Mechanical valve thrombosis in a chronic animal model: differences between monoleaflet and bileaflet valves.

摘要: BACKGROUND AND AIM OF THE STUDY The occurrence of mechanical valve thrombosis was studied in a chronic sheep model implantation the pulmonary position. METHODS Six monoleaflet and six bileaflet valves were implanted young sheep. Anticoagulation stopped at one week postoperatively, after which weekly fluoroscopic evaluation performed. Animals sacrificed moment any abnormality on image or, if no occurred, fixed time intervals two three months. After explantation, examined macroscopically, by stereomicroscopy, histology scanning electron microscopy. Lung biopsies taken. RESULTS All remained functionally intact for up to months without anticoagulation, but explantation or revealed thrombi attached struts, cuspal surface ring. valves, except one, showed obvious dysfunction fluoroscopy (one both cusps fixed) within frame eight weeks implantation. Histology microscopy primary thrombotic material hinges, obstructing further cusp movement. embolism detected only animal among biopsy specimens. CONCLUSION low-pressure environment position caused changes all valves. severe probably due their delicate hinge mechanism. These findings may be used development an thrombosis.