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.