Autonomic modulation of heart rate and blood pressure in normotensive offspring of hypertensive subjects

Abstract

Predominant sympathetic cardiovascular modulation in the hyperkinetic phase of arterial hypertension has been well described. Less information is available on autonomic control in persons with a family history of arterial hypertension. To investigate this question, we selected 61 normotensive subjects (mean age 30.9 ± 1.8 years) whose mother or father or both had arterial hypertension and 30 normotensive patients (mean age 30.1 ± 1.4 years) whose parents had not had arterial hypertension (neither mother nor father) to undergo short-term power spectral analysis of RR interval and arterial pressure variabilities. The same recordings were used to determine baroreflex sensitivity or the alpha index by means of the transfer function. Normotensive offspring of hypertensive subjects had higher diastolic blood pressures (P <.05) and left ventricular mass index (P <.05) than did normotensive offspring of non-hypertensive subjects. They also had higher spectral densities of low frequency expressed in normalized units, both for R-R intervals (P <.05) and systolic pressure variabilities (P <.05); they also had a greater ratio of low-frequency to high-frequency powers of R-R interval variability (P <.05). No difference was observed between the two normotensive groups for baroreflex sensitivity. Our spectral data indicate that normotensive persons with a positive family history of arterial hypertension have lower parasympathetic modulation than those with a negative history. In normotensive persons with a family history of arterial hypertension, normal baroreflex sensitivity could be the mechanism that buffers the tendency for pressures to increase. The gradual loss of this regulatory mechanism may favor rising arterial pressures. (J Lab Clin Med 2000;135:145-52)