Correlation of Heart rate variability analysis to Blood pressure indices in young healthy subjects

Background and objectives: Heart rate variability (HRV) is related to lifestyle in adults.Regular physical exercise has beneficial effect on autonomic control of heart, with decreased resting HR often accompanied with increase in HRV.The purpose of the present study was to determine whether readily measured BP indices and responses to autonomic reflex tests could be used as surrogates of short term HRV, which is an established marker of autonomic regulation of SA node.Therefore, we examined the correlation between short-term HRV and heart rate (HR), BP indices viz.systolic BP, diastolic BP, pulse pressure (PP), and ratepressure product (RPP), during supine position and standing erect.Methodology: The study evaluated 75 male subjects for their resting cardiovascular parameters.HR, and systolic and diastolic BP were recorded, and RPP calculated using HR and systolic BP, along with autonomic function test parameters.Valsalva ratio was calculated after Valsalva maneuver, and change in diastolic BP and PP after isometric hand grip test.They were also subjected to short term heart rate variability recording in supine and standing erect positions.Results: Non-parametric Wilcoxon signed rank test was applied to analyze the changes in HRV parameters because of the peculiar distribution of data.Pearson correlation coefficient was used for correlation matrix and p value less than 0.05 was considered significant.Mean R-R interval and SDNN (standard deviation of normal-to-normal RR intervals) of time domain analysis, and LF and HF power, total power and LFnu (low frequency in normalized units) of frequency domain analysis were highly significant on comparing supine to standing positions.We looked for correlation between short term HRV and resting cardiovascular parameters, but no significant correlation was observed.Conclusion: Our data indicated a decrease in HRV that seems to be an expression of reduction in autonomic modulation in postural change from supine to erect.The findings were suggestive of a shift in cardiac autonomic regulation towards sympathetic activation in response to real life stressors, which includes the decrease in parasympathetic modulation in sinus node.Results suggested no significant correlation between readily measured BP indices to HRV in the study group.Hence we suggest that mean HR, SBP, DBP and RPP cannot be used as surrogates of HRV.