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Fractional Flow Reserve Tips & Tricks on Lesion Assessment Kwan S Lee MD FSCAI FACC Associate Professor of Medicine Sarver Heart Center University of Arizona Relevant Disclosures Speaker for St Jude Medical What is FFR? • Fractional Flow Reserve (FFR) is a physiologic measurement that looks at the ratio of maximal blood flow in a stenotic artery compared to normal maximal flow • FFR 0.75 Ischemia very unlikely, sensitivity 88% FFR < 0.75 Ischemia, specificity 100% “Measurement of Fractional Flow Reserve to asses the Functional Severity of Coronary Artery Stenoses”, Pijls et al; The New England Journal of Medicine; Vol 334: 1703-1708 (1996) FFR accounts for Interactions • • • • Epicardial stenosis severity Extent of perfusion territory Myocardial blood flow Collateral filling FFR Accounts for size of perfusion area 100 60 Normal myocardium FFR = 0.60 Scar tissue 100 80 Normal myocardium FFR = 0.80 Calibration • Care should be taken with calibration • All lines should be flushed with saline and transducer height set to zero • Make sure to remove the introducer Influence of Transducer Height Equalization • The pressure sensor (3 cm from wire tip) should be positioned to mm distal to the guiding catheter tip • The Introducer should be removed again • The pressures should be identical, then electronically equalized Influence of Introducer Wiring and Measuring • The sensor should be advanced into the distal part of the artery, at least to cm distal to the stenosis where post-stenotic laminar flow is restored • In general, wire as distal as possible • Be aware of accordion effect in tortuous vessels • Document wire position angiographically Tortuosity and Accordion Effect Administering Adenosine • Intracoronary adenosine, use a 10 ml syringe filled with 200 micrograms fo adenosine • ml (100 mcg) for the RCA, 10 ml (200 mcg for the LCA • Inject briskly with guide engaged, then quickly switch back to Pa signal, and disengage guide • Record for minute to capture, beginning of maximal hyperemic phase and recovery Recognizing Hyperemia signs to look for: 15% change in MAP Adenosine effects felt Ventricularization of Pd (distal, green) waveform Checking for Drift • All pressure sensors are susceptible to signal drift • Drift should be absent or minimal for optimal measurement • Check for drift immediately after the measurement • Pullback wire carefully to guide starting point and make sure measured pressures are equal (1.0) • If not, repeat measurement Recognizing Drift Ostial Lesions Serial Stenoses • • • • Important to measure in the distal vessel Recommend iv adenosine Pullback will show lesion with highest contribution After PCI, important to recheck FFR as distal lesion affects proximal lesion measurements and vice versa • Distal lesion artificially reduces pressure gradient across proximal lesion, leads to proximal lesion overestimation • In left main, important to therefore place wire in the vessel without stenosis if available Future Directions and Limitations • Expanding indication for lesions
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