THE MICROCIRCULATION AND HYPERTENSION

Aim: To review published evidence on the effects of arteriolar changes in primary and secondary hypertension. Background: Pressure profile analyses have shown that the microcirculation is a major site of vascular resistance. With the recent refinement of intravital microscopy techniques detailed information has become available on mechanisms of the microvascular resistance increase in hypertension. Three mechanisms play an important role: (1) a decrease in arteriolar diameter; (2) arteriolar vessel wall hypertrophy; and (3) small arteriolar and capillary rarefaction. Method: The evidence was synthesized into a hypothesis on the role of the microcirculation in primary forms of hypertension. Hypothesis: The hypothesis formulated contains two important elements in that (1) diminished outgrowth of the microvascular bed in different tissues is seen as an important early pathogenic mechanism; and (2) the decreases in arteriolar diameter and vessel wall hypertrophy are seen as adaptive mechanisms that maintain a constant wall stress. The three factors together maintain the increase in vascular resistance that is common to all established forms of primary hypertension.