Secondary flow velocity patterns in a pulmonary artery model with varying degrees of valvular pulmonic stenosis: pulsatile in vitro studies

The objective of this study was to characterize in detail the secondary flow velocity patterns in an in vitro model of a human (adult) pulmonary artery with varying degrees of valvular pulmonic stenosis. A two-dimensional laser Doppler anemometer (LDA) system was used to map the flow fields in the main (MPA), left (LPA), and right (RPA) branches of the pulmonary artery model. The study was conducted in the Georgia Tech right heart pulse duplicator system. A pair of counter-rotating secondary flows were observed in each daughter branch in which the fluid moved outwardly along the side walls and then circled back inwardly toward the center of the vessel. For the case of the "normal" valve, the two counter-rotating secondary flows were symmetric about the centerline. The strength of secondary flows in the RPA was much stronger than in the LPA. However, as the pulmonic valve became more stenotic, the two counter-rotating secondary flows in both the LPA and RPA were no longer symmetric. In addition, the strength of secondary flows in both daughter branches increased with increasing degree of valvular stenosis. The increment in the LPA was, however, greater than in the RPA. The study demonstrates the importance of analyzing complex biological flows from a three-dimensional viewpoint.