Guide PCI with coronary physiology, the clinically validated choice
- By Philips
- March 17 2025
- 2 min read
Clinical studies demonstrate that physiologic lesion assessment to determine lesion significance and guide revascularization decisions is superior to angiographically guided treatment, and benefits patients with reduced rates of cardiac events [1,2]. Philips provides you the opportunity to use one of two clinically validated indices: iFR or FFR.
At-a-glance:
- Coronary physiology fundamentals
- Index definition
- Benefit’s of iFR’s wave-free period
- iFR (instantaneous wave-Free Ratio)
- Simplifying workflow
- iFR vs. FFR: same wire, same system, fewer steps
- iFR pullback technology vs. FFR pullback
- Single dichotomous cut-point back by data [2,3]
- FFR (Fractional Flow Reserve)
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 proximal aortic pressure. When resistance is constant, this ratio represents the potential decrease in coronary flow distal to the coronary stenosis.
Index definition
The FFR modality uses hyperemic agents to achieve a state of constant resistance.
Pressure = flow x resistance
Fundamental equation for relating pressure flow derived from Poiseuille's Law for fluid dynamics
The iFR modality measures pressure during the wave-free period of the cardiac cycle when resistance is naturally constant.
Benefits of iFR’s wave-free period [2,3,4]
- Noise from compression and suction waves is minimized
- Resistance is constant so ΔP is proportional to ΔQ (flow)
- Velocity is higher so better power to discriminate
iFR (instantaneous 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 a Class 1A recommendation and is proven to reduce procedure time, patient discomfort and cost compared to FFR [6,7].
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
Single dichotomous cut-point back by data[2,3]
Both DEFINE FLAIR and iFR Swedeheart were designed with the dichotomous cut-point of iFR in the iFR arm[3,4]. 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.
FFR (Fractional Flow Reserve)
FFR ischemia scale
An FFR lower than .80 is generally considered to be associated with myocardial ischemia.
- FFR is a Class 1A recommendation from the ACC/AHA/SCAI and ESC[5].
- FFR > 0.80 is highly likely to be nonischemic
iFR Coronary Physiology technology
Learn how you can guide PCI by using iFR index for measuring pressure in diagnostic & interventional procedures. See patient outcome data.
- 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.
- Berntorp K, et al. Instantaneous wave-free ratio compared with fractional flow reserve in PCI: A cot-minimization analysis. Int J Cardiol 2021 1;344:54·59
- 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.
- 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.
- 2024 ESC Guidelines for the management of chronic coronary syndromes: Developed by the task force for the management of chronic coronary syndromes of the European. Society of Cardiology (ESC) Endorsed by the European Association for Cardio-Thoracic Surgery (EACTS), European Heart Journal, 2024;, ehae177.