Pathophysiology of hypertension in older patients.

More than half of the United States population over 65 years of age has essential hypertension. In 1984, there were 10 million elderly hypertensive persons and this number will reach 25 million in the near future. These patients are at high risk for congestive heart failure, stroke, heart attack, and dissecting aneurysm. Successful reduction of blood pressure can lower these risks considerably, but rational treatment depends on understanding the complex pathophysiology of hypertension in older patients. In fact, treatment that does not take into account the combined effects of aging and hypertension on the cardiovascular system and the kidneys may do more harm than the hypertension itself. Among the prominent age-related cardiovascular changes are stiffening of the arterial tree, with or without a contribution from atherosclerosis. This reduces arterial compliance and increases afterload, resulting in the left-ventricular hypertrophy seen in old age and leading to a progressive rise in systolic pressure. There is considerable shrinkage of the kidneys, due primarily to loss of glomerular and tubular tissue in the cortex, along with sclerosis of the glomeruli and formation of tubular diverticula. Arteriolar changes lead to reduced renal blood flow, the shunting of blood around the glomeruli, and thus a reduction in glomerular filtration rate. Renal water and electrolyte excretion are changed, making homeostasis more difficult to maintain, and the renin-angiotensin system is altered, helping to blunt the kidneys' response to pressure changes. Essential hypertension superimposed on all the foregoing effects exacerbates them. Peripheral resistance is usually markedly elevated in older hypertensive persons, which increases afterload directly.(ABSTRACT TRUNCATED AT 250 WORDS)