Intravascular ultrasound lumen area parameters for assessment of physiological ischemia by fractional flow reserve in intermediate coronary artery stenosis

Abstract

A fractional flow reserve (FFR) of <0.8 is currently used to guide revascularization in lesions with intermediate coronary stenosis. Whether there is an intravascular ultrasound (IVUS) measurement or a cutoff value that can reliably determine which of these intermediate lesions requires intervention is unclear. We assessed IVUS measurement accuracy in defining functional ischemia by FFR. The analysis included 205 intermediate lesions (185 patients) located in vessel diameters >2.5 mm. Positive FFR was considered present at <0.8. IVUS measurements were correlated to the FFR findings in intermediate lesions with 40%-70% stenosis. Fifty-four (26.3%) lesions had FFR<0.8. There was moderate correlation between FFR and IVUS measurements, including minimum lumen area (MLA) (r=0.36, P<.001), minimum lumen diameter (MLD) (r=0.25, P=<.001), lesion length (r=-0.43, P<.001), and area stenosis (r=-0.33, P=.01). A receiver operating characteristic curve (ROC) identified MLA<3.09 mm(2) (sensitivity 69.2%, specificity 79.5%) as the best threshold value for FFR<0.8. The correlation between FFR and IVUS was better for large vessels compared to small vessels. ROC analysis identified the best threshold value for FFR<0.8 of MLA<2.4 mm(2) [area under curve (AUC)=0.74] in lesions with reference vessel diameters of 2.5-3 mm, MLA<2.7 mm(2) (AUC=0.77) in lesions with reference vessel diameters of 3-3.5 mm, and MLA<3.6 mm(2) (AUC=0.70) in lesions with reference vessel diameters >3.5 mm. Anatomic measurements of intermediate coronary lesions obtained by IVUS show a moderate correlation to FFR values. The correlation was better for larger-diameter vessels. Vessel size should always be taken into account when determining the MLA associated with functional ischemia.