Background: The hemodynamic characteristics of different heart valve prostheses have been investigated in vitro with a novel pulse duplicator. A novel valved stent for transapical or percutaneous valve implantation has been compared with a native heart valve and mechanical heart valves.
Methods: All experiments were designed to imitate both physiologic pressure ratios and flow characteristics in diastole and systole. After calibrating the system using a human aortic valve (primary orifice diameter: 22.0 mm), the following valves were studied under aortic pulsatile flow conditions: Hall-Kaster (Medtronic-Hall, 20.0 mm), St. Jude Medical (20.0 mm), a newly developed tricuspid valved stent (Tricumed TM4, 20.7 mm) and a newly developed biomechanical valve (Engage aortic valve Model 6000, 21.0 mm). All valves including the human aortic valve were assessed by videotape observation under pulsatile flow conditions. Measured flow-related parameters include in vitro mean transvalvular pressure, regurgitant volume, effective orifice area and performance index.
Results: The optical assessment of all five valves demonstrated a complete opening during systole and closing at the beginning of diastole. All valves were optically sufficient during diastole. Engage aortic valve Model 6000 showed the highest maximum transvalvular pressure (27.5 +/- 8.2 mmHg), whereas both Hall-Kaster (17.9 +/- 1.5 mmHg) and St. Jude Medical (16.7 +/- 0.7 mmHg) had a lower gradient than the native aortic valve (24.0 +/- 0.2 mmHg) and Tricumed TM4 (21.8 +/- 3.8 mmHg). The maximum effective orifice area of St. Jude Medical amounted to 258.7 +/- 3.4 mm(2), followed by Tricumed TM4 with an area of 222.1 +/- 1.9 mm(2) and the human aortic valve with 160.4 +/- 2.9 mm(2). Hall-Kaster and Engage aortic valve Model 6000 had an area of 198.9 +/- 1.6 mm(2) and 176.7 +/- 3.1 mm(2), respectively.
Conclusions: The pulse duplicator proved to be highly accurate and yielded reproducible results. Since it has been calibrated with a human aortic valve, the hemodynamics of any heart valve prosthesis can be compared with the human valve. This system can evaluate and promote the development of new biological and mechanical heart valve prostheses.