ANALYSIS OF THE PROXIMAL ORIFICE FLOWFIELD UNDER PULSATILE FLOW CONDITIONS AND CONFINING WALL GEOMETRY - IMPLICATIONS IN VALVULAR REGURGITATION

Hemodynamic studies of regurgitant lesions in the heart focus on ident ifying a reliable noninvasive method of volumetric flow calculation. I n these studies the influence of blood viscosity to the flowfield unde r pulsatile flow conditions and constraining wall geometry has not bee n examined in detail. Pulsatile flow studies in straight tubes have sh own that viscous effects significantly influence the periodic flowfiel d, especially near the wall. The purpose of this study is to investiga te the significance of transient effects in the flowfield proximal to a lesion under constraining wall geometry. The proximal flowfield was analyzed with computational fluid dynamics (CFD) computer simulations and color flow Doppler mapping (CFM). Three different stroke volumes a nd regurgitant waveforms were investigated for upstream wall orientati ons that varied from -64 degrees to 64 degrees (measured from the orif ice plane). Results showed that for each upstream wall orientation, a single instantaneously normalized centerline velocity distribution cha racterized the flowfield throughout the cycle. The centerline distribu tions were in phase with the pressure gradient and almost identical to the corresponding steady-state distributions. Minor deviations were o bserved near the wall, where visions effects were predominant. Transie nt flow effects such as blunt profiles and pressure velocity phase shi fts, which were observed in straight circular tubes, were not observed in regurgitant orifice flowfields. This is true even under severe con finement conditions.