Significance of ventricular configuration and myocardial fibrosis in the manifestation of chronic cardiac insufficiency

On the basis of experimental findings in rats with chronic pressure overload of the left ventricle (spontaneous and renal hypertension) the significance of structural dilatation in the manifestation of cardiac insufficiency is discussed. Furthermore, the role of fibrosis in impaired myocardial contractility and a possible causal relation between fibrosis and dilatation are considered. Although congestive insufficiency practically always went hand in hand with a considerable degree of dilatation in these models, cardiac pump failure can be attributed to altered geometric configuration per se only when dilatation has reached extreme dimensions. Severe fibrosis impairs myocardial performance to a higher degree, as can be expected from the loss of contractile material. Apparently, connective tissue can act as a diffusion barrier. The findings in extremely dilated hearts are consistent with the assumption that a causal relationship exists between fibrosis and structural dilatation, although direct evidence can only be obtained by measurements of individual fibre (cell) length. There are indications that β-adrenergic blockade can accelerate structural dilatation, possibly by inhibiting hypertrophic mass increase. Circulating blood volume and thus water and electrolyte balance influence ventricular configuration.