1. Concept and practical set-up of CFR, FFR, IMR
Zsolt Piróth MD
Gottsegen György Hungarian Institute of Cardiology

2. We all love coronary angiography, but
Intermediate lesions (30-70%)
Ostial lesions
Left main coronary artery disease
Diffusely diseased vessels
Complex lesions
Sequental lesions
Loose relationship between angiography and prognosis
Even best flat panel has resolution limited to 3 line pairs per mm, i. e. 9 line pairs or 9 pixels for a 3 mm vessel
Coronary arteries are notoriously hard to image sharply: they are small and mobile.

3. Limitations of coronary angiography
Circulation 1995; 92:

4. What else than morphology?
What kind of a physiologic parameter truly reflects the impact of a stenosis?
Blood flow? – no meaning w/o the extent of perfusion area
Flow derived parameters? – dependent on perfusion pressure
Transstenotic gradient? – coronary blood flow is often not representative of myocardial flow

5. So, who do we believe? Complaints of pt Non-invasive tests
Courtesy of Attila Kónyi, MD

6. The ideal parameter Reflects
Severity of the stenosis in the subepicardial coronary artery (PCI)
Amount of myocardium perfused by the diseased vessel
Full myocardial perfusion, including collaterals
Inducible ischemia
FFR

7. FFRmyo
Circulation 1993; 87:

8. Definition of FFRmyo
FFRmyo … is defined as the ratio of maximal achievable flow in the myocardium supplied by the stenotic vessel to the maximal achievable flow in the same territory in the hypothetical case that the vessel were normal.
Circulation 1995; 92: 39-46

9. Mathematics of FFRmyo E = mc2 Assumptions:
Resistances are constant and minimal
CVP is negligible
E = mc2

10. Characteristics of FFRmyo
Specific index of the lesion in the subepicardial vessel
„Pullback curve” conveys unparalelled spatial resolution
Independent form HR, BP and contractility
Normal value is 1,0 always and in all coronaries
Well defined cut-off value: (0,75 - ) 0,80
Reflects collaterals
Accounts for the amount of myocardium perfused by the vessel
Applicable both in single vessel disease and MVD (no need for normal reference vessel)
Measurement is simple, safe and possible in 99% of cases
NHJ Pijls, B de Bruyne (eds): Coronary Pressure

11. Evaluating FFRmyo
Sensitivity: 90%
Specificity: 100%

12. Practical assets of FFRmyo
Helpful in the indication of PCI
Helps to avoid unnecessary interventions
Identifies the „culprit lesion”
Quality control of PCI, giving some prognostic implications
Highly reproducible
Relatively cheap, easy to perform, steep learning curve
NHJ Pijls, B de Bruyne (eds): Coronary Pressure

13. Practice of measuring FFRmyo
Standard preparation for PCI (TF/TR, venous access, anticoagulation, optimal GC, Y-connector)
Set-up of Radi Analyzer® / Ilumien® / Quantien ®
Flush PW, connect to interface then calibrate
Zero aortic pressure signal
Equalize pressure signals (Pa and Pd) when PW sensor is at the tip of the GC /preferably in the aorta/
Advance PW across the stenosis
Induce MAXIMAL hyperemia (do not forget Ngl!)
Measure FFR, perform pullback recording if necessary
Perform PCI if indicated /possibility of measuring Pw, may not need any other guidewire/
Check post PCI FFR, perform pullback recording if necessary
After pulling back the PW to the tip of the GC verify absence of pressure drift

14. Some practical tips
Incorporate Analyzer into cath lab equipment (no nuisance to measure anymore)
Perform measurement systematically, step-by-step
Do it always the same way
Act according to the result (do not discredit your own measurement)
Make your coworkers understand what you are doing (assistants, surgeons...)
If possible, get access to adenosine infusion for i. v. administration

15. FFR in critical anatomy
ZI (Mrs. Tough MI Pt)
53-year-old lady
Hx: hypertension, type II diabetes mellitus, s/p nephrectomy
March 4, 2006: anterior STEMI (3 hrs)
Coronary angiography
Echo: LVH, good LVF, anterior akinesis w/o thinning

16. ZI
Tecnic 3,0x15 mm
RCA PCI of the LAD

17. ZI
RAO cranial AP

18. Should we intervene?
Courage trial
NEJM 2007; 356:

19. Importance of ischemia
Courage trial: 314 pt w/NPS
Circulation 2008; 117:

20. ZI: Left coronary artery
140 μg/kg/min iv adenosine

21. ZI: Right coronary artery
140 μg/kg/min iv adenosine

22. ZI
No further treatment
Pt continues to be symptom-free

23. Pull-back recording
By inducing long-lasting hyperemia, one may slowly pull the PW back under fluoroscopy and determine how different segments of the vessel (lesions) contribute to the resistance to flow.
By doing this, we are offered a lesion-specific index of ischemia
By contrast, exercise ECG can be considered patient-specific (unable to determine ischemia localization), SPECT can be held vessel-specific.
If an ischemic FFR value is obtained, and revascularisation is performed, FFR should be remeasured thereafter, because fixing one lesion may unmask the physiological significance of another.

24. Two compartments
Epicardial Artery
Microvasculature
FFR
IMR
CFR

25. General principle of coronary thermodilution: F= V/Tmn
One word on CFR
General principle of coronary thermodilution: F= V/Tmn
Since CFR= Fhyp/Fbas
CFR= Tmnbas/Tmnhyp
PW sensor acts as distal thermistor, PW shaft proximal thermistor
Mean transit times measured by 3 brisk injections of 3 ml saline
Issues with CFR:
Highly dependent on resting flow
Not specific for epicardial stenosis
Normal value not clearly defined
Distance of the sensor from GC tip is important
Large sidebranches just proximal to distal stenosis
GC position crucial (stable but not too deep)

26. IMR= Pd x Tmn at maximal hyperemia
R= Pd-Pv/flow
Since Flow ≈ 1/Tmn
IMR= Pd/(1/Tmn)
IMR= Pd x Tmn at maximal hyperemia
Practical set-up identical to measuring simultaneous FFR and CFRthermo
Limitations:
Somewhat dependent on distance of PW down the vessel
Clinical value not established

27. Measurement of IMR
IMR = Pd x Th = 78 x 0,12 = 9,36