MEDICAL DEVICE INNOVATION - Medical Device Daily

MEDICAL DEVICE INNOVATION 2010
New artificial heart may have
continuous, pulseless blood flow
By LYNN YOFFEE
Medical Device Daily Staff Writer
Can a human survive with no pulse It’s a long-standing
argument that one prominent heart surgeon is seeking to
prove in his efforts to develop a total artificial heart that
produces a continuous, pulseless blood flow.
The future of artificial heart development to treat people
with deadly congestive heart failure may lie in this simpler
design one that eliminates the need for a pulse.
“Since the introduction of the heart/lung machine,
there’s been controversy about how important a pulse is
for circulation,” said O.H. Frazier, MD, chief of
Cardiopulmonary Transplantation, chief of The Center for
Cardiac Support, and director of Surgical Research at Texas
Heart Institute (THI; Houston) and director of Transplant
Service at St. Luke’s Episcopal Hospital (Houston).
“My position is that the only thing that needs a pulse is
the heart itself,” he told Medical Device Daily. “The blood
that is delivered everywhere else pulseless. This was an
ongoing debate. But more and more, we’ve gotten interested
in continuous flow because it offers an opportunity to
replace function of the heart with a device that’s much
more user friendly than pulsed devices.”
Frazier, who is reported to have performed more heart
transplants than any other surgeon in the world – 1,000+ –
said the big advantages of this proposed cardiac device are
size, durability and cost. The National Institutes of Health
(NIH; Bethesda, Maryland) has just awarded THI a $4.1 million
grant so that Frazier and his team can continue their
work to determine the effects of pulseless blood flow on
bodily functions.
Continuous flow pumps were first introduced for partial
support of failing hearts, but they have never been used
for total heart replacement. Currently available artificial
hearts are expensive, often too big to fit most patients and
last just a few years.
“A continuous, pulseless blood flow heart, we think, will
last 15-20 years,” he said. “There are no valves, so it’s potentially
much less expensive.”
Frazier has been working on hearts since he as a medical
student in the 1960s. Just two years ago, he took a heart
out of a calf and replaced it with continuous pumps.
“The animal woke up fine,” he said. “Since that time,
we’ve been very interested in it as a total artificial heart
131
replacement. It’s been very gratifying that these experimental
animals tolerate this very well. Hopefully we can
learn much more. We do think there is a need for long-term
reliable cardiac replacement that will render a patient capable
of living a normal life.”
In the new THI study, calves’ or sheep’s hearts will be
replaced with two small, continuous flow blood pumps that
operate according to the principle of centrifugal force.
Compared to existing assist devices, the new total artificial
heart will function more like a natural heart, in that it can
adjust how much blood it pumps depending on how much
blood is in the heart.
Being able to assess how the device responds to the
body’s changing needs for blood is a key objective of the
study.
“We’re working with engineering groups to see if we
can determine some way of working on responsivity of the
pumps,” Frazier said. “The other advantage of continuous
flow pumps is that their flow is increased by increasing
inflow pressure much like the native heart, which only
increases output if it needs more blood. These pumps will
do the same. There are instances where we’d like to
increase the RPM. In clinical pumps we’ve used, we could
only run them at a fixed rate and haven’t cracked the code
on that yet. We’re also going to look at microcirculation in
non-pulsatile animals.”
He said a pulse may be necessary for some people, particularly
those with atherosclerosis.
“They may need a pulse to wash out the blockages in
the arteries,” he said. “By varying the speed, we could
induce a pulse. In this study, we may be able to come to
some conclusion about the role and utility of inducing pulsativity.
The effects on the arteries will be studied.”
Frazier said that, until a few years ago, nobody else was
working on this theory. After a presentation of his early
findings at a medical conference, four other groups have
since emerged that are working on the same theory, one
the U.S. at the Cleveland Clinic as well as teams in Japan,
Berlin and Australia.
“People are skeptical at first, but once they realize to
possibilities, everybody wants to get involved,” he said. “It’s
important to have other people working on it. You need a
certain critical mass of people, particularly at the outset.”
Anecdotally, Frazier said he’s had five patients with no
heart function supported by continuous flow pumps. They
went into ventricular fibrillation, but were fairly well supported
by the pumps.
“I’ve heard of another colleague of mine who replaced a
To subscribe, please call MEDICAL DEVICE DAILY Customer Service at (800) 888-3912; outside the U.S. and Canada, call (404) 262-5547.
Copyright © 2010 AHC Media LLC. Reproduction is strictly prohibited.