Development of "subaortic stenosis" after pulmonary arterial banding for common ventricle

Progressive narrowing of the bulboventricular foramen is documented in four patients with single ventricle. The morphologic features in each case corresponded to single left ventricle with infundibular chamber. Two patients had a D-ventricular loop and the other two an L-loop. All four patients had transposition of the great arteries. Restriction of the bulboventricular foramen thus resulted in functional subaortic stenosis because the aorta originated above the infundibular chamber. The development of subaortic obstruction was documented by serial cardiac catheterization studies in two infants, one of whom underwent unsuccessful surgical enlargement of the bulboventricular foramen. In the other two patients the initial cardiac catheterization revealed no pressure gradient between the ventricle and aorta, but examination at necropsy revealed very severe obstruction at the bulboventricular foramen, thus suggesting that the obstruction had been acquired. In each patient, the progressive narrowing of the bulboventricular foramen occurred after pulmonary arterial banding and may have been causally related to this procedure. This functional subaortic obstruction developed in 4 of 31 patients (12.9 percent) with single left ventricle, transposition of the great arteries and pulmonary arterial banding. Clinical recognition of this development is predicated on (1) awareness that narrowing of the bulboventricular foramen in patients with single ventricle and pulmonary arterial banding may be common; (2) presence of symptoms such as angina; and (3) lack of continued clinical improvement in a patient whose pulmonary arterial band has significantly reduced pulmonary blood flow. Management of this subaortic stenosis requires surgical intervention. In the infant, a ventriculotomy in the outlet chamber will usually provide excellent exposure of the bulboventricular foramen, and surgical enlargement can be accomplished. In the older child with severe obstruction, marked muscle hypertrophy may obliterate the ventricular cavity, making ventricular partitioning difficult if not impossible.