Demonstration of Dual Parallel ) et Interaction in an In Vitro Model of Multivalvular Disease by Use of Optical Visualization and Color Doppler Flow Mapping Robin Shandas, MS, Valdir Moises, MD, Benedito Maciel, MD, and David Sahn, MD, Portland, Oregon 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 mm 2 orifice, and the other higher peak velocity, smaller mass through two orifices, 0.2 7 mm 2 and 1.5 mm>, 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 mm 2 small jet orifice than for the 0.27 mm 2 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 em 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. (JAM Soc EcHOCARDIOGR 1993;6:124- 33.) Turbulent and laminar jet flows produced in the heart due to stenotic and regurgitant valves can be visualized noninvasively by color Doppler echocar- diography.1·8 Although the qualitative clinical use, semiquantitation, and understanding of color flow images produced by valvular disease have improved over the last few years, there still is for the most part a poor understanding of the color Doppler imaging of more complex intracardiac phenomena, for ex- From the Division of Pediatric Cardiology, University of Cali- fornia San Diego, and the Clinical Care Center for Congenital Heart Disease, Oregon Health Sciences University, Portland. Supported in part by a grant from the National Institutes of Health, #R01 HL42387. Reprint requests: David J. Sahn, MD, Oregon Health Sciences University, Division of Pediatric Cardiology, 3181 SW Sam Jack- son Park Road, UHN60, Portland, OR 97201. Copyright© 1993 by the American Society ofEchocardiography. 0894-7317/93 $1.00 + .10 27/l/43337 ample, multiple jets such as those produced in mul- tivalvular disease (combined mitral stenosis and aor- tic insufficiency). On clinical color flow examples of mitral stenosis and aortic insufficiency, there has of- ten been confusion because the jets appear to merge, 13 making it difficult to localize or measure them. 9 - Further, color Doppler imaging of multiple jets and their interaction is dependent on the interrogating plane of examination because both jets do not nec- essarily have to lie in the same two-dimensional plane. Our study was designed to explore the hydro- dynamics and color Doppler imaging of multiple jets within an enclosed chamber such as those that occur in multivalvular disease. We reproduced dual jet in- teraction in a flow model allowing optical visualiza- tion and color Doppler imaging. The questions that we wanted to answer were: Do dual parallel jets de- viate towards or away from each other? What causes 124