Physiology

Guide PCI with coronary physiology

Contact information

* This field is mandatory
*
*
*
*
*
*
*
*
*
By specifying your reason for contact we will be able to provide you with a better service.
*
*
frame graph

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.

Wave icon

Index definition

wave-free icon

Wave-free period

Index definition

Pd Pa vessels
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

Pd Pa equation
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.

Benefits of iFR’s wave-free period3

The cardiac cycle
Pressire, resistance, and intensity during the wave-free period
  • Noise from compression and suction waves is minimized
  • Resistance is constant so ΔP is proportional to ΔQ (flow)
  • Velocity is higher so betterpower to discriminate

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

iFR workflow

FFR workflow

IntraSight iFR

Single dichotomous cut-point back by data2,3

iFR cut point
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 cut point

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

Green check icon
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
Orange x icon
Limitations of FFR pullback5
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
iFR Co-registration

Easily determine lesion location with iFR Co-registration.

FFR (Fractional Flow Reserve)

iFR cut point

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)

The wire you choose, the technology you can trust

Seamlessly measure iFR and FFR with the Philips Verrata Plus pressure guidewire that reliably connects and disconnects and resists kinks for an improved workflow and reliable pressure measurement

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.