REGURGITANT HEART-VALVE FLOW FROM 2-D PROXIMAL VELOCITY-FIELD - CONTINUED SEARCH FOR THE IDEAL METHOD

It has been suggested that flow through a leaking heart valve can be d etermined by studying the proximal velocity field. Normally, only the centre-line velocity is studied as a potential method. The aim of the study is to improve this method by using information from the entire r econstructed proximal velocity field. Four methods are compared: use o f the centre-line velocity; use of velocities at three different angle s; integration of velocities over a hemisphere; and integration of vel ocities over an estimated hemi-elliptical isovelocity line. Measuremen ts are performed in a hydraulic model with 4, 6 and 8 mm circular orif ices, and these are compared with Those from computer simulation. From the results presented in the study, it is suggested that the velociti es should be integrated over a hemisphere within a best zone. This zon e is dependent on the instrument settings, but in this case it is posi tioned 1.2-1.4 orifice diameters from the orifice inlet, with an angle of up to +/-45 degrees from the centre axis, and contains velocities in the range 0.15-0.45 ms(-1).