Correlation between fractional flow reserve and intravascular ultrasound lumen area in intermediate coronary artery stenosis

AIMS: Fractional flow reserve (FFR) of <0.8 or 0.75 is currently used to guide revascularisation in lesions with intermediate coronary stenosis. We assessed whether there is an intravascular ultrasound (IVUS) measurement that can reliably be used to predict when patients should undergo intervention. METHODS AND RESULTS: The analysis included 92 intermediate lesions (84 patients) located in vessel diameters >2.5 mm. Positive FFR was considered present at <0.8 and 0.75. IVUS minimum lumen area (MLA) was correlated to the FFR findings in intermediate lesions with 40-70% stenosis. The mean FFR value was 0.89 ± 0.08. Twenty-four patients (26.1%) had FFR <0.8; 17 (18.5%) <0.75. Positive correlations between FFR and IVUS measurements included MLA (r = 0.34, p<0.001), minimum lumen diameter (MLD) (r=0.31, p=0.004), lesion length (r=-0.5, p<0.001), and area stenosis (r=-0.31, p=0.01). There was no significant correlation between FFR and quantitative coronary angiography in MLD (r=0.19, p=0.06), diameter stenosis (r=0.08, p=0.4), or lesion length (r=-0.14, p=0.17). A receiver operating characteristic curve identified MLA <2.8 mm2 (sensitivity 79.7%, specificity 80.3%) as the best threshold value for FFR <0.75; and MLA <3.2 mm2 as best for FFR <0.8 (sensitivity 69.2%, specificity 68.3%). CONCLUSIONS: Anatomic measurements of intermediate coronary lesions obtained by IVUS show a moderate correlation to FFR values, although they differ according to vessel size. IVUS MLA may be used as an alternative to FFR when assessing the need for intervention in intermediate coronary lesion. Vessel size, however, should always be taken into account.