Kangaroo Versus Freestyle Stentless Bioprostheses in a Juvenile Sheep Model: Hemodynamic Performance and Calcification Behavior

Background: Glutaraldehyde‐preserved bioprosthetic heart valve substitutes have limited performance and longevity due to tissue degeneration and calcification. The Freestyle valve (Medtronic Heart Valves, Inc, Minneapolis, MN) combines zero fixation pressure and ∝‐amino oleic acid (AOA) as antidegeneration and antimineralization measures. The aim of this study was to compare the calcification behavior of glutaraldehyde‐preserved kangaroo aortic valves with Freestyle stentless bioprostheses in a juvenile sheep model. Methods: Pulmonary artery and valve replacements were performed in juvenile sheep with Freestyle stentless aortic valves (n = 4) or glutaraldehyde‐preserved kangaroo stentless aortic valves with no antimineralization measures (n = 6), and explanted at 200 postoperative days. Results: Freestyle stentless valves and stentless kangaroo aortic valves showed normal valve function immediately postoperatively and up to 120 days. Valve leaflets of all valves were macroscopically free of visible calcification with normal histology. Valve leaflet calcification (μg Ca/mg tissue) was less in kangaroo than Freestyle (1.27 ± 0.43 versus 2.38 ± 1.37, p = 0.856). Aortic wall tissue calcification was severe in kangaroo and Freestyle (127.93 ± 12.22 versus 122.19 ± 11.99, p = 0.596). Conclusions: We conclude that glutaraldehyde‐preserved kangaroo aortic valve leaflets are equal to AOA‐treated Freestyle stentless valve leaflets with regard to calcification in juvenile sheep. Both bioprostheses are prone to aortic wall calcification. The low calcification features of the kangaroo aortic valve leaflets without antimineralization treatment may benefit the longevity of the valve.