Review Abstract Clinical applications of fractional flow reserve in bifurcation lesions Sang Hyun Park, Bon-Kwon Koo Seoul National University College of Medicine, 101 Daehang-ro, Chongno-gu, Seoul 110-744, South Korea Journal of Geriatric Cardiology (2012) 9: 278−284 ©2012 JGC All rights reserved; www.jgc301.com • Open Access • Percutaneous coronary intervention (PCI) for coronary bifurcation lesions has been associated with lower procedural success rates and worse clinical outcomes compared with PCI for simple coronary lesions. Angiographic evaluation alone is sometimes inaccurate and does not reflect the functional significance of bifurcation lesions. The fractional flow reserve (FFR) is an easily obtainable, reliable, and reproducible physiologic parameter. This parameter is epicardial lesion specific and reflects both degree of stenosis and the myocardial territory supplied by the specific artery. Recent studies have shown that FFR-guided provisional side branch intervention strategy for bifurcation lesions is feasible and effective and can reduce unnecessary complex interventions and related complications. However, an adequate understanding of coronary physiology and the pitfalls of FFR is essential to properly use FFR for PCI of complex bifurcation lesions. J Geriatr Cardiol 2012; 9: 278−284. doi: 10.3724/SP.J.1263.2012.05091 Keywords: Coronary stenosis; Bifurcation lesion; Physiology; Fractional flow reserve 1 Introduction Coronary bifurcation lesions have been one of the most challenging lesion subsets in the field of percutaneous coronary intervention (PCI). Bifurcation intervention is asso- ciated with higher procedural cost, higher complication rate, higher restenosis rate and worse outcomes when compared with PCI of simple coronary artery lesions.[1–4] The provi- sional side branch (SB) interventional strategy is preferred for most bifurcation lesions as most previous studies have failed to show the benefit of systematic two stenting over this strategy.[3–7] Though there have been many studies about how to treat bifurcation lesions, it is still not clear which SB should be treated and how the functional significance of these lesions ought to be assessed. Although various angiographic or flow criteria are currently used for the decision of SB intervention, there is no validated criteria yet. Furthermore, angiographic assessment of bifurcation lesions is sometimes inaccurate because of the innate limitations of angiography. Therefore, a more physiologic and standardized measurement modality is required for better evaluation in the treatment of bifurcation lesions. Correspondence to: Bon-Kwon Koo, MD, PhD, Seoul National University College of Medicine, 101 Daehang-ro, Chongno-gu, Seoul 110-744, South Korea. E-mail: bkkoo@snu.ac.kr Telephone: +82-2-2072-2062 Fax: +82-2-3675-0805 Received: May 9, 2012 Revised: July 10, 2012 Accepted: July 11, 2012 Published online: August 14, 2012 http://www.jgc301.com; jgc@jgc301.com | Journal of Geriatric Cardiology 2 What is fractional flow reserve (FFR)? FFR is a parameter that defines the physiologic signi- ficance of a coronary artery stenosis and is the ratio of maximal blood flow in a stenotic artery to normal maximal flow.[8] Since the resistance is minimal under maximal hyperemia and the venous pressure is negligible compared to coronary arterial pressure, FFR can be simply calculated as the ratio of distal coronary pressure (Pd) to proximal aortic pressure (Pa) (Figure 1). It can be easily determined during coronary angiography by calculating the fraction of distal coronary pressure measured with a coronary pressure wire to aortic pressure measured simultaneously with the guide catheter as shown in Figure 1. FFR is an epicardial lesion-specific physiologic parameter reflecting both the degree of stenosis and the myocardial territory supplied by the specific artery.[8–12] This parameter is nearly independent of hemodynamic conditions such as heart rate, blood pressure, and myocardial contractility.[11] In a study by Pijls et al.,[8] an FFR value of 0.75 or less almost invariably identified ischemia-causing coronary artery stenoses with high sensitivity (88%), specificity (100%), positive predictive value (100%), and overall accuracy (93%). Considering the presence of a grey zone (0.75−0.80) and the results of the FAME study,[13] an FFR cutoff value of 0.8 has become more popular in recent days. An FFR-guided revascularization strategy has been validated in various lesion subsets. In the DEFER study, the rate of cardiac death or myocardial infarction in the DEFER group according to