DISPROPORTIONATE ENLARGEMENT OF THE PULMONARY AUTOGRAFT IN THE AORTICPOSITION IN THE GROWING PIG

Purpose: This study was aimed to demonstrate growth in the pulmonary a utograft after transplantation to the aortic position. Methods and mat erials: In 20 piglets (weight 25.4 +/- 3.5 kg) (mean +/- standard devi ation) a Ross operation was performed and in five piglets (weight 9.3 +/- 0.7 kg) (mean +/- standard deviation) the ascending aorta was repl aced with a valveless pulmonary autograft, Animals were allowed to gro w as much as possible. Postmortem explanted autografts were studied by direct measurements of the valve cusps in the Ross group and of the w all segments in the valveless autograft group. Measurements of the fir st group were compared with the values of a separate control group, an d values of the second group were compared with values of samples take n at operation. Results: In the Ross group, cuspal weight, height, and width increased significantly by comparison,vith body weight (p less than or equal to 0.003), The rate of increase did not differ significa ntly from that of the control group,vith a native pulmonary valve. How ever, there was a rapid adaptation of the autograft valves resulting i n a significantly higher mean cuspal weight, height, and width. In the valveless autograft group, wall circumference, thickness, and height increased significantly (p less than or equal to 0.001), The circumfer ence increased significantly more than that of the native pulmonary wa ll. Compared with the native aortic wall, the pulmonary autograft medi a showed retained pulmonary architecture on microscopic study. Conclus ion: These data suggest that the dimensional increase of the pulmonary autograft in the aortic position in the growing pig is determined by growth and dilatation, that the valve mass increases more than that of the native pulmonary valve, and that the characteristic pulmonary mic roscopic architecture is retained.