Porcine valves.

To date, the glutaraldehyde porcine aortic valve xenograft has proved a good choice for valve replacement in both the aortic and mitral positions. Late thromboembolisms in the absence of long-term anticoagulation is virtually nonexistent in aortic valve replacement and very low in mitral valve replacement patients without a predisposing history. The hemodynamic performance of the porcine xenograft is adequate and comparable to that of mechanical prostheses. The potential for improved hydrodynamic function, particularly of very small sized valves, is great and already being realized. In spite of over 8 yr of xenograft experience, long-term durability remains the primary concern. Histologic study suggests that these valves undergo progressive postimplantation morphological alteration. However, to date, the incidence of tissue failure is very low. Although detailed reports of long-term valve series are surprisingly few, at present, there is no valve replacement device with a 10-yr experience proven structural integrity and a negligible incidence of valve-related morbidity. It will be 3-4 yr before a significant number of porcine xenograft patients either reach this point or experience valve failure. While this review of the valve literature does not permit a statistical comparison of valve types, we feel that it does allow us to attempt a general projection. On the basis of combined survival and valve-related complication rates, at 4 yr, the porcine xenograft appears to be a better choice than the mechanical prosthesis. Excessive tissue failure during the next 3-4 yr might reverse this opinion. However, even if an increase in valve failure does occur, the advantage of noncatastrophic disfunction and decreased valve-related complications may balance the risk of reoperative morbidity and mortality and continue to favor the porcine exnograft. Thus we could speculate that: (1) The tissue valve would be the valve of choice if (A) durability of 10 yr or more is proven, and valve complications with the xenograft remain as presently reported; (B) the incidence of valve complications with the mechanical prostheses at 10-yr follow-up continues to increase. (2) Mechanical prostheses would be the valves of choice if (A) xenograft valve failure is greater than 20% at 10 yr of follow-up; (B) the incidence of valve complications with the mechanical prostheses remains unchanged. (3) The choice of xenograft versus mechanical prosthesis will remain an open issue if valve failure and related complications with both types of device remain below 20% at 10-yr follow-up...