Cleft mitral valve in transposition with intact ventricular septum.

We describe two cases of an isolated cleft of the mitral valve in transposition with intact ventricular septum. The cleft is positioned leftward in the pulmonary leaflet, at about 2 o'clock, when viewed from below looking at the cardiac short axis with the right ventricle to one's left hand. Such clefts, when seen in the Taussig-Bing malformation are also positioned leftward. In keeping with our current knowledge of cardiac development, our cases provide further evidence that transposition with an intact ventricular septum is the end-point of the Taussig-Bing spectrum.