Power Spectral Analysis of HRV for Evaluation of Sym - pathovagal Imbalance in Thyroid Dysfunctions

Thyroid hormone impacts on the cardiovascular system. The cardiovascular system is influenced by the autonomic nervous system and ANS abnormalities may increase cardiovascular morbidity and mortality . The aim of the study was to assess the cardiac autonomic functions by power spectral in patients with hypothyroidism, hyperthyroidism and to compare it with healthy controls. Autonomic functions were evaluated by measurement and analysis of frequency domain parameters of HRV by ECG method and scored in 50 hypothyroid, 50 hyperthyroid patients, 20 - 60 years and compared with 25 controls. The present study was conducted in the Dept. of Physiology, SMS Medical College, Jaipur with the collaboration of Deptt. of Endocrinology of the Institute. Informed written consent was obtained from all the subjects included in the study. Biochemical estimation of TSH, fT 3 , fT 4 was done. Results were presented as Mean ± SD. For statistical analysis, One Way ANOVA (Post Hoc Tukey) test was used. Result shows that frequency parameters of HRV except LF nu and LF/HF ratio were reduced in subjects of hypothyroidism and hyperthyroidism as compared to controls suggesting sympathovagal imbalance with sympathetic overactivity and diminished parasy mpathetic activity.