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Why Stents?
Coating Overflow Removal Tool
Team Vimage (aka Team #3)
Mario H. Gonzalez
November 1, 2004
EXECUTIVE SUMMARY
The intent of this report is to depict the stent in a larger context. Since stents are
used to treat medical conditions, a mechanical description of a stent is not suffice for this
report. After a remedial description on how blood circulates through the body, the report
will focus on a specific disease for which stents are implemented in the treatment for it.
Initially, the report will focus more on medical subjects laying a foundation in order to
talk about the evolution of the stent right up to the Drug Eluting Stents (DES) which are
said to revolutionize the cardiovascular medical industry. Depending on a person’s
lifestyle, plaque composed of fatty particles, can build up on the inner diameter of the
artery which slows the blood flow, which is called Coronary Artery Disease (CAD).
Bare-metal stents are becoming obsolete with the introduction of DESs because of many
advantages that the DES has over the bare-metal stent. The drug that coats the stent is
released overtime and it basically fools the body into thinking that the stent is not a
foreign object.
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Table of Contents
INTRODUCTION ................................................................................................................... 1
REMEDIAL DESCRIPTION OF BLOOD CIRCULATION ......................................................... 1
CORONARY ARTERY DISEASE ........................................................................................... 2
STENTS ................................................................................................................................ 2
BARE METAL STENTS..................................................................................................... 3
DRUG ELUTING STENTS ................................................................................................. 3
REFERENCES....................................................................................................................... 5
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INTRODUCTION
For people who suffer from heart disease a stent can save their lives. The intent
of this report is to depict the stent in a larger context. Since stents are used to treat
medical conditions, a mechanical description of a stent is not suffice for this report. After
a remedial description on how blood circulates through the body, the report will focus on
a specific disease for which stents are implemented in the treatment for it. Initially, the
report will focus more on medical subjects laying a foundation in order to talk about the
evolution of the stent right up to the Drug Eluting Stents (DES) which are said to
revolutionize the cardiovascular medical industry.
REMEDIAL DESCRIPTION OF BLOOD CIRCULATION
Our bodies need oxygen to survive. Every breath we take our lungs introduce
oxygen into our bloodstream. Arteries carry oxygen enriched blood to all parts of the
body while veins carry carbon dioxide waste back to the lungs where we breathe it out.
People who are diabetic or who have bad eating habits tend to have restrictions in their
blood circulation. If there is poor circulation in a coronary artery it can cause a heart
attack, which can be fatal. Restrictions to circulation to an extremity can cause that
extremity to slowly die, which will cause infection and eventually the extremity will have
to be amputated.
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CORONARY ARTERY DISEASE
There are many types of arteries in the body and they range in size and
importance, the larger arteries carry more blood. Coronary arteries carry O2 enriched
blood to the heart. Depending on a person’s lifestyle, plaque composed of fatty particles,
can build up on the inner diameter of the artery which slows the blood flow, which is
called Coronary Artery Disease (CAD). Untreated this will eventually lead to a heart, 2
out of 3 diabetics die from CAD [1]. Current treatments for CAD range from diet and
exercise, medications, to very intrusive surgeries, such as angioplasty (removal or
compression of the plaque) or bypass grafting (detouring around the blockages) [2].
STENTS
Stents were not the first treatment method for coronary disease. It was not until
1987 that the first coronary stent was reportedly used, but physicians had been trying to
unblock arteries far before then. The technology that preceded stents is called
angioplasty balloons. The procedure called, balloon dilation, consisted of a small balloon
that would be fed through a main artery, such as the femoral artery, with a catheter to the
problem area. Once the balloon is in place, it is inflated which compresses the plague
against the wall of the artery. This treatment directly led to stents because without a way
to hold the artery open restenosis, the blockage an artery after corrective surgery, would
occur. Stents were designed to act as a scaffold and hold the artery open. Stents are
categorized into two distinct groups, bare-metal stents and the more advanced DES.
DES’s have shown in clinical studies that they further reduce the occurrence of restenosis
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when compared to bare-metal stents. For this reason about 95% of stents being used to
treat patients are DESs [3].
Bare Metal Stents
Bare-metal stents are becoming obsolete with the introduction of DESs. As the
name implies this type of stent comes into direct contact with the arterial wall tissue.
Although some physicians believe that there should be a test to distinguish patients who
may not need a DES to save money. Bare-metal stents on average cost $2000 dollars less
than there drug coated counterpart [4]. In stent restenosis, blockage that recurred inside
the stent, occurred about 24.4 % of the time during clinical studies of bare-metal stents
[4]. I believe patients that do not have sensitive immune systems, such as AIDS patients,
would be prime candidates for bare-metal stents because there bodies may not have the
resources to attack the stent.
Drug Eluting Stents
On the other hand there are DESs, which are basically bare-metal stents covered
in a immunosuppressant, that may cost more, but have more of a guarantee that restenosis
will not occur. The drug that coats the stent is released overtime and it basically fools the
body into thinking that the stent is not a foreign object. In a study of 1300 patients
comparing bare-metal stents to DESs, a major adverse cardiac event was reduced from
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15%, for bare-metal stents to 8.5% for DESs. Diabetics, a subgroup in this study, a group
that is at high risk for restenosis have even a larger gap in occurrence of restenosis
between bare-metal stents and DESs, 42.9% and 7.7% respectively for those diabetics on
insulin and 29.7% and 5.8% respectively for diabetics taking oral medications [3]. With
results like these one can understand why DESs are gaining popularity with doctors
despite the higher cost.
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REFERENCES
[1] www.diabetes.org
[2] www.angioplasty.org/articles/taxus
[3] Interview of Greg W. Stone, MD, Director of Cardiovascular Research and
Education, Cardiovascular Research Foundation, Lenox Hill Hospital, New York City
[4] Real-World Bare Metal Stenting: Identification of Patients at Low or Very Low Risk,
Stephen G. Ellis, MD, Wiley-Liss Inc.
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