IS A CLEFT IN THE ANTERIOR LEAFLET OF AN OTHERWISE NORMAL MITRAL-VALVE AN ATRIOVENTRICULAR-CANAL MALFORMATION

Objectives. This study sought to ascertain the surgical anatomy of a c left in the left atrioventricular (AV) valve. Background. Important mo rphologic differences exist between hearts with a cleft in the anterio r leaflet of an otherwise normal mitral valve and those with a so-call ed cleft in the left AV valve when there is an AV septal defect, but i t has been customary to link the lesions together on developmental gro unds. Methods. Eight autopsied specimens with a cleft in the aortic (o r anterior) leaflet of the mitral valve were studied in detail, and ec hocardiograms from 21 patients with such a cleft were compared with th e specimens and with findings typical of the so-called partial AV cana l and other forms of AV septal defect.Results. The structure and direc tion of the cleft, location of the papillary muscles within the left v entricle and AV junctional morphology of hearts with an otherwise norm ally structured mitral valve were significantly different from typical findings in hearts with AV septal defects. Conclusions. It is necessa ry to distinguish morphologically a cleft in an otherwise normally str uctured mitral valve in hearts with separate right and left AV junctio ns from the trifoliate left component of a common AV valve in hearts w ith an AV septal defect and a common AV junction because the dispositi on of the AV conduction tissues varies markedly between the lesions.