DOWNSIZING OF VALVE ALLOGRAFTS FOR USE AS RIGHT HEART CONDUITS

In recent years, there has been a worsening shortage of small and inte rmediate-sized aortic and pulmonary allografts for use as right ventri cular-to-pulmonary artery conduits in infants and children. However, t here is a surfeit of large pulmonary and aortic allografts from adult donors. The feasibility of reducing a large allograft to a more useful size was examined using human pulmonary and aortic allografts. Eleven pulmonary allografts (11 to 26 mm in diameter) and nine aortic allogr afts (5 to 27 mm in diameter) were studied. Valve competence before do wnsizing was tested with a column of saline to a static pressure equiv alent to the normal pulmonary pressure (20 mm Hg). Regurgitant now was measured for 15 minutes. One complete cusp of the valve was excised, together with a longitudinal strip of the arterial wall. A bicuspid va lved conduit was created by suturing the allograft longitudinally. The diameter of the bicuspid valve was measured with a dilator. A nomogra m was constructed that predicts the size of the bicuspid allograft bas ed on the size of the original allograft. The competence of the bicusp id allograft was tested and the regurgitant now was compared with that of the original tricuspid allograft. The transvalvular systolic press ure gradient was measured with the bicuspid allograft placed in a puls atile extracorporeal perfusion circuit at a now rate of 1 L/min and a mean pressure of 20.5 +/- 2.6 mm Hg. The regurgitant now before and af ter downsizing was 242.9 +/- 297.9 mL/15 min and 7.3 +/- 9.5 mL/15 min (p = 0.016), respectively, for pulmonary allografts and 113.6 +/- 149 .5 mL/15 min and 1.5 +/- 2.1 mL/15 min (p = 0.039), respectively, for aortic allografts. The pressure gradient after downsizing was 1.1 +/- 1.3 mm Hg for pulmonary allografts and 2.5 +/- 2.1 mm Hg for aortic al lografts. The diameter after downsizing ranged from 7 to 18 mm for pul monary allografts and from 4 to 18 mm for aortic allografts. The linea r regression equation with respect to the diameter before downsizing w as Y = 0.713X - 1.338 (r = 0.986) for pulmonary allografts and Y = 0.6 40X + 0.460 (r = 0.995) for aortic allografts. Bicuspid allografts wer e found to be significantly more competent than the original allograft s and to have minimal pressure gradients in an in vitro system. We con clude that it is feasible to downsize allografts for use as right vent ricular-to-pulmonary artery conduits.