Double - Inlet Left Ventricle Two

Two pathological specimens are presented in which the morphological left ventricle contains the right atrioventricular ostium, completely or in its major portion and, totally, the left atrioventricular ostium. It is suggested from a consideration of these cases and of the pathological material available in the literature that this constitutes an entity that can be usefully separated from the heterogeneous group of single ventricle with which it has previously been classified. The entity is called double-inlet left ventricle and is defined as existing when two separate atrioventricular ostia open in a morphological left ventricle. An ontogenetic explanation is presented based on the study of normal human embryos. These cases resemble the heart of the embryo during the horizons XIII to XVI of Streeter. It is suggested that there has been a partial arrest in the widening of the atrioventricular canal and the changing relation of the atria with the ventricles at these stages. It is noted that both atria open into the morphological left ventricle whether situated to the left or to the right. This is an expected finding, since the left ventricle is derived from the primitive ventricle and the primitive ventricle is always connected with both atria during the early stages of embryological development. Other malformations include transposition of the great arteries in both cases and ventricular inversion in one.