Inheritance of hypertension and blood pressure reactivity.

A lthough there is general agreement that there / \ is a strong genetic component to essential A. \ hypertension, it is not clear exactly what is inherited. A popular but largely unsubstantiated view is that sustained hypertension may be preceded by a period of increased reactivity to noxious stimuli. In this issue of Hypertension, Ravogli et al provide important new data that help'to resolve this question. By using four different tests of blood pressure reactivity, they found that normotensive young adults with one or both parents hypertensive do not show any increased reactivity when compared with subjects with normotensive parents, although they did show slightly higher blood pressures during casual measurement and 24-hour monitoring, with a proportional increase in left ventricular mass. The reactivity hypothesis was first proposed more than 50 years ago by Hines and Brown, who claimed that "prehypertensive" individuals show an exaggerated pressor response to a cold pressor test. In its stronger form, this hypothesis states that increased reactivity plays a causal role in the development of hypertension and that the repeated transient pressor episodes the increased reactivity engenders eventually lead to a sustained elevation of pressure. In its weaker form, the hypothesis proposes that the reactivity is merely a marker for future hypertension, without necessarily having any direct causal role. A recent review of 39 studies comparing reactivity in hypertensive and normotensive individuals concluded that although the majority do show an increased reactivity, it is by no means a universal finding. If it is accepted that the positive studies outweigh the negative ones, the question is raised as to whether the increased reactivity is a cause or a consequence of the hypertension. By studying individuals who are still normotensive but who have a family history of hypertension, it should be possible to answer this question. A review of studies of reactivity in subjects with and without a family history claimed that increased reactivity is typical of individuals with a positive family history,