Concept and practical set-up of CFR, FFR, IMR

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 2333-42
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
Complaints of pt
Non-invasive tests
So, who do we believe?
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 1354-67
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

• 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 1503-1516
19
Importance of ischemia
Courage trial 314 pt w/NPS
Circulation 2008 117 1283- 1291
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
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

• 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
28
(No Transcript)