January
17,
2009 -- 19:30 EST
FAME: "Back to the Future"
The leading story about stents this past
week has been the publication of the FAME study and how a new St.
Jude Medical device that measures blood pressures inside the artery
can reduce the number of unnecessary angioplasty and stent procedures.
Well...it's not a new device; it's definitely not
a new concept; and St. Jude doesn't exactly get the credit for it
either, since their chief role was to acquire
the company that created
the product. But it is an important study!
First off, read Angioplasty.Org's article
on the FAME study, which clarifies some of this; then read my
exclusive interview with the FAME study's co-principal
investigator, Dr. Nico Pijls.
OK.
Now, let's get in the time machine and return to the genesis of coronary
angioplasty. It's 1977 and Andreas Gruentzig
has fashioned
a balloon catheter to open a blockage in a patient's
coronary artery. The balloon, which he is holding in the picture
to the left, not only can open a blockage in a coronary artery but,
oddly enough, also has the capability of measuring the blood
flow or pressure at the proximal and distal
ends of the
stenosis (a.k.a. "blockage"). If
the blockage is significant, the two pressures are widely divergent,
demonstrating that there is a diminished blood flow through this
arterial segment. These "pressure gradients" would be displayed
on the monitor behind him, if there were an actual procedure
going on.
Gruentzig continually
monitored the pressure gradient during procedures and, when the
distal and proximal pressures were similar, due to the dilatation
or expanding of the balloon and compression of the plaque, he judged
the procedure finished. Optimal dilatation of the stenosis had been
achieved! Gruentzig
was
also very conservative regarding the ability of angioplasty to achieve
a result. He called dilatation "a controlled injury" of the artery
and was adamant that the decision to intervene needed to be made
with great care and understanding of the downsides of the procedure.
In these early days, the measurement of pressures
required a separate lumen, which made the balloons were pretty
wide and unable to get into narrow arterial spaces. Then Dr. John
Simpson invented a much thinner balloon catheter: he got into the
narrow spaces, but he sacrificed the ability to measure pressures.
Gruentzig was not entirely comfortable with this "advance". But
unfortunately he died in a plane crash in 1985, and well....
Fast-forward to the 21st century. For two decades, angioplasty
has been done without monitoring the procedure with pressure gradients.
Decisions were made primarily by eye (a.k.a. the oculo-stenotic reflex):
there's a narrowing there; let's put in a stent.
Now, thanks to Dr. Nico Pijls and others, cardiologists
can measure pressures with a guide wire, using Doppler sensors et
al. We are now able to measure gradients and
make intelligent, data-based decisions about whether or not to dilate
a blockage.
The results? Well, don't intervene on a lesion/blockage
that is not significant. It may do more harm than good. Gruentzig
would have said the same. And now the FAME study reaffirms what
he already knew, but which has been forgotten through the years.
Back to the Future!
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