In vivo relation between cineangiographic jet width and jet width imaged by color-coded Doppler

Measurement of jet velocity distal to a flow obstruction permits estimation of pressure drop, and the resulting value can be used to assess the clinical impact of a cardiac or great vessel lesion. Pressure drop, however, is flow dependent.¹ Valve area, which is computed using a flow term derived from catheterization¹ or ultrasonic data,² is probably more desirable information than pressure drop alone. Another approach to computation of valve area might be accurate measurement of jet area. Jets can be imaged by cineangiography and a somewhat similar display can be imaged by color-coded Doppler. With color-coded Doppler, a "jet" imaged distal to an obstruction is displayed as a mosaic or aliased pattern, which has some morphologic characteristics similar to those observed on a cineangiogram. The coefficient of discharge (also called the coefficient of contraction and vena contracta) is the ratio of jet area to obstructive orifice area. Although the coefficient of discharge may assume a range of values, many circumstances have a value approximating 0.7.¹ Because color-coded Doppler images a pattern distal to an obstruction that has morphologic characteristics similar to those of a jet, it would be very convenient if that pattern actually represented the jet. If this were true, measurement of this unage and use of the ratio could approximate the area of the obstructive orifice. Yoganathan et al3 reported that the color-coded image of an in vitro jet is an indirect indicator of orifice size, but that the jet, as imaged, is about 20% larger than the true jet. This study examines the in vivo relation between the flow disturbance imaged by color-coded Doppler and the jet width detected by cineangiography. If a relation could be established, Doppler jet width would be a diameter that could be converted to an area [area = ( width 2)² · π] and that area could be used to predict orifice area. Our hypothesis was that width (or area) of the in vivo Doppler jet will exceed width (or area) of the cineangiographic jet.