public figures Mother Theresa, Regis Philbin and Vice President
Dick Cheney have all received at least one of these devices during
a heart procedure.
What is it?
A stent—a wire mesh tube that is used to help keep open a
collapsed or clogged artery.
How much do you know about stents?
More than 700,000 coronary stent procedures are performed annually
in the United States, according to the American College of Cardiology.
Needless to say, stent procedures are very common.
One of the biggest benefits of the stent is that it can be used
as an alternative to coronary artery bypass surgery. In most cases,
a stent procedure is less risky than bypass surgery,
requires less hospital monitoring and recovery time, is less expensive,
and may prove more effective.
Stents are beneficial to patients who have blockages of multiple
vessels or multiple blockages of a single artery. Stents are also
used following angioplasty to open reclogged arteries or repair
an artery that has been damaged, torn, or dissected by balloon angioplasty.
Most people know that stents are used in the coronary arteries to
treat angina and prevent heart attacks. But did you know that stents
can be placed in the brain, neck, kidneys, pelvis and legs to ensure
blood flow and prevent disease? Carotid stents are successful in
preventing stroke by treating narrowed blood vessels that lead to
the brain. Stents placed in the renal or kidney arteries treat renal
insufficiently and hypertension. Abdominal stents placed in the
pelvis or legs are used to treat abdominal aneurysms, impotence,
claudication (leg pain), gangrene, and to prevent limb loss.
Stents remain in arteries permanently. In the days and weeks following
the placement of a stent, tissue will begin to grow over the metal
mesh of the stent, forming a new lining inside the artery. This
tissue growth is part of the natural healing of the artery following
a stent procedure. But in some patients, tissue growth can get out
of hand. When too much tissue grows at the site of treatment, the
artery can become clogged again. The medical tern for the recurrent
blockage of arteries is restenosis.
New Technologies to Reduce Restenosis
An estimated 100,000 heart patients will experience restenosis this
year in the United States. What is being done to address this problem?
For several years, doctors have tried lasers, cutting tools, drug
therapies, and modifications of the conventional stent to improve
results. The stent we use today for conventional balloon angioplasties
has been able to reduce rates of restenosis from about 40 to 20%
Studies are currently underway to see if the use of new materials
and coatings for stents can lower the rates of restenosis even further.
Drug-coated stents are offering the most promising results. By delivering
a predictable, slow-release, therapeutic dose of medication directly
to an artery wall, drug-coated stents are able to inhibit the tissue
growth that causes restenosis. Several companies are currently at
work on this process, testing a number of different drugs. Two such
drugs under investigation are rapamycin, a medication used to prevent
organ rejection after kidney transplants and Taxol®, a drug
used to treat cancer.
Other new treatment for restenosis that have proven effective include:
Radiation therapy. In this procedure, a catheter
is threaded inside the blocked stent and radioactive beads are placed
within the catheter for a few minutes, then withdrawn. The radiation
kills cells that cause recurrent blockage in the artery.
Vitamin therapy. A recent study reported in The
New England Journal of Medicine has shown that use of vitamin
B6, vitamin B12, and folic acid can reduce the risk of restenosis
when used for six months following stent placement. This combination
of vitamins is commercially available and is currently being prescribed
to patients on a routine basis.
Stent technology and other treatments for restenosis are developing
rapidly. As doctors and scientist keep searching, medical science
is sure to lead us to even more solutions. Therapies of the not-so-far-off
future hold the promise of preventing restenosis, correcting restenosis,
and providing a better treatment option for high-risk patients who
are not good candidates for the conventional stent–including
patients with long blood vessels, tiny blood vessels, and diabetes.