ABSTRACT
Since the work of Bright and Johnson, it has been recognized that the walls of medium-sized arteries are thickened in hypertension. However, it has to be conceded that their contribution to vascular resistance is small. The histopathological change appears to be hypertrophy. Indeed the heart and medium-sized blood vessels demonstrate this hypertrophic response to hypertension. In addition, until the heart dilates, it is of interest to note that the hypertrophic response takes place at the expense of the ventricular cavity: in other words there is inward encroachment on the chamber space. Therefore, the hallmark of any form of sustained hypertension is an alteration in the architecture of the circulation that inevitably occurs in consequence. At the level of the resistance artery where the internal diameter of the blood vessels is around 250 m or less, there is evidence of a reduced lumen diameter and increased media thickness: lumen diameter ratio. This was originally reported in necropsy specimens and subsequently confirmed in segments of artery mounted as isometric ring preparations on wires and in vessels perfused in vitro. Detailed histological analyses more recently carried out have suggested that eutrophic inward remodeling occurs at this point in the circulation. By this it is meant that there is a narrowing of the vascular lumen without having to invoke a growth response of the arterial wall (3). A small amount of hypertrophy may be observed in some pathological states where hypertrophy may supervene and is an adverse prognostic sign.
