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Catheter-Based Aortic
Valve Replacement Equal to Surgery in High Risk Patients
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Edwards
SAPIEN
Transcatheter Heart Valve |
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April 3, 2011 --
The much-anticipated findings from the PARTNER trial, comparing
the standard surgical procedure of aortic valve replacement (AVR)
to the newer and, as of yet, unapproved in the U.S. transcatheter-based
version (TAVR), were presented today at the American College
of Cardiology's 60th Annual
Scientific
Session in New Orleans -- and the two methods of treatment were
judged virtually equivalent at one year.
The study reported results from "Cohort A" of the
PARTNER trial which randomized patients who were at high risk
for surgery
either to the tried-and-true
surgical approach or to treatment with the SAPIEN
valve, manufactured by Edwards Lifesciences (NYSE: EW ), which
is delivered via
catheter, usually
via the femoral artery. |
Transcatheter aortic valve replacement is
an extension of the multiple therapies that have grown out of the
field of interventional cardiology, started over three decades
ago by Andreas Gruentzig with the first coronary angioplasty. At
that
time, surgeons were strongly opposed to this new unproven technology,
but with
the significant technical advances that have occurred over time,
angioplasty and stenting have made a major impact on the treatment
of coronary artery disease.
Which brings us to PARTNER, so-named because the exploration of
this new therapy was done via a strong partnership between surgeons
and interventional cardiologists. The PARTNER study was in fact presented
by principal investigator Dr. Craig Smith, Chairman of the Department
of Surgery at Columbia University -- and the co-investigator was
Dr. Martin B. Leon, also of Columbia, who, as founder of the annual
TCT
meeting, is one of the foremost proponents of catheter-based
treatment of heart disease.
So the future of this therapy is one that is adjudicated
by both surgical and interventional physicians.
Primary Endpoints Equivalent with
Some Caveats
The primary endpoint of Cohort A was freedom from death at one-year
-- and the results were identical between the surgical and catheter-based
arms: 26.8% for the surgical arm and 24.2% for the catheter-based
arm -- statistically insignificant, given the total number of 699
patients.
Where the data did diverge was in the stroke rate
(2.4% for surgery vs. 5.1% for catheter-based TAVR at one year),
in major bleeding (19.5% for surgery vs. 9.3% for TAVR), and in
vascular complications (3.2% for surgery vs. 11% for TAVR).
What is important to understand is that this trial
measured a brand-new first generation transcatheter device against
a surgical procedure which has been utilized for many years. And
since
the start
of the PARTNER Trial, significant changes to the transcatheter device
have been made. As Dr. John Webb of St. Paul's Hospital in Vancouver,
BC, stated
on theheart.org:
"This
is a trial of a first-generation transcatheter-valve system,
and with operators, many of whom had only done two cases before
doing
this trial, compared with the very best surgeons, at the very
best sites in the United States -- a very high bar. And
[the patients enrolled] were really just the top 10% of surgical
candidates—the
worst patients. Despite that, you have a mortality rate that's
lower [numerically] with transcatheter-valve implantation. The
study was
powered as a noninferiority trial, and it met that benchmark."
Last fall, the results from cohort B were presented
at the TCT annual meeting -- these were patients who were judged
as too sick for surgery. So these patients were randomized to best
medical therapy or TAVR -- and TAVR showed a 46% relative risk reduction
in mortality over medical therapy. So for patients too sick for surgery,
TAVR is clearly a better therapy -- and for patients at high risk
for surgery, TAVR is equivalent.
The Future of TAVR
Time will tell, of course, whether
the transcatheter valve is as durable as the surgical implant. One
concern is whether the transcatheter valve is more prone to leaks.
Surgical valves have been studied for many years, and currently the
transcatheter valve studies cover two or three years at
most.
However, for the populations studied in cohorts
A and B, the TAVR procedure has fared well and Edwards Lifesciences
is anticipating FDA approval for cohort B-type patients later this
year.
Medtronic is also a player in this space, with
their CoreValve
device, currently approved in Europe. Even though
the PARTNER Trial was done by their chief competitor, Medtronic today
issued the following statement:
"Medtronic welcomes the findings released
today on the Partner Cohort A, which
demonstrate
the clinical benefit of transcatheter aortic valve implantation
(TAVI) therapy in select patients with aortic stenosis.
TAVI studies including both the Partner and the CoreValve U.S, Pivotal trials address
the needs of an under-served patient population that today has only one
clinically-effective treatment option, surgical valve replacement.
The results
of the Partner study
show in particular that the outcomes of TAVI therapy are similar to those
of surgical replacement in high-risk patients. TAVI therapy is therefore a viable
alternative to surgical replacement for this patient group. CoreValve,
which
is a self-expanding valve with an 18 Fr platform, has been implanted in
more than 15,000 patients worldwide; the Partner A results are consistent with
the
CoreValve worldwide clinical experience in high and extreme risk patients.
Medtronic is committed to delivering new treatment solutions and improving outcomes
for
Americans with severe aortic stenosis. The Medtronic CoreValve U.S. Pivotal
Trial in
partnership with 40 leading U.S. medical centers is a critical step toward
making this a reality. To date, 35 centers have been activated in the trial
and patient enrollment is ongoing."
One of the significant differences between surgery
and transcatheter procedures was the vascular complication rate
(injury to and needed repair of the femoral artery) which was four-fold
in the transcatheter arm. The first generation valve required a
24F arterial opening, which is quite
large.
The newer
devices from Edwards and Medtronic only require an 18F opening, 25%
smaller.
Cost-Effectiveness of TAVR
According to various
financial analysts, TAVR (if validated) may reach a billion dollar
industry
in just a
few
years.
But more importantly, it may make available a therapy that will extend
life for patients too sick for surgery. In a separate presentation
today, a study sponsored by Edwards and performed by the Harvard
Clinical Research Institute (HCRI) in collaboration with the Saint
Luke's Mid America Heart and Vascular Institute, found that TAVR
was also cost-effective.
Matthew R. Reynolds, M.D., M.Sc., Director of
the Economics and Quality of Life Research Center at HCRI, stated that:
"For these patients who are not candidates
for surgery, transcatheter aortic valve replacement significantly
increases
life
expectancy
at an incremental cost per life year gained well within the range
of other commonly utilized cardiovascular technologies."
Reported by Burt Cohen, April 3, 2011
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