Bulboventricular foramen size in infants with double-inlet left ventricle or tricuspid atresia with transposed great arteries: Influence on initial palliative operation and rate of growth

Bulboventricular foramen obstruction nay complicate the management of patients with single left ventricle. Bulboventricular foramen size was measured in 28 neonates and infants >5 months old and followed up for 2 to 5 years in those patients whose only sytemic outflow was through the foramen. The bulboventricular foramen was measured in two planes by two-dimensional echocardiography, its area calculated and indexed to body surface area. One patient died before surgical treatment. The mean initial bulboventricular foramen area index was 0.94 cm²/m² in 12 patients (Group A) in whom the foramen was bypassed as the first procedure in early infancy. The remaining 15 patients underwent other palliative operations but the bulboventricular foramen continued to serve as the systemic outflow tract. There was one surgical death. Six (Group B) of the 14 survivors developed bulboventricular foramen obstruction during follow-up (mean initial bulboventricular foramen area index 1.75 cm²/m²). The remaining eight patients (Group C) did not develop obstruction during follow-up and had an initial bulboventricular foramen larger than that in the other two groups (mean initial bulboventricular foramen area index 3.95 cm²/m²). All patients with an initial bulboventricular foramen area index <2 cm²/m² who did not undergo early bulboventricular foramen bypass developed late obstruction. Although the bulboventricular foramen area increased sightly with growth, when indexed to body surface area it decreased with time. An excellent correlation was found between antemortem echocardiographic measurements and the bolboventricular foramen dimensions measured in 11 heart specimens (2 from the patients who died before or during operation, 5 from patients who died late postoperatively and 4 additional specimens from patients who were not followed up longitudinally). It is concluded that 1) biplane two-dimensional echocardiography is reliable for determining bulboventricular foramen size; 2) bulboventricular foramen size in the neonate is an important predictor of late obstruction; and 3) although the bulboventricular foramen appears to grow, its growth does not keep pace with somatic growth in most patients.