Park SH & Koo BK. Clinical application of FFR in bifurcation lesions 281 Figure 6. Comparison between FFR and angiographic percent diameter stenosis in jailed side branches. follow-up, there was no change in SB FFR in lesions without SB angioplasty (0.87 ± 0.06 to 0.89 ± 0.07, P = 0.1). When compared to the conventional angiography-guided group, FFR-guided intervention strategy required less SB intervention (30% vs. 45%, P = 0.03) and showed similar nine month cardiac event rates (4.6% vs. 3.7%, P = 0.7). In the SB FFR sub-study of the Nordic-Baltic Bifurcation III trial, complete angiographic and FFR eight month follow up was obtained in 21 of the no-kissing balloon dilatation group,[38] and there was no significant change in mean SB FFR during the follow-up period in these patients (0.87 vs. 0.87; P = 0.91). These results suggest that FFR- guided revascularization strategy can guide revascularization for jailed SB and can reduce unnecessary complex interventions. Moreover, a computational fluid dynamic study demonstrated that the additional balloon angioplasty of a functionally insignificant SB lesion cannot improve local flow conditions.[39] However, it should be remembered that published data which compared the FFR and angiographic percent diameter stenosis were obtained in short SB ostial lesions and that any visual or QCA assessment cannot be free from subjectivity. Therefore, the results, especially percent diameter stenosis, cannot be applied to diffuse, multiple or non-ostial SB lesions. Moreover, considering the technical difficulty of SB re- crossing of the pressure wire through the MB strut and the mechanism of discrepancy between FFR and angiographic severity, FFR measurement for jailed SB is not recommended in SB with severe angulation, heavy calcification and in lesions with diffuse and/or multiple stenoses. Finally, regardless of stenosis severity, FFR should be measured in a clinically significant SB which warrants complex interventions. 5 FFR after SB balloon angioplasty Although various criteria for SB stenting after balloon angioplasty are currently in use, none of them have yet been validated (Figure 7). An aggressive SB angioplasty with a large balloon and with high pressure can cause vessel dissection requiring SB stent implantation, which may increase the risk of stent thrombosis,[40,41] and may have a worse influence on flow dynamics of the MB.[39, 42] Therefore, adequate assessment of SB lesion after balloon angioplasty is very important. As shown in previous studies, the application of the angiographic criterion may overestimate lesion severity after SB angioplasty and IVUS also have limited ability to assess the functional significance of SB lesions. Therefore, SB FFR measurement after SB balloon angioplasty in bifurcation lesions maybe a better tool to guide interventional treatment compared to angiographic assessment. However, there is a possibility that SB FFR measured immediately Figure 7. Different criteria and different portions of side branch stenting in a provisional arm of recent major randomized clinical trials.[5,7,47,48] TIMI: thrombolysis in myocardial infarction. http://www.jgc301.com; jgc@mail.sciencep.com | Journal of Geriatric Cardiology