Different concepts of univentricular heart. Experimental embryological approach.

A brief historical review of the main descriptions, definitions, classifications and nomenclatures of the univentricular heart within the historical context of the evolution of the technical and scientific knowledge, is made. The development of the ventricles and particularly the posterior interventricular septum (posterior smooth plus posterior trabeculated septa), were studied experimentally in the chick embryo, by the vivo labelling technics, since they are very important for the definition of the univentricular heart. It was demonstrated: 1. In the apical region of the embryonic heart only a primitive interventricular septum develops and this gives origin to the posterior interventricular septum. 2. The walls of the bulbus cordis and the primitive ventricle adjacent to the primitive interventricular septum contribute to the development of this septum. 3. Cell division and cell movement are the basic processes of development which seem to take part in the development of the posterior interventricular septum.