Pulmonary artery hemodynamics with varying degrees of valvular stenosis: an in vitro study

The study was to investigate the effects of varying degrees of valvular ste nosis on the hemodynamics of the main (MPA), left (LPA), and right (RPA) pu lmonary arteries. Particle flow visualization was used to examine the flow patterns in a series of pulmonary artery models manufactured out of glass. These glass models were made based on the geometry of the porcine pulmonary arteries with dilatation in the MPA and LPA. Also, detailed pressure mappi ngs in the models were conducted using a side-hole catheter. As the valve b ecame stenotic, a jet-like flow was observed in the MPA. A higher degree of valvular stenosis corresponded to a narrower jet. This jet-like flow was n oted to deflect away from the centerline and impinge on the roof of the dil ated MPA. Additionally, a notable pressure gradient across the deflected je t-like flow in the direction of its radius of curvature was seen. Moreover, secondary flows started to appear in the dilated MPA. This suggested that the change in geometry in the MPA, due to its dilatation, had a marked effe ct on the pulmonary artery hemodynamics. In the LPA and RPA, the strengths of the secondary flows increased as the valve became more stenotic. The flo w patterns observed in the LPA appeared to be more disturbed than in the RP A, due to the poststenotic, dilatation present in the LPA. Pressure recover y along the axial direction in the MPA was observed for all the stenotic va lves studied. As the degree of valvular stenosis increased, the transvalvul ar energy loss increased. Moreover: it was observed that the energy loss de creased progressively as the flow traveled downstream. This tendency was co nsistent with the phenomenon of pressure recovery observed in the pressure measurement. The study demonstrates the importance of analyzing biological flows from a three-dimensional viewpoint. (C) 1998 Elsevier Science Ltd. Al l rights reserved.