Comparison of heart rate variability in normotensive and newly detected hypertensive adults in a tertiary care hospital, Mysuru, Karnataka.

Background and objectives Autonomic dysfunction plays a key role in blood pressure regulation, and heart rate variability (HRV) is a sensitive non-invasive marker of autonomic function. This study aimed to compare HRV among newly detected hypertensive and normotensive adults and to examine the association of HRV parameters with blood pressure levels. Methods This hospital-based case-control study included 52 participants (26 hypertensives and 26 normotensives). Time-domain HRV parameters, standard deviation of all normal-to-normal RR intervals (SDNN), and root mean square of successive differences (RMSSD) and frequency-domain parameters, low frequency (LF), high frequency (HF), and LF/HF ratio, were derived from electrocardiographic recordings. HRV parameters were compared between normotensive and hypertensive groups. Correlation with blood pressure and LF/HF was assessed using Spearman's correlation, and logistic regression was used to examine the independent association between HRV and blood pressure parameters. Significance was set at 5% (P< 0.05). Results Time-domain measures of HRV among hypertensives had lower SDNN [28.16 (21.75-39.50) ms2, P=0.020], and lower RMSSD [16.88 (11.79-25.51) ms2, P=0.003]. In the frequency domain, hypertensive individuals showed significantly lower HF [102.25 (53.73-209.75), P<0.001], and the LF/HF ratio was significantly higher [1.94 (1.60-3.19), P< 0.001]. LF/HF ratio correlated positively with systolic (rₛ=0.49) and diastolic blood pressure (rₛ= 0.50), both P<0.001. Multinomial logistic regression shows that higher systolic blood pressure was significantly associated with increased odds of sympathetic dominance [Odds ratio (OR) 1.09, 95% Confidence interval (CI) (1.04-1.15), P<0.001]. Interpretation and conclusions Newly detected hypertensive adults demonstrated reduced parasympathetic activity and increased sympathetic dominance, with the LF/HF ratio showing a significant positive association with systolic and diastolic blood pressure and independently predicted hypertension.