The role of intravascular ultrasound and quantitative angiography in the functional assessment of intermediate coronary lesions: Correlation with fractional flow reserve

Background: The correlation between fractional flow reserve (FFR) and intravascular ultrasound (IVUS) metrics including minimal lumen area (MLA), plaque burden and morphology remain a matter of debate. Methods: Between June 2008 and May 2013, 132 intermediate stenoses in 109 patients were assessed by FFR, IVUS and quantitative angiography. Receiver-operating characteristic (ROC) curve analyses were used to identify MLA/lesion length/plaque burden cut-off values predictive of FFR < 0.80. Results: FFR <0.80 was observed in 39 lesions. In the entire cohort, MLA value <2.70mm² had 79.5% sensitivity, 76.3% specificity, 0.822 area under curve (AUC), 58.5% positive predictive value, 89.9% negative predictive value and 77.3% accuracy in predicting a positive FFR. In lesions with reference diameter vessel (RVD) ≥3.0mm, the MLA cut-off value was 2.84mm² (sensitivity 72.2%, specificity 83.0%, AUC 0.842) whereas in lesions with RVD <3.0mm, 2.59mm² (sensitivity 90.5%, specificity 69.6%, AUC 0.823). A moderate correlation was observed between MLA and FFR (r=0.429, p<0.001). The cut-off lesion length predictive of FFR <0.80 was 11.0mm with a weak correlation between the two (r=-0.348, p<0.001). Plaque morphology did not significantly affect FFR (p=0.485). On multivariable analysis, MLA (OR: 0.15; 95% CI: 0.05-0.40; p<0.001) and plaque burden (OR: 1.11; 95% CI: 1.04-1.20; p<0.003) were independent predictors of FFR <0.80. Conclusion: A modest, yet significant correlation was observed between MLA and FFR. The high negative predictive value of large MLAs (using afore-mentioned cut-off values) may provide some degree of confidence that the lesion in question is not functionally significant.