280 Park SH & Koo BK. Clinical application of FFR in bifurcation lesions Figure 2. The influence of proximal stenotic lesion on SB FFR. Coronary angiography shows a significant stenosis at the ostium of a diagonal branch (left panel) and FFR measured at a diagonal branch was 0.73. However, pullback pressure recording from distal diagonal branch to left main ostium shows a pressure step-up at the distal left main (right mid panel, arrow). This was confirmed by another pullback pressure recording from distal LAD to left main ostium (right lower panel). Pressure step-up was located mainly at the distal left main lesion. FFR: fractional flow reserve; LAD: left anterior descending artery; SB: side branch. Figure 3. Different criteria and different portions of side branch angioplasty in a provisional arm of recent major randomized clinical trials.[5,7,47,48] TIMI: thrombolysis in myocardial infarction. Figure 4. Case example of variability of visual estimation and quantitative coronary angiography (QCA) for jailed side branch lesions. Angiographic percent diameter stenosis was assessed by 3 observers and 3 different QCA systems (Data from the study by Shin DH et al.[32]). Moreover, it is well known that there is a variability in a visual and quantitative coronary angiography (QCA) assess- ment for jailed SB lesion, as shown in Figure 4.[32] Figure 5. Mismatch between angiographic severity and functional significance. Despite the tight angiographic stenosis, no perfusion defect was found on myocardial SPECT scan (right panel). FFR at this jailed diagonal branch was 0.81. Previous studies have demonstrated that angiographic evaluation of SB compromised by the MB stent does not reflect functional significance (Figure 5).[33–38] Figure 6 shows the comparison between FFR and angiographic percent diameter stenosis in jailed SB after MB stent im- plantation from our registry data. Angiographic percent dia- meter stenosis overestimates the functional severity in ge- neral and lesions with similar anatomical severity can have a wide range of FFR. Therefore, when jailed SB is clinically important, only FFR can provide accurate information on whether revascularization is indicated. Moreover, functional and clinical outcomes of FFR-guided revascularization strategy in jailed SB are reported to be excellent. In a study by Koo et al.,[34] SB FFR was measured in 91 patients after MB stent implantation and this SB FFR measurement was repeated at 6-month follow-up angiography. During 6-month Journal of Geriatric Cardiology | jgc@jgc301.com; http://www.jgc301.com