الفهرس 
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Abstract
Background: One of the primary pathologies associated with hypertension is a complex autonomic dysfunction with evidence of sympathetic hyperactivity and/or vagal withdrawal. Heart rate variability (HRV) is a useful non invasive tool to assess cardiac autonomic function. Altered autonomic modulation of heart rate and HRV have been described in systemic hypertension. However, less information is available on autonomic control in subjects with a family history arterial hypertension. Aim: So, the aim of this study was to investigate the possibility for detection of early autonomic malfunction that may be predictive of future hypertension in normotensive children and adolescents of hypertensive parent(s), on the basis of the analysis of HRV which reflect autonomic control. Material and Methods: The study included healthy normotensive subjects and according to the family history of hypertension, the following groups were specified group (1): normotensive children and adolescents of hypertensive parent(s) (n=27, age= 14.25 (R+ (B2.75 years) and group (2) normotensive children and adolescents of normotensive parents (n=13, age= 132.41 years). HRV (R+ (Bwas assessed by time domain analysis, and frequency domain analysis for all cases and controls by computerized analysis of short term heart rate samples (512 beats) which recorded in supine position during spontaneous breathing, using Schiller Cardiovit At60. Also, we evaluated the following * Clinical characteristics including: weight, height, body mass index (BMI), body surface area (BSA) systolic and diastolic blood pressure (SBP, DBP) and heart rate (HR). * Biochemical analysis including total cholesterol and fractions, triglycerides, plasma renin activity (PRA), plasma noradrenalin and hematocrite value. * Findings of other cardiac investigations including 12lead ECG, stress ECG and echo cardiography. Results: We found that normotensive children and adolescents of hypertensive parent(s) in contrast to controls had: (1) significant greater low frequency/high frequency (LF/HF) ratio (sympathovagal index) (1.94(R+(B1.19 vs 1.27 (R+ (B0.78, P=0.05) and tendency towards lower values of HF component which represents parasympathetic modulation of HRV. (2) Significant greater values of BP. (3) an exaggerated HR and BP response at peak levels of dynamic exercise. (4) Significant higher plasma noradrenalin level. (5) Significant higher PRA. (6) Clinical but not statistical significant lower level of HDLcholesterol and higher level of plasma triglycerides. (7) Absence of functional and structural changes in left ventricle of the heart. Conclusion: The power spectrum analysis of HRV can be considered an earlier predictive non invasive tool for future hypertension in normotensive subjects of hypertensive parent(s) as it detects early altered cardiovascular regulatory mechanisms (early autonomic malfunction) that may exist before clinical detection of hypertension, or evidence of functional and structural cardiac alteration.