Intracuspal hematomas in implanted porcine valvular bioprostheses: clinical and experimental studies.

Intracuspal hematomas were found in three of 57 porcine valvular bioprostheses implanted as substitute cardiac valves in 50 patients and in 11 of 29 similar bioprostheses implanted in sheep. The three values implanted in patients had been in the mitral position for 27, 65, and 107 months. Of the valves implanted in sheep, six had been in the mitral position and five in the tricuspid position for periods of time ranging from 20 minutes to 7 months. In each patient and in four of 11 sheep, the hematomas involved more than one cusp. These lesions were localized in the spongiosa, extended from the basal region toward the free edge of the cusp, and formed a plane of dissection which involved the spaces left in the spongiosa by the removal of proteoglycan material during preimplantation commercial processing. In one patient, the hematomas limited the mobility of the cusps and appeared to have been the cause of clinically significant prosthetic mitral stenosis; in the other two patients and in the experimental animals, the hematomas were smaller and of uncertain hemodynamic significance. Intracuspal hematomas may become sites of eventual formation of calcific deposits. The pathogenesis of intracuspal hematomas is related to the entry of blood into the space between the sewing ring and the most basilar region of the bioprosthetic tissue. This space extends throughout the circumference of the bioprosthesis and is continuous with the spongiosa, the layer in which the hematoma develops. The blood penetrates into this space through the suture line between bioprosthetic tissue and sewing ring on the inflow surface of porcine valvular bioprostheses which have been mounted on atrioventricular type stents. Intracuspal hematomas were not found in bioprostheses mounted on aortic type stents, in which these sutures are more protected and more closely spaced, or in pericardial bioprostheses, which do not have a spongiosa.