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FFR and iFR can be obtained during routine coronary angiography by using a pressure wire to calculate the ratio between coronary pressure distal to a stenosis and the aortic pressure proximal. When resistance is constant, this ratio represents the potential decrease in coronary flow distal to the coronary stenosis.
Learn more about index definition and the wave-free period by clicking below.
Distal Coronary Pressure (Pd)
Proximal Coronary Pressure (Pa)
(During maximal hyperemia)
Change in pressure =
change in flow x constant resistrance
Distal Coronary Pressure (Pd)
Proximal Coronary Pressure (Pa)
(During wave-free period)
Unlike FFR, iFR does not require administration of vasodilators because hyperemia is not necessary when measuring pressure during the wave-free period of the cardiac cycle.
iFR is proven to reduce procedure time, patient discomfort and cost compared to FFR.2,3,4
The iFR modality provides a hyperemia-free measurement in as few as five heartbeats.
iFR Scout pullback technology reveals the physiologic profile of the entire vessel, so when you encounter diffuse disease or serial lesions you can make informed treatment decisions.
| No hyperemic agent required |
| Simple graphical display of iFR values through the vessel |
| Maps the ischemic contribution of each lesion without the confounding effects observed with FFR pullback1 |
| Easily bookmark areas of interest |
| Requires IV hyperemia |
| Can be difficult to interpret |
| There is an interdependency of pressure gradients in serial lesions1 |
| Requires a second FFR pullback after treating the first lesion to assess the “updated” severities of the remaining lesions |
| No hyperemic agent required | Requires IV hyperemia |
| Simple graphical display of iFR values through the vessel | Can be difficult to interpret |
| Maps the ischemic contribution of each lesion without the confounding effects observed with FFR pullback1 | There is an interdependency of pressure gradients in serial lesions1 |
| Easily bookmark areas of interest | Requires a second FFR pullback after treating the first lesion to assess the “updated” severities of the remaining lesions |
Philips physiology wires enable measurement of both FFR and iFR, both supported by key industry guidelines including ESC Class IA designation.6
FFR ischemia scale
An FFR lower than 0.75-0.80 is generally considered to be associated with myocardial ischemia.7
1. Tonino PA, De Bruyne B, Pijls NH, et al. Fractional flow reserve versus angiography for guiding percutaneous coronary intervention. N Engl J Med. 2009;360:213–24.
2. Davies JE, et al., Use of the Instantaneous Wave-free Ratio or Fractional Flow Reserve in PCI. N Engl J Med. 2017 May 11;376(19):1824-1834.
3. Gotberg M, et al., iFR-SWEDEHEART Investigators.. Instantaneous Wave-free Ratio versus Fractional Flow Reserve to Guide PCI. N Engl J Med. 2017 May 11;376(19):1813-18233.
4. Patel M. “Cost effectiveness of instantaneous wave-Free Ratio (iFR) compared with fractional flow reserve (FFR) to guide coronary revascularization decision-making.” Late-breaking clinical trial presentation at ACC March 10, 2018.
5. Nijjer S, et al. Pre-Angioplasty Instantaneous Wave-Free Ratio (iFR) Pullback Provides Virtual Intervention and Predicts Hemodynamic Outcomes for Serial Lesions and Diffuse Coronary Artery Disease. JACC: Cardiovasc Interv 2014; 12:1386-1396.
6. Neumann, F-J et al. 2018 ESC/EACTS Guidelines on myocardial revascularization. European Heart Journal (2018).
7. Pijls NH, De Bruyne B, Peels K, et al. Measurement of fractional flow reserve to assess the functional severity of coronary-artery stenosis. N Engl J Med 1996 Jun 27. 334(26): 1703-8.
