Conduction tissue in the transplanted human heart.

Eleven orthotopically transplanted human hearts have been examined at retransplantation or necropsy. They were selected to cover the period up to 3 years after transplantation. The recipient SA node was examined in six, the donor SA node in eight and the AV conduction tissue in all eleven. Each of these areas has been examined by serial sectioning. All the conduction tissue is discretely involved in rejection and this involvement is no more severe than in the adjacent myocardium. In the AV tissue there is a tendency for the peripheral parts to be more frequently involved than the proximal. There is little evidence of permanent structural damage to the AV tissues by recurrent episodes of mild to moderate rejection. In the atrial nodes there is about a 50 per cent chance of surgical or procurement damage to both the recipient and the donor tissue.