[Absence of the tricuspid valve. A case report].

An anatomical embryological and histological study of a malformed heart is presented in which the right concordant atrioventricular connexion is unguarded by the tricuspid valve, due to absence of the three leaflets, chordae tendinae and papillary muscles; only the fibrous ring is present in the atrioventricular junction. This very rare malformation is associated with atresia of the valve connected with the right ventricle generally being the pulmonary valve; the ventricular septum is intact. This congenital lesion always present fibrosis in the free wall of the right ventricle. We believe a primary pathogenetic step occurs in the wall of the right ventricle which prevents the morphogenesis of the tricuspid valve from this ventricle. This malformation must be distinguish from Ebstein's disease and Uhl's disease, although they are pathogenetically related.