It has long been contentious as to whether the presence of bilateral infundibulums, or conuses, is a prerequisite for the diagnosis of double-outlet right ventricle. As the use of such a criterion would abrogate the so-called “morphological method”, which correctly states that one variable entity should not be defined on the basis of another entity that is itself variable, it is now accepted that double outlet can exist in the setting of fibrous continuity between the leaflets of the atrioventricular and arterial valves. Although this debate has now been resolved, there are other contentious areas still requiring clarification in the setting of hearts unified because of the presence of this particular ventriculo-arterial connection – for example, it is questionable whether the channel between the ventricles should be described as a “ventricular septal defect”, whereas it is equally arguable that the mere presence of fibrous continuity between the leaflets of the arterial valves does not necessarily place the channel in a doubly committed location. In this review, we describe a series of autopsied hearts in which the anatomical features serve to illuminate these various topics. We then discuss recent findings regarding cardiac development that point to the individuality of the building blocks of the ventricular outflow tracts, specifically the outlet septum, the inner heart curvature, or ventriculo-infundibular fold, and the septomarginal trabeculation, or septal band.

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.

We studied 11 autopsied cases of the Eisenmenger malformation, comparing the findings with 11 hearts with intact ventricular septal structures, and nine hearts having perimembranous ventricular septal defects in the absence of aortic overriding. We found variable lengths for the subpulmonary infundibulum in the hearts with Eisenmenger defects. It was well developed in three hearts, of intermediate length in seven, and very short in one of the specimens. The muscular outlet septum was also of variable length compared with the free-standing subpulmonary infundibular sleeve. Except for one, all hearts had fibrous continuity between the aortic and tricuspid valvar leaflets, such that the ventricular septal defect was then perimembranous. In the remaining case, there was a completely subaortic muscular infundibulum, with the ventricular septal defect showing only muscular borders. The medial papillary muscle was absent in the majority of cases, but was well formed in three hearts, all with relatively short muscular outlet septums. We identified mild, intermediate, and severe degrees of rightward rotation of the aortic valve, and these findings correlated with the extent of aortic valvar overriding. In nine of the 11 hearts, the ventriculo-arterial connections were concordant, but there was double-outlet from the right ventricle in the other two specimens. Based on our anatomic and morphometric observations, we conclude that the hearts we have defined as having Eisenmenger defects show marked individual variation in their specific phenotypic anatomy.

We examined the echocardiograms of 40 patients with double oudet right ventricle, proven either at autopsy or during surgery. By way of the subcostal approach, it proved possible to determine the insertion of the outlet (infundibular) septum and to categorize the malformations within the classification proposed by de la Cruz and her colleagues. It was also possible to ascertain the relationships of the atrioventricular valves with one or with both infundibulums, and these features could be correlated with infundibular interrelationships. The interrelationship of the great arteries, in contrast, was not always in accordance with the infundibular interrelationships, indicating that the arterial interrelationship may not prove to be a good parameter for surgical decision-making. Of greatest importance was the visualization and echocardiographic appraisal of the spatial position and size of the ventriculoinfundibular fold, since this anatomic feature was the key to determining the optimal surgical approach. This is so because the ventriculoinfundibular fold constitutes one of the borders of the ventricular septal defect, and separates it from the plane of the leaflets of the arterial valves. Furthermore, the fold frequendy contributes to infundibular obstruction. Our echocardiographic studies, based on a better anatomic knowledge, permitted us to choose the most suitable surgical technique in our patients.