ABSTRACT
Background: Essential hypertension is associated with altered cardiovascular autonomic nerve function. Heart Rate Variability (HRV) analysis is an important tool for quantitative measurement of autonomic nerve activity. Objective: To assess the cardiac autonomic nerve function status in essential hypertension by analyzing power spectral measures of heart rate variability. Methods: This cross sectional study was carried out in the Department of Physiology, Bangabandhu Sheikh Mujib Medical University between July 2008 and June 2009. Sixty male hypertensive patients with age range 40-60 years (group B) were enrolled from the Out Patient Department of Cardiology,BSMMU, Dhaka. Thirty age and sex matched apparently healthy normotensive subjects (group A) were studied as control, Hypertensive patients were further divided into group B1 consisting of 30 untreated patients on their 1st day of diagnosis and group B2 consisting of 30 patients under antihypertensive therapy. Power Spectral measures of Heart Rate Variability (HRV) such as total power, low frequency (LF) and high frequency power(HF) LH/HF ratio were assessed by a digital Polygraph. For statistical analysis , Independent sample t-test, One-way ANOVA test and Pearson’s correlation coefficient test were done as applicable. Results: Mean TP,LF,HF and HF norm was significantly (p<0.001) lower and LF/HF ratio and LF norm were significantly (p<0.001) higher in both untreated and treated hypertensive patients compared to those of normotensive subjects. Again, significant differences of LF norm and HF norm and LF/HF ratio were found between the two hypertensive groups. The LF/HF ratio and LF norm were positively and HF norm was negatively correlated with SBP and DBP in both the hypertensive groups. However, all these findings were more marked in untreated hypertensive patients than those of treated group. Conclusion: Sympathovagal balance in hypertensive patients is towards higher sympathetic and lower vagal modulation and effective treatment of the patients can return the balance towards normal.
ABSTRACT
Background: The main cause for most of the old age complication is due to derangement of cardiovascular and autonomic nervous activity. This study was proposed to record and asses the HRV in elderly population involved with respect to Body mass index to predict and prevent further deterioration and thereby help the elder to lead more normal, healthy and active life. Materials& methods: 80 normal volunteers were selected, with ages between 55 to 85 years. They were evaluated clinically for Heart rate variability (HRV) and body mass index. Based on BMI, subjects were divided in to two groups. Group I with 40 subjects whose BMI was ≤25 and group II with 40 subjects whose BMI was 25 to 30. To assess the autonomic changes, in this study different parameters of HRV were recorded in both the groups and compared during normal (N), deep breathing (DB) and cold pressor test (CPT) conditions. Results showed that the SDANN, Time domain HRV was more in subjects with high BMI when compared to subjects with normal BMI during normal condition, in CPT condition parasympathetic activity was more in subjects with high BMI compared to subjects with normal BMI. Conclusion; This study showed in old age higher the BMI more the HRV and the degree of parasympathetic activity was more in higher BMI.
ABSTRACT
The early prediction of pregnancy-induced hypertension (PIH) is based on the demonstration of increased sympathetic activity in early part of pregnancy. However, the mechanisms that increase sympathetic activity in PIH have not yet been fully elucidated. Therefore, in the present study we have investigated the link of albumin-globulin ratio (AGR) to sympathovagal imbalance in PIH patients. Spectral analysis of HRV was performed in three groups of subjects (Group I: normal pregnant women; Group II: pregnant women with risk factors for PIH, but did not develop PIH; Group III: pregnant women with risk factors and developed PIH) and their biochemical parameters including AGR were recorded. It was observed that LF-HF ratio, the most sensitive indicator of sympathovagal balance was significantly high (P<0.01) since early pregnancy in group III compared to other groups, which was considerably correlated with AGR in group III (PIH subjects). It was suggested that alteration in AGR could have direct contribution to the sympathovagal imbalance that plays a critical role in the genesis of PIH.
ABSTRACT
The aim of the study was to investigate the role of spectral analysis of heart rate variability (HRV) for assessing the type and degree of sympathovagal imbalance (SVI) and their link to cardiovascular morbidities in thyroid dysfunctions. Forty-five female subjects (15 control subjects and freshly diagnosed untreated 15 hypothyroid and 15 hyperthyroid patients) were recruited for the study. Thyroid profile, body mass index (BMI), basal heart rate (BHR), blood pressure (BP) and spectral indices of HRV (TP, LFnu, HFnu and LF-HF ratio, mean RR, SDNN and RMSSD) were assessed in all the three groups. LF-HF ratio was correlated with thyroid profile, BMI, BHR and BP. SVI was more prominent in hyperthyroid (P<0.001) compared to hypothyroid (P<0.05) subjects. LF-HF ratio was correlated with thyroid profile in both hypo and hyperthyroid subjects; but correlation with BHR and BP was significant only in hyperthyroidism. Though the SVI was found to be due to both vagal withdrawal and sympathetic activation, especially in hyperthyroidism, contribution by vagal inhibition was prominent. Vagal inhibition contributes significantly to SVI in thyroid dysfunctions, especially in hyperthyroidism. As the present study indicates poor cardiovascular health due to vagal inhibition in patients suffering from thyroid dysfunctions, attempt should be made to improve vagal tone especially in hyperthyroid subjects to attain a stable sympathovagal and cardiovascular homeostasis.
ABSTRACT
OBJECTIVES: Power spectrum analysis decomposes the heart rate signal into its frequency components and facilitates separation of sympathetic (low frequency) and parasympathetic (high frequency) activity. In congestive heart failure, augmented sympathetic tone and decreased parasympathetic tone were found. Autonomic nervous system was normalized 6 months after myocardial infarction. So we compared the autonomic nervous system activity by the heart rate variability in congestive heart failure and old myocardial infarction. METHODS: The protocol involved 20 healthy subjects (Group 1), 5 congestive heart failure patients not caused by myocardial infarction (Group 2), 4 congestive heart failure patients due to myocardial infarction and 11 old myocardial infarction patients without heart failure. We took 24 hour Holter monitoring by Del Mar Avionic tape recorder. All Holter tapes were analyzed with use of Model 563 Stratascan Holter Analysis System. We computed power spectra on each 256 sec segment of each hour during 24 hour recording. So, RR interval, SD of RR interval by time domain, and LF, HF, LF/HF ratio, Total PSD by frequency domain were measured. RESULTS: In congestive heart failure, nocturnal HF peak and diurnal variation of LF/HF ratio was decreased relative to healthy subjects. Nocturnal HF peak in old myocardial infarction was not visualized. All of LF, HF and Total PSD in congestive heart failure and old myocardial infarction patients relative to healthy subjects. CONCLUSION: On heart rate variability analysis using by 24 hour Holter monitoring, abnormal autonomic nervous activity was demonstrated in congestive heart failure and old myocardial infarction patients relative to healthy subjects.