsistency of the motor-evoked potentials is such patients, limits its clinical utility. D-wave is a robust but less utilized technique for corticospinal tract monitoring. The comparative clinical value of these two techniques has not been evaluated in the patients with preoperative deficits.

Objectives:

The objective of the study was to compare the predictive utility of myogenic Motor Evoked Potentials (m-MEP) and D-wave in terms of recordability and their sensitivity and specificity in predicting transient and permanent new motor deficits.

Materials and Methods:

Thirty-one patients with preoperative motor deficit scheduled to undergo spinal surgery were included in the study. Intraoperative m-MEP and D-wave changes were identified and correlated with postoperative neurology in the immediate postoperative period and at the time of discharge.

Results:

The mean preoperative motor power of the patient pool in left and right lower limb was 2.97 ± 1.56 and 3.32 ± 1.49, respectively. The recordability of m-MEPs and D-wave was observed to be 79.4% and 100%, respectively. The m-MEP predicted the motor deterioration in immediate postoperative period with 100% sensitivity and 80% specificity, while D-wave had 14% sensitivity and 100% specificity. At the time of discharge, m-MEPs' specificity reduced to 61%, while D-wave demonstrated 100% specificity.

Conclusions:

D-wave has a better recordability than m-MEPs in neurologically compromised patients. D-wave predicts development of long-term deficits with 100% specificity, while m-MEPs have a high sensitivity for transient neurological deficit. A combination of D-wave and m-MEP is recommended for monitoring the integrity of the corticospinal tract in patients with preoperative motor deficits.

The Cardiovascular Variability during Transient 6° Head Down Tilt and Slow Breathing in Yoga Experienced Healthy Individuals

OBJECTIVE

The intervention of yoga has been shown to improve autonomic conditioning in humans and better adaptability to orthostatic challenges. Similarly, slow breathing at 0.1 Hz akin to pranayama also increases baroreflex sensitivity (BRS). Hence, we intended to investigate whether yoga practitioners have different autonomic responses at rest,during slow deep breathingas well as during 6° head down tilt (HDT) compared to naive group individuals.

AIM

The aim of the study was to evaluate the acute effects of slow breathing on cardiovascular variability during HDT in yoga practitioners compared to yoga-naïve individuals.

SETTINGS AND DESIGN

This was a comparative study with repeated measures design conducted in Autonomic Function Test lab of the Department of Physiology, All India Institute of Medical Sciences, New Delhi, India.

MATERIALS AND METHODS

Time domain and frequency domain parameters of heart rate variability, blood pressure variability (BPV), and BRS were evaluated during 6° HDT and slow breathing at 0.1 Hz on forty yoga-naïve individuals and forty yoga practitioners with an average age of 31.08 ± 7.31 years and 29.93 ± 7.57 years, respectively. All of the participants were healthy.

STATISTICAL ANALYSIS USED

General Linear Mixed Model ANOVA was applied with yoga experience as a between-group factor in repeated measures. Independent sample t-test was applied for between group comparison of respiratory rate, demographic, and anthropometric data. P <0.05 is considered statistically significant.

RESULTS

Between-group comparison during HDT with spontaneous breathing has shown a significantly lower heart rate (P = 0.004) with higher RR interval (RRI) (P = 0.002) and pNN50% (P = 0.019) in yoga practitioners. The sequence BRS (P < 0.0001) and α low frequency (LF) of spectral BRS (P = 0.035) were also significantly higher in the yoga group compared to the naïve group. Similarly, during HDT with slow breathing, the heart rate was lower (P = 0.01); with higher RRI (P = 0.009); pNN50% (P = 0.048). Standard deviation of successive RR interval difference of systolic BPV was lower (P = 0.024) with higher sequence BRS (P = 0.001) and α LF of spectral BRS (P = 0.002) in yoga group than naïve group.

CONCLUSION

The yoga experienced individuals exhibit higher resting parasympathetic activity, lower systolic BPV, and higher BRS than naïve to yoga individuals. It is inferred from the findings that yoga practitioners were better adapted to transient cephalad fluid shift that happens during 6° HDT. Furthermore, acute slow breathing during 6° HDT reduced the systolic blood pressure in all the participants suggesting the beneficial role of slow breathing during exposure to extreme conditions such as microgravity which might help in the prevention of adverse effects of cephalad fluid shift during long-term weightlessness and maintain the astronaut health. Future mechanistic studies with active yoga intervention are necessary to understand the adaptive mechanisms involving central and vascular modulations contributing to either attenuation or accentuation of the cardiovagal baroreflex during HDT and slow breathing in healthy individuals.

Effect of Disease Severity on Respiratory Impedance in Parkinson's Disease

Background:

Parkinson’s disease (PD) is a progressive neurodegenerative disorder. PD has been traditionally perceived as a motor disorder. However, it is frequently associated with pulmonary dysfunction which has been assessed by Spirometry, an effort-dependent technique.

Purpose:

To evaluate in patients with PD the effect of disease severity on respiratory impedance using Impulse Oscillometry (IOS) and to correlate with Spirometry.

Methods:

The study was conducted on 30 patients diagnosed with PD. Pulmonary function was assessed by IOS and spirometer. IOS is an effort-independent technique that uses sound waves of different frequencies to measure airway resistance. Spirometer measures the lung volume and generates flow–volume and volume–time relationship.

Results:

The mean age of patients was 60.1±9.45. Resistance at 5 Hz (R5) was found to be negatively correlated with forced expiratory volume in the first second of the FVC manoeuver (FEV₁) (r = –0.628, P = .002), FEV₁/FVC (forced vital capacity) (r = –0.487, P = .025), and PEF (r = –0.599, P = .004), and resistance at 20 Hz (R20) with FEV₁ (r = –0.474,

P = .029) and PEF (r = –0.522, P = .015). There was significant increase in R5 (0.32(0.36–0.28) vs 0.47(0.60–0.36); P = .04) and R20 (0.25(0.28–0.20) vs 0.30(0.40–0.25); P = .04) in stage II as compared to stage I of Hoehn–Yahr scale.

Conclusion:

IOS might be a promising tool for diagnosis of respiratory dysfunction in addition to Spirometry, especially in cases where patients are not able to perform forced manoeuvers.

Longitudinal electromyographic changes in masseter and anterior temporalis muscle before and after temporomandibular joint arthroplasty in ankylosis patients

PURPOSE

The literature lacks evidence about activity of masseter and anterior temporalis muscles in temporomandibular joint ankylosis (TMJA) patients. The purpose of this study was to evaluate longitudinal electromyography (EMG) changes in masseter and anterior temporalis muscle before and after gap arthroplasty in unilateral TMJA patients. Specific aim was to investigate the EMG activity restoration to the level of non-ankylosed side after arthroplasty.

METHODS

The investigator implemented a prospective longitudinal study amongst TMJA patients treated with gap arthroplasty. EMG of masseter and anterior temporalis were recorded bilaterally on ankylosed and non-ankylosed side. EMG signals of masseter and anterior temporalis were recorded preoperatively and 1 week, 3 month and 6 month postoperatively at rest and at maximum voluntary clench (MVC).

RESULTS

The study sample was composed of 16 (male:female = 1:1.28) unilateral TMJA patients. The mean duration of ankylosis was 3.25 ± 1.18 years. The difference in EMG root-mean-square (RMS) values of ankylosed side when compared to the preoperative values of non-ankylosed side was found to be statistically significant (p < 0.001) preoperatively, 1 week and 3 month postoperatively, while it was statistically not significant (p > 0.99) at 6-month postoperatively.

CONCLUSION

The present study concludes that the TMJA patients have hyperactivity of masseter and anterior temporalis muscle. Restoring the function causes the muscle activity to progress to the values of normal side. EMG activity as measured on follow-up may be one of the predicting factor for re-ankylosis.

Improvement in Angiotensin 1-7 precedes and correlates with improvement in Arterial stiffness and endothelial function following Renin-Angiotensin system inhibition in type 2 diabetes with newly diagnosed hypertension

BACKGROUND AND AIM

Studies in cell cultures and animal models have revealed the possible pathophysiological factors associated with vascular endothelial dysfunction. However, the same in human subjects has not been clearly established. The current study uses a novel approach to identify the factors associated with endothelial function and arterial function by altering these vascular parameters using Angiotensin-Converting-Enzyme (ACE) inhibition.

METHODS

Diabetic patients with newly diagnosed hypertension (n = 60) were recruited for the study. Flow-mediated-dilation (FMD), carotid-femoral (cf), carotid-radial (cr) Pulse-wave-velocity (PWV), Augmentation-Index, Carotid-Intima-Media-Thickness (CIMT), serum levels of Renin, Angiotensin II (AngII), Angiotensin-Converting-Enzyme2 (ACE2), Angiotensin1-7 (Ang1-7), E-selectin, Vascular-Cell-Adhesion-Molecule-1 (VCAM-1), Highly-sensitive-C-Reactive-Protein (hsCRP) and Interleukin-10 were measured at baseline (V1), after 1 week (V2) and 3 months (V3) of ACE inhibition in patients of diabetes with newly diagnosed hypertension. The amplitude of change after 1 week (V₂-V₁) and 3 months (V₃-V₁) for the clinical and various parameters were correlated with the change in endothelial function and arterial stiffness.

RESULTS

Carotid radial-PWV_V2-V1 (p = 0.001) and Ang1-7_V2-V1 (p = 0.01) emerged as independent predictors of FMD_V2-V1. Renin_V2-V1 and VCAM-1_V2-V1 independently predicted E-selectin_V2-V1 [(p = 0.01) and (p = 0.001), respectively]. ACE 2_V2-V1 was the only independent predictor of cf-PWV_V2-V1. The same parameters remained as independent predictors of the respective vascular factors after 3 months of ACE inhibition.

CONCLUSION

The study highlights the role of AngII/Ang1-7 balance in alteration of endothelial function and central arterial stiffness in humans in addition to identifying the interrelationship between the renin-angiotensin-aldosterone-system components and clinically ascertainable parameters.

Is There a Difference in Autonomic Dysfunction Between Multiple System Atrophy Subtypes?

Background

Autonomic dysfunction forms the diagnostic cornerstone in MSA. Data are limited on autonomic dysfunction differences between the two subtypes, MSA-C and MSA-P.

Objectives

To assess autonomic dysfunction in MSA subtypes and Parkinson's disease (PD) and compare it to healthy controls.

Methods

We conducted a cross-sectional study. A validated questionnaire (Scales for Outcomes in Parkinson's Disease-Autonomic Dysfunction; SCOPA-AUT) was used for symptom screening. Cardiovascular autonomic testing included deep breathing (change in heart rate, E: I ratio), Valsalva ratio, diastolic blood pressure (BP) rise (hand grip, cold pressor), and postural (tilt, 30:15 ratio) tests. Disease severity was assessed by the Unified MSA Rating Scale (UMSARS), H & Y stage, and International Parkinson and Movement Disorder Society Unified Parkinson's Disease Rating scale part III.

Results

MSA-P (48 subjects; age, 63.6 ± 9.7 years; UMSARS, 45.0 ± 16.5), MSA-C (52 subjects; age, 58.0 ± 8.1 years; UMSARS, 44.0 ± 12.8), PD (50 subjects; age, 57.6 ± 6.7 years), and healthy controls (50 subjects; age, 58.0 ± 8.0 years) were enrolled. MSA patients had higher SCOPA-AUT scores in gastrointestinal, urinary, cardiovascular, and sexual domains than controls and in gastrointestinal, urinary, and cardiovascular domains compared to PD. The two MSA subtypes did not differ in autonomic dysfunction. Heart-rate change on tilt and deep breathing, and diastolic BP rise on cold pressor test, differed significantly between MSA and PD patients.

Conclusions

Autonomic dysfunction symptomatology and cardiovascular autonomic tests were similar between MSA-P and MSA-C patients. Autonomic symptoms were more prominent in MSA than PD. Emphasis on these domains may improve likelihood of accurate clinical diagnosis of MSA at earlier stages.

Severe Cardiac Dysautonomia and Sudden Death in a Patient Presenting with Anginal Symptoms in Absence of Cardiovascular and Other Diseases: A Case Report

Angina is a type of chest pain, experienced by patients with ischemic heart diseases. Cardiac autonomic modulation as assessed by heart rate variability and baroreflex sensitivity is found reduced in ischemic heart disease patients. Marked reduction in heart rate variability and baroreflex sensitivity in ischemic heart disease patients is found associated with sudden cardiac death. We report a case of a 35-year-old man who presented with angina for the last few months. Thorough investigations showed no evidence of any cardiac or other systemic diseases. However, his cardiovascular autonomic modulation (as assessed by heart rate variability) and spontaneous baroreflex sensitivity were markedly reduced. The patient had sudden death within 6 months of follow-up. Reportedly, no other specific abnormalities were found before death. This case report suggests that patients presenting with typical chest pain as angina may have severe dysautonomia and risk of sudden death even in the absence of cardiovascular or any other known end-organ diseases.

Acute sleep deprivation elevates brain and body temperature in rats

Available sleep deprivation studies lack data on simultaneous changes in hypothalamic, cortical and body temperature during sleep deprivation and recovery. Ten adult male Wistar rats chronically implanted with electroencephalogram, electro-oculogram and electromyogram electrodes for recording sleep were used in this study. Hypothalamic and cortical temperatures were measured by pre-implanted thermocouples. A radio transmitter (TA10TAF-40, DSI USA) was implanted intraperitoneally to measure body temperature. All the temperatures were measured simultaneously at 15-s intervals during baseline conditions, sleep deprivation and recovery sleep. Sleep deprivation was carried out for 24 hr by the gentle handling method; however, sleep and temperature were only recorded during the first 12 hr of deprivation. During sleep deprivation the body, hypothalamic and cortical temperatures increased significantly as compared to baseline. During recovery sleep, body and cortical temperature recovered earlier than the hypothalamic temperature. Hypothalamic temperature remained higher than the baseline values throughout 12 hr of recovery sleep. In the recovery sleep, cortical temperature decreased immediately and reached near baseline by 4 hr. We observed a quicker return of cortical temperature towards control temperature during recovery sleep compared with hypothalamic and body temperature. The results of the present study show that acute sleep deprivation results in a rise in both cortical and hypothalamic temperature, along with body temperature. A rise in cortical temperature may be a contributing factor for cognitive dysfunction resulting from sleep deprivation.

Sequential analysis of heart rate variability, blood pressure variability and baroreflex sensitivity in healthy pregnancy

OBJECTIVE

The aim of this study was to demonstrate the temporal profile of changes in heart rate variability (HRV), blood pressure variability (BPV), and cardiac baroreflex sensitivity (BRS) during the course of a healthy pregnancy.

MATERIALS AND METHODS

This was a longitudinal study during which autonomic variability parameters (HRV, BPV, BRS) were assessed in 66 pregnant women at 11-13, 20-22 and 30-32 weeks of gestation. A lead II electrocardiogram tracing and beat-to-beat blood pressure were recorded with the subject breathing spontaneously in the supine position. Changes in the parameters were analyzed using repeated measures analysis of variance.

RESULTS

Overall HRV (SDNN; standard deviation of all NN intervals) was found to decrease significantly over the course of pregnancy (p < 0.05). Similarly, indices which represent the parasympathetic component of these variables (SDSD [standard deviation of differences between adjacent NN intervals]; pNN50 [NN50 count {number of pairs of adjacent NN intervals differing by more than 50 ms} divided by the total number of all NN intervals]; high-frequency [HF] power) were also found to decrease significantly from the first to third trimester of pregnancy (p < 0.05). Low-frequency (LF) power increased over the course of pregnancy (p < 0.05). The LF/HF ratio increased significantly from first to third trimester of pregnancy (median: 0.66 [first trimester] vs.1.02 [second] vs. 0.91 [third]; p < 0.05) Overall BPV increased during the course of pregnancy, with a significant rise in the HF component of BPV and a significant fall in the LF component of BPV with advancing gestation (p < 0.05). BRS decreased over the course of pregnancy (median: 16.31, interquartile range [IQR] 11.04-23.13 [first trimester] vs. 11.42, IQR 8.54-19.52 [second] vs. 8.84, IQR 7.15-12.45 [third] ms/mmHg; p < 0.05).

CONCLUSION

Pregnancy is associated with decreased vagal and increased sympathetic modulation of cardiac autonomic tone with advancing gestation, together with increased BPV. The reduction in cardiac BRS may play a role in increasing BPV and decreasing HRV over the course of pregnancy.

Imbalance between Angiotensin II - Angiotensin (1-7) system is associated with vascular endothelial dysfunction and inflammation in type 2 diabetes with newly diagnosed hypertension

AIM

Diabetes is associated with Renin-angiotensin-aldosterone-system (RAAS) activation. Protective role of Angiotensin (1-7) has been recently identified. The study aims to identify associations between imbalance in RAAS components with vascular endothelial dysfunction and inflammation in diabetics with newly diagnosed hypertension.

METHODS

Brachial Flow-mediated-dilation (FMD), Carotid Intima-media-thickness (CIMT), pulse-wave-velocity (PWV), Serum E-selectin, Vascular-Cell-Adhesion-Molecule-1 (VCAM-1), high-sensitivity C-Reactive Protein (hsCRP), Interleukin-10 (IL-10), Renin, AngiotensinII, Angiotensin-Converting-Enzyme 2 (ACE2) and Angiotensin1-7 were measured in 60 diabetic patients with newly diagnosed hypertension. Patients with AngiotensinII/Angiotensin1-7 ratio <1 were classified as Favourable-Axis (FA) group (n = 22) and those with ratio >1 were classified as Unfavourable-Axis (UA) group (n = 38).

RESULTS

hsCRP was higher [9.52 (4.64-16.19) vs 3.62 (1.77-13.09) (mg/l), p = 0.04], IL-10 was lower [2.26 (1.34-12.05) vs 10.98 (4.44-17.78) (pg/ml),p = 0.006], %FMD was lower [(5.51 ± 2.97) vs (7.66 ± 3.38) (%), p = 0.01] and CIMT was higher in UA compared to FA group [0.7 (0.55-0.79) vs 0.51 (0.49-0.65) (mm), p = 0.001]. Renin correlated positively with pressure, PWV, E-selectin and VCAM-1, opposing associations were obtained for Angiotensin1-7 and ACE2.

CONCLUSION

Imbalance between AngiotensinII - Angiotensin1-7 is associated with increased inflammation and vascular dysfunction in diabetics and can contribute to development of hypertension in these patients.

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.

Regional arterial stiffness in central and peripheral arteries is differentially related to endothelial dysfunction assessed by brachial flow-mediated dilation in metabolic syndrome

The interrelationship between endothelial function and arterial stiffness may be different for central and peripheral arteries due to their structural and functional differences. The study aims to assess the interrelationship between central and peripheral vascular function and haemodynamics in metabolic syndrome. Thirty-seven patients [63.0 (57.5-66.0) years, 68.4% males] of metabolic syndrome (National Cholesterol Education Program - Adult Treatment Panel-III criteria) were studied. Carotid-femoral, carotid-radial pulse wave velocity and augmentation index (AI_x@75) were assessed using applanation tonometry. Endothelial function was evaluated by brachial flow-mediated dilation using B-mode ultrasonography. Central and peripheral pressures were measured by radial tonometry and sphygmomanometer, respectively. Carotid-radial pulse wave velocity correlated significantly with peripheral diastolic blood pressure ( r = 0.33, p = 0.04) and inversely with flow-mediated dilation ( r = -0.61, p = 0.0001). AI_x@75 correlated significantly with carotid-femoral pulse wave velocity ( r = 0.35, p = 0.03) and with aortic pulse pressure ( r = 0.43, p = 0.01). In principal component analysis, an inverse relationship was observed between flow-mediated dilation and carotid-radial pulse wave velocity but not with carotid-femoral pulse wave velocity. Regional arterial stiffness assessed by pulse wave velocity in central-elastic and peripheral-muscular arteries differentially relates to endothelial dysfunction. The central arteries might be predominantly influenced by endothelial dysfunction-induced structural changes, while the peripheral arteries are majorly affected by functional alterations.

Reduced Baroreflex Sensitivity, Decreased Heart Rate Variability with Increased Arterial Stiffness in Predialysis

High cardiovascular morbidity and mortality is observed in predialytic chronic kidney disease (CKD) patients. The underlying mechanism of cardiovascular dysfunction often remains unclear. The present study was designed to perform multiparametric assessment of baroreflex sensitivity (BRS), arterial stiffness indices, and cardiovascular variabilities (heart rate variability [HRV] and blood pressure variability [BPV]) together in predialytic CKD patients; compare it with normal healthy controls; and determine their relationships in predialytic nondiabetic CKD patients. Thirty CKD Stage 4 and 5 predialytic non-diabetic patients and 30 healthy controls were enrolled in the study. BRS was determined by spontaneous sequence method. Short-term HRV and BPV were assessed using 5 min beat-to-beat data of RR intervals and blood pressure by time domain and frequency domain analysis. Arterial stiffness indices - carotid-femoral pulse wave velocity (PWV) and augmentation index - were measured using SphygmoCor Vx device (AtCor Medical, Australia). Predialytic CKD patients had significantly low BRS, high PWV, and low HRV as compared to healthy controls. Independent predictors of reduced systolic BRS in predialytic CKD patient group on multiple regression analysis emerged to be increase in calcium-phosphate product, increase in BPV, and decrease in HRV. Predialytic nondiabetic CKD Stage 4 and 5 patients have poor hemodynamic profile (higher PWV, lower HRV, and reduced BRS) than healthy controls. Reduced HRV and altered calcium-phosphate homeostasis emerged to be significant independent predictors of reduced BRS.

Decreased Spontaneous Baroreflex Sensitivity as an Early Marker for Progression of Haemorrhage

INTRODUCTION

Blood donation provides an ideal setup for assessment of cardiovascular responses to mild hypovolemia for understanding the underlying mechanisms.

AIM

To evaluate cardiovascular responses in time and magnitude by estimating the spontaneous baroreflex sensitivity (BRS) during and after donation of 450 ml of blood.

METHODS

Continuous beat-to-beat blood pressure and lead II ECG was recorded before, during and after blood donation in 54 healthy volunteers (age 34.7 ± 5.08 years; weight 77.9 ± 8.20 kg), followed by offline analyses of baroreflex sensitivity.

RESULTS

The systolic, diastolic or mean blood pressures did not change during or after the blood donation. Decrease in pulse pressure and increase in heart rate was observed post donation. The spontaneous BRS decreased during [8.68 (6.038-12.69) ms/mmHg] and after blood donation [9.401 (6.396-11.59) ms/mmHg] as compared to the baseline [12.83 (6.884-18.18) ms/mmHg] with a significant decrease in α-HF on spectral analysis.

CONCLUSION

Mild blood loss (450 ml) results in non-hypotensive haemorrhage with a decrease in spontaneous BRS before the rise of heart rate during blood donation.

Modulation of cardiac autonomic tone in non-hypotensive hypovolemia during blood donation

Non-hypotensive hypovolemia, observed during mild haemorrhage or blood donation leads to reflex readjustment of the cardiac autonomic tone. In the present study, the cardiac autonomic tone was quantified using heart rate and blood pressure variability during and after non-hypotensive hypovolemia of blood donation. 86 voluntary healthy male blood donors were recruited for the study (age 35 ± 9 years; weight 78 ± 12 kg; height 174 ± 6 cms). Continuous lead II ECG and beat-to-beat blood pressure was recorded before, during and after blood donation followed by offline time and frequency domain analysis of HRV and BPV. The overall heart rate variability (SDNN and total power) did not change during or after blood donation. However, there was a decrease in indices that represent the parasympathetic component (pNN50 %, SDSD and HF) while an increase was observed in sympathetic component (LF) along with an increase in sympathovagal balance (LF:HF ratio) during blood donation. These changes were sustained for the period immediately following blood donation. No fall of blood pressure was observed during the period of study. The blood pressure variability showed an increase in the SDNN, CoV and RMSSD time domain measures in the post donation period. These results suggest that mild hypovolemia produced by blood donation is non-hypotensive but is associated with significant changes in the autonomic tone. The increased blood pressure variability and heart rate changes that are seen only in the later part of donation period could be because of the progressive hypovolemia associated parasympathetic withdrawal and sympathetic activation that manifest during the course of blood donation.

Impaired systemic vascular reactivity & raised high-sensitivity C reactive protein levels in chronic obstructive pulmonary disease

BACKGROUND & OBJECTIVES

Chronic obstructive pulmonary disease (COPD) is characterized by slowly progressive airflow limitaion, chronic lung inflammation and associated systemic manifestations. The objective of this preliminary study was to investigate the levels of high sensitivity C reactive protein (hs CRP) and tumour necrosis factor-α (TNF-α) as markers of systemic inflammation and assessment of systemic vascular reactivity that may play an important role in development of cardiovascular disease in COPD patients.

METHODS

Systemic vascular reactivity was assessed non-invasively by measuring peripheral pulse waveform changes during reactive hyperemia (RH) in 16 COPD patients and 14 controls by photoplethysmography technique (PPG). Parameters measured were pulse wave amplitude (PWA), slope and pulse transit time (PTT). Tumour necrosis factor-α (TNF-α) and hs CRP were measured as markers of inflammation.

RESULTS

PWA during the 1 st , 2 nd and 3 rd minutes post release of occlusion were significantly higher than the baseline means in controls, whereas in the patient group there was no significant change in the PWA during any of the observed time periods following release of occlusion, in comparison to the baseline means. Similar results were observed in slope values for patients and controls. Maximum percentage change in PWA during RH with reference to baseline was significantly lower in patients as compared to controls (26.78±20.19 vs 57.20±19.80%, p<0.001). Maximum percentage change in slope during RH with reference to baseline was significantly lower in patients as compared to controls (19.77±10.73 vs 39.25±13.49%, P<0.001). A vascular tone response as represented by PTT was also impaired in the 3 rd minute of RH as compared to baseline mean values in COPD patients only.

INTERPRETATION & CONCLUSIONS

Our findings showed raised hs CRP levels and impaired systemic vascular reactivity in COPD patients. Whether these may increase the risk of cardiovascular disease in COPD patients need to be confirmed in future studies with large sample size and appropriate study design.

Description and Validation of a Novel Method of Measuring Pharyngeal Pressure in New-born

Study background: Measurement of delivered pharyngeal pressure during continuous positive airway pressure (CPAP) therapy is not in routine practice due to lack of a simple and affordable technique of intrapharyngeal pressure measurement. To overcome the lack of the gold standard solid-state catheter-tip pressure measurement technology in our set up, we improvised a novel method of pressure measurement and tested its validity in a simulated pharynx.

METHODS

A low-cost pressure transducer was improvised by attaching an orogastric tube to its one end. The other end of the orogastric tube was sealed into an artificial pharynx - a 20 ml syringe. The pressure transducer readings were compared with that obtained by a digital manometer attached to the tip of the syringe. Bland-Altman statistic was used to quantify the measurement reliability of the novel method against the digital manometer. Effect of tube length on the measurement agreement was also studied. The developed technique was applied in new-borns.

RESULTS & CONCLUSION

Pressures measured by this technique were in good agreement with that obtained using a digital manometer. This technique has the potential to be used as an alternative to catheter-tip pressure transducers for bedside pharyngeal pressure measurement in new-born babies, especially in under-resourced setups.

Cardiovagal Baroreflex Sensitivity in Parkinson's Disease and Multiple-System Atrophy

Background and Purpose

Parkinson's disease (PD) and multiple-system atrophy of the parkinsonian type (MSA-P) are progressive neurodegenerative disorders that in addition to dysfunction of the motor system also present with features of dysautonomia, frequently manifesting as orthostatic hypotension (OH). The pathophysiology of OH has been proposed to differ between these two disorders. This study investigated the spontaneous and cardiovagal baroreflex sensitivity (BRS) in Parkinson's disease patients with orthostatic hypotension (PD_OH) and multiple system atrophy of Parkinsonian type with orthostatic hypotension in an attempt to differentiate the two disorders.

Methods

Two methods were used for determining the BRS: a spontaneous method (spontaneous BRS) and the reflexive baroreflex gain (cardiovagal BRS) from phases II and IV of the Valsalva maneuver (VM) in PD_OH and MSA-P_OH.

Results

The spontaneous BRS (5.04±0.66 ms/mm Hg vs. 4.78±0.64 ms/mm Hg, p=0.54) and the cardiovagal BRS from phase II of the VM (0.96±0.75 ms/mm Hg vs. 1.34±1.51 ms/mm Hg, p=0.76) did not differ between PD_OH and MSA-P_OH, but the cardiovagal BRS from phase IV of the VM (0.03±0.07 ms/mm Hg vs. 2.86±2.39 ms/mm Hg, p=0.004) was significantly lower in PD_OH.

Conclusions

The cardiovagal BRS from phase IV of the VM has potential for differentiating PD_OH and MSA-P_OH, indicating a difference in the pathophysiological mechanisms underlying the autonomic dysfunction in the two disorders.

Baroreflex dysfunction in chronic kidney disease

Chronic kidney disease (CKD) patients have high cardiovascular mortality and morbidity. The presence of traditional and CKD related risk factors results in exaggerated vascular calcification in these patients. Vascular calcification is associated with reduced large arterial compliance and thus impaired baroreflex sensitivity (BRS) resulting in augmented blood pressure (BP) variability and hampered BP regulation. Baroreflex plays a vital role in short term regulation of BP. This review discusses the normal baroreflex physiology, methods to assess baroreflex function, its determinants along with the prognostic significance of assessing BRS in CKD patients, available literature on BRS in CKD patients and the probable patho-physiology of baroreflex dysfunction in CKD.

Waist Circumference Rather than Body Mass Index is Better Indicator of Insulin Resistance in Type 2 Diabetes Mellitus in North Indian Population

Obesity and insulin resistance (IR) are associated with type 2 diabetes mellitus (DM). Obesity can be quantified by body mass index (BMI) and waist circumference (WC). Similarly, IR is commonly quantified by fasting-plasma-insulin (FPI) and Homeostatic model assessment (HOMA-IR). We aimed our study to find correlation between obesity-parameters and IR especially in the Indian population where despite lower BMI there is more prevalence of type 2 DM. In 34 uncomplicated patients of type 2 DM weight and WC were measured and BMI was calculated. HOMA-IR and FPI level were estimated to assess IR. Significant correlation was found between HOMA-IR and WC (r = +0.368, P = 0.0324) but it was non-significant between HOMAIR and BMI. Correlations were also not significant between FPI and WC or BMI. In conclusion, HOMA-IR and WC are better measures of IR and obesity as compared to FPI and BMI, respectively in type 2 DM.

Correlations between endothelial function in the systemic and cerebral circulation and insulin resistance in type 2 diabetes mellitus

Insulin resistance is associated with endothelial dysfunction in type 2 diabetes mellitus, which can lead to impaired vascular reactivities of both systemic and cerebral circulations. Appropriate 'correction' of vascular reactivity results for non-endothelium-dependent systemic effects avoids misinterpretation of endothelial function. Therefore, we 'corrected' vascular reactivity results and explored the potential correlations between systemic vascular reactivity, cerebrovascular reactivity and insulin resistance. In 34 patients, 'systemic vascular reactivity' was assessed by quantifying reactive hyperaemia. Cerebrovascular reactivity was assessed by quantifying changes in cerebral blood flow velocity during hypercapnia. To minimize the influence of non-endothelium-dependent systemic effects on vascular reactivity results, 'corrected systemic vascular reactivity' was calculated by normalizing systemic vascular reactivity using the measurements from the contralateral side; and cerebrovascular reactivity results were corrected by calculating percentage and absolute changes in cerebrovascular conductance index ('percent cerebrovascular conductance index' and 'delta cerebrovascular conductance index', respectively). Insulin resistance was estimated by homeostatic model assessment. Correlation between conventional cerebrovascular reactivity and systemic vascular reactivity was not significant. But correlations between 'corrected systemic vascular reactivity' and 'percent cerebrovascular conductance index' (r = 0.51; p = 0.002) and 'corrected systemic vascular reactivity' and 'delta cerebrovascular conductance index' (r = 0.50; p = 0.003) were significant. Among all vascular reactivity parameters, only 'delta cerebrovascular conductance index' was significantly correlated with homeostatic model assessment of insulin resistance (r = -0.38; p = 0.029). In conclusion, endothelial function in the systemic and cerebral circulations is moderately correlated, provided that vascular reactivity estimates are corrected for non-endothelium-dependent influences.

Correction for blood pressure improves correlation between cerebrovascular reactivity assessed by breath holding and 6% CO(2) breathing

BACKGROUND

Changes in cerebral blood flow velocity to hypercapnia are associated with changes in systemic blood pressure (BP). These confounding BP-dependent changes in cerebral blood flow velocity cause misinterpretation of cerebrovascular reactivity (CVR) results. The objective of the study was to determine the relationship between CVR assessed by breath holding and 6% CO2 breathing after correcting for BP-dependent changes in cerebral blood flow velocity.

METHODS

In 33 patients of uncomplicated type 2 diabetes mellitus, CVR was assessed as percentage changes in cerebral blood flow velocity and cerebrovascular conductance index.

RESULTS

Percentage change in cerebral blood flow velocity during breath holding was positively correlated with that of during 6% CO2 breathing (r = .35; P = .0448). CVR during breath holding and 6% CO2 breathing were better correlated when expressed as percentage changes in cerebrovascular conductance index (r = .49; P = .0040). Similarly, breath-holding test results expressed as percentage changes in cerebral blood flow velocity correctly identified only 37.5% of the poor reactors to 6% CO2 breathing. However, when the breath-holding test results were expressed as percentage changes in cerebrovascular conductance index, 62.5% of the poor reactors to 6% CO2 breathing were correctly identified indicating a better agreement between the test results obtained by the 2 methods.

CONCLUSION

Cerebrovascular response to breath holding is better correlated with that of 6% CO2 breathing when changes in cerebral blood flow velocity were corrected for associated changes in BP.

Renal transplantation normalizes baroreflex sensitivity through improvement in central arterial stiffness

BACKGROUND

In end-stage renal disease (ESRD) patients, the most common cause of mortality and morbidity are cardiovascular events. This could be attributed to the impaired baroreflex function observed in this group of patients. The effect of renal transplantation (RT) on the baroreflex sensitivity (BRS) in ESRD patients has been inadequately addressed. Therefore, we investigated baroreflex function and its relation to arterial stiffness indices and cardiovascular variability parameters (heart rate and blood pressure variability--HRV and BPV) in ESRD patients before and after transplantation to decipher the underlying mechanism of attenuated BRS in ESRD patients.

METHODS

We studied 23 ESRD patients (mean age; 36 years) prospectively before and at 3 and 6 months after RT. Baroreflex function was determined by spontaneous method (sequence and spectral indices). Short-term HRV and BPV were assessed using power spectrum analysis of RR intervals and systolic blood pressure by frequency domain analysis. Arterial stiffness indices were assessed by carotid-femoral pulse-wave velocity (PWV), augmentation index (AI) and central pulse pressure using Sphygmocor Vx device (AtCor Medical, Australia).

RESULTS

RT was associated with the normalization of BRS by 6 months. Arterial stiffness indices, such as AI and central pulse pressure, showed a significant reduction as early as 3 months after RT. PWV and frequency domain measures of HRV after RT did not show statistically significant changes except the LF/HF ratio which had a significant increase at 6 months when compared with baseline. Systolic BPV total power showed a significant reduction by 3 months after RT.

CONCLUSIONS

Our data suggest that RT normalizes BRS in ESRD patients by 6 months which follows the improvement in the AI and central pulse pressure.

Decreased autonomic modulation of heart rate and altered cardiac sympathovagal balance in patients with Cushing's syndrome: role of endogenous hypercortisolism

BACKGROUND/AIMS

Endogenous Cushing's syndrome is associated with a higher risk of cardiovascular morbidity and mortality. Previous literature suggested multiple possible links by which hypercortisolism may alter the autonomic control of cardiovascular functions. We investigated the impact of chronic endogenous hypercortisolism on the autonomic regulation of cardiac functions by short-term heart rate variability analysis.

METHODS

Eighteen patients with endogenous Cushing's syndrome and 20 age-, gender- and BMI-matched controls participated in the study. ECG signal was acquired in lead II configuration for 5 min and heart rate variability assessment was made in both time and frequency domain using the extracted RR interval data.

RESULTS

All time and frequency domain measures of heart rate variability were significantly (p < 0.05) lower in the patient group compared to the control group. The patient group had an altered sympathovagal balance with low frequency/high frequency band ratio significantly higher than the control group [1.857 (0.6747-2.610) vs. 0.8581 (0.4779-1.352); p = 0.0253]. A significant negative correlation was obtained between normalized high frequency power of heart rate variability and basal cortisol levels (r = -0.6594; p = 0.0029). Multiple linear regression analysis identified age, disease duration (in months), basal cortisol levels and systolic blood pressure as independent predictors of normalized high frequency power.

CONCLUSION

Findings of the study clearly portrayed the diminished autonomic modulation of heart rate in endogenous Cushing's syndrome and its possible relationship with hypercortisolism as the main causative factor. Diminished heart rate variability may be an indicator of the increased risk of cardiac mortality in these patients.

Reduction in augmentation index after successful renal transplantation

BACKGROUND

Patients of end stage renal disease (ESRD) have an increased risk of cardiovascular events. Arterial stiffness is an established independent predictor of cardiovascular morbidity and mortality in ESRD patients. Carotid femoral pulse wave velocity (c-f PWV) and augmentation index (AI) are the indices which are used for the noninvasive assessment of arterial stiffness. Renal transplantation (RT) as a treatment modality in ESRD patients is associated with improvement in cardiovascular survival. Whether this improvement is due to attenuation of arterial stiffness has been inadequately investigated. The present study was conducted in ESRD patients before and 3 months after RT to assess the reversibility of the abnormalities of vascular compliance that are known to be associated with adverse outcome.

METHODS

Arterial stiffness indices (c-f PWV and AI) were measured using the principle of applanation tonometry with a SphygmoCor CvMS system (Atcor Medicals, Australia) in 23 ESRD patients (age: 35.9 ± 9.3 years) before and 3 months after successful RT.

RESULTS

After transplantation, augmentation index values reduced significantly as compared to their pre-transplant values (27.7 ± 11.3 % vs. 17.1 ± 9.0 %; P < 0.0001), while the carotid femoral pulse wave velocity values did not differ significantly (8.7 ± 2.0 vs. 8.6 ± 3.2 m/s). The augmentation index was correlated with the biochemical parameters of serum creatinine (Pearson r = 0.3628; P = 0.0128) and calcium phosphate product (Pearson r = 0.3868; P = 0.0079).

CONCLUSIONS

Restoration of renal function following successful RT is associated with differential effects on the two indices of arterial stiffness. The salient finding of our study is that 3 months after transplantation, functional changes in vasculature lead to a significant reduction in the augmentation index, while the pulse wave velocity may take longer to show an improvement.

Validity of heart rate based nomogram fors estimation of maximum oxygen uptake in Indian population

Maximal oxygen uptake (VO2max) during a graded maximal exercise test is the objective method to assess cardiorespiratory fitness. Maximal oxygen uptake testing is limited to only a few laboratories as it requires trained personnel and strenuous effort by the subject. At the population level, submaximal tests have been developed to derive VO2max indirectly based on heart rate based nomograms or it can be calculated using anthropometric measures. These heart rate based predicted standards have been developed for western population and are used routinely to predict VO2max in Indian population. In the present study VO2max was directly measured by maximal exercise test using a bicycle ergometer and was compared with VO2max derived by recovery heart rate in Queen's College step test (QCST) (PVO2max I) and with VO2max derived from Wasserman equation based on anthropometric parameters and age (PVO2max II) in a well defined age group of healthy male adults from New Delhi. The values of directly measured VO2max showed no significant correlation either with the estimated VO2max with QCST or with VO2max predicted by Wasserman equation. Bland and Altman method of approach for limit of agreement between VO2max and PVO2max I or PVO2max II revealed that the limits of agreement between directly measured VO2max and PVO2max I or PVO2max II was large indicating inapplicability of prediction equations of western population in the population under study. Thus it is evident that there is an urgent need to develop nomogram for Indian population, may be even for different ethnic sub-population in the country.

Cardiovascular autonomic functions & cerebral autoregulation in patients with orthostatic hypotension

BACKGROUND & OBJECTIVES

Patients of orthostatic hypotension may or may not have symptoms of the cerebral hypoperfusion despite fall in the blood pressure. The present study was done to quantify autonomic functions and cerebral autoregulation in patients of orthostatic hypotension with or without symptoms.

METHODS

The study was conducted in 15 patients of orthostatic hypotension and 15 age, sex matched control subjects. The sympathetic reactivity was measured by diastolic blood pressure response to handgrip test (ΔDBP in HGT) and cold pressor test (ΔDBP in CPT). The parasympathetic reactivity was measured by E:I ratio during deep breathing test (DBT) and Valsalva ratio (VR) during Valsalva maneuver. The cerebral autoregulation was computed from the changes in the cerebral blood flow, cerebrovascular conductance and blood pressure measured during different time points during head-up tilt (HUT).

RESULTS

The sympathetic reactivity was lower in patients as compared to controls [ΔDBP in HGT: 10 (4 - 16) vs 18 (12 - 22) mmHg, P<0.01; ΔDBP in CPT : 10 (4-12) vs 16 (10-20) mmHg, P<0.01]. The parasympathetic reactivity was also lower in patients as compared to controls. The sympathetic and parasympathetic reactivity was comparable in the symptomatic and asymptomatic patients. The maximum fall in blood pressure during HUT was comparable between symptomatic and asymptomatic patients (29.14 ± 10.94 vs 29.50 ± 6.39 mmHg), however, the percentage fall in the cerebral blood flow was significantly higher in the symptomatic (P<0.05) compared to asymptomatics.

INTERPRETATION & CONCLUSIONS

Patients with orthostatic hypotension had deficits in sympathetic and parasympathetic control of cardiovascular system. Cerebral autoregulation was present in asymptomatic patients (increase in cerebrovascular conductance) during HUT while it was lost in symptomatic patients.

Pattern and prevalence of cardiovascular autonomic neuropathy in diabetics visiting a tertiary care referral center in India

The cardiovascular autonomic neuropathy (CAN) is a known complication of long standing diabetes. In the present study, the prevalence of sympathetic and parasympathetic abnormalities in diabetic patients was evaluated on retrospective analysis of standard tests done for the assessment of CAN. Three different scoring systems were utilized for assessment of CAN namely, Ewing's crtieria, Bellavere's criteria and the criteria followed at the Autonomic Function Test laboratory. All the three criteria use different set of tests for classification. A total of 124 patients' laboratory data was analysed. The abnormality of single test ranged from 6.49% in Valsalva Maneuver to 47.41% in cold pressor test. When Bellavere's criteria was used only 53 patients had evidence of CAN while Ewing's criteria revealed that 100 patients had CAN however 69 of these patients could not be categorized. The criteria used by AFT laboratory revealed that isolated sympathetic (49 patients) and paraysmpathetic (10 patients) abnormality can be seen in CAN along with those with combined deficits (42 patients). If the Bellavere's criteria is used then patients with dominant sympathetic neuropathy are likely to be missed during testing. High prevalence of CAN in tertiary care referral centre suggests that the testing of autonomic functions in diabetics should be done routinely. It is recommended that full battery of test to evaluate both the arms of autonomic drive namely sympathetic and parasympathetic should be done and reported as such.

Impaired endothelium mediated vascular reactivity in endogenous Cushing's syndrome

Endogenous Cushing's syndrome (CS) is associated with a high incidence of cardiovascular morbidity and mortality resulting from the co-existence of multiple cardiovascular risk factors which probably induce a state of endothelial dysfunction. Recently, studies conducted in vitro as well as in normal human subjects suggest a direct role of cortisol in the causation of vascular dysfunction in this disorder. We non-invasively assessed the vascular reactivity and its potential association with elevated cortisol levels in patients of CS. A single time point observational study was conducted in 18 patients of CS and 15 age and gender matched healthy subjects. Vascular reactivity was assessed non-invasively by measuring the peripheral pulse wave form changes during reactive hyperemia (RH) using digital photoplethysmography (PPG). Parameters measured were pulse wave form amplitude (PWA), slope and pulse transit time (PTT). Maximal percentage changes in PWA during RH with reference to baseline were significantly lower in the patients as compared to controls [23.19% (13.19-53.54) vs 61.71% (38.21-95.36); p=0.0079]. Normalized PTT responses during the 1(st) minute of RH were blunted in the patients as compared to controls (1.036 ± 0.026 vs 1.056 ± 0.029; p=0.0425). Percentage changes in PTT during the 2(nd) minute of RH were negatively correlated to the morning cortisol levels in patients (r = -0.6328; p=0.0064). The present study showed that endothelium mediated vascular reactivity along with myogenic regulation of vascular tone is impaired in CS. Hypercortisolism possibly plays an important role in the causation of impaired vascular reactivity and endothelial dysfunction in CS.

Heart rate variability and autonomic function tests in HIV positive individuals in India

Supine heart rate variability (HRV) and autonomic tests were carried to determine whether autonomic activity was affected in HIV positive patients. The pressor response following handgrip and cold pressor test was blunted in HIV+ patients, and the degree of dysfunction correlated with CD4 cell counts. The extent of autonomic impairment was mild and subclinical.

Effect of Chyawanprash and vitamin C on glucose tolerance and lipoprotein profile

Chyawanprash is an ancient Indian dietary supplement containing vitamin C (34 mg/100 g) derived from amla (Emblica officinalis). In addition, Chyawanprash also contains several other herbal products. The present study was designed to compare the effects of vitamin C with those of Chyawanprash. Ten normal healthy adult male volunteers (age 20-32 years) participated in the 16-week study. They were placed randomly in either the Chyawanprash group (n = 5) or vitamin C group (n = 5). Those in the former received 15 g/d of Chyawanprash while those in the latter received 500 mg/d vitamin C during the first 8 weeks of the study. For the next 8 weeks, no supplement was given. For each individual, an oral glucose tolerance test was performed, and lipoprotein profile in peripheral serum samples was determined at 0 weeks, 4 weeks, 8 weeks, 12 weeks and 16 weeks. In the Chyawanprash group, the 8 weeks Vs 0 weeks value (mean +/- S.D.) respectively for various indices which were significantly different were fasting plasma glucose (100.2 +/- 5.58 mg/dl vs 116.2 +/- 11.6 mg/dl), area under 2-h plasma glucose curve (245.9 +/- 15.13 mg.dl-1.h vs 280.8 +/- 37.09 mg.dl-1.h), HDL cholesterol (53.2 +/- 4.56 mg/dl vs 42.7 +/- 7.17 mg/dl), LDL cholesterol (82.4 +/- 8.80 mg/dl vs 98.26 +/- 12.07 mg/dl), LDL/HDL ratio (1.56 +/- 0.28 vs 2.38 +/- 0.63). In the Vitamin C group, only the LDL/HDL ratio was significantly lower at 8 weeks than at 0 weeks (1.99 +/- 0.44 vs 2.29 +/- 0.43). All the variables that changed significantly were no longer significantly different from the 0 weeks value at 16 weeks. Chyawanprash reduces postprandial glycemia in the oral glucose tolerance test and reduces blood cholesterol level to a significantly greater extent than vitamin C.