Functional Measurement
Wouldn't it be great if there were an objective measure to judge
whether or not revascularizing a coronary artery was going to benefit
the
patient? Such an evaluation would bolster the decision of whether
to perform PCI or surgery or to defer any procedure and go with
optimal medical therapy instead. And wouldn't it be odd to learn
that such a test exists, but that less than 20% of cases
use this technology?
We're speaking about Fractional Flow Reserve (FFR) -- a simple,
quick measurement that can be done as part of diagnostic angiography
-- and one which will measure the functional significance of a
specific lesion or lesions -- i.e., not how severe the blockage
looks on the fluoroscopic image, but how severe the restriction
of blood flow actually is -- with a number to boot.
The number is 0.80 and in multivessel disease, an artery that
measures less than 0.80 is considered ischemia-producing and therefore
is a candidate for revascularization.
Jennifer Tremmel, MD |
Which Artery to Stent?
Much has been written
about the oculo-stenotic reflex where one can look at an angiogram
and
say, "There's a narrowing.
We should open that up." It makes intuitive sense. You have
a patient with chest pain. You cath the patient and two narrowings
are revealed: one stenosis in the circumflex and a relatively mild
one in the LAD. The circ lesion is clearly more narrowed on the angiogram,
so
you
decide
to
stent that and leave the LAD alone. Sounds intuitive but, as Dr.
Jennifer Tremmel recently showed in her presentation on FFR at the
CICT Meeting, you would have been wrong...two fold. You would have
unnecessarily stented a non-ischemia-producing lesion (the circ)
and you would have left the problem LAD untreated.
Further evidence of FFR's benefit
was provided by the now well-publicized
FAME study, but an most
interesting analysis of the FAME data was
published last year in JACC. You can read about this analysis in
our feature article, "To
Stent or Not To Stent: Fractional Flow Reserve (FFR) Trumps Angiography
in Diagnosing Blockages up to 90%", but the bottom
line was that two-thirds of the lesions measured by angiography
to be in the 50-70% range were "not functionally significant" and
did not need revascularization. Two-thirds. In fact in the 71-90% range,
one out of five lesions was insignificant.
FFR Recognized by Guidelines and Leaders
in Cardiology
So with the recent ramping up of cries of over-stenting
and inappropriate stenting
which have
echoed
throughout
interventional
cardiology, one would think that a tool like FFR would be gaining
credence. And it has. The 2009
Focused Updates to the ACC/AHA/SCAI Guidelines on PCI increased
the "level of evidence"
for FFR to an "A" and stated that FFR "can be
useful to determine whether PCI of a specific coronary lesion is
warranted."
And the following comments were made to
Angioplasty.Org by leaders in cardiology, specifically in the context
of judging the appropriateness
of PCI. Dr. Ralph Brindis, immediate Past President of the American
College of Cardiology (ACC) told us:
Ralph
Brindis, MD |
"My own personal feeling
and bias is that FFR is an extremely important tool and that
it hopefully will increasingly be utilized
in terms of appropriate decision-making related to PCI going
forward. And I also predict that, as we come up with different
payment models, particularly related to disease-bundling or
episodes of care, that it will become even more encouraged
at the local hospital level, so that a stent is put in, after
a demonstration of ischemia, particularly in intermediate lesions.
I will say that within my own institution at Kaiser Permanente,
we are finding increasing value in the use of FFR at the time
of catheterization for decision-making." |
And Dr. Greg Dehmer, Past President of the Society for Cardiovascular
Angiography and Interventions (SCAI) stated:
Greg
Dehmer, MD |
"Guidelines are now getting
stronger in their recommendations to use FFR on intermediate
severity stenoses or in situations where you don't have
an exercise test beforehand.
I
think that will only help to make that better
as more people use that technology and become very familiar
with that technology"
|
And Dr. William O'Neill, Executive
Dean at Miami's Miller School of Medicine and pioneer of angioplasty
for the treatment of heart attack:
William
O'Neill, MD |
"We've known for almost 25
years that visual assessment of angiograms is reproducible and
inaccurate. Every angiographer knows you can make a lesion anywhere
from 20 to 70%, just by the frame that you pick when you look
at an angiogram. The lesson that the interventional community
needs to learn is that you have to be really careful about documenting
why you are treating moderate severity lesions. And when in doubt,
either use IVUS or FFR to make sure that you can prove to people
that the lesion is severe enough to be treated."" |
So the question remains, if the evidence
is clear, if the guidelines have promoted FFR to an "A" level, if
leaders in the field feel it's
a valuable tool, why isn't it used more than 20% of the time? The
answers lie certainly in reimbursement issues. Adding FFR capability
to a cath lab, while actually relatively easy, is still an expense.
The catheters themselves also add on a charge. But if, in fact, this
technology can save significant costs for our healthcare system,
shouldn't its use be higher than it currently is?
Not to mention that, as shown
by FAME, patient outcomes are improved!
|
