Aortic valve allografts for mitral valve replacement

Between May, 1967, and April, 1971, 122 patients underwent mitral valve replacement with fresh aortic valve allografts mounted on rigid support rings. The operative mortality rate was 6.6 percent. Current evaluation was obtained on all patients; the average postoperative follow-up interval for surviving patients is 4.8 years (range, 3.3 to 7.1). Survival rates 1, 2, and 5 years after mitral valve replacement are 89, 86, and 71 percent, respectively. The average functional class of 90 current survivors is 1.6, as compared to 2.9 preoperatively. Thirty-six thromboembolic episodes have occurred in 28 patients, generating a thromboembolism rate of 7 percent per patient year of analysis. Allograft valve dysfunction has occurred in 64 patients, requiring reoperation in 16 and causing death in two. The linearized valve dysfunction rate is 13 percent per patient year. Pathological examination of recovered allograft valves revealed predominantly leaflet fibrosis and calcification, acellular collagenous valve matrix, and infiltration with chronic inflammatory cells. The results of this long-term analysis indicate that mitral valve replacement with fresh aortic allografts provides significant functional improvement and an acceptably low rate of thromboembolism. However, the time-related rate of allograft valve dysfunction is unacceptably high and does not justify further clinical use of this type of bioprosthesis.