[Embryologic and pathogenetic aspects of the common atrioventricular canal development].

Atrioventricular canal (AVC) is an inherited defect the embryological basis of which is deficiency of the affluent part of the interventricular septum (IVS). Folds of the atrioventricular (AV) valves are formed from the myocardium and not from the endocardial thickening but much later than the IVS formation. Under the conditions of the affluent part of IVS the mode of connection of the anterior fold of the left AV valve creates the narrowing of the left ventricular effluent part. Endocardial thickenings play a role of a glue fixing corresponding structural components of AV valves and primary heart partitions. The degree of sticking together determines great variants of the defect anatomy. Important deficiency of the affluent part of IVS is possible this making the function difficult due to space change of the endocardial thickenings. The common valve ring with freely floating bridge-like folds is frequently revealed in such case. The notion "deficiency of the endocardial thickenings" has the only manifestation as an isolated splitting of the anterior fold of the mitral valve and exhibits main features of AVC.