Fractional flow reserve (FFR) is a pressure-derived, lesion specific index used to determine the functional significance of coronary artery stenosis. Several studies showed that FFR is a safe and feasible method to assess the significance of an ostial SB stenosis after provisional stenting. Quantitative coronary angiography (QCA) has been shown to be unreliable in assessing the functional significance of SB after stent implantation in MV (the area under the curve 0.64, 41.5% sensitivity and 83.1% specificity) suggesting that treatment decisions for jailed SB should not be based on angiographic findings alone. A recent report demonstrated a better ability of post-PCI 3D-OCT to predict the functional significance for SB ostial lesions caused by a jailed SB outcome.