Your heart is the
engine inside your body that keeps everything running.
Basically, the heart is a muscular pump that maintains oxygen
circulation through your lungs and
body. In a day, your heart pumps about 2,000 gallons of blood.
Like any engine, if the heart is not well taken care of it can
break down and pump less efficiently, a condition called heart
Photo courtesy Abiomed
The AbioCor is the first artificial heart to
be used in nearly two
Until recently, the only option for many severe heart
failure patients has been heart transplants. However, there
are only slightly more than 2,000 heart transplants performed
in the United States annually, meaning that tens of thousands
of people die waiting for a donor heart. On July 2, 2001,
heart failure patients were given new hope as surgeons at Jewish
Hospital in Louisville, Kentucky, performed the first
artificial heart transplant in nearly two decades. The
AbioCor Implantable Replacement Heart is the first
completely self-contained artificial heart and is expected to
at least double the life expectancy of heart patients.
In this edition of HowStuffWorks,
you will get an in-depth look at how this new artificial heart
works, how it's implanted into a patient's chest and who might
be a candidate for receiving one of these mechanical hearts.
We will also compare the AbioCor heart to the artificial
hearts that have failed in the past.
A Hydraulic-driven Heart
The average adult
human heart pumps blood at a rate of 60 to 100 beats per
minute. If you've read How Your Heart
Works, then you know that the heart contracts in two
muscle then relaxes before the next heartbeat. This allows
blood to fill up the heart again.
- In the first stage, the right and left atria
contract at the same time, pumping blood to the right and
- In the second stage, the ventricles contract
together to propel blood out of the heart.
Chambers of a natural
Patients with an implanted AbioCor heart will still have
atria that beat at the same time, but the artificial heart,
which replaces both ventricles, can only force blood out
one ventricle at a time. So, it will alternately send
blood to the lungs and then to the body, instead of both at
the same time as a natural heart does. The AbioCor is able to
pump more than 10 liters per minute, which is enough
for everyday activities.
Diagram of the AbioCor
The AbioCor, developed by Abiomed, is a very
sophisticated medical device, but the core mechanism of the
device is the hydraulic pump that shuttles hydraulic fluid
from side to side. To understand how it works, let's look at
the various components of the system:
- Hydraulic pump - The basic idea with this device
is similar to the hydraulic
pumps used in heavy equipment. Force that is applied at
one point is transmitted to another point using an
incompressible fluid. A gear inside the pump spins at 10,000
revolutions per minute (rpm) to create pressure.
- Porting valve - This valve opens and closes to
let the hydraulic fluid flow from one side of the artificial
heart to the other. When the fluid moves to the right, blood
gets pumped to the lungs through an artificial ventricle.
When the fluid moves to the left, blood gets pumped to the
rest of the body.
- Wireless energy-transfer system - Also called the
Transcutaneous Energy Transfer (TET), this system
consists of two coils, one internal and one external, that
transmit power via magnetic force from an external battery
across the skin without piercing the surface. The internal
coil receives the power and sends it to the internal battery
and controller device.
- Internal battery - A rechargeable battery is
implanted inside the patient's abdomen. This gives a patient
30 to 40 minutes to perform certain activities, such as
showering, while disconnected from the main battery pack.
- External battery - This battery is worn on a
Velcro-belt pack around the patient's waist. Each
rechargeable battery offers about four to five hours of
- Controller - This small electronic device is
implanted in the patient's abdominal wall. It monitors and
controls the pumping speed of the heart.
The AbioCor heart, which is composed of titanium and
plastic, connects to four locations:
The entire system weighs
about 2 pounds (0.9 kg). In the next section, you will learn
how surgeons implanted the AbioCor heart during a seven-hour
- Right atrium
- Left atrium
- Pulmonary artery
The Seven-hour Surgery
The surgery to
implant a AbioCor artificial heart is extremely delicate. Not
only are the surgeons cutting off and extracting the natural
heart's right and left ventricles, but they are also placing a
foreign object into the patient's chest. The patient must be
placed on, and later removed from, a heart-lung
machine. The surgery requires hundreds of stitches,
to properly secure the heart to artificial ventricles.
Grafts connect the AbioCor to remaining parts of the
natural heart. Grafts are a kind of synthetic tissue used to
connect the artificial device to the patient's natural tissue.
Photo courtesy Abiomed
Surgeons implanting the AbioCor
Jarvik-7In 1982, Dr.
William Devries implanted the Jarvik-7, the
first device designed to be a completely permanent
replacement heart. The surgery was done at the
University of Utah, and the patient was Dr. Barney
Clark, a dentist from Seattle. Clark lived for 112
days on the heart before succumbing to complications
caused by the device. Click
here to see a photo of the Jarvik-7.
The Jarvik-7 was an air-driven heart designed by Dr.
Willem Kolff and Dr. Don Olsen. Unlike the
self-contained AbioCor, the Jarvik-7 heart required
several external wires, which protruded from the patient
and connected to a large external unit. These protruding
wires led to several infections in Clark.
Four more patients received the Jarvik-7 before it
was discontinued due to complications, including stroke,
mechanical failure and anatomical fit issues. It has
since been enhanced and renamed, now called the
CardioWest heart. It is used only in experimental
situations and as an investigative
Due to the complexity of the surgery, there are lots of
medical personnel on-hand during the operation. The surgery on
July 2, 2001, which was the first of its kind in the world,
included a team of the two lead surgeons, 14 nurses,
and other support staff.
Here is the procedure, as described by University of
Louisville surgeon Robert Dowling:
- Surgeons implant the energy-transfer coil in the
- The breast bone is opened and the patient is placed on a
- Surgeons remove the right and left ventricles of the
native heart. They leave in the right and left atria, the
aorta and the pulmonary artery. This part of the surgery
alone takes two to three hours.
- Atrial cuffs are sewn to the native heart's right and
- A plastic model is placed in the chest to determine the
proper placement and fit of the heart in the patient.
- Grafts are cut to an appropriate length and sewn to the
aorta and pulmonary artery.
- The AbioCor is placed in the chest. Surgeons use "quick
connects" -- sort of like little snaps -- to connect the
heart to the pulmonary artery, aorta and left and right
- All of the air in the device is removed.
- The patient is taken off the heart-lung machine.
- The surgical team ensures that the heart is working
Abiomed officials have cautioned against overly-optimistic
results for the first patients to receive a transplant. While
doctors hope for more, the device is only designed to
double life expectancy for patients who had only about
30 days to live prior to the operation. The most optimistic
predictions are that a patient could currently live up to
six months with the AbioCor heart.
Robert Tools, the patient who received the heart
transplant on July 2, 2001, at Jewish Hospital in Louisville,
remains hospitalized. Doctors have not said when or if the
patient will be able to return home. To find out more about
Tools and who is a candidate for the four other initial
operations, read the next section.
The Sickest of the Sick
Food and Drug Administration (FDA) has cleared Abiomed to
perform five initial implants. The surgery to implant
these hearts will take place at medical centers in Houston,
Los Angeles, Boston and Philadelphia. Dates or candidates for
the operation are still unknown as of July 23, 2001. The FDA
will review the results of these transplants on a case-by-case
basis to determine the future of the AbioCor device. If the
$70,000 to $100,000 device is successful, meaning it can
prolong the life of a patient without complications, it could
be approved for use in more heart centers around the United
Laman Gray said that initial candidates for the heart will
be the "sickest of the sick." FDA and Abiomed officials have
laid a few parameters for who can become one of the initial
recipients of the artificial heart. The patient must fit the
- Have end-stage heart failure
- Have a life-expectancy of less than 30 days
- Is not a candidate for a natural heart transplant
- Have no other viable treatment option
Another requirement is that the grapefruit-sized device
must fit inside the patient's chest. To determine the fit of
the device, the patient must undergo a CAT
scan and chest X-ray.
Then, using a computer-aided design (CAD) program, the natural
heart is virtually removed and the AbioCor heart is virtually
placed in the patient's chest. If the computer program shows
that the device will fit, doctors can proceed with the
operation to implant the artificial heart.
Photo courtesy Abiomed
X-ray of the AbioCor device implanted in a
For nearly two months following the surgery, hospital and
AbioMed officials kept the name of the first recipient
a secret. However, on August 21, 2001, it was revealed that
Robert Tools, a Kentucky resident and former telephone
company employee, was the history-making patient. Although
Tools has battled an infection and needed a ventilator
following his surgery, his doctors report that the mechanical
heart continues to function without problems.
Photo courtesy Jewish Hospital
Patient Robert Tools with Dr. Laman Gray
(left) and Dr. Robert Dowling
Here is what was known about Tools prior to his surgery:
- He suffered from class IV heart failure.
- He had severe bi-ventricular failure.
- He was turned down by a heart transplant center.
- He has undergone previous coronary bypass surgery.
- He has had multiple heart
- He has diabetes.
Currently, there are between 2 million and 3 million
Americans living with heart failure, and 400,000 new cases are
diagnosed annually. Heart failure causes 39,000 deaths per
year, according to the National
Heart, Lung, and Blood Institute (NHLBI). Most people
diagnosed with heart failure can expect to live about five
years, and will usually need to have a heart transplant to
extend their life.
In the United States alone, 2,184 heart transplants were
performed in 1999, and 2,340 were performed in 1998. However,
thousands of potential recipients die annually while waiting
for a heart transplant. Doctors still encourage the public to
become organ donors, but the AbioCor may save many of those
who don't have the option of a natural transplant or of
waiting for an available heart.
For more information on the AbioCor and related topics,
check out the links on the next page.
Lots More Information!
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