Experimental creation of univentricular heart in the chick embryo.

An experimental study on the heart of the chick embryo demonstrates that the atrio-ventricular canal does not migrate towards the right, but that it is the inter-ampullar ring which almost completely migrates to the left. Consequently: 1. absence of migration of the interampullar ring will be responsible for the development of type A univentricular heart with an accessory chamber; 2. incomplete migration will result in a special type in which the right atrioventricular orifice overrides the septum; 3. excessive migration may be the explanation for the development of type B univentricular heart; 4. lacking or incomplete development of the inter-ampullar ring is the cause for the development of type C or D univentricular heart. In most of the cases, the univentricular heat can be considered the result of arrest of the normal embryogenesis at a more or less early state.