Embryology of congenital ventriculo-coronary communications: a study on quail-chick chimeras.

Ventriculo-coronary arterial communications are rare congenital heart defects which have been explained traditionally on the basis of abnormal persistence of such communications found in the normal developing heart. Recent studies, however, have suggested that these embryonic communications might be an incidental finding rather than a normal feature. Thus, it has been suggested that congenital ventriculo-coronary communications do not represent remnants of normal embryonic vessels, but rather represent acquired lesions. In the present study, hearts were constructed in embryonic chicks in which the coronary vasculature was almost completely derived from a quail-donor. After immunohistochemical staining of the quail-derived coronary endothelium, chimeric hearts were analysed with respect to the presence of embryonic ventriculo-coronary communications, and with respect to the origin of these structures from either coronary arteries or endocardium. The results demonstrate the normal presence of ventriculo-coronary communications in avian embryonic hearts. They show, furthermore, that these structures are of coronary endothelial origin. The findings are in accord with the traditional view on the pathogenesis of congenital ventriculo-coronary communications. The roles of elevated ventricular pressure, abnormal remodelling of the developing myocardium, and of abnormal growth of the coronary vasculature are discussed relative to the pathogenesis of congenital ventriculo-coronary communications.