Cardiovascular Autonomic Responses to Exercise in Normotensive Healthy Adults with Parental History of Hypertension

Hypertension(HTN) is a major public health problem in India. The diagnosis of hypertension is made when the average of 2 or more diastolic blood pressure(BP) measurements on at least 2 subsequent visits is consistently 140mm Hg. Positive family history of hypertension is one of the risk factors for being hypertensive in future life for their children. It is a major cardiovascular risk factor and contributes significantly to cardiovascular mortality. Hypertension is reported to be associated with sympathetic nervous system overactivity. Normotensive subjects with parental history of hypertension have greater sympathetic activity and early parasympathetic attenuation. Those with parental history of hypertension also show a high blood pressure response known as exaggerated response, to exercise testing. This detects cardiovascular autonomic changes in younger age groups and helps us to identify those prone to hypertension later in life though the subjects be normotensive initially. It helps to delay or prevent the onset of hypertension.

1. To compare variation in blood pressure at rest and post-exercise between normotensives with parental history of hypertension and normotensives without parental history of hypertension.

To compare heart rate variability at rest and post-exercise between normotensive with parental history of hypertension and normotensives without parental history of hypertension.

To evaluate whether these changes have predisposition to hypertension.

The present study was performed in Electrophysiology laboratory, Upgraded Department of Physiology, Osmania Medical College.40 subjects with parental history of HTN as study group, 40 subjects without parental history of HTN as control group were selected between the age group 18-30years. BP was measured using ambulatory BP monitor and Heart rate variability(HRV) was analyzed by low frequency/high frequency ratio(LF/HF ratio) using software LABCHART version 8 provided by AD-INSTRUMENTS. Both the parameters were recorded at rest and after subjecting to exercise on treadmill for 3minutes, after achieving desirable HR of moderate exercise (100–125 beats/minute).

Paired t-test has been used to find significance between subjects with parental history of hypertension and without parental history of hypertension. One-way ANOVA has been used to find out the significant p values between the study and control group. There was no significant difference between age(p=0.7) and BMI(p=0.71) between two groups. While the mean basal systolic BP was significantly higher in the study group than in the control group, there was no significant difference in the basal diastolic BP in the two groups. Post-exercise recovery systolic BP was significantly higher in the study group than control group. There was no significant difference in post-exercise recovery diastolic BP between the two groups. Basal LF/HF ratio was also higher in the study group than control group.

A difference in basal systolic blood pressure and basal LF/HF ratio, found in offspring of hypertensive parents may be an early marker of cardiovascular change predisposing to HTN. Regular monitoring of autonomic activity may prove to be a useful tool in predicting the future hypertension.