Intracuspal hematomas in bioprosthetic valves: pathologic findings and clinical implications.

The presence of intracuspal hematomas (ICHs) was investigated in 156 valvular bioprostheses, including 57 (all porcine aortic valvular bioprostheses) that had been implanted in patients and 99 (64 porcine aortic valvular bioprostheses, 29 bovine pericardial bioprostheses and six human dura mater bioprostheses) that had been implanted in sheep. ICHs were found in three mitral bioprostheses in patients and in 14 porcine aortic valvular bioprostheses (nine mitral and five tricuspid) in sheep. Hematomas were not found in the dura mater or pericardial bioprostheses. In each patient and in six of the 14 sheep, the hematomas involved more than one cusp and consisted of erythrocyte accumulations in the spongiosa. They extended from the basal region toward the free edge of the cusp and formed a plane of dissection that involved the spaces left in the spongiosa by removal of proteoglycan material during commercial processing. ICHs may become sites of formation of calcific deposits. ICHs result from 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 this space through the suture line between bioprosthetic tissue and sewing ring on the inflow surface of porcine valvular bioprostheses mounted on atrioventricular-type stents. ICHs were not found in porcine valvular bioprostheses mounted on aortic-type stents, in which the sutures are more protected and more closely spaced, on in bioprostheses constructed of tissues (parietal pericardium and dura mater), which lack a spongiosa.