Anatomy of the muscular subpulmonary infundibulum with regard to the Ross procedure.

BACKGROUND: To clarify the precise anatomical relationship of the muscular subpulmonary infundibulum.
METHODS: Eleven hearts were dissected, and microscopic sections taken through the arterial trunks of a 37-week-old fetus and of a neonate. The anatomy was also investigated during operative Ross procedures.
RESULTS: The sinotubular junctions of the pulmonary and aortic roots cross obliquely. The leaflets of the pulmonary valve are lifted away from the ventricular septum by the free-standing subpulmonary infundibulum, whereas the aortic valve is deeply wedged between the atrioventricular junctions. The muscular infundibulum spirals around the aortic root, being longest below the right-facing aortic sinus and shortest below the left. The first septal perforating artery pierces the septum below the shortest part of the infundibulum, sometimes within a millimeter of the pulmonary valvar hinge, but a muscular sleeve lifts the pulmonary leaflets from the septal musculature.
CONCLUSIONS: The pulmonary valvar leaflets are supported entirely by free-standing musculature, having no direct relationship with the ventricular septum. This makes possible the Ross procedure.