In the first section of this interview
we discuss the early days and current status of LVADs, left ventricular
assist devices that are implanted to assist the weakened hearts
of patients with heart failure. In the following section we discuss
Abiocor, a new artificial heart that is now ready for human trials.
The FDA recently approved a new artificial heart device for
human trials called Abiocor. Can you tell us about that?.
A: The Abiocor system is an exciting alternative to VADs.
There are patients who have failure on both left and right side
of heart, or who have other problems that limit the use of LVADs.
In that setting we had no choice but to let the patient die. There
is now for the first time a totally implantable artificial heart
that could potentially allow us to implant a device that allows
patients to live for a long period of time. This is a new, well-designed
device. The design tales advantage of the fact that the right and
left sides of the heart don't have to pump blood at the same time
to provide compliance between each chamber. The company also designed
a battery system that allows transcutaneous electrical transfer.
This device has combined many of the lessons we have learned with
VADs and other heart devices about the management of critically
ill patients. This device could offer a new option to a lot of people.
While no human has yet received one of these devices, there have
been many cows operated on with considerable success. There's no
question in my mind that the device will be implanted in the near
future. The real decision for us will be to decide how many will
need the device. We don't really know what percentage of people
that we couldn't help with LVADs we would be able to help with the
total artificial heart.
This was tried before with the JARVIK7. That product marked
the end of research in that area for quite a while. What has happened
since to encourage another try?
A: The JARVIK7 experience early on was probably too big
a step. It was actually a success to the extent that the scientists
proved they could replace the human heart and keep patient alive
with an artificial heart. However, the device did not provide the
quality of life that most of us would want. For that reason the
American public soured on the thought that you can use high technology
to build a bionic man The experience with JARVIK7 killed interest
in this area for almost a decade. It took a long time to rekindle
an interest in these device and convince the public that we were
not creating a Frankenstein, but instead developing an option that
might be viable for our loved ones. The Abiomed system is well designed
and I don't think we will fall into those pitfalls. However it will
be challenged by several factors. First, there is the LVAD that
can provide support for some patients. Patients will be faced with
a choice. They will usually choose based on the maturity of the
system. So it is important the Abiocor be used and become a mature,
patient friendly system. Of course it will depend how well the device
delivers what it needs to- high quality of blood pushed through
the body without a high incidence of stroke or infection.
How did the developers overcome the previous limitations seen
A: There were three big challenges to overcome. One, we
need a surface material that would allow blood to flow without a
high thromboembolic (clotting) incidence; two, we needed a mechanism
for having the blood be ejected from one chamber without needing
a big compliance chamber within the chest; third, we needed a battery
system that could power this device without risk of infection. One
by one these were addressed.
The Abiomed company created one of the first LVADs. It is perhaps
the most commonly used one in US today. But it is only used for
short-term support, as a bridge to transplant. One reason they are
popular is the very slick surface, made of a coating compound that
we believe reduces the incidence of stroke. As a physician I like
to use the pump, but only for a couple of days. The same coating
is used in the Abiocor heart. We had to make up for the fact that
the left and right heart don't actually pump the same amount of
blood all the time. We had to make up for that difference. This
device takes this into consideration. Finally, we had to solve the
power problem. Battery supply problems have plagued all VAD systems.
The creation of TETS is a novel innovation that allowed the creation
of a 'wireless' artificial heart. This is an experimental device,
not a panacea. These devices, as with previous devices, are likely
to be fraught with early failure. There will be people who will
die directly as a result of these pumps not working perfectly. Unfortunately
there is no way to know until we try the pumps. The measure of success
initially will be more a matter of how do we respond to these problems,
to continue to develop the system so that it will be successful
for a majority of patients.
The main problem with all implantables has been the increased
risk for stroke. How do the new devices address this?
A: Device surfaces have improved dramatically. The one used
in the Heartmate device is remarkably resistant to thromboembolism.
It tricks mother nature with a very rough surface. If blood going
by sticks to the surface, it can't come off again. This means this
stuff cannot chip off and cause problems like stroke. In addition
to new surfaces, there are improved anticoagulation systems. As
we understand more about how platelets function we can target anticoagulation
a bit better. The reality is that it is a much more global picture.
When you put a machine in a man, it is not just the machine you
have to understand or the man, you have to understand the man/machine
interface.The machine changes the way man responds to stressors
including infection and stroke. You have a diffuse inflammatory
process which is associated with the coagulation process, creating
a prothrombotic (clot-inducing) milieu. You are asking for trouble.
A better understanding of the man/machine interface will help us
to prevent these problems.
Biological research has made incredible progress in recent decades.
How have advances in the basic sciences affected cardiovascular
A: The heart was a black box 50 years ago. If you saw the
heart the patient would die. Some surgeons thought it would be malpractice.
This was still the case when aviator Charles Lindbergh developed
one of the first heart pumps in the 1950s. At that time the heart
surgeons were developing ways of stopping and restarting the heart,
while on the medical side, cardiologists were pioneering ways of
diagnosing heart disease. The two fields have now met, with very
little gap between them. Research has defined some of the pathologies
that kill people with heart disease. It also helped us to better
understand the physiological functions that alter as we age and
develop coronary and valvular disease. Without an understanding
of why these things were happening we really could not address the
big problems. Probably the biggest benefit over the last decade
is that we have moved from an autopsy-based model of understanding
the heart, where we used to look at the heart after the patient
died to figure out what was wrong, to developing techniques to understand
the physiology of the living heart. For example, we can now look
at the plaque in the heart and identify the active plaque more likely
to close off an artery, more likely to cause an heart attack. That
is when we can intervene. Not when the guy is already dead.
There is no question that the headline grabbing features we see
in mechanical heart devices today would never have come to fruition
had it not been for the ability to build a broad based approach
to managing heart disease. It starts in the basic sciences, and
not just in universities and world famous research labs. It starts
in middle and high school science classes where people receive the
initial training. This creates the basis for subsequent interaction
between basic science researchers and clinicians to create the applied
research endeavors that creates these pioneering projects such as
VADs and artificial hearts.
This interview was conducted by Sean Henahan on February 27,
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