Coronary artery disease (often referred to as heart
disease) is a condition in which some areas of the
heart are narrowed and hardened. It's usually caused
when plaque accumulates along the inner walls of the
arteries. Soft formations of plaque may break open,
or fracture, releasing some of the inner contents of
the deposit into the bloodstream. The body senses
this as an "injury" and may send blood
clots to cover and seal the area. A clot can block
the flow of blood through the artery.
Sometimes plaque hardens into a thick deposit.
The thickened area can impede blood flow through
that part of the artery. The plaque can also
accumulate enough to completely close off the artery
and obstruct blood flow.
When an artery that feeds the heart becomes
blocked, cells in the area below the point of
blockage are deprived of oxygen and begin to die.
This is a heart attack, or myocardial infarction.
Medical intervention is needed to prevent permanent
damage or death.
According to the American Heart Association,
about 15.8 million people in the U.S. have coronary
artery disease. This year alone, 700,000 Americans
will have a heart attack. Heart disease is the
leading cause of death in this country, killing
452,327 men and women in 2004. Many heart attack
survivors face higher risk of health complications,
like heart failure (an inability of the heart to
pump enough blood to meet the needs of the body) and
arrhythmia (irregular heart rhythm).
Treating Coronary Artery Disease: Angioplasty
One of the treatments for narrowed coronary
arteries is angioplasty. A balloon-tipped catheter
is inserted into a blood vessel in the leg. Then,
using X-rays for guidance, the catheter is fed
through the circulatory system up to the point of
narrowing in the heart. Next, the balloon is
inflated. As the balloon expands, it compresses the
plaque against the walls of the artery. A device,
called an expandable stent, may be placed in the
area to hold the plaque against the wall and keep
the artery open. Finally, the balloon is deflated
and the catheter is withdrawn.
Angioplasty is now performed about three times
more often than coronary artery bypass surgery. In
2004, there were 1.285 million angioplasties
performed in the U.S. and 427,000 bypass surgeries.
Stem Cells for the Heart
After a heart attack, the body tries to
repair some of the heart muscle damage. Stem cells
are mobilized from the bone marrow and sent to the
site. These stem cells have the capability to
develop into whatever cell is needed by the body -
in this case, heart muscle cells.
Researchers are now trying to see if placing
additional stem cells in the heart can improve
long-term function of the heart muscle. The trial is
called the "Amorcyte Myocardial Repair Study -
A Phase I Trial of Intra-Coronary Infusion of Bone
Marrow Derived Autologous CD34+ Selected Cells in
Patients with Acute Myocardial Infarction (AMRS)."
It is a Phase I study.
Arshed Quyyumi, M.D. Cardiovascular Researcher at
Emory Crawford Long Hospital, is the principal
investigator of the study. He explains when a heart
attack patient has angioplasty, he/she is assessed
for heart muscle damage. If damage is found, the
patient will be asked to participate in the study.
Half of the participants will be randomly assigned
to receive treatment. The others will be followed.
For those in the treatment group, a bone marrow
aspiration is performed between 6 and 9 days after
the heart attack. A small amount of bone marrow is
taken from the back of the hip bone and processed.
Specialized stem cells, called CD34 positive (CD34+)
cells are removed. The next day, the patient is
taken back into the catheterization lab. A
balloon-tipped catheter is once again snaked through
the circulatory system to the previously treated
area of the artery. The balloon is inflated and the
patient's stem cells are infused directly into that
area of the artery. The balloon temporarily halts
the flow of blood to allow the stem cells to better
permeate the damaged area of heart muscle. The
balloon is then deflated and the catheter is
withdrawn.
Researchers hope the stem cell treatment can help
repair some of the heart muscle damage caused by the
heart attack. Quyyumi says this may occur in one of
two ways. First, the stem cells may encourage growth
of new blood vessels into the portion of the heart
muscle that has been injured, but still able to
recover. Second, the treatment may halt the death of
some of the heart muscle cells.
In addition to Emory, the study is taking place
at Texas Heart Center in Houston and Vanderbilt
Hospital in Nashville. Patients who have had heart
attacks must contact the researchers within four to
five days to be considered for the study. For more
information, call (404) 783-5908. The study is being
funded by the biotech company, Amorcyte, that is
performing the stem cell separation.
In addition to Emory, the current study is taking
place at Texas Heart Center in Houston and
Vanderbilt Hospital in Nashville. Patients who have
had heart attacks must contact the researchers
within four to five days to be considered for the
study. For more information, call (404) 783-5908.
Information about the trial is also available by
logging on to http://www.clinicaltrials.gov.
At the search box, type in the trial ID #:
NCT00313339.
