CAPILLARY DISTRIBUTION IN THE VENTRICLES OF HEARTS WITH PULMONARY ATRESIA AND INTACT VENTRICULAR SEPTUM

Background Pulmonary atresia and intact ventricular septum (PA-IVS) can be complicated by the presence of a severely hypoplastic thick-walled right ventricle with or without ventriculo-coronary arterial communications. A variable amount of myocardial pathology has been described in these hearts, probably the result of ischemic conditions and a high pressure in the right ventricle. We studied whether the capillary network is still intact, allowing a sufficient perfusion of the myocardium, which will be important for the success of palliative surgery. Methods and Results We studied the distribution of capillaries in the myocardium of hearts with PA-IVS and compared the results with normal hearts. The capillaries were detected by immunohistochemistry using a monoclonal antibody (408) against endothelium. Remarkable abnormalities in capillary distribution were found in the right ventricle of hearts with PA-IVS and reflect the arrangement of the myocytes. Thus, disorganization of capillaries, which is found to be the most common pattern, always paralleled the myocardial disarray. A low density of capillaries is always found in areas with a low density of myocytes, ie, with hypertrophied myocytes, compact fibrotic tissue, or diffuse fibrosis. Disarray and other disturbances in orientation of capillaries and myocytes are present in hearts with PA-IVS, a hypoplastic right ventricle, and ventriculo-coronary arterial communications. These disturbances are more extensive when interruptions of the coronary arteries are also present. In hearts with PA-IVS and a hypoplastic right ventricle only, extensive regions with low capillary densities and severe myocyte pathology are observed. On the contrary, hearts with PA-IVS and a normal-size right ventricle show minor abnormalities in capillary and myocyte organization. Conclusions In hearts with PA-IVS, various abnormal capillary distribution patterns are found. Our findings correlate well with clinical data that reported the best surgical results in hearts in which the major part of the myocardium showed a normal capillary distribution and myocyte morphology. This suggests that the capillary distribution may be an important parameter for the function of the heart. Because the distribution of the capillaries is found to be a good reflection of the arrangement of the myocytes, antibody 408 is also a useful tool in detecting abnormalities of the myocardium in a fast and easy way.