In Vitro Evaluation Of A Stentless Porcine Aortic Bioprosthesis

Although the clinical results of aortic valve replacement with currently available bioprostheses are satisfactory,suboptimal hemodynamic performance, tissue calcification,and limitation in long-term durability have been encountered. It is believed that these problems are caused directly or indirectly by the stents of the bioprostheses.To address these deficiencies,the designs of the stenting mechanism for new generation stented bioprostheses have optimized by increasing flexibility of the commissures and reducing the annular area of the sewing ring.However,the turbulent shear stresses distal to the new stented bioprotheses,again attributed to the stents,were still large enough to be of concern.To further enhance the performance of the bioprosthetic heart valves in the aortic position,we undertook the development of a stentless porcine bioprosthesis.Our study evaluates the hemodynamic performance and durability of this stentless porcine aortic bioprostheis(SPAB) in special chambers with near physiologic compliance.The results are compared to those obtained from a stented XJ bioprosthesis.Aims: 1.To evaluate hemodynamic performance of this stentless porcine aortic bioprosthesis.The results are compared to those obstained from a stented XJ bioprosthesis.2.To evaluate durability of this stentless porcine aortic bioprosthesis.The results are compared to those obstained from a stented XJ bioprosthesis.Methods:1.Two sizes(19mm,23mm) of the new stentless porcine aortic bioprosthesis were prepared in sterility.In vitro pulsatile flow tests were performed on the stentless and stented valve in according to ISO5840 guideline.Effective orifice area,transvavular pressure gradient and regurgitation ratio were recorded at various flow volume,compared with XJ stented porcine aortic bioprosthesis.2.We observed and analyzed the cause of the appearance of wearing by 50 million,100 million and 150 million cycles in accelerated wear test for long-term durability of this stentless bioprosthesis and selected stented counterparts.3.We compared the biomechanical characteristic and ultrastructure of stentless bioprosthesis of wearing by 50 million cycles,100 million cycles and the fresh one in durability test.4.We investigated the sterile condition of an accelerated durability equipment.Results:1.The mean gradient of stentless bioprosthesis(19mm,23mm) is lower than that of XJ stented bioprosthesis at all flow.The effective orifice area of stentless bioprosthesis is larger than that of stented porcine aortic bioprosthesis in selected size.However,at the flow of 2.0L/min,there is no significant difference between the effective orifice area of 19mm stentless bioprosthesis and that of 19mm stented bioprosthesis.2.Direct comparisions of the simultaneous performance of the stentless bioprosthesis and the control valve documented the superior durability of the stentless bioprosthesis under these controlled in vitro conditions.Evidence of wear in control valve was apparent by 150 million,whereas there was no evidence of wear at that time in the stentless bioprosthesis.3.The value of elastic modulus and ultimate tensile strength after 50 million cycles of fatigue test was greater than that after 100 million cycles,while the value of ultimate tensile displacement was less.The ultrastructure order of collagen fiber of the fresh and 50 million cycles appeared to be well arranged,but that of 100 million cycles appeared to not well arranged.4.The sterile period of group F is longer than that of group G and H.Conclusions:1.The hemodynamic performance of stentless porcine aortic bioprothesis is superior to XJ stented porcine aortic bioprosthesis in vitro pulsatile test.2.These in vitro studies show that stentless bioprosthesis has better durability when compared under identical in vitro conditions with the XJ stented bioprosthesis.3.Our sterile method is effective in fatigue test.