Guide PCI with coronary physiology, the clinically validated choice
By Philips ∙ Aug 06, 2019 ∙ 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.1,3,4 Philips provides you the opportunity to use one of two clinically validated indices: iFR or FFR.
Article at a glance
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 period5
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 data3,4
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.
Footnotes
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. 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 3. 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. 4. 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.
5. Sen, Sayan et al. Development and validation of a new adenosine-independent index of stenosis severity from coronary wave-intensity analysis: results of the ADVISE (ADenosine Vasodilator Independent Stenosis Evaluation) study. Journal of the American College of Cardiology vol. 59,15 (2012): 1392-402. doi:10.1016/j.jacc.2011.11.003
6. Lawton JS. et al. 2021 ACC/AHA/SCAI Guideline for Coronary Artery Revascularization: A Report of the American College of Cardiology/American Heart Association Joint Committee on Clinical Practice Guidelines. Circulation vol. 145,3 (2022): e18-e114. doi:10.1161/CIR.0000000000001038
7. Vrints, C, et al. 2024 ESC Guidelines for the management of chronic coronary syndromes. European heart journal, ehae177. 30 Aug. 2024, doi:10.1093/eurheartj/ehae177
