In Vitro Fluid Dynamics of the St Jude Valve Prosthesis in Steady and Pulsatile Flow

Abstract

The flow downstream from the St Jude valve prosthesis is studied in vitro in both steady and pulsatile flow. Conditions for the pulsatile flow studies approximate the in vivo resting state. Laser-Doppler anemometry (LDA) is used to measure instantaneous point velocities at numerous locations pre-selected to conform to a systematic, flow-mapping measurement methodology. Overall, the results for the St Jude valve indicate a relatively undisturbed forward flow through the prosthesis. The acceleration ratios, defined as the maximum mean axial velocity for the St Jude valve divided by that for no valve obstructing the flow, are small, being 1.2 and 1.4 for steady and pulsatile flow, respectively. Both the secondary flow structure and the flow disturbance produced by this valve are minimal. Maximum mean velocities in the radial and azimuthal directions are only about 5–10 per cent of that in the axial direction. There is, however, notable evidence of flow wakes generated by the valve's opened leaflets. Velocity defects caused by these wakes are found to be as much as 50 per cent. The bulk flow through this valve is in this sense quite unlike that reported by others for the natural aortic valve studied in vitro.

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