Anatomic and functional assessment of stenosis severity with intravascular ultrasound imaging in vitro.

An in vitro study was performed to evaluate the accuracy of intravascular ultrasound imaging compared with roentgenography for determining the cross-sectional area of a lumen; and to determine if the functional significance of an irregular stenosis is predicted more accurately by intravascular ultrasound than roentgenography. Varying degrees of stenosis were made in 17 rubber tubings by adjusting a plastic constrictor. The cross-sectional areas at the normal and the stenotic segments were determined by intravascular ultrasound, roentgenography, and then measured directly from an acrylamide gel cast of the lumen. To evaluate the functional significance of a stenosis, the pressure drop across the stenosis was measured using a fluid pumping circuit. The actual pressure drop was then compared with the predicted pressure drop derived from hydrodynamic equations using cross-sectional areas obtained by intravascular ultrasound or roentgenography. There was an excellent correlation between the cross-sectional areas at the tightest stenosis measured by intravascular ultrasound compared with the area from the acrylamide cast (7.2 +/- 2.6 v 6.6 +/- 2.4 mm 2, mean +/- SD, r = .93). Measurements of cross-sectional area from the roentgenograms (10.9 +/- 3.9 mm 2) also provided a relatively good correlation with those from the acrylamide casts (r = .84); however, the roentgenograms consistently overestimated the cross-sectional area of the stenosis. The mean values of the actual pressure drop and the predicted pressure drop by intravascular ultrasound and roentgenograms were 15.7 +/- 13.5, 11.3 +/- 11.9, and 4.3 +/- 4.5 mmHg, respectively.(ABSTRACT TRUNCATED AT 250 WORDS