Heart Rate Variability in Hyperthyroidism

Abstract

Background: Hyperthyroidism is associated with altered cardiac autonomic nervous activity (CANA). Heart Rate Variability (HRV) analysis is a promising technique to quantify CANA and therefore can be done in hyperthyroidism. Objective: To observe the HRV parameters in patients with hyperthyroidism to find out the influence of excess thyroid hormone on cardiac autonomic nervous activities. Method: The cross sectional study was carried out on 60 hyperthyroid patients (groupB)aged 30-50 years in the Department of Physiology, BSMMU, Dhaka from 1 st July 2007 to 30 th June 2008. Age and sex matched 20 apparently healthy euthyroids were also studied for comparison (group A). On the basis of treatment, they were further divided into group B 1 consisting of 30 untreated newly diagnosed patients and group B 2 consisting of 30 hyperthyroid patients treated with antithyroid drugs for at least 2 months. The patients were selected from the Out Patient Department of Endocrinology, BSMMU, Dhaka. To assess thyroid status, serum TSH and serum FT 4 levels were measured by AxSym system and time domain measures of HRV such as mean R-R interval, mean heart rate, SDNN and RMSSD were assessed from 5minute(short term) ECG recording by a polygraph. For statistical analysis Mann-Whitney U test was done. Results: Mean R-R interval was significantly (P<0.001) lower but mean heart rate was significantly (P<0.001) higher in untreated patients than those of treated and euthyroids subjects. These values were found almost similar when compared between euthyroids and treated hyperthyroids. Similarly SDNN and RMSSD were significantly lower in untreated hyperthyroids than both euthyroids (P<0.001) and treated hyperthyroids (P<0.01). Conclusion: This study concluded that decreased vagal modulation on heart rate may occur in hyperthyroidism, which may be restored following adequate treatment of the disease.

Power Spectral Analysis of Heart Rate Variability in Female Rheumatoid Arthritis Patients

“…11,12,14,15 and also from our country. [19][20][21] In this study, significantly higher resting pulse rate, diastolic blood pressure points comparatively higher sympathetic activity in RA which are similar to those findings reported by some researchers. 22 Again, findings of Total power, HF and HF norm suggest lower parasympathetic activity and higher value of LF, LF norm and LF/HF indicate higher sympathetic activity in RA patients which are similar to those reported by some investigators of different countries.…”

Power Spectral Analysis of Heart Rate Variability in Hypertensive Male

“…But these values showed no statistically significant difference between healthy normotensive and treated hypertensive groups. Similar type of findings was also reported by the various investigators from different countries 4,11,14,15,18 .…”

“…However, no significant difference was observed between two groups of hypertensive patients. Similar findings were also reported by different researchers of various countries 8,[12][13][14][15][16][17][18]22 The LF norm and LF/HF ratio were significantly higher and HF norm power was significantly lower both in both groups of hypertensive than those of healthy control. Again, untreateded hypertensive patients had significantly higher values of LF norm and LF/HF ratio and significantly lower HF norm than those of treated groups.…”

“…In the present study, values of HRV parameters in healthy control group were almost similar to those reported by the various investigators from different countries 12,14,15,18 and also from our country [19][20][21] In this study, the mean resting pulse rate and blood pressure was significantly higher in untreated hypertensive patients in comparison to those of healthy normotensive and treated hypertensive groups. But these values showed no statistically significant difference between healthy normotensive and treated hypertensive groups.…”

“…10,14,18,2 Essential hypertension is commonly neurogenic and attributed to sympathetic overdrive and may be associated with parasympathetic inhibition. 5,25 It has also been suggested that increased rate of sympathetic nerve firing and also increase in density of sympathetic innervations might cause sympathetic over activity in hypertensive patients.…”