Acute aortic stenosis of a porcine valve heterograft apparently caused by graft rejection: case report with discussion of immune mediated host response.

This report describes a patient with a gluteraldehyde preserved porcine xenograft in which acute prosthetic aortic valve stenosis developed during the postoperative period. Thrombotic occlusion was ruled out by direct visualization at reoperation, when a fibrin fusion of two leaflets was released to relieve the stenosis. After a fatal arrhythmia (79 days following insertion of the prosthesis), histological evaluation of the xenograft revealed a reaction on the leaflets, interpreted as predominantly transformed or blast lymphocytes. Microscopically, a thin layer of fibrin was visible over these cells. This fibrin layer could have stitched the commissure closed, producing the aortic stenosis. Such a sequence of events is unique in our past experience with 68 porcine xenograft valves. We believe that this case is an example of an immune mediated host response caused by rapid early fibrin fusion of prosthetic aortic leaflet margins, which resulted in prosthetic stenosis.