Intravascular ultrasound-derived predictors for fractional flow reserve in intermediate left main disease

Objectives: The aim of this study was to determine the best intravascular ultrasound (IVUS) criteria for predicting physiological significance of left main (LM) stenosis with fractional flow reserve (FFR) as the standard. Background: For identifying significant LM disease, optimal cutoff of minimal lumen area (MLA) and its accuracy remain debatable. Methods: We identified 55 patients (31 stable and 24 unstable angina) with an isolated LM lesion of 30% to 80% angiographic diameter stenosis who underwent IVUS and invasive physiological assessment before intervention. Results: The FFR at maximum hyperemia significantly correlated with IVUS-measured MLA within the LM (r = 0.623, p < 0.001), plaque burden (r = -0.548, p < 0.001), angiographic diameter stenosis (r = -0.449, p = 0.002), and angiographic length of the lesion (r = -0.292, p = 0.046). The FFR was significantly lower in 18 lesions with plaque rupture than 37 lesions without plaque rupture (0.76 ± 0.09 vs. 0.82 ± 0.09, p = 0.018). The independent determinants of FFR as a continuous variable were MLA (beta = 0.598, p < 0.001) and plaque rupture (beta = -0.255, p = 0.038). Furthermore, the MLA within the LM was the only independent determinant for FFR <0.80 (adjusted odds ratio: 0.312, p < 0.001) and for FFR <0.75 (adjusted odds ratio: 0.196, p = 0.001). The IVUS MLA value within the LM that best predicted FFR <0.80 was <4.8 mm ² (89% sensitivity, 83% specificity). In addition, the cutoff value of plaque burden to predict FFR <0.80 was <72% (73% sensitivity, 79% specificity). The best cutoff values of the MLA and plaque burden for predicting FFR <0.75 were <4.1 mm ² (95% sensitivity, 83% specificity) and <76% (79% sensitivity, 80% specificity), respectively. Conclusions: In isolated LM disease, an IVUS-derived MLA <4.8 mm ² is a useful criterion for predicting FFR <0.80.