Assessment of coronary stenoses by Doppler wires: A validation study usingin vitro modeling and computer simulations

The present study evaluates the use of intracoronary velocity measurements by Doppler guidewires for assessing coronary obstructions. In vitro experim ents were performed in a flow model using acrylic phantoms of coronary sten oses with different configurations (stenosis area: 56%, 75% and 89%; stenos is length: 1 and 5 mm; stenosis border: tapering or abrupt). Nonpulsatile l aminar Bow conditions of a test fluid were established at flow rates rangin g from 0.5 to 2.0 mL/s to simulate baseline flow and Bow after vasodilation . Peak Doppler velocity was measured proximal to, within and distal to the model stenoses. Computer simulations were employed to calculate radial how profiles with and without a Doppler,wire aligned with the vessel center. In 84 in vitro flow experiments, peak Doppler velocity correlated well with t he average flow velocity as calculated from the actual dow rate and the ves sel's cross-sectional area proximal to (r = 0.98, SEE = 1.4,p < 0.001) and within (r = 0.97, SEE = 16.4,p < 0.001) the stenosis. However, the ratio of calculated average velocity to Doppler-measured peak velocity was signific antly different from 0.5, the expected value for a parabolic Bow profile (0 .76 +/- 0.08, 0.81 +/- 0.14; p < 0.001). Acceptable accuracy was found for the Doppler estimation of stenosis severity using the continuity equation t error: 0.9 +/- 1.2% and -4.6 +/- 3.5% for stenosis with a length of 5 mm an d 1 mm, respectively. Doppler velocity reserve significantly underestimated the true flow reserve for the 56+/- and 75% stenoses (p < 0.01). Computer simulations demonstrated significant alterations of how profiles by the wir e, which explained the observed underestimation of the true flow reserve by the Doppler velocity reserve. Thus, Doppler guidewire measurements of intr acoronary flow velocities are useful to assess the severity of coronary ste noses. However, the in vitro results and computer simulations indicate that guidewires alter the flow profile, so that Doppler velocity reserve may un derestimate the true flow reserve. (C) 1999 World Federation for Ultrasound in Medicine & Biology.