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

Predominant sympathetic cardiovascular modulation in the hyperkinetic phase of arterial hypertension has been well described, Less information is avai lable on autonomic control in persons with a family history of arterial hyp ertension, To investigate this question, we selected 61 normotensive subjec ts (mean age 30.9 +/- 1.8 years) whose mother or father or both had arteria l hypertension and 30 normotensive patients (mean age 30.1 +/- 1.4 years) w hose parents had not had arterial hypertension (neither mother nor father) to undergo short-term power spectral analysis of RR interval and arterial p ressure variabilities. The same recordings were used to determine barorefle x sensitivity or the alpha index by means of the transfer function. Normote nsive offspring of hypertensive subjects had higher diastolic blood pressur es (P <.05) and left ventricular mass index (P <.05) than did normotensive offspring of non-hypertensive subjects. They also had higher spectral densi ties of low frequency expressed in normalized units, both for R-R intervals (P <.05) and systolic pressure variabilities (P <.05); they also had a gre ater ratio of low-frequency to high-frequency powers of R-R interval variab ility (P <.05), No difference was observed between the two normotensive gro ups for baroreflex sensitivity. Our spectral data indicate that normotensiv e persons with a positive family history of arterial hypertension have lowe r parasympathetic modulation than those with a negative history. In normote nsive persons with a family history of arterial hypertension, normal barore flex sensitivity could be the mechanism that buffers the tendency for press ures to increase. The gradual loss of this regulatory mechanism may favor r ising arterial pressures.