The Surgical Significance of Phenotypic Variability in the Setting of Tetralogy of Fallot

The phenotypic feature of tetralogy of Fallot is anterocephalad deviation of the muscular outlet septum, or its fibrous remnant, relative to the septoparietal trabeculation, coupled with hypertrophy of septoparietal trabeculations. Although this feature permits recognition of the entity, no two cases are identical. Once diagnosed, treatment is surgical. The results of surgical treatment have improved remarkably over recent decades. The results are now sufficiently excellent, including those in the developing world, that attention is now directed toward avoidance of morbidity, while still seeking, of course to minimize any fatalities due to surgical intervention. It is perhaps surprising that attention thus far has not been directed on the potential significance of phenotypic variation relative to either mortality or morbidity subsequent to surgical correction. The only study we have found specifically addressing this variability focused on the extent of aortic override, and associated malformations, but made no mention of variability in the right ventricular margins of the interventricular communication, nor the substrates for subpulmonary obstruction. In this review, therefore, we assessed the potential significance of known morphological variability to the outcomes of surgical intervention in over 1,000 individuals undergoing correction by the same surgeon in a center of excellence in a developing country. We sought to assess whether the variations were associated with an increased risk of postoperative death, or problems of rhythm. In our hands, double outlet ventriculoarterial connection was associated with increased risk of death, while the presence of a juxta-arterial defect with perimembranous extension was associated with rhythm problems.