Guide PCI with coronary physiology
Physiology fundamentals
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.
Index definition
Wave-free period
Index definition
FFR =
Distal Coronary Pressure (Pd)
Proximal Coronary Pressure (Pa)
(During maximal hyperemia)
The FFR modality uses hyperemic agents to achieve a state of constant resistance.
Change in pressure =
change in flow x constant resistrance
Fundamental equation for relating pressure flow derived from Poiseuille's Law for fluid dynamics
iFR =
Distal Coronary Pressure (Pd)
Proximal Coronary Pressure (Pa)
(During wave-free period)
The iFR modality measures pressure during the wave-free period of the cardiac cycle when resistance is naturally constant.
iFR (instant wave-Free Ratio)
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
Simplifying workflow
The iFR modality provides a hyperemia-free measurement in as few as five heartbeats.
iFR vs. FFR: same wire, same system, fewer steps
iFR workflow
FFR workflow
Single dichotomous cut-point back by data2,3
Both DEFINE FLAIR and iFR Swedeheart were designed with the dichotomous cut-point of iFR in the iFR arm. With comparable MACE rates to FFR, these results mean the 0.89 cut-point for iFR is proven and backed by more than 4500 patients of outcome data
iFR Scout pullback technology
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.
- Provides beat-by-beat pressure measurements across the entire vessel, artery by artery
- Establishes the physiological significance of each vessel and/or individual lesion (focal or diffuse)
- Provides a clear view of the functional gain
- Facilitates multiple assessments before, during and after the procedure (without the need for hyperemia)
iFR Scout pullback technology vs. FFR pullback
Benefits of iFR Scout pullback technology5
| 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 |
Limitations of FFR pullback
| Requires IV hyperemia |
| Can be difficult to interpret |
| There is an interdependency of pressure gradients in serial lesions |
| 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 lesions |
| Easily bookmark areas of interest | Requires a second FFR pullback after treating the first lesion to assess the “updated” severities of the remaining lesions |
Easily determine lesion location with iFR Co-registration.
FFR (Fractional Flow Reserve)
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
- FFR < 0.75 was validated against the 3 gold standard tests to correlate with ischemia with 100% specificity
- FFR between 0.75 and 0.80 may indicate ischemia
- FFR > 0.80 is highly likely to be non‑ischemic
- AUC guidelines reflect the FAME cutoff of 0.80
(≤ 0.80 Treat, > 0.80 Defer)
OmniWire: the world’s first solid core pressure wire
With an all new workhorse design only OmniWire pressure guide wire combines confidence in wire performance with proven iFR outcomes2,3 and iFR Co-registration, making it easy to benefit from physiology throughout the case.
Resources
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.
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