Compact Mock Loops of the Systemic and Pulmonary Circulation for Blood Pump Testing

Mock loops are an important tool for in vitro investigations of artificial blood pumps. The simple windkessel, throttle, and atrium principle was used for the mock loop design presented. The components of the systemic and the pulmonary mock loop were designed according to calculated numerical simulation parameters. The loops offer a compact design and simple handling. For simulating biventricular assist or total artificial heart (TAH), both loops can be coupled correspondingly. The numerical simulation and the first results with the loops show very good similarity to physiological data of systemic and pulmonary circulation. The measurements of pump characteristics are significant for quantitative comparison of different pump sizes and types, or driving systems.

Finite element stress analysis of a new design of synthetic leaflet heart valve

This paper presents a parametric finite element analysis of the stresses in the leaflets of a new design of polyurethane heart valve in the closed position. The alpharabola geometry of the valve has previously been reported by Leat and Fisher (1) and has been shown to demonstrate good opening characteristics. The effects of variations in leaflet offset parameter, g, length, h, and local thickening have been determined for a valve where the frame is assumed rigid. A spherical leaflet geometry has also been analysed for comparative purposes. Results have shown that the alpharabola leaflet geometry can reduce the maximum principal tensile stress to 60 per cent of that for a spherical valve of the same mesh density.

Calcification and fatigue failure in a polyurethane heart value

The prosthetic heart valves were fabricated from a polyurethane containing a 4,4'-diphenylmethane diisocyanate hard segment, chain-extended with butanediol and with a polyether soft segment. The rate of calcification of these polyurethane heart valves was much slower in a dynamic in vitro test system than similar bioprosthetic heart valves. The calcified deposits were located exclusively at regions of material failure. Fourier transform infrared (FTIR) spectroscopy indicated the involvement of the polyether soft segments of the polymer directly in the calcification process. Calcification of polymer fractions also suggested that small molecular weight extractable components are accelerating factors in the calcification process.