Validation of intravascular ultrasound-derived parameters with fractional flow reserve for assessment of coronary stenosis severity.

BACKGROUND: We assessed optimal intravascular ultrasound (IVUS) criteria for predicting functional significance of intermediate coronary lesions. METHODS AND
RESULTS: Overall, 201 patients with 236 coronary lesions underwent IVUS and invasive physiological assessment before intervention. 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% confidence interval [CI], 0.008 to 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(2) (β=-0.003; 95% CI, -0.005 to -0.001; P=0.005), and left anterior descending 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(2), with a diagnostic accuracy of 68% (90% sensitivity, 60% specificity, and area under the curve=0.800; 95% CI, 0.742 to 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 to 0.810; P<0.001). The cutoff value of lesion length with a lumen area <3.0 mm(2) was 3.1 mm (84%sensitivity, 63%specificity, and area under the curve=0.765; 95% CI, 0.706 to 0.818; P<0.001). Among 117 lesions with an MLA ≥2.4 mm(2), 112 (96%) had an FFR ≥0.80,; and all but 1 showed FFR ≥0.75. Conversely, 44 (37%) lesions with an MLA <2.4 mm(2) had an FFR <0.80.
CONCLUSIONS: IVUS-derived MLA ≥2.4 mm(2) may be useful to exclude FFR <0.80, but poor specificity limits its value for physiological assessment of lesions with MLA <2.4 mm(2). Thus, FFR or stress tests may be necessary to accurately identify ischemia-inducible intermediate stenoses.