Characteristics of chronic left ventricular dysfunction induced by coronary embolization in a canine model

We have characterized the coronary vascular reserve, left ventricular function and inotropic response in dogs with chronic heart failure consequent to intracoronary embolization (EMB) with 50 microns spheres. We conducted studies 12-39 months after embolization and contrasted the findings with normal (CON) dogs. Acute embolization produced sustained LV volume enlargement and increased wall thickness, reduction of LV ejection fraction and elevated end-diastolic pressures; resting catecholamine levels were also increased. Responses to phenylephrine, nitroprusside, and dobutamine were identical in CON and EMB and coronary vasodilator reserve was reduced despite larger coronary vascular volume. Analysis by light microscopy showed a diffuse focal and interstitial fibrosis distributed uniformly from endocardium to epicardium associated with 14% loss of myocytes. This created a functional separation of myocardial muscle bundles and a disruption of the syncytial nature of the heart. Electron microscopy of the areas of fibrosis revealed myocytes in states ranging from normal appearing, to ghosts with evidence of cytolysis and loss of the sarcolemma. This model of chronic congestive heart failure with LV systolic dysfunction and elevated LV diastolic pressures shares a number of features with the syndrome in humans.