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

Background Pulmonary atresia and intact ventricular septum (PA-IVS) ca n be complicated by the presence of a severely hypoplastic thick-walle d right ventricle with or without ventriculo-coronary arterial communi cations. 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 net work is still intact, allowing a sufficient perfusion of the myocardiu m, which will be important for the success of palliative surgery. Meth ods and Results We studied the distribution of capillaries in the myoc ardium of hearts with PA-IVS and compared the results with normal hear ts. The capillaries were detected by immunohistochemistry using a mono clonal antibody (408) against endothelium. Remarkable abnormalities in capillary distribution were found in the right ventricle of hearts wi th PA-IVS and reflect the arrangement of the myocytes. Thus, disorgani zation of capillaries, which is found to be the most common pattern, a lways paralleled the myocardial disarray. A low density of capillaries is always found in areas with a low density of myocytes, ie, with hyp ertrophied myocytes, compact fibrotic tissue, or diffuse fibrosis. Dis array and other disturbances in orientation of capillaries and myocyte s are present in hearts with PA-IVS, a hypoplastic right ventricle, an d ventriculo-coronary arterial communications. These disturbances are more extensive when interruptions of the coronary arteries are also pr esent. In hearts with PA-IVS and a hypoplastic right ventricle only, e xtensive regions with low capillary densities and severe myocyte patho logy are observed. On the contrary, hearts with PA-IVS and a normal-si ze right ventricle show minor abnormalities in capillary and myocyte o rganization. Conclusions In hearts with PA-IVS, various abnormal capil lary distribution patterns are found. Our findings correlate well with clinical data that reported the best surgical results in hearts in wh ich the major part of the myocardium showed a normal capillary distrib ution and myocyte morphology. This suggests that the capillary distrib ution may be an important parameter for the function of the heart. Bec ause the distribution of the capillaries is found to be a good reflect ion of the arrangement of the myocytes, antibody 408 is also a useful tool in detecting abnormalities of the myocardium in a fast and easy w ay.