Design goals for a mechanical heart valve include duplicating the hemodynamic performance of the natural valve, eliminating the need for anticoagulants, and maintaining safety. The Lapeyre-Dassault (Dassault-Aviation, Paris, France) prosthetic valve, undergoing development, addresses these goals. The unique trileaflet design consists of a solid titanium ring and three leaflets. Prototypes of the valve fabricated with Delrin leaflets were implanted in the mitral position in six calves (70-90 kg). Four calves (Studies 1, 2, 3, 5) had long-term survival of 165, 158, 219, and 281 days, respectively. Two calves were killed, one on Day 37 and one on Day 39, after complications unrelated to the valve developed. In all calves heparin was given intravenously to maintain partial thromboplastin time at 1.5 to 2.0 x baseline for approximately 1 week. In Studies 1 and 2 full anticoagulation and antiplatelet therapy was given (orally administered sodium warfarin to maintain prothrombin time at 1.5 to 2.0 x baseline, along with aspirin (1 g/day) and dipyridamole 400 mg/day). In Study 3, all anticoagulation and antiplatelet therapy was discontinued at 1 month after implant. In Study 5, no anticoagulation therapy was given after the initial week of intravenous heparin; however, antiplatelet therapy was started on the fifth postoperative month and maintained until the study's end at 9 months. At 1, 2, 3, and 5 months, the mean plasma free hemoglobin level in the four long-term animals was 5.0 +/- 2.16, 6.0 +/- 3.83, 8.5 +/- 4.93, and 11.3 +/- 6.74 mg/dl, respectively. Hemolysis was not a problem. Valve performance during normal activity was excellent in all the calves, as evidenced by echocardiography and the overall appearance of good health. In the four completed long-term studies, left heart catheterization showed a mean valve pressure gradient of 11.57 +/- 1.26 mmHg and no apparent valvular regurgitation. Histopathologic examination of major organs showed no evidence of thromboembolic events. This study shows that the innovative design of this trileaflet valve performed well in initial in vivo testing, justifying further development.

Animals↗

PubMedDate not supplied

Computational fluid dynamics and experimental validation of a microaxial blood pump.

Intravascular application of microaxial blood pumps as heart assist devices requires a maximum in size reduction of the pump components. These limitations affect the design process in many ways and restrict the number of applicable experimental procedures, but a detailed knowledge of the hemodynamics of the pump is of great interest for efficiency enhancement and reduction of blood trauma and thrombus formation. Computational fluid dynamics (CFD) offers a convenient approach to this goal. In this study, the inlet, vane, and outlet regions of a microaxial blood pump used as an intraaortic left ventricular assist device are analyzed by CFD and 3-dimensional (3-D) particle tracking velocimetry (PTV). For this purpose, a mock loop is set up that facilitates 3-D flow visualization. Flow in the main part of this testing device is modeled and computed by means of CFD. Pump head/flow (HQ) characteristics, axial pressure distribution, and particle images are then compared with numerical flow data. Results show that the pump performance characteristics, as well as inlet and outlet swirl predicted by the CFD model, are quite accurate compared with measured data. Proper boundary condition definitions and spatial discretization topology requirements for satisfactory results are discussed.

Biomedical Engineering↗