Abstract
Heterologous aortic valves are used in many clinics as replacements for diseased human aortic and mitral valves. These valves possess all the advantages of homologous aortic valves and are more easily available to the surgeon. The heterologous valve also provides a greater choice of valve size than does the homograft; this can be of importance when replacing the mitral valve. Heterograft valves, like homografts, are usually preserved for periods ranging from a few days to a few months before insertion into a patient. Four methods of preservation, described, are currently in use. This study compares the effects of these four methods of preservation when pig valves are transplanted into the dog's aorta.