Sick vessel syndrome: vascular changes in hypertension and atherosclerosis.

Hypertension and atherosclerosis are associated with structural and functional changes that may be collectively described as a 'sick vessel syndrome'. Structural changes in blood vessels (remodelling and hypertrophy) may be protective and adaptive. Functional changes in blood vessels include impairment of endothelium-dependent relaxation and impaired relaxation in response to activation of ATP-sensitive potassium channels. In general, vasorelaxation in response to direct activation of adenylate and guanylate cyclase is preserved in chronic hypertension and atherosclerosis. Vasoconstrictor responses to selected stimuli, such as serotonin, may be greatly potentiated. Impairment of endothelial function in combination with exaggeration of vasoconstrictor responses may predispose to vasospasm particularly during atherosclerosis.