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Better Outcomes for
Stents When Fractional Flow Reserve
(FFR) is Used
Measuring Intracoronary
Pressures Reduces Major Cardiac Events by 28% in FAME Study,
Published in the New England Journal of Medicine
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January 15, 2009 -- Published
in today's
New England
Journal of Medicine, are the results of the FAME study (Fractional
Flow Reserve vs. Angiography for Multivessel Evaluation). The study concludes that:
"Routine
measurement of FFR in patients with multivessel coronary
artery disease who
are undergoing
PCI with drug-eluting stents significantly reduces the
rate of the composite end point of death, nonfatal myocardial
infarction,
and repeat revascularization at 1 year."
Conducted in 20 European and U.S. centers, FAME
randomized over a thousand patients with multivessel coronary artery
disease
for treatment with angioplasty and drug-eluting stents
into two groups. In the control group, standard
angiography and previously performed stress or other tests were used
to determine
which lesions
(blockages) needed stenting. This is the norm in most cath labs today:
cardiologists look at a blockage, determine its size or severity
and, if it is judged "significant", it is opened by a balloon and
stented.
The second group relied on a measurement called
Fractional Flow Reserve or FFR, in which a tiny wire with a sensor
is threaded to the blockage, and the blood flow is measured on both
ends of the narrowing to determine if the lesion is restricting blood
flow to the heart, and causing ischemia -- a high risk factor for
poor outcomes. In this group only lesions that measured 80% of normal
blood flow or less were stented, no matter what the visually-oriented
angiogram showed.
The result was that one-third fewer stents were
used in the FFR group and the difference in outcomes at one year
were significant: the FFR group showed a 28% lower incidence of major
adverse cardiac
events (repeat procedure to open the artery, heart attack or death)
-- 18.3% vs. 13.2%. The implication in these results is that placing
stents in lesions that are not responsible for ischemia is not
only not necessary,
but may cause worse outcomes.
Nico H. J.
Pijls, MD, PhD
Professor of Cardiology
Catharina Hospital
Eindhoven,
The Netherlands |
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Co-principal investigator,
Dr. Nico Pijls, told Angioplasty.Org that the study is about
refining the procedure of stent placement (PCI) to make it more
accurate, safer and cost-effective, while providing better patient
outcomes, and he cautioned against misinterpreting the results
as being "anti-stent".
He stated:
"Patients
should not be disquieted or scared and they should not lose
their trust
in interventional cardiology...stenting in itself is a very
good procedure, but by this new technique, we can best
define where we have to place the stent in the best possible
way.
So it's not a matter of stenting
or not stenting. But it is a matter of placing the right
stent in the right spot...at the end, 94% of all patients
were stented, but they had less stents. They were stented
in a more refined way."
Dr. Pijls explained the outcomes further. A non-ischemic lesion
may have a 1% chance of causing a heart attack, whereas an ischemic
lesion may carry a 5-10% risk. It is known that placement of
a stent results in a 3% risk, so stents are good for reducing
risk in severe lesions, but actually can increase the risk
if used in areas where they are not necessary. |
Another benefit seen in the FFR
group was procedural cost. Since less stents were used per patient,
the average cost of the procedure was $700 lower (this includes the
specialized guide wire used to measure FFR). Less stents also meant
approximately 10% less contrast dye. The procedural time
was virtually the same for both groups.
Dr. Pijls initially presented the FAME results at last fall's TCT
meeting
in
Washington.
Today's
publication in the
peer-reviewed
NEJM is titled "Fractional
Flow Reserve versus Angiography for Guiding Percutaneous Coronary
Intervention", and is accompanied by an editorial, authored
by Dr. Steve Ellis of the Cleveland Clinic, which asked several questions
about how stenting in the angiography only group was determined,
the use of pharmacologic agents during the procedures and the rate
of periprocedural MI. Dr. Pijls responded to those questions in
his
exclusive interview with Angioplasty.Org:
"The decision-making on what to stent was made
in a classical traditional clinical way. We used the clinical data,
the results of noninvasive testing, if they were available, the angiogram,
and we only included a particular stenosis in the study if it was
more than 50% and in a major coronary artery.... So our selection
of patients was completely according to normal routine. That was
the purpose of the study: that it reflect the normal routine.
"...the rate of peri-procedural myocardial infarction...was
actually 3.4% in the angio group
and 2.4% in the FFR group. So it was not higher than in the other
studies. And in the FAME study, we had a
lot of severe disease with an average of three vessels which were
stenotic. We also had patients with very low ejection fractions,
patients with acute coronary syndrome -- that was 30% of the population
-- we had patients with previous PCI, so we had a population typical
of the every day population we see in the cath lab. During the
procedure, we used also used thiopyridines, or Plavix: a loading
dose of 600mg was used in all patients and
IIb/IIIa inhibitors
were used in 31% of the patients, which is also the average."
Dr. Ellis' editorial concluded with a thought that
"perhaps the research question addressed in the trial was itself
something of a 'straw man,' since FFR does not have to be used on
all or none of the stenoses that might be treated but rather can
be used selectively". Dr. Pijls took issue with that observation,
saying, "We have known already for years that we could use
FFR in some lesions; the purpose of this study was just to show
that
it made sense to use it routinely."
Whether or not FFR will start being used routinely
as a result of the FAME study is
yet to be seen -- it is
estimated
that
only
5%
of procedures done in the U.S. use this technology. As for stents,
some believe the results of the FAME study will mean less stents
will be used. Dr. Pijls feels differently:
"I think that per patient, less stents would
be used. But more patients will qualify for PCI – because
you have a treatment, and let’s say that you can decrease
the risk of the treatment by 30% -- so the threshold to apply that
treatment
will become lower. What I believe is that you can do it better,
by less stents per patient. And because you do it better, there
are
more patients, either from medical therapy who were previously
treated only medically, or patients who need surgery at the moment
-- all
those patients can also be helped by PCI. So I think that in the
end, the number of stents used will be the same, but they will
be redistributed."
The FAME study
was supported by Radi Systems, a privately-held Swedish company
which manufactures an FFR wire. Radi was acquired only three weeks
ago by St. Jude Medical. Volcano Corporation also manufactures
an
FFR wire, along with a number of other intravascular devices, such
as IVUS, OCT, etc. It may be that these various intravascular imaging,
measuring and treatment devices will have a role in changing and
refining the practice of interventional cardiology in the future.
Reported by Burt Cohen, January 15, 2009
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