Pathophysiology of systemic hypertension

Systemic hypertension can be regarded as a quantitative disorder of blood pressure regulation. No single cause of hypertension has been identified, and it is likely that different mechanisms may be dominant in different individuals. In patients with sustained hypertension, there is usually increased peripheral resistance and normal cardiac output. The hemodynamic pattern of hypertension appears to vary according to the subject's age. Factors that may increase peripheral resistance are a decrease in the number of arterioles, changes in the caliber of the arterioles and increase in blood viscosity. Possible components of increased vascular tone in hypertensive patients include elevation of levels of circulating catecholamines and angiotensin II, increased number/affinity of receptors, changes in membrane permeability and increased excitation-contraction coupling. The major hormonal component that mediates vasoconstriction is the renin-angiotensin-aldosterone system. Genetic, environmental and psychologic factors may also play a role in hypertension.