A 31-year-old woman with partial atrioventricular septal defect underwent left atrioventricular valve (LAVV) replacement. Her initial repair was at 8 years of age. At 23 years of age, she underwent reoperation due to a combination of severe left ventricular outlet obstruction and moderate LAVV regurgitation. At that reoperation, she had a Dacron patch enlargement of the infundibular septum and repair of her LAVV with a xenograft (bovine) pericardial patch sutured into the superior bridging leaflet. LAVV replacement was required 8 years later because of valve insufficiency. There was a perforation in the patch with fibrosis, thickening due to pannus, and calcification of the pericardial tissue and the leaflet tissue, leading to stiffening of the tissue.