Is hypertension a tissue perfusion disorder? Implications for renal and myocardial perfusion.

Structural alterations in the microcirculation form a major link between hypertension and target organ damage. More than 60% of the overall peripheral resistance of the circulatory system arises at the level of the microcirculation. The primary function of the microcirculation is to supply oxygen and nutrients to tissues. In hypertension, remodelling of the microvascular vessels occurs, leading to an early, functional then anatomical reduction in the number of arterioles or capillaries in a given vascular bed. Such changes have been seen in the structure and density of the microvasculature of different target organs such as the myocardium and the kidneys. In hypertension, capillary rarefaction induces an increase in blood pressure, a relative decrease in tissue perfusion and an increased cardiovascular risk. Recent in-vivo non-invasive techniques for exploring the human microcirculation have allowed the detection of myocardial and renal microvascular impairment in hypertensive patients. In comparative therapeutic studies, antihypertensive drugs have been shown to have different capacities for preventing or reversing changes to the microvasculature of affected organs.