MYOCARDIAL-INFARCTION, CARDIAC ANATOMY AND VENTRICULAR LOADING

To see whether the hypertrophic response of the surviving myocardium a fetr infarction leads to a complete reconstitution of ventricular mass , the left coronary artery was ligated in rats and the animals killed one month later. In infarcts affecting an average of 38% of the free w all of the left ventricle, the ratio of wall thickness to chamber radi us remained essentially constant. On the other hand, the ratio decreas ed significantly in the presence of infarcts involving an average of 6 0% of the ventricular wall. In addition, inadequate growth adaptations were detected in both groups of infarcts with respect to myocyte volu me and length and to capillary volume and length. These defects in the regeneration of myocardial structures were associated with elevations in diastolic wall stress which were more prominent in the larger infa rct group. The limited growth reaction of the myocyte and vascular com partments may be implicated in the persistence of cardiac dysfunction and failure late after infarction.