Validation of Intravascular Ultrasound-Derived Parameters With Fractional Flow Reserve for Assessment of Coronary Stenosis Severity

The authors assessed optimal intravascular ultrasound criteria for predicting functional significance of intermediate coronary lesions. Overall, 201 patients with 236 coronary lesions underwent intravascular ultrasound and invasive physiologic assessment preintervention. Fractional flow reserve (FFR) was measured at maximal hyperemia induced by intravenous adenosine infusion. FFR <0.80 at maximum hyperemia was seen in 49 (21%) of the overall 236 lesions. The independent determinants of FFR were minimal lumen area (MLA; β=0.020; 95% CI, 0.008–0.031; P=0.032), plaque burden (β=−0.002; 95% CI, −0.003 to 0.001; P=0.001), lesion length with a lumen area <3.0 mm (β=−0.003, 95% CI, −0.005 to −0.001; P=0.005), and left anterior descending coronary artery location (β=−0.035; 95% CI, −0.055 to −0.016; P=0.001). The best cutoff value (with a maximal accuracy) of the MLA to predict FFR <0.80 was <2.4 mm with a diagnostic accuracy of 68% (90% sensitivity, 60% specificity, and area under the curve=0.800; 95% CI, 0.742–0.848; P<0.001). The cutoff value of plaque burden to predict FFR <0.80 was ≥79% (69% sensitivity, 72% specificity, and area under the curve=0.756; 95% CI, 0.696–0.810; P<0.001). Among 117 lesions with an MLA ≥2.4 mm, 112 (96%) had an FFR ≥0.80, and all but 1 showed FFR ≥0.75. Conversely, 44 lesions (37%) with an MLA <2.4 mm had an FFR <0.80. Intravascular ultrasound-derived MLA ≥2.4 mm may be useful in excluding FFR <0.80, but poor specificity limits its value for physiologic assessment of lesions with MLA <2.4 mm. Thus, FFR or some other functional assessment may be necessary to accurately identify ischemia-inducible intermediate stenoses.