Acute thrombosis of Sorin tilting disc mitral prostheses

We observed four cases of prosthetic thrombosis in 77 patients who had had a tilting disc valve (Sorin model) inserted in the mitral position. In all cases, the clinical findings on admission consisted of congestive heart failure, absence of prosthetic closing click and mitral regurgitation murmur. M-mode and cross-sectional echocardiography were invariably diagnostic. Surgery was performed without delay and consisted of thrombectomy in one case and valve replacement with porcine xenograft in three. Examination of the explanted prostheses disclosed fibrous tissue overgrowth surrounding the valvular ring, as well as thrombotic vegetations on the ventricular and atrial sides. The disc appeared blocked in a semiopening position at an angle of 45 degrees. Our experience suggests that the thrombosis is secondary to disc malfunction itself produced by periannular tissue growth. It is related to the porosity of the fabric which surrounds the metal ring, the valve design and its orientation. Correct anticoagulation therapy, performed in all cases, had no significant effect on tissue overgrowth. The high postoperative mortality rate depended on the severity of the preoperative clinical condition of the patients.