Imaging and Physiology for Intermediate Left Main Stem Stenosis

Inclusion Criteria: \- age \>/= 18 years; * patients who have an intermediate (40-70% diameter stenosis) lesion located in the LMS and a concomitant significant (\>/=70% diameter stenosis) in one of the two major downstream vessels (the LAD or the LCx). The severity of LMS and downstream lesions will be assessed by visual estimation of the coronary angiography; * need of complementary diagnostic work up to ascertain the functional/physiological significance of the LMS lesion, that is not possible from the analysis of angiographic images only: * Intermediate severity of LMS lesion, or angiographic ambiguity; * Impossibility to conclusively associate the LMS lesion with the patient's symptoms/clinical presentation due to confounders introduced by the significant downstream lesion; * Impossibility to conclusively determine the severity and functional/physiological significance of the LMS lesion solely by the visual analysis of the coronary angiography; * Impossibility to conclusively determine the relative contribution of the LMS lesion to the ischemic burden determined by non-invasive functional tests due to the presence of a significant downstream lesion; * Clinical indication for PCI of the downstream lesion located in the LAD or LCx: * stable angina unresponsive to optimized medical treatment; * important ischemic burden (\> 10% of myocardial mass in territories supplied by the diseased vessels); * Reduced FFR/iFR values indicative of myocardial ischemia wi…