To stent or not to stent
Clinical Utility of Fractional
Flow Reserve
Assessment of coronary artery
stenosis
• Inducible myocardial ischemia during functional
testing has crucial prognostic significance in
determining whether or not to treat coronary
artery stenosis.
• In real-world practice, however, fewer than half
of all patients are evaluated noninvasively for
myocardial ischemia before revascularization
therapy.
• Coronary angiograms are still frequently used as
a cornerstone of decision making
Assessment of coronary artery
stenosis by angiogram
• Luminogram
• Purely anatomical
• Inter and intra observer variability
• Oculostenotic reflex
Angiographic severity of stenosis
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Normal
Minor disease
Mild irreguralities
Minimal disease
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Severe stenosis
Super tight
99 percenter !
Die now ! if not treated
Fractional flow reserve
• Equivocal or intermediate lesions , and in the absence of
demonstrated ischaemia, decision making based on
angiography alone is challenging.
• FFR has been extensively described and validated as a
technique capable of identifying functionally significant
lesions
• FFR value below the threshold value of 0.75 corresponds to
inducible ischaemia
• Studies have shown that a strategy of revascularization based
on FFR results in this context is acceptable.
Coronary resistance
• First compartment consists of
large epicardial vessels which are
also referred to as ‘conductance
vessels’
• Minimal resistance to blood flow.
• Therefore, the pressure in the
distal part of a healthy coronary
artery should be equal to central
aortic pressure.
• The second compartment
consists of arteries smaller than
400 microns, or ‘resistive vessels’
• Myocardial flow is controlled
predominantly by resistive
vessels.
Fractional flow reserve
• FFR is the ratio of maximal myocardial blood
flow in a stenotic artery to maximal
myocardial blood flow if that same artery
were to be normal
• Normal value is 1
• FFR is a ratio of two flows
• This ratio can be derived from two pressures
(distal coronary pressure and aortic pressure),
provided they are both measured during
maximal hyperaemia.
FFR = Pd/Pa
Questions
• What is the safety of using a coronary pressure wire
for the measurement of FFR ?
• Does the use of a coronary pressure wire for the
measurement of FFR improve diagnostic accuracy?
• Does the use of a coronary pressure wire for the
measurement of FFR change patient management?
• Does the use of a coronary pressure wire for the
measurement of FFR improve patient outcome?
• What is the cost-effectiveness of using a coronary
pressure wire for the measurement of FFR ?
Features of FFR
• FFR has a theoretical normal value of 1 for
every patient, for every artery and for every
myocardial bed
• FFR is not influenced by systemic
haemodynamics
• FFR takes into account the contribution of
collaterals
• FFR specifically relates the severity of the
stenosis to the mass of tissue to be perfused
Fractional flow reserve: clinical
applications
• Intermediate stenosis and deferring PCI/surgery
• Multivessel disease and FFR directed PCI in
multivessel disease.
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Left Main stem disease
Bifurcation disease ; evaluation of side branch
Post stenting
After Myocardial Infarction
• What is the safety of using a coronary pressure wire
for the measurement of FFR
• Does the use of a coronary pressure wire for the
measurement of FFR improve diagnostic accuracy?
• Does the use of a coronary pressure wire for the
measurement of FFR change patient management?
• Does the use of a coronary pressure wire for the
measurement of FFR improve patient outcome?
• What is the cost-effectiveness of using a coronary
pressure wire for the measurement of FFR ?
Is it safe ?
• 6415 coronary
angiographies, FFR was
measured in 407 (6.3%)
patients (469 lesions)
• The only FFR related
complication was an
occlusive dissection due
to a plaque dissection
by the pressure wire.
DEFER trial
• Twenty six studies involving 2639 participants
were identified that met the eligibility criteria
for the safety component
• Great majority of adverse effects reported
were self limiting in nature
Is it accurate ?
Intermediate stenosis
• Value of 0.75 has shown good corelation with
non-invasive stress test, especially myocardial
perfusion study
• Sensitivity, specificity and accuracy 90% when
compared to perfusion tests.
Value of 0.75
NEJM 1996
Piljs et al
• In 45 consecutive patients with moderate coronary stenosis
and chest pain of uncertain origin, bicycle exercise testing,
thallium scintigraphy, stress echocardiography with
dobutamine, and quantitative coronary arteriography and
compared the results with measurements of FFR
• In all 21 patients with an FFR of less than 0.75, reversible
myocardial ischemia was demonstrated unequivocally on at
least one noninvasive test.
• After coronary angioplasty or bypass surgery was performed,
all the positive test results reverted to normal
• Sensitivity of FFR in the identification of reversible ischemia
was 88 percent, the specificity 100 percent, the positive
predictive value 100 percent, the negative predictive value 88
percent, and the accuracy 93 percent.
Does it alter patient management
4-year single-centre experience
Angiogram for any reason
Intermediate lesions 40% - 60% on QCA
6415 coronary angiographies, FFR was measured in
407 (6.3%) patients (469 lesions)
2/3rds of patients with ‘intermediate’ lesions were
left unrevascularized, with a favourable
outcome, when FFR was above 0.80.
DEFER Trial
DEFER
DEFER
Does routine use improve patient
outcome
FFR directed PCI in multivessel
disease : FAME trial
FAME
EVENTS AT 2 YEARS
Is it cost effective ?
Am Heart J. 2003 May;145(5):882-7.
Cost-effectiveness of measuring fractional flow reserve to guide coronary
interventions
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Decision model to compare the long-term costs and benefits of 3 strategies for treating
patients with an intermediate coronary lesion and no prior functional study:
1) deferring the decision for percutaneous coronary intervention (PCI) to obtain a nuclear
stress imaging study (NUC strategy)
2) measuring fractional flow reserve (FFR) at the time of angiography to help guide the
decision for PCI (FFR strategy);
3) stenting all intermediate lesions (STENT strategy).
Estimated the cost of FFR to be 761 dollars, the cost of nuclear stress imaging to be 1093
dollars, and the cost of medical treatment for angina to be 1775 dollars per year. The extra
cost of splitting the angiogram and PCI as dictated by the NUC strategy was 3886 dollars by
use of hospital cost-accounting data.
The FFR strategy saved 1795 dollars per patient compared with the NUC strategy and 3830
dollars compared with the STENT strategy. Compared with the FFR strategy, the NUC strategy
was expensive Both screening strategies were superior to (less cost, better outcomes) the
STENT strategy.
In patients with an intermediate coronary lesion and no prior functional
study, measuring FFR to guide the decision to perform PCI may lead to
significant cost savings compared with performing nuclear stress imaging
or with simply stenting lesions in all patients.
All in one approach for suspected CAD
?
• What is the safety of using a coronary pressure wire
for the measurement of FFR ?
• Does the use of a coronary pressure wire for the
measurement of FFR improve diagnostic accuracy?
• Does the use of a coronary pressure wire for the
measurement of FFR change patient management?
• Does the use of a coronary pressure wire for the
measurement of FFR improve patient outcome?
• What is the cost-effectiveness of using a coronary
pressure wire for the measurement of FFR ?
• AHA/ACC guidelines are IIa for FFR ( level of evidence A), and
European PCI guidelines have recommendation I (level of
evidence A) for FFR without objective evidence of ischemia.
• Although the use of FFR measurement has increased steadily
over the past decade, FFR is not frequently used in the cath
lab.
• Multiple factors, including habit, bias, training experience,,
financial incentives, misconceptions by patients, a perception
by referring physicians of the need to stent coronary stenosis,
cumbersome set-up time, and reimbursement for pressure
wires.