Heart Rate Variability(HRV) in Normotensive Subjects with Family History of Hypertension

The study is aimed to find out the early changes in the cardiac autonomic modulation by analyzing Frequency and Time domain measures of Heart rate variability among normotensive subjects with family history of hypertension.

To compare HRV between subjects with family history of hypertension and subjects without family history of hypertension.

40 Normotensive male subjects between the age group of 18–25 years with family history of hypertension(either one parent or both the parents) were selected as study group and 40 Normotensive male subjects between the age group 18–25 years without family history of hypertension were selected as controls. The study was carried out in Electrophysiology laboratory of Physiology department in Osmania Medical College. Baseline blood pressure was measured using sphygmomanometer and height in meters and weight in kgs were measured and BMI calculated. Each subject was made to relax in supine position and ECG was recorded for 10 minutes in lead I using Power lab data recording system, AD instruments and analyzed by lab chart software. HRV was analyzed using frequency domain measures like Low Frequency in normalisedunits(LFnu), High Frequency in normalized units(HFnu) and ratio of Low frequency to High frequency(LF/HF), and time domain measures like Standard deviation of NN interval(SDNN), Root mean square successive Differences between the intervals (RMSSD).

Statistical analysis was done using Unpaired t-test. There was a significant increase in frequency domain parameters like LFnu and LF/HF(P<0.001) and a significant reduction in HFnu in study group(P<0.001) compared to controls. Time domain parameters like SDNN and RMSSD were significantly reduced in study group(P<0.01) compared to controls.

Cardiac autonomic imbalance in the form of increased sympathetic activity and decreased parasympathetic activity was found in study group compared to controls.