Hypertension Treatment and Prevention of New Atherosclerotic Plaque Formation

Summary

The effect of hypertension on the arterial vascular wall is characterised primarily by morphological changes to the endothelium and hypertrophy of smooth muscle cells within the arterial media. Endothelial dysfunction is manifest through increased permeability to high molecular weight compounds as well as mitogenic and vasoactive substances. At the same time, denudation of the vascular endothelium promotes platelet aggregation and subsequent release of platelet-derived growth factor (PDGF). In conjunction with endothelium- and monocyte-derived growth factors, this mitogen stimulates subintimal smooth muscle cell proliferation and migration and arterial wall thickening, resulting in a haemodynamically important increase in vascular resistance, particularly at the precapillary level. In addition, focal endothelial dysfunction allows entry of lipids into the vascular wall, thereby promoting formation of a lipid-rich fatty streak, the primary ‘early’ atherosclerotic lesion.

Most of these changes, including endothelial injury, subintimal lipid-binding, cellular proliferation and migration, platelet aggregation and PDGF release are common to both hypertensive and early atherosclerotic processes and involve the participation of calcium ions as ‘second messengers’. Thus, antihypertensive treatment with calcium antagonists may not only lead to a protective decrease in wall shear stress through a reduction in blood pressure, but may also inhibit those cellular processes within the vascular wall that are responsible for initiating atherosclerosis. Indeed, experimental as well as human studies have demonstrated a beneficial suppressant effect of calcium antagonists on the early stages of atherosclerosis.