The cryopreserved homologous heart tissue grafts normally used can be broken down into two classes:

1. Heart valves for the treatment of adult aortic valve disease;
2. Heart valves for the treatment of complex congenital heart disease in children.

When the aortic valve fails or is stenotic, the left ventricle does not work properly and suffers from what is known as contractile failure, eventually reaching a point when valve replacement is mandatory. Biological implants do not need anticoagulant therapy, nor do they degenerate on account of calcification. In Italy, many heart surgeons see the use of homologous aortic or lung tissue as almost compulsory for patients who:

• are young;

• are women of childbearing age and want to have children;

• suffer from aortic valve endocarditis;

• have an infected aortic prosthesis;

• have a small aortic root;

Homologous graft material is used even more frequently in children, not least because of the limited number of implantable mechanical prostheses of a size suitable for paediatric cases. Donor valves are used in a very wide range of complex congenital diseases, especially to reconstruct hypoplastic or atresic heart structures, in pulmonary atresia, atresia of the common arterial trunk, or hypoplastic left heart. Operative mortality rates of 1% for elective surgery and 8% in the case of emergency surgery have been reported. Moreover, the incidence of calcific degeneration is very low, with 80% of all homologous tissue grafts functioning normally at 15 years.