fractional flow reserve

1. FFR
DIPAK PATADE

2. Challenges in daily practice
• Patients with recent myocardial infarction , questions pertain to lesions not
responsible for symptoms or infarct—so called “non culprit” lesions .
• Subsequent cardiovascular events appear equally likely in no culprit lesions
following MI .
• Patients with stable angina, questions surround the choice between medical
therapy and revascularization .Difficulty is identifying specific lesions that are
functionally significant or that will likely lead to adverse events.
• Frequent occurrence of multivessel disease poses additional challenges.
• Noninvasive tests may lack sensitivity and specificity to detect multivessel disease
and treatment decisions can be complex .

4. Coronary blood flow
• ~5% of the total CO
• increase up to 5 times with exercise, hypoxia, local metabolite release
(nitric oxide), and microcirculatory vasodilators
• microcirculatory resistance is the only resistance to myocardial flow
• epicardial vessels are just conductance vessels that offer no resistance
• systolic compression of the microcirculation- left coronary blood
flows mainly during diastole (>80% occurs in diastole).
• Tachycardia- increasing O2 demands + reduces myocardial O2 supply
by reducing diastolic time

5. Coronary blood flow
• tachycardia - increases the relative systolic contribution to coronary
flow.
• RV - thin, its microcirculation is not as affected by systole ;~50% of the
mid right coronary-to-RV flow occurs in systole
• autoregulation, that is, microcirculatory vasodilation, maintains
coronary perfusion at a constant level over a wide range of coronary
pressure.
• Reduced perfusion pressure distal to a stenosis is compensated by
autoregulatory dilation of resistance vessels.
• Autoregulation allows myocardial flow past the stenosis to remain
normal at rest despite a reduction in pressure; however, flow cannot
increase enough with exercise or with maximal vasodilation

6. • Determined not only by variations in pressure arising proximally (as in
the aorta and other systemic arteries) but also concurrent variations
arising distally in the microcirculation
• inaccurate to assess the severity of a coronary stenosis by measuring
the decrease in mean or peak pressure across a stenosis under basal
conditions
• distal coronary pressure is not simply a residuum of the pressure
transmitted from the aortic end but is also due to a pressure
component arising from active compression and decompression of
the coronary microcirculation

10. Pressure flow dynamics at stenotic segment

16. FFR
• Technique used in
coronary catheterization
to measure pressure
• differences across a
coronary artery stenosis
(narrowing, usually due to
atherosclerosis) to
determine the likelihood
that the stenosis impedes
myocardial ischemia.
• FFR=Pd/Pa

20. Fractional flow reserve
• FFR is used to assess the physiologic consequences of obstruction with a goal of
predicting benefit from revascularization or which lesions should be treated .
• Derived from the ratio of the mean distal coronary artery pressure (Pd) to the
mean aortic pressure (Pa) during the period of maximum hyperemia.
• Fractional flow reserve is not affected by changes in the hemodynamic conditions
or microcirculation.
• ‘‘normal’’ ratio is expected to be 1.
• Values less than 0.75 to 0.80 are considered functionally ischemic, while those
0.94 to 1.0 normal.

22. What Fractional Flow Reserve Value defines
Ischemia ?
• FFR value <0.75 was associated with reversible ischemia on
noninvasive stress testing (exercise stress test, nuclear scan, and
dobutamine stress echocardiogram)
• with 88% sensitivity,
• 100% specificity,
• 100% positive predictive value,
• 88% negative predictive value, and
• 93% accuracy.

23. What Fractional Flow Reserve Value defines
Ischemia ?
• DEFER study and other studies have used an FFR value of <0.75 as the
cutoff for ischemia.
• FFR value >0.80 has been shown to exclude an ischemia producing
lesions, with predictive value of >95%.
• 3 landmark trials have validated FFR cut off values-
• DEFER
• FAME
• FAME II

29. Coronary stenosis can be arbitrarily classified into 3 groups on
the basis of FFR values:
a. non–ischemic stenosis with FFR >0.80
b. ischemia-producing stenosis with FFR <0.75.
c. gray zone with FFR values between 0.75 and 0.80.

30. Applications for Fractional Flow Reserve in
Coronary Artery Disease
Single-Vessel Disease-
• DEFER study has shown that patients with single vessel stenosis and FFR
>0.75 who did not undergo PCI had excellent outcomes.
• The risk of cardiac death or myocardial infarction (MI) related to the stenosis was
<1% per year and was not reduced with PCI.
• patients with single-vessel stenosis and FFR <0.75 are 5× more likely to
experience cardiac death or MI within 5 years, despite undergoing
revascularization.
• medical treatment of patients with proximal left anterior descending stenosis and
FFR >0.80had excellent 5-year outcomes

31. • patients with small coronary arteries (diameter <2.8 mm), FFR can
safely determine stenosis that necessitate revascularization.
• In the Physiologic and Anatomical Evaluation Prior to and After
Stent Implantation in Small Coronary Vessels (PHANTOM) trial, 60
patients with small coronary arteries underwent FFR. group with FFR
<0.75 underwent revascularization.
• At 1 year, there was no occurrence of MI or death in either group.
• patients with FFR <0.75, 24% underwent a repeat PCI, but only
2.6% of patients with FFR >0.75 underwent revascularization.

32. Left Main Stenosis
• Nonischemic FFR values (>0.80) in left main lesions are associated with excellent
long-term outcomes.
• accurate LM FFR reflects flow through both the LAD and the CFX.
• myocardial bed for the LM is the summed territories of both the LAD and
the CFX.
• LM bed can be even larger if the RCA is occluded and there is collateral
supply from the left coronary system.
• isolated LM narrowing with no LAD, CFX, or RCA stenosis reflects the
physiologic significance of just the LM narrowing.
• LM narrowing plus LAD stenosis could produce a higher LM FFR because
the LM bed is reduced in size.
• LM FFR alone cannot be accurately measured just as when there are serial
lesions.

33. Tandem Lesions-
• Tandem lesions are defined as 2 separate lesions with >50%stenosis each
in the same coronary artery, separated by an angiographically normal
segment.
• If the FFR is<0.75 PCI for the stenosis that showed marked narrowing
first and then repeating the FFR measurement.
• If the FFR remains<0.75,the other stenosis was revascularized as well ,
In contrast, if the FFR value of the first lesion increased after PCI to >0.75,
then these second lesion was treated only medically.

34. diffuse coronary disease
• If FFR < 0.80 but pressure pullback reveals a gradual decline in
pressure without focal drop-This may be seen in patients with mild or
moderate diffuse disease and small coronary arteries.
• 8% of arteries with mild diffuse coronary atherosclerosis without a
focal stenosis have a graded continuous fall in pressure along the
arterial length with FFR <0.75, explaining myocardial ischemia and
angina without angiographically obstructive disease.

37. FFR and a bypass graft
• myocardial territory receiving a bypass graft is supplied by 2 vessels
• graft
• native vessel if not totally occluded
• During hyperemia, the drop in pressure distal to a graft stenosis
reflects the drop in flow across the supplied myocardium
• an angiographically severe stenosis across the graft may not lead to a
significant flow reduction, depending on the adequacy of native
vessel flow.
• FFR reflects a net FFR from all sources of flow to that region.

38. Ostial disease
• Ostial disease with too deeply engaged GC- pressure at its tip does
not correspond to the aortic pressure but to the pressure distal to the
lesion.
• guiding pressure (false Pa) and the sensor pressure (Pd) correlate
closely and the FFR is falsely increased.
• guiding catheter is outside the ostium but the wire is just distal to the
ostium-pressure distal to the stenosis is equalized to the aortic
pressure
• FFR may be overestimated and the lesion underestimated
• disengage the guiding catheter and the sensor part of the wire during
equalization.
• guide may then be temporarily engaged while wiring the artery but
must be disengaged when FFR measurements are obtained.

39. MI and FFR
• Maximal hyperemia is lower
• FFR may be overestimated (lesion underestimated).
• not be used to assess the culprit lesion of MI that occurred within the
last 5 days.

40. Old infarcted myocardium
• When part of the territory supplied by a coronary artery is infarcted, this
territory receives reduced myocardial flow , maximal achievable flow
across this myocardial territory is reduced.
• FFR dependent - amount of viable myocardium and the severity of
microcirculatory impairment.
• FFR <0.75 correlates not only with the size
• large increase in transstenotic pressure gradient or flow with adenosine -
sign of the presence of viable myocardium with healthy microcirculation
• absence of a vasodilatory response -sign of non-viability (ie, "FFR" number
remains unchanged before and after adenosine infusion

41. Persistent low FFR after PCI
• incomplete stent expansion
• stent malapposition
• geographical miss
• plaque protrusion
• edge dissection
• plaque shift at the stent edge
• pullback manoeuvre :continuous gradual reduction in FFR = diffuse
CAD.
• diffuse CAD -impaired post-stent FFR, despite an angiographically
optimal PCI

44. FFR Limitation & Disadvantage
• FFR assess of lesion severity.
• FFR invasive test and allows real-time estimation of the effects of a
narrowed vessel.
• No plaque morphology information.
• physical exercise or some intravenous medication is to increase the
workload and oxygen demand of the heart muscle, and ischemia is
detected using ECG changes or Nuclear imaging.