AORTIC-VALVE REPLACEMENT WITH PULMONARY HOMOGRAFTS - EARLY EXPERIENCE

The increasing use of the aortic homograft as aortic valve substitute and the limited availability of donor valves prompted us to consider t he pulmonary homograft as an alternative substitute for aortic valve r eplacement. The aim of our study is to compare the ultrastructural and biomechanical properties of pulmonary homograft leaflets with those o f their aortic counterpart and to present the early results of using t he pulmonary homograft for aortic valve replacement. Light and transmi ssion electron microscopy have shown that pulmonary homograft leaflets are thinner than the aortic with a lesser content of elastic tissue i n the ventricularis layer. However there were no substantial differenc es in the ultrastructure. Uniaxial tensile tests were done on 69 cusps from human pulmonary and aortic valves using an Instron testing machi ne. The strain at 200 KPa was found to be similar for both pulmonary a nd aortic leaflets (8.20% +/- 2.87% versus 8.98% +/- 1.90%) cut circum ferentially. Radial strips appear to be more extensible in pulmonary l eaflets than in aortic (32.6% +/- 7.5% and 28.6% +/- 11.1%, respective ly). The ultimate tensile strength for circumferential strips was foun d to be similar for both aortic and pulmonary valves (1460 +/- 857 kPa versus 1450 +/- 689 kPa), but there was relatively little difference between the radial strips (295 +/- 95 kPa versus 252 +/- 104 kPa). A t otal of 123 patients whose ages ranged between 13 and 78 years receive d either fresh antibiotic sterilized or cryopreserved pulmonary homogr afts for aortic valve replacement. The pulmonary homograft was inserte d in place of the patient's diseased aortic valve by using one of two different techniques: freehand in the subcoronary position or as a ''s hort cylinder'' inside the aortic root. There were three hospital deat hs (2.43%; 70% confidence limits = 1.08% to 4.83%). Cumulative follow- up was 184 patients years (range 1 to 39 months). All surviving patien ts have been followed up with serial color flow Doppler echocardiograp hy. There were no late deaths. Actuarial late survival was 97.5% (70% confidence limits = 95.7% to 98.6%) at 3 years. Four patients (2.2%/pt -yr) underwent reoperation because of severe aortic regurgitation (1, 4, 12, and 15 months after the operation) because of technical problem s (mismatch in size between the pulmonary homograft and aortic anulus) in three patients and