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Pulseless pumps &
artificial hearts
Mehmet Oz MD
Irving Assistant Professor of Surgery
Columbia University
New York, NY
Patrick McCarthy MD
Surgical Director, Kaufman Center for Heart Failure
Cleveland, OH
Program Director, Heart Transplantation
Cleveland Clinic Foundation
Cleveland, OH
LVADs
Left ventricular assist devices
Portable battery-powered devices that allow
hospital discharge are currently being used in
virtually all patients.
Implanting these devices has become routine;
from 1 per month in the early 1990s to 1 per
week currently.
New implantable LVADs are being developed
that are much smaller, continuous flow pumps.
Jarvik 2000
The Jarvik 2000 was implanted at the Texas
Heart Institute in April 2000.
It is a valveless, electrically powered,
miniature axial flow pump about the size of a
"C" battery.
It fits directly into the left ventricle and
pushes oxygenated blood throughout the body
DeBakey VAD
The DeBakey heart has recently been approved
for use in the US by the FDA.
It is a miniaturized axial flow device that pumps
blood from the left ventricle through a titanium
inflow cannula inserted into the heart's apex.
It increases blood flow up to 10 L/min in
patients suffering from congestive heart failure.
The only moving part is the inducer-impeller;
magnets in its blades cause it to spin between
7 500 to 12 500 rpm.
Clinical trials
DeBakey VAD
Clinical trials began in Europe in November
1998.
As of June 8, 2000, 32 patients had received a
DeBakey implant.
The US has recently received FDA approval to
begin clinical trials.
Centrifugal LVADs
Rotary centrifugal LVADs have 2 sealed chambers
 a pump chamber that moves the blood
 a motor chamber which contains the
mechanism that drives the pump
Power is transmitted between the chambers by
magnetism.
Two tubes leaving the pump chamber carry the
blood between the LVAD and the heart.
The third tube to the motor chamber contains the
wires to power the unit.
HeartSaver VAD
The HeartSaver, weighing about 500 grams, is a fully
implantable device for long-term use that can be
remotely powered, monitored and controlled using
TET and biotelemetry technologies.
Its shape follows the contour of the chest wall and
connects via short conduits to the apex of the left
ventricle of the natural heart and to the ascending
aorta.
It is intended for long-term circulatory support and
recipients are expected to leave the hospital and
resume near normal day-to-day activities.
TET coils
Power supply
The TET (transcutaneous energy transmission)
system transfers electrical energy through the
user's intact skin and tissue to directly power
the implanted VAD and the implanted, internal
back-up battery.
Permanent LVADs
Advantages
 better quality of life
 eliminates the need to take
immunosuppressive medications
The transition to more permanent LVADs
will be gradual.
LVADs
The durability and engineering of the pumps is much
better than it was.
Our understanding of heart failure management has
advanced, with innovative new drugs and surgical
reparative approaches.
To tailor our therapies, we need to better understand
the impact that immunology has and the way
patients with artificial devices respond to foreign
bodies.
The most commonly used pump today owes its
success in part to the fact that it prevents
anticoagulation.
Design challenge
Pulsitile flow
It was first thought that the lack of pulsitility with
axial flow pumps would have some impact to the
body.
However, the first cases from Europe using the
Debakey pump have shown that this isn’t the case.
In a few isolated instances pulsitile flow may be
important (e.g., in the case of a traumatic insult to
an organ for which optimal conditions are required
for full recovery).
However, for the average daily existence, it is
probably not necessary.
The heart
Not just a pump
This very complicated field is still in the
earliest phase.
The heart is not just a pump, it is also a
neuroendocrine organ.
There are signs that the heart recovers,
which opens the possibilities for
adjunctive therapies to LVADs like
angiogenesis factors, myoblasts and
growth hormone.
Selecting patients
Bridge to recovery
The inability to predict who will have a
sustainable recovery has led to the practice of
leaving pumps in.
The biochemistry of the heart may help us
understand why an individual cell of the heart
stops carrying its workload, why it doesn't
process fatty acids, or why it doesn’t take up
calcium the way it once did.
Dealing with these underlying metabolic problems
may help us make these recoveries sustainable
Once response to treatment can be predicted,
heart devices can be used as a bridge to recovery
instead of a bridge to transplant.
Abiomed
Total artificial heart
The Abiomed total artificial heart is a
biventricular assist device implanted inside the
chest to replace the heart.
Whereas the LVAD is only for the left side, the
artificial heart is for both sides.
The Abiomed total artificial heart uses a
centrifugal pump to move silicone hydraulic
fluid, which drives the device.
A sleeved, rotating valve shuttles the fluid
between the left and right blood pumps.
Biventricular support
Candidates
 patients who are plagued with continuing
moderate rate heart failure on the LVAD
 patients with ventricular arrhythmias that
may inhibit their recovery while on an LVAD
alone
 patients who have very severe right heart
failure
 patients who have ventricular arrhythmias
 patients with acute MI complicated by such
things as a ventricular septal defect
Stroke prophylaxis
It is very difficult to predict from animals
what the stroke rate is going to be in
humans.
Caution and some anticoagulation will
probably be the recommended course of
action to begin with.
HeartMate device
An electrically powered device, which, unlike
the LVAD, does not need a vent to the
outside.
The current LVADs have a vent that allows
the air to go back and forth as a pusher
plate moves inside the device.
Risk of stroke with the HeartMate device is
extremely low.
Progress report
With the Jarvik-7, it was hardly worth living
because quality of life was so low.
LVADs
Today's LVADs are portable and patients are
discharged from hospital.
Total artificial heart
Patients will be discharged with battery
powered devices that have a low risk of
mechanical failure.
It is expected that risk of stroke will also be
low.
Ideal candidates
Total artificial heart
Patients who have end-stage heart disease; a
patient population similar to the heart
transplantation group.
People who have a very limited quality of life
and length of life because of their heart
disease but who do not have other major
organ limitations.
Not patients who are in their 80s, who have
end-stage diabetes and numerous other
organs with complications.
LVAD as a bridge
Candidates
 patients with ventricular arrhythmias on LVAD
support
 patients for whom LVAD isn't adequate
 patients who have had failed heart
transplants, whether there is transplant
coronary disease or some type of refractory
rejection
 patients who have lymphomas related to the
immunosuppression
New developments
In various stages of development
 8 axial flow pumps
 2 artificial hearts
Media attention
The idea of using devices for supporting the
heart is becoming more accepted.
Economic issues will probably be the most
controversial topic.
Leading role for investigators
Emphasize the importance of basing
conclusions on the first 100 patients, not on
the first patient.
The next step
Cardiac support
The next step in cardiac support will never
be heart transplantation.
Heart transplantation can only supply 2200
hearts per year.
Mechanical devices are things that will have
epidemiologically significant impact on
cardiac support