IN-VITRO ASSESSMENT OF THE FLOW-FIELDS IN A 3-DIMENSIONAL PULMONARY-ARTERY MODEL WITH VARYING DEGREES OF VALVULAR STENOSIS

This study was conducted to assess the effects of varying degrees of v alvular stenosis on the flow fields in a three-dimensional pulmonary a rtery model. Porcine pulmonary arteries procured from a slaughterhouse were used as test models. To produce dilated main (MPA) and left (LPA ) pulmonary arteries similar to those clinically observed in valvular pulmonic stenosis, an epoxy fixation technique was employed. A three-d imensional echocardiographic reconstruction method for color Doppler f low mapping was used to examine the flow fields in the test models. Ad ditionally, transvalvular pressure drops were measured by a side-hole catheter and predicted by a Doppler-derived Bernoulli equation. Change s in flow fields in the MPA were observed as the pulmonic valve became stenotic. A jet-like flow was present distal to the stenotic valve. T he change in geometry in the MPA, due to its dilatation, had a marked effect on the pulmonary artery hemodynamics. The jet-like flow seen di stal to the valve deflected away from the centerline and impinged on t he roof of the MPA. The force impinging on the stenotic valve and the roof of the MPA increased with increasing degree of valvular stenosis. Clinically, this may impair the stenotic valve and make the dilatatio n of the MPA more profound. The Doppler-predicted pressure drops corre lated well with the catheter-measured pressure drops. The measured tra nsvalvular pressure drops increased with increasing degree of valvular stenosis, As a result of increasing pressure drop, the transvalvular energy loss increased as the valve became more stenotic. Some degree o f pressure recovery, reflected by a decrease in transvalvular pressure drop with increasing distance from the valve, was observed for each s tenotic valve. The extent of pressure recovery increased as the valve became more stenotic. The study demonstrates the necessity of consider ing complex biological flows from a three-dimensional viewpoint.