ABSTRACT
Background: Cardiovascular complications are common in hypothyroids .Time domain measures of HRV is useful to determine the cardiac autonomic regulation by assessing sympathovagal balance. Objective: To assess the cardiac autonomic nerve function activity by time domain measures of heart rate variability in patients with hypothyroidism. Methods: This cross sectional study was carried out in the Department of Physiology, Banghabandhu Sheikh Mujib Medical University between July 2008 to June 2009 on 60 female patients with hypothyroidism aged 30-50 years. 30 age matched apparently healthy euthyroid subjects were also studied as control. Hypothyroid patients were divided into 2 subgroups ,one group includes patients on their 1st day of diagnosis, before starting of treatment and another group includes patients with medication for 12-18 months. The patients were selected from the Out Patients Department of Endocrinology Wing BSMMU. Serum TSH and FT4 levels of all subjects were measured by AxSYM system. For assessing HRV by time domain method, mean R-R interval, mean heart rate, SDNN, RMSSD and variance were measured by a Polyrite. For statistical analysis, Independent Sample t test and One Way ANOVA were used. Results: The mean serum TSH was significantly higher and FT4 was significantly lower (p<0.001) in newly diagnosed hypothyroids than those of control and treated group. In untreated hypothyroid patients the mean values of heart rate, SDNN , RMSSD,variance were found significantly (p<0.001) lower in comparison to both control and treated patients. No significant difference in these hormonal levels and all these time domain measures were found between control and treated group. Conclusion: This study concludes that decrease parasympathetic nerve activity may be a consequence of hypothyroidism, if not treated properly.
ABSTRACT
Background: Hypothyroidism is one of the common clinical problems with high incidence in women particularly in older age. It has profound effect on metabolic processes in almost all tissue of the body and heart is particularly sensitive to thyroid hormone action. Power spectral analysis (PSA)is useful to determine the cardiac autonomic regulation by assessing sympathovagal balance. Objectives: To assess the cardiac autonomic nervous activity by power spectral analysis of heart rate variability in patients with hypothyroidism.Method: This cross sectional study was carried out in the Department of Physiology, Banghabandhu Sheikh Mujib Medical University from 1st July 2008 to 30th June 2009 on 60 female patients of 30-50 years with hypothyroidism (group B). For comparison, 30 age sex matched apparently healthy euthyroid subjects (group A) were also studied. Based on treatment, hypothyroid patients were divided into B1 (patients on their 1st day of diagnosis, before starting of treatment) and B2 (patients with medication for 12-18 months). The patients were selected from the Out Patients Department of Endocrinology, BSMMU. Serum TSH and FT4 levels of all subjects were measured by AxSYM system. To perform power spectral analysis of HRV Total Power(TP), Low Frequency(LF),High Frequency(HF),LF norms (nu),HF norms (nu) and LF/HF ratio were assessed by a Polyrite. For statistical analysis of data, Independent Sample t test, One Way ANOVA and Pearson’s correlation coefficient test were done as applicable.Results: The mean serum TSH(38.16 vs2.18;2.04) was significantly higher and FT4(5.12vs 15.13; 15.08) was significantly lower(p<0.001) in group B1 than those of group A and B2.The mean values of all the spectral parameters of HRV in euthyroid subjects were within normal range. In untreated hypothyroid patients the mean values of TP ( 77.11vs2702.87;2683.73), HF power(56.68 vs 342.02; 437.34) HF nu( 24.79 vs 36.35;34.55) were found significantly (p<0.001) lower LF/HF(1.7±0.3,3.16±.84 and 1.93±.58) and LF nu(75.32 vs 63.71, and 65.90) were significantly (p<0.001) higher and in comparison to both euthyroids and treated patients. Conclusion: Alteration in cardiac autonomic nervous activity characterized by reduced vagal modulation and higher sympathetic activity may occur in the hypothyroid patients..