Vascular Changes in the microcirculation. Arterial remodeling and capillary rarefaction

Hypertension impacts the vasculature through the mechanical effects of blood pressure and shear stress, as well as those of hormonal systems such as the renin-angiotensin-aldosterone system, endothelin, catecholamines, substances produced in perivascular fat, and inflammatory and immune mediators such as lymphocytes and macrophages and their products. The vascular phenotype of hypertension varies according to the age of subjects. In younger individuals with elevated blood pressure, vascular remodeling occurs in small arteries and arterioles and is eutrophic with reduced lumen diameter and unchanged media cross-sectional area, reduced or enhanced stiffness, and increased extracellular matrix deposition and endothelial dysfunction. In severe or long-standing hypertension and in secondary forms and refractory hypertension, hypertrophic vascular remodeling of small arteries and arterioles is more typically found. In subjects older than 50 years of age, vascular changes are increasingly found in aorta, which becomes stiffer as arteriosclerosis develops, resulting in increased pulse pressure. Enhanced pulsatility may injure small arteries and arterioles, leading to remodeling of these and endothelial dysfunction. Arteriolar and capillary rarefaction promotes tissue underperfusion that contributes to myocardial ischemia and cardiovascular events, heart failure, stroke, nephrosclerosis and chronic kidney disease, and peripheral vascular disease