Assessment of Cardiac Autonomic Functions in Prehypertensive Individuals with and without a Family History of Hypertension: A Cross-sectional Study

Abstract

Introduction: Individuals with prehypertension are at an increased risk of developing hypertension. Family history is one of the paramount non modifiable risk factors for developing hypertension. Hence, it becomes mandatory to assess the cardiac autonomic functions, which play an important role in the regulation of Blood Pressure (BP), in prehypertensive individuals with a family history. Aim: To compare the variations in parameters of cardiac autonomic function tests in prehypertensive individuals with and without a family history of hypertension. Materials and Methods: This cross-sectional study was conducted at the Institute of Physiology and Experimental Medicine, Madras Medical College, Chennai, Tamil Nadu, India from October 2020 to October 2021. The study included 30 prehypertensive individuals without a family history of hypertension and 30 prehypertensive individuals with a family history of hypertension, aged between 20 and 50 years, of both genders. They were recruited from the non communicable diseases Outpatient Department (OPD) at Rajiv Gandhi Government General Hospital, Chennai, Tamil Nadu, India. The prehypertensive range refers to a Systolic Blood Pressure (SBP) of 120-139 mmHg or a Diastolic Blood Pressure (DBP) of 80-89 mmHg. After obtaining informed consent, baseline parameters such as resting Heart Rate Variability (HRV) using AD instruments powerlab recorder, deep breathing test, Valsalva maneuver, isometric handgrip test, and Cold Pressor Test (CPT) were evaluated. The data obtained was statistically analysed using a Student’s t-test. Results: The mean age of prehypertensive individuals without a family history was 36.90±4.6 years, and in prehypertensive individuals with a family history, it was 36.43±5.3 years. The male to female ratio was higher. The resting SBP and DBP, as well as the basal heart rate, were significantly increased in the prehypertensive subjects with a family history. Time domain variables such as the mean RR, Root Mean Square of Successive Difference (RMSSD), and pRR50 were reduced in prehypertensive individuals with a family history. Among the frequency domain variables, the total power was reduced, while the low-frequency component and LF:HF ratio were significantly increased. The E/I ratio and Valsalva Ratio (VR) were also significantly reduced in prehypertensive individuals with a family history. Thus, the results emphasise that there is significant autonomic dysfunction in prehypertensive individuals with a family history of hypertension compared to prehypertensive individuals without a family history. Conclusion: Cardiac autonomic function tests in prehypertensive individuals with a family history indicate a definite sympathovagal imbalance in the form of sympathetic overactivity. This may substantiate the role of genetic predisposition in them. Chronic activation of the sympathetic nervous system makes them more prone to developing early hypertension.