Cardiac autonomic functions in hypertensive and normotensive subjects: a comparative study

Abstract

Background

Hypertension, is considered one of the principal risk factors for cardiovascular disorders, increases the mortality. Dysfunction of the autonomic nervous system (ANS) is closely associated with this clinical condition. Heart rate variability (HRV) is a biomarker and noninvasive tool for the quantitative estimation of cardiac autonomic function. The aim of the study was to assess the cardiac autonomic nerve function status in hypertensive patients by analyzing time domain measures of HRV.

Methods

Equal numbers (n=50, in each group) of hypertensive and normotensive male subjects (40-60 yrs) were participated in this study. Electrocardiogram (ECG) was recorded and time domain measures of HRV such as mean RR intervals, mean heart rate (HR), Standard Deviation of Normal-Normal (SDNN) interbeat interval (ms), root mean square successive differences (RMSSD) and percentage of differences between adjacent normal RR interval > 50 msec (pNN50%) were assessed as an indicative of ANS function status. Statistical analysis was done by using unpaired t-test.

 Results

Significant reduction was observed in SDNN, RMSSD, pNN50% amongst hypertensive subjects compared to normotensives.

Conclusion

Impaired cardiac autonomic nerve function characterized by sympathetic over activity and reduced vagal activity was found amongst hypertensives. A decrease in the baroreceptor reflex increases risk for occurrence of cardiac arrhythmias in future. So cardiac ANS tests could be considered as diagnostic criteria for the hypertensives and early detection, can increase curability and save lives.