Is the Morphologic Mitral Valve in Discordant Atrioventricular Connections Always Normal?

Background The purpose of this study was to determine structural features and variations in the mitral valve guarding inflow of the morphologic left ventricle in hearts with discordant atrioventricular connections. Methods Morphologic investigation was carried out on the inlet valve to the morphologic left ventricle in 48 autopsied specimens with this particular entity of malformation. Results The tension apparatus was straddling to the morphologic right ventricle in 2. Another 34 hearts had a bifoliate valve and the papillary muscles abnormally oriented; a solitary papillary muscle in 3, two papillary muscles but deviated in 5, one of two papillary muscles being dysmorphic in 9, and three or more papillary muscles in 17. The origin of these papillary muscles was frequently deviated. In 5 hearts with a trifoliate or quadrifoliate valve, multiple papillary muscles were also the case. One of these had thick leaflets, a part of which was adherent to a membranous flap around the ventricular septal defect as well as to subpulmonary fibrous tissue tags. Eventually, the valve was comparable with the mitral valve seen in the normally structured heart in only 7 hearts (15%). There was no obvious correlation noted between the presence of abnormality in the mitral valve and that in the tricuspid valve. Conclusions Architectural abnormalities are not rare in the morphologic mitral valve in this setting. The valvar structure needs precise recognition.