The anatomical heterogeneity of hearts lacking a patent communication between the left atrium and the ventricular mass (‘mitral atresia’) in presence of a patent aortic valve.

Thirty-five hearts were studied with no patent communication between the left atrium and the ventricular mass (‘mitral atresia’). In ten, an imperforate and hypoplastic membrane separated the left atrium from a hypoplastic left ventricle. The imperforate valve ranged from a tiny membrane with no evidence of tension apparatus, through a larger membrane supported by muscular columns in the ventricular inlet portion, to an aneurysmal imperforate sac attached to a single hypoplastic papillary muscle. The ventriculo-arterial connection was concordant in nine of the ten hearts and double outlet from the right ventricle in one. In one further heart, there was double inlet left ventricle with imperforate left atrioventricular valve, a rudimentary right ventricle and ventriculo-arterial discordance. In the other 24 hearts the muscular floor of the left atrium was completely separated by the atrioventricular sulcus from the ventricular mass (absent left atrioventricular connection). In II of these hearts, the tight atrium was connected to a right ventricle and there was a posterior and left-sided rudimentary left ventricular chamber which had no connection with the atrial chambers. The left ventricle supported the aorta in five of the II hearts, but in the other six it was simply a pouch of left ventricular morphology. In ten cases the right atrium was connected to a dominant left ventricle. An anterior rudimentary right ventricle was present in each but had no connection with the atrial chambers. It was to the left of the left ventricle in seven, directly anterior in one and to the right in two cases. The right ventricle supported the aorta in eight cases, the pulmonary trunk in one and neither great artery in the remaining case. Lastly, there were three cases in which a sole ventricular chamber of indeterminate morphology was present and gave rise to both great arteries. [ABSTRACT FROM PUBLISHER]