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

BACKGROUND: 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.

AIMS: We assessed IVUS measurement accuracy in defining functional ischemia by FFR.

METHODS: 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.

RESULTS: 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.

CONCLUSION: 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.