Correlating the morphological features of tetralogy of Fallot and the Eisenmenger malformation

We studied a series of 43 autopsied cases of tetralogy of Fallot, assessing the mode of insertion of the outlet septum relative to the limbs of the septomarginal trabeculation, and compared the findings in retrospective fashion with our previous observations of a group of hearts with the so-called Eisenmenger malformation. In the majority of hearts with tetralogy of Fallot, the outlet septum inserted frontally relative to the septomarginal trabeculation, but in a minority of cases the outlet septum inserted in lateral fashion, as had been observed in all our hearts studied with the Eisenmenger malformation. The different modes of insertion were found to correlate, first, with the axis of anatomical aortic rightward rotation, coincident with the commissure between the right coronary and the left coronary leaflets of the aortic valve. The different modes of insertion of the outlet septum also correlated with the level of attachment of the arterial valvar leaflets on its subpulmonary and subaortic surfaces; concomitantly, correlation was found between the length of the subpulmonary infundibulum and the length of the muscular outlet septum itself. In the majority of hearts showing tetralogy of Fallot, the elongated infundibulum was also uniformly narrow, but in a minority the infundibulum was well expanded, obstructed only at its mouth, but widening at the valvar level. In all the hearts with the Eisenmenger malformation, in contrast, the unobstructed infundibulum was well expanded. The morphological findings of the present study show unequivocally that tetralogy of Fallot and Eisenmenger malformation are two phenotypically different congenital cardiac anomalies.