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To Stent or Not To Stent:
Fractional
Flow Reserve (FFR) Trumps Angiography in
Diagnosing Blockages up to 90%
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June 23, 2010 -- The FAME
study,
published in January 2009, showed that using Fractional Flow
Reserve (FFR) instead of standard angiography to determine whether
or not to stent a blocked coronary artery resulted in one-third
fewer stents being placed and, more importantly, resulted in
almost one-third fewer serious adverse cardiac events, such as
heart attack and death.
These results have remained intact, even
after two years of follow-up. |
Now, an ancillary study of the FAME data, has been published in
the June 22 issue of the Journal of the American College of Cardiology and, as the authors conclude:
"In patients with multivessel CAD, coronary angiography is an inappropriate
tool to identify ischemia-producing stenoses as detected by the FFR.
This discrepancy between angiographic and functional stenosis severity
is not only present in the 50% to 70% stenosis range but also in
the 71% to 90% stenosis range."
Angiography, long considered the "gold standard"
in diagnosing coronary artery disease, is now being labeled as inappropriate
and inaccurate by those who are utilizing a new technique for determining
ischemia. (The authors also note that noninvasive stress testing
is similarly inaccurate in determining ischemia in multivessel disease.)
An angiogram is a shadow image
of the coronary artery, produced by X-rays and contrast dye to
show if any blockages exist. When a cardiologist sees a blockage
greater
than 50%, he or she often decides to open the artery using balloon
angioplasty and places a stent to hold the artery open.
Criticism
has been leveled at this diagnostic method and has been labeled
as the "oculo-stenotic reflex" -- if you see a blockage (stenosis)
you automatically assume it needs to be stented. However, this is
not always the case. |
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The FAME study refuted this methodology for patients
with multivessel coronary disease (narrowings in more than one artery).
Using a catheter to measure the blood pressure on both sides of the
blockage,
called the fractional
flow reserve (FFR), cardiologists were able to determine more accurately
whether the plaque build-up was actually causing significant ischemia
(loss
of blood flow). When guided by FFR, less stents were placed and outcomes
for the patients were better by 28%, when compared to stent placement
guided only by the angiogram.
What the authors of this week's JACC paper have shown is that the
advantage of FFR-guided stent placement exists not only in what
might be called "intermediate lesions" of 50-70% (as measured by
angiography)
but also in more severe blockages. Two-thirds of
the coronary narrowings in the 50-70% range were measured by FFR
as being functionally insignificant. In other words, only one out
of three blockages in this range was causing ischemia; placing a
stent in two-thirds of these lesions was not only unnecessary, but
could result in more adverse events.
However, even in the more severe
range of 71-90% blockages, one out of five stenoses were
measured by
FFR
as being
functionally
insignificant -- no stent needed. It was only in the range of 91%
or greater narrowing that virtually all of the lesions were significant
and the patient would benefit from stenting.
The implications of these studies are wide-ranging.
The authors show that many patients diagnosed with triple-vessel
disease may in fact only have one or two vessels causing a problem.
They also note that if many of the angioplasty vs. .surgery studies
had used FFR instead of angiography to determine whether or not to
use a stent, the improved results may have favored angioplasty more.
Likewise, the COURAGE trial may also have shown a greater benefit
for angioplasty and stenting.
Andreas
Gruentzig holding
his original balloon catheter |
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Interestingly enough, the original
balloon catheter, as designed by Andreas Gruentzig, the inventor
of coronary angioplasty, had a built-in capacity to measure coronary
pressures. Gruentzig insisted on this feature to determine if
the balloon had sufficiently opened the artery. He was a strong
proponent of documenting the results of his procedures and of
using intracoronary blood pressures as a guide for dilatation.
But as balloon angioplasty grew and started being applied
in more complex and sophisticated cases, the relatively bulky
pressure measurement
designs had to be discarded by catheter manufacturers in order
to create balloons of smaller and smaller profile, balloons
which could reach into narrower arteries and negotiate more
tortuous
coronary anatomy. |
Until now, that is. Today, specialized FFR catheters
are manufactured by two companies: Volcano Corporation
and St. Jude
Medical (which funded this week's JACC study, as well as the original
FAME trial). But despite the clear advantages shown in these studies,
FFR is still only utilized in 10-15% of all percutaneous coronary
interventions (PCI). Both companies feel that this is
changing and that, with the advances
in design
and the integration of FFR technology into the cath lab, this new
diagnostic tool will be adopted by cardiologists in increasing numbers,
resulting in better outcomes for patients and potentially lower costs
(less stents) for the healthcare system.
Reported by Burt Cohen, June 23, 2010
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