Hypertension: Microvascular complications.

The arterioles, vessels situated before the capillary bed, are responsible for the increased systemic resistances characteristic of hypertension. In short, three abnormalities are observed in the arterioles of hypertensiv es : - abnormally high vasoconstrictor tone, essentially due to sympathetic hype ractivity, - hypertrophic remodelling or increased wall thickness/radius ratio of the arteriole promoting both the increase in vasoconstriction tone and reductio n of the vascular lumen, - rarefaction of the microvascular bed which contributes to the increase in the haemodynamic resistances, These three factors are observed to different degrees in all forms of hyper tension; their influence varies with the organ involved and the stage of th e disease. A change in therapeutic strategy has occurred over the last 20 y ears in the field of hypertension. Before the 1980's, anti-hypertensive therapy was essentially aimed at a vas omotor target : the drugs used had a vasodilatory effect on the resistive a rterioles or decreased their response to vasoconstricor agents. From the mi d-1980's, a lot of research was made into the therapeutic possibilities of limiting or correcting the hypertrophic remodelling of the arteries and art erioles of hypertensive patients. In the last few years, the vascular raref action in hypertension has been considered to be a significant factor and t he possibility of correcting the structural abnormality has become a new th erapeutic option.