Postoperative histological diagnosis in two cases of unsuspected bioprosthetic endocarditis

Two cases of preoperatively unsuspected porcine bioprosthetic endocarditis are presented. Both cases, thought to be a sterile thrombosis and a primary tissue failure respectively, were correctly diagnosed only with histological examination. Cultures and histological examination of the explanted tissue are necessary for a definite diagnosis in every case of prosthetic malfunction.