Factors influencing the structure and shape of stenotic and regurgitant jets: An in vitro investigation using doppler color flow mapping and optical flow visualization

To evaluate factors influencing the structure and shape of stenotic and regurgitant jets, Doppler color flow mapping and optical flow visualization studies were performed with use of a syringe model with a constant rate of ejection to simulate jets of valvular regurgitation and a pulsatile flow model of the right heart chambers to simulate jets of mild, moderate and severe valvular pulmonary stenosis. Ink-(0 to 40%) glycerol-water jets (viscosity 1 to 3.5 centiPoise) were produced by injecting the fluid at a constant rate into a 10 gallon rectangular reservoir of the same still fluid through 1.4 and 3.4 mm needles. The Doppler color flow scanners imaged the laminar jet length within 3 mm of actual jet length (2 to 6 cm) and the jet width within 2 to 3 mm of the actual jet width. Jet flows with Reynolds numbers ranging from 230 to 1,200 injected into still fluid yielded jet length/width ratios that decreased with increasing Reynolds numbers and leveled off to a length/ width ratio of 5-6:1 at a Reynolds number near 600. When the fluid reservoir was swirled to better mimic the effect of flow entering the same cardiac chamber from a second source, the jetts showed diminution of the jet length/width ratio and a clearly defined zone of turbulence. Studies of the pulsatile flow model were performed at cardiac outputs of 1 to 6 liters/min for the normal and each stenotic valve. Mild stenosis had an orifice area of 2.8 cm², moderate stenosis an area of 1.0 cm² and severe stenosis an area of 0.5 cm². Laminar jet length represented the length of the total jet, which had a symmetric width and was measured from the valve opening to a region where the jet exhibited a spray effect. Laminar jet lengths (0.2 to 1.1 cm) were imaged by Doppler color flow mapping and optical visualization only in the moderate and severely stenotic valves and only at flows ≤3 liters/min (mean Reynolds numbers ≤3,470). Beyond this flow rate the jets exhibited a spray effect. Laminar jet length/width ratio approached unity with an increased amount of valvular stenosis and higher flow volumes (cardiac output). Proximal aliasing was present in each valve studied. The length of aliasing (0 to 3.2 cm) proximal to the valve was longer with increased flow rates and increased amounts of stenosis. In summary, the structure and shape of jets were dependent on the orifice diameter, driving pressure (cardiac output), fluid viscosity and presence or absence of radial flow velocities that interact with the jet.