HeartMate II |
"He looked great today — and
this is a patient who could hardly take a step before,"
beams Dr Renzo Cecere. The heart surgeon couldn't be
happier for 65-year old Gerald Langevin, who recently
became the first Canadian to be implanted with the new
HeartMate II. After an exemplary recovery, Mr Langevin
was back at home in time for the holidays, outfitted
with a new mechanical heart that could soon become the
first viable, long-term alternative to transplant. He
says he feels more alive than he has in years —
ironic for a man who no longer has a discernable pulse.
BLOOD,
UNINTERRUPTED
The HeartMate II has already been implanted at selected
American test sites, but the McGill University Health
Centre is the first of only two Canadian hospitals who've
received permission to put it to use. Comparable in
size and weight to a D-size battery, the implant is
the latest device designed to assist the function of
the left side of the heart. But while older models were
pulsatile in nature, the HeartMate II produces a continuous
flow of blood. "With the previous generation of mechanical
pumps, it would fill with each cycle and then trigger
a response to squeeze the blood out of the chamber and
back in towards the aorta," Dr Cecere explains. "That's
what the pulse is all about — it's a filling and
emptying cycle."
But the HeartMate II operates under
different principles. "It's like an Archimedean screw
which spins at a high speed and propels blood along
its path, so it doesn't produce any pulsation at all,"
says Dr Cecere. "If you were to place a blood pressure
cuff around a recipient's arm, you wouldn't be able
to measure blood pressure."
THE
GREAT UNDEAD
But is it really safe to live without vital signs?
"That's a very important question,"
responds Dr Cecere. "At the cellular level — where
the oxygen of the blood is exchanged with the cells
of the body — there's never pulsitivity because
the blood cells travel one at a time and are continually
flowing. So one argument is that the cells never see
pulsitivity anyway."
He adds that even if living without
vital signs proves to be unhealthy, our leg muscles
can naturally create a surrogate pulse. "My personal
bias — and I don't have hard data to support this
yet — is that every time we walk, the contracting
muscles in the legs produce a sort of a fake pulsitivity.
Perhaps that's enough to mimic the normal pulse that
we're all accustomed to." In about three years of human
testing, Dr Cecere adds, there haven't been any problems
related to the lack of a pulse. So far, the biggest
known risks are bleeding — because of the small
amount of blood thinners patients are given — and
infection.
WHO
NEEDS IT
As it stands, only patients with end stage left ventricular
failure can enrol in the HeartMate II clinical trials.
But Dr Cecere foresees this device being appropriate
for many Canadians.
"Because of the longevity we expect
to get out of this device [10 years], we see it as a
true alternative to a heart transplant," he says. Patients
like Mr Langevin who aren't candidates for a transplant
— whether because of their age or other medical
conditions — would have a viable option that could
give them the same expected lifespan as those lucky
few who do get a new heart.
Dr Cecere gives the example of
an older cardiac patient who'd been diagnosed with lymphoma
two years earlier. "Just about any cancer represents
a relative contraindication to transplantation because
the immunosuppression we give to transplant patients
could revive a dormant cancer," he says. "[This device]
is a strategy for giving patients 10 years of life that
they otherwise wouldn't have."
STICKER
SHOCK
The HeartMate II costs about $100,000. If it were to
get Health Canada approval for more general use, Dr
Cecere imagines policymakers will have some tough decisions
to make.
"Right now expenditure for heart
failure is somewhat limited — if you're only talking
about heart transplantation as a therapy for end-stage
heart disease, you'll only be spending a finite amount
because of the small number of donors," he says. In
Canada, there's somewhere between 170 and 200 donors
a year. "Once the pump is approved it's going to be
on the shelf — mass produced — so in theory
there's no limit to the number we could implant," he
explains. "If we did, the system would go bankrupt in
a week."
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