Genetic and environmental factors in the function and structure of the arterial wall.

In large arteries the structure of the arterial wall determines pulsatile hemodynamics of pressure and flow. Mechanical wall stiffness, wall thickness, and elastin and collagen content vary along the arterial tree. The contribution of genetic and environmental factors to such structural properties is not yet known, but some data are available on possible functional correlates. In hypertensive rats diastolic and pulse pressure have been shown to be linked to two different genes on separate chromosomes. Although a genetic component contributes to intimal calcification, medial hypertrophy is not associated with genetic factors. A study of French West Indies families showed a preferential genetic determinant for pulse pressure in contrast to systolic or diastolic pressure. Environmental and geographic factors are associated with markedly different prevalences of hypertension and age-related increases in arterial stiffening in urban and rural communities in China. Salt consumption has also been implicated in modifications of pulse wave velocity. Recent data on structural parameters of the aortic trunk in oriental (Chinese) and occidental (American and Australian) subjects have shown that the ascending aorta in oriental subjects is of a relatively large diameter and thinner media. This suggests that in this population a relatively higher primary pressure pulse would be generated because of increased stiffness of the proximal aorta. This suggests that factors other than arterial pressure are responsible for structural differences in the aortic wall and that oriental populations may have a predisposition to increased arterial pressure based on structural factors that affect the interaction between ventricular ejection and arterial load.