Autonomic nervous system adjustment (ANSA) in patients with hypertension treated with enalapril

Background and aim: Reduced baroreflex sensitivity (BRS), decreased heart rate variability (HRV) and increased blood pressure (BP) variability have serious consequences for target organ damage in patients with hypertension, beside the BP level. The study was aimed to evaluate acute and long-term effects of enalapril, on BRS and HRV in individuals with prehypertension and mild essential hypertension. Methodology: We enrolled in the study 85 patients (male 53%, age 42-67) with prehypertension and mild hypertension (systolic blood pressure >= 120 mmHg or diastolic blood pressure >= 80 mmHg). All patients were tested before, 30 minutes after first oral enalapril dose and three weeks after monotherapy with enalapril. The methodology included: beat to beat HRV analysis, BRS measurements with sequence technique, ECG with short term and 24-hour HRV analysis, 24-hour ambulatory blood pressure monitoring with systolic and diastolic BP variability analysis. Patients were divided into groups with sympathetic or vagal predominance based on Autonomic Nervous System Adjustment (ANSA) method. Results: 1) 30 min after initial dose enalapril significantly and effectively reduced systolic BP with shift towards the parasympathetic predominance as reflected in decreased heart rate and low frequency (LF) to high frequency (HF) ratio (LF/HF ratio); 2) chronic enalapril therapy effectively reduced BP, including both systolic BP, diastolic BP and pulls pressure, had positively influence on dipping status, but did not significantly change BP variability; 3) in the whole patient group chronic enalapril therapy did not significantly change HRV, but it significantly decreased LF(nu) in the patient with high basal sympathetic activity, and significantly increased LF(nu) in patients with high basal vagal activity; enalapril also significantly decreased HF (nu) in patients with high basal parasympathetic activity; 4) despite initial, transit changes in maximal and minimal slope of BRS enalapril did not significantly affect sensitivity of spontaneous baroreflex activation. Conclusion: Initial enalapril dose significantly reduced systolic BP and had beneficial effects on autonomic tone and baroreflex sensitivity. Chronic enalapril therapy effectively reduced BP without significant influence on BRS, but had significant autonomic effects on HRV when initial autonomic profile in each patient was analyzed by ANSA. Analyzed by ANSA method chronic enalapril therapy managed to retrieve disturbed sympathovagal balance and established autonomic equilibrium.