Significant coronary disease of the left main coronary artery (LMCA) is found in 4%-5% of all coronary angiography procedures. Classically, it has been determined that a significant angiographic stenosis should reach at least 50% of the vessel diameter by visual estimation, which corresponds to 75% of the vessel area. However, angiography has a number of limitations inherent to the technique and location of stenosis, and other techniques are therefore available for evaluation. Intracoronary ultrasound (IVUS) deserves, together with the pressure guidewire, special consideration in determining the severity assessment (anatomical and functional) of lesions in this location. Using IVUS the most commonly used cut-off value is 6 mm2. in ambiguous lesions of the LMCA, a MLA \>6 mm2 would indicate no revascularisation, a MLA \<4.5-5 mm2 would indicate revascularisation, and MLA values between 4.5-5 and 6 mm2 would make it advisable to use FRF/iFR to decide. Optical coherence tomography (OCT) is another intracoronary imaging modality, with greater resolution and significant differences from IVUS. no MLA cut-off point with OCT has been demonstrated for the management of LMCA lesions. Due to the differences in imaging with both techniques, the thresholds established as cut-off points in IVUS cannot be extrapolated to OCT. The objective is to compare the minimal luminal area by IVUS and OCT of angiographically intermediate LCMA lesions and to assess the prognostic value of TCFA assessed by OCT.