The pathophysiology of hypertension. Differences between young and elderly patients.

While structural and functional signs of a genetic predisposition to hypertension may sometimes be detected in the juvenile cardiovascular system, the borderline phase characteristic of young hypertensive patients is often dominated by a 'hyperkinetic' circulatory state. The modest pressure elevation is then mainly due to an increase in cardiac output and accentuated responses to neurohormonal stimuli. During the development of established hypertension, cardiac output gradually returns to normal and the high pressure state is largely a result of chronically elevated systemic resistance with cardiovascular 'structural upward resetting'. Signs of increased neurohormonal influences usually become less prominent. In general, the chronic high pressure state tends to accelerate ordinary cardiovascular aging, and therefore the advanced stages of primary hypertension are characterised by considerable interstitial infiltration with consequent wall stiffening and reduced aortic 'Windkessel' function. This further enhances the end-systolic afterload for the left ventricle, while at the same time myocardial strength and coronary reserve tend to decline. Age-related reductions in barostat function, reflex efficiency, and renal excretory capacity are also accentuated, and endothelial function suffers. Thus, the cardiovascular system in elderly hypertensive patients is generally characterised by pronounced and apparently poorly reversible structural changes. Nevertheless, recent studies indicate that even late phases of hypertension in elderly patients may respond favourably to treatment. This may predominantly reflect the high risk of serious cardiovascular damage in the elderly, but also that therapeutic intervention is able to reverse the structural changes observed in the advanced stages of hypertension.