EFFECTS OF ADJACENT SURFACES OF DIFFERENT SHAPES ON REGURGITANT JET SIZES - AN IN-VITRO STUDY USING COLOR DOPPLER IMAGING AND LASER-ILLUMINATED DYE VISUALIZATION

Objectives. The present study was designed to estimate the influence o f different shaped adjacent surfaces on regurgitant jets as assessed b y color Doppler imaging and laser-illuminated dye optical visualizatio n. Background. Because color Doppler techniques provide real time two dimensional imaging of flow, the evaluation of valvular regurgitation by analysis of variance-encoded regurgitant jets by this method has be en widely used in clinical studies. However, recent studies have demon strated that color Doppler jet sizes are affected not only by several hemodynamic factors and instrument settings but also by the interactio n between jets and adjacent wall surfaces. In clinical conditions, jet s may interact with adjacent walls of variable shapes that might have different effects on the jet size. Methods. An in vitro model was cons tructed consisting of a rigid, optically clear receiving chamber that had no outlet resistance and had a pulsatile pump ejecting through 1.5 , 2.3 and 3.1 mm(2) inflow orifices into the chamber. The surfaces wer e Bat or smoothly and equally curved, convex and concave aluminum posi tioned at 0, 2 and 4 mm from and to the side of the inflow orifices. T he pump was run with stroke volumes from 0.5 to 3.0 ml and with a puls e frequency of 70 beats/min. The echocardiographic and laser beams wer e aimed at the inflow orifice imaging jets perpendicular to the surfac es (vertical view) through the central plane of the jet flows. Maximal jet areas were measured by both color Doppler techniques and laser-il luminated dye visualization. Results. Color Doppler study showed fair correlation between the jet areas and the stroke volumes (r = 0.83 to 0.99), but the jet sizes under different surface conditions were varia ble. All the surface jet areas at a jet surface distance of 0 and 2 mm were smaller than free jet areas at the same stroke volume for both f lat and convex surfaces (p < 0.001). Flow constraint by the concave su rface resulted in the smallest jet areas (p < 0.001). The color Dopple r jet areas on the curved surfaces were significantly smaller than the laser illuminated dye visualization jet areas (p < 0.01 to 0.0001). H owever, at intermediate jet surface distances (4 mm and sometimes 2 mm with higher velocity flows), jet interaction with the Bat and especia lly with the convex surface resulted in larger jets. This effect was m ost pronounced on dye fluorescence studies because how around these je ts consisted mainly of low velocity vortical events with only partial surface adherence and these low velocity swirling flows were not well imaged by color Doppler technique. Conclusions. Our study suggests tha t the different shaped adjacent surfaces with different degrees of flo w alterations resulted in variable decreases in jet size and that colo r Doppler imaging could not encode and image the angled and low veloci ty swirling events well when jets flowed along the curved surfaces. Th ese effects need to be taken into account when interpreting color Dopp ler images.