Original Article Inflammation and infection in nine surgically explanted Medtronic FreestyleR stentless aortic valves Jagdish Butany a,d, 4 , Taylor Zhou a,d , Shaun W. Leong a , Kristopher S. Cunningham a,d , Molly Thangaroopan b , Anusha Jeggatheeswaran c , Christopher Feindel c , Tirone E. David c a Department of Pathology, Toronto General Hospital/University Health Network, Toronto, Canada b Department of Cardiology, Toronto General Hospital/University Health Network, Toronto, Canada c Department of Cardiac Surgery, Toronto General Hospital/University Health Network, Toronto, Canada d Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, Canada Received 6 July 2006; received in revised form 2 January 2007; accepted 29 January 2007 Abstract Background: The Medtronic Freestyle valve is 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 little has been reported about its long-term pathology. Methods and results: Nine Freestyle valves explanted between 2003 and 2005 were reviewed to assess the reasons for bioprosthesis failure (six implanted at our institution). All valves were examined in detail, using histochemistry and immunohistochemistry to identify the cellular response. One Freestyle valve, explanted for mitral valve endocarditis on the fifth postoperative day, was excluded from analysis. Average implant duration was 52.8F35.5 months. Four valves were explanted for infective endocarditis, three for aortic insufficiency, two for aortic stenosis with cusp calcification seen in five valves, pannus and thrombus in all valves and a chronic inflammatory reaction involving the xenograft arterial wall seen in eight of nine valves. This was associated with significant damage to the porcine aortic wall in seven cases, and cusp myocardial shelf damage in six cases. Conclusions: In this series of valves, we found (1) infective endocarditis; (2) pannus, thrombus, and calcification; and (3) unusual and significant inflammatory reaction and aortic tissue damage, which could by itself lead to aortic incompetence. D 2007 Elsevier Inc. All rights reserved. Keywords: Stentless valves; Inflammation; Prosthetic heart valves; Infection; Freestyle valves 1. Introduction Prosthetic heart valves may be mechanical or biological. Bioprosthetic heart valves (BHV) can be stented for structural support, or nonstented, using the native (host) aortic wall for support. Stentless BHVs are recently developed PHV, technically more challenging to implant and with a slightly higher operative morbidity and mortality than stented valves [1], although early data suggest that subsequent improvements in hemodynamics may offset these initial difficulties [2]. Stentless valves were designed to minimize the residual pressure gradient [3]. These valves have shown a larger effective orifice area than stented PHVs [4]. The lower transvalvular gradient is important for regression of hyper- trophy and remodeling of the left ventricle. The Medtronic Freestyle valve (Medtronic Heart Valve Division, Irvine, CA, USA) has been reported to reduce left ventricular mass index by 75% within 2 postoperative years [3]. Aortic valve replacement with stentless porcine valves has better 5- and 8-year survival rates than stented BHV over the same time frame [2,3]. Common clinical modes of failure of both stented and stentless BHV have been extensively reviewed [5]. The Freestyle valve is composed of a porcine aortic root with attached valve cusps and approximately 3 cm of the ascending aorta [6]. The porcine aortic root is fixed in glutaraldehyde under 40 mm Hg of pressure, whereas 1054-8807/07/$ – see front matter D 2007 Elsevier Inc. All rights reserved. doi:10.1016/j.carpath.2007.01.009 4 Corresponding author. Toronto General Hospital, 200 Elizabeth Street, E11-420, Toronto, Ontario, Canada M5J 2C4. Tel.: +1 416 340 3003; fax: +1 416 586 9901. E-mail address: jagdish.butany@uhn.on.ca (J. Butany). Cardiovascular Pathology 16 (2007) 258 – 267