Congenital Malformations of the Mitral and Aortic Valves and Related Structures

¹ Mayo Clinic and Mayo Foundation; Section of Experimental and Anatomic Pathology, Rochester, Minnesota

Normal embryogenesis of the left heart depends upon several phenomena, both independent and related, which include: (1) looping of the primitive heart tube; (2) atrial septation; (3) partitioning of the atrioventricular canal; and (4) derivation of the left ventricular outflow tract and its proper connection to the aorta whose development depended upon partitioning of the truncus arteriosus. The latter two events are most complex and abnormalities of them are responsible for a variety of congenital malformations of the left heart. Many of the malformations resulting from abnormal partitioning of the A-V canal and development of the outflow tract of the left ventricle are represented by the varieties of persistent common atrioventricular canal, that is, the group of malformations resulting from abnormality of the atrioventricular endocardial cushions.