New Insights into Stentless Porcine Bioprosthesis Failure
V Nair, KB Law, K Phillips, AY Li, TE David, J Butany. Toronto General Hospital/UHN, Toronto, Canada; University of Toronto, Toronto, Canada; Mcmaster University, Hamilton, Canada
Background: The Medtronic Freestyle valve is a stentless porcine valve fixed in glutaraldehyde at “zero” pressure on the cusps and treated with a-amino oleic acid. This valve reportedly has excellent clinical and hemodynamic results, but has had some failures, however little has been reported about its long-term pathology.
Design: Seventeen Freestyle valves (explanted 2003 to2009) were reviewed to assess reasons for bioprosthesis failure. Clinical data, including implant age, gender, native aortic valve lesion and implant duration were recorded. All valves were examined in detail, using histochemistry and immunohistochemistry to identify morphological changes and cellular and humoral responses.
Results: One Freestyle valve, explanted for mitral valve endocarditis on the fifth postoperative day, was excluded from analysis. The average implant duration was 71±35.2 months (6±2.9 years). Six valves were explanted for infective endocarditis, six for aortic insufficiency, and four for aortic stenosis. Infective endocardititis was seen in six, calcification in eleven, pannus in fifteen, twelve showed thrombus, cusp tears in nine and 10 showed old needle tract like injuries in the porcine aorta. Acute inflammation was seen in one and a chronic inflammatory reaction involving the xenograft arterial wall was seen in fifteen of sixteen valves. The cells were comprised of macrophages and lymphocytes. The lymphocytes were T cells(CD8 positive) and B cells. Significant damage to the porcine aortic wall was seen in fifteen cases and cusp myocardial shelf damage in seven cases. All cases stained positively for IgG and C4d par.
Conclusions: The porcine aortic cusps showed no significant cellular reaction. The porcine aortic tissue showed multifocal T cell mediated rejection associated with significant porcine aortic medial damage, consistent with dilatation of the porcine aortic root. This likely lead to porcine valular incompetence. The demonstration of IgG and C4d staining suggests the likelihood of humoral rejection, in addition to the cellular. One possibility underlying this is, that the porcine aortic tissues are inadequately fixed and hence the retained antigenicity. This is one of the few demonstrations of a rejection reaction to porcine bioprosthetic tissues, associated with bioprosthesis failure, and needs further studies.
Wednesday, March 24, 2010 1:00 PM
Poster Session VI # 31, Wednesday Afternoon