Demonstration of Dual Parallel Jet Interaction in an In Vitro Model of Multivalvular Disease by Use of Optical Visualization and Color Doppler Flow Mapping

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Parallel jets, such as those occurring in the heart in multivalvular diseases like combined mitral stenosis and aortic insufficiency, have created difficulty when color Doppler flow mapping or continuous wave Doppler has been used to localize or to measure the jets because they appear to merge. Dual jet interaction was reproduced in an in vitro transparent model by driving two parallel adjacent jets, one lower velocity, higher mass, through a 19 mm2 orifice, and the other higher peak velocity, smaller mass through two orifices, 0.27 mm2 and 1.5 mm2, by use of a solution of India ink and cornstarch to optically visualize the jet interaction and image the interaction by color Doppler. Consistent deviation of the lower velocity jet towards the higher velocity jet was observed, and the large jet angled more strongly towards the small jet for the 1.5 mm2 small jet orifice than for the 0.27 mm2 orifice for constant large and small jet velocities. There was a better linear correlation of the amount of large jet angulation to the ratio of both jets' Reynolds numbers than to the ratio of both flow rates. The jets interacted as close as 1.3 cm from their point of origin, and the region after the jets merged was a highly turbulent mixing zone where neither jet could be separately imaged or visualized. These observations suggest that relative velocity plays a primary role in determining jet interaction which is a recruitment phenomena but that other hydrodynamic parameters, such as flow rate and Reynolds numbers, determine the degree to which the jets deviate.