Hypertension, the silent killer has not only increased mortality rates in adults but also is an important risk factor for stroke, cardiac arrest, kidney disease etc. There is a massive 30% prevalence of hypertension in India. Heart Rate Variability (HRV) is a physiological phenomenon of variation in the time interval between heartbeats and is a gold-standard to assess the perpetually changing oscillations of a salubrious heart.  Aim The purpose was to study the autonomic correlates of cardiovasular health in hypertension in terms of short term HRV and to analyse the association between HRV indices and elevated blood pressure.  Methods It was a cross-sectional observational study carried out in Sports Physiology Laboratory in Department of Physiology of a rural medical college in central India. 25 known cases of hypertension in the age group of 35-60 yrs and 75 age matched normotensives as controls were selected. ECG was recorded using Power lab data recording system, AD instruments and analysis was done by HRV Module of Lab chart software. The subjects performed an incremental ramp exercise test to the limit of tolerance on a motorized treadmill.  Results The mean age of control males was 39.80±6.68 and mean age of control females was 37.05±2.75. There was statistically significant difference observed in SDNN, RMSSD, HF%, HFnu between control and cases males but no significant relationship was observed among other parameters in males. On comparing the sympathovagal ratio (LF/HF), female cases were having high ratio than control females indicating a dominant sympathetic response. From Pearson correlation analysis, a positive non-significant relationship was observed between systolic BP and Frequency domain indices in controls while in cases a negative correlation was found which was also statistically non-significant. A strong positive correlation was found between Systolic BP and SDNN in hypertensives. The time domain parameters were also found to be negatively correlated with mean heart rate in both controls and cases.  Conclusions This study analysed the association between heart rate variability indices and hypertension. The analysis of HRV can distinguish parasympathetic from sympathetic influences on the heart and provides important insights into the role of the autonomic nervous system in the pathogenesis of essential hypertension. HRV is reduced in women along with men accompanied by systemic hypertension. Among normotensive men, lower HRV was associated with greater risk for developing hypertension. These findings clearly exhibit that autonomic dysregulation is present in the early stage of hypertension.

Keywords : Hypertension, HRV, Frequency Domain Indices, Time Domain Indices.