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Drug Eluting Stents & Balloons
- A Breakthrough In Interventional Cardiology
In an age of fast cars and
fast food, it is little surprise that speedy, minimally
invasive treatments have taken centre stage in important
treatment arenas. However, unlike care and food, medical
treatment, when administered without delays and with
minimal incisions to the human body, can prove enormously
effective at saving time and cost for the patient and for
the healthcare system, in general. That many of these
procedures are also clinically effective and sometimes,
far superior to regular treatments, is a factor that makes
their availability as an option indispensable in modern
healthcare institutions.
Angioplasty, as a treatment
for a range of vascular indications, found its way in to
the medical mainstream as a contending option to surgeries
procedures that involve cutting open the body for suitable
access to lesions, long hospitalization periods, longer
recovery times (equalized to longer periods away from
income-generating work) and huge medical bills.
In 1977, the angioplasty
procedure was developed by Dr. Andreas Gruentig and
patients had the option of using a balloon in an effort to
open a blocked coronary artery. The procedure could be
performed in a Cathlab (an imaging area) in a span of a
few hours and the patient could go home, usually on the
same day, greatly reducing the time and expense burden on
the patient, the hospital and the payers (where
applicable).
The balloon angioplasty or
POBA (plain old balloon angioplasty, as popularly called)
offered short-term benefits. However longer-term outcomes
showed many arteries re-closing and requiring repeated
intervention; up to 30-40% of angioplasty patients were
found to require further angioplasty within six months. In
an effort to reduce the frequency of patients requiring
re-intervention, scientists and clinicians developed
stents (metal wire-mesh scaffoldings) that could be left
behind to hold the artery open once the balloon was
withdrawn. The first stent was used in late 1980’s and by
the end of the last century; stents were being used in
majority of PTCA (Percutaneous Transluminal Coronary
Angioplasty) Procedures.
Bare metal stents, the
earliest scaffoldings, however carried the risk of
restenosis, or the renarrowing of the arteries, resulting
in occlusion of the stents.
To address this issue, drug
eluting stents (DES) were developed as tools for
delivering medication directly to the arterial wall, to
induce delayed healing in order to reduce the incidence of
restenosis. Drugs, such as those from a family of
immunosuppressants (the Limus Group) and mitotic
inhibitors (Paclitaxel) are used for the purpose. Polymers
(drug Carriers) are attached to the stents and these carry
different chemical components (drugs). The bioavailability
of the drug in question is vastly triggered by the carrier
system, and depending on whether it is a constant polymer,
biodegradable polymer or even a non-polymer, elution times
for the drug range from a few days to a few months.
DES was a major breakthrough
in the space of interventional cardiology. Drug eluting
stents have been extensively studied, and are generally
considered superior to bare-metal stents as they have
shown a remarkable reduction in restenosis and target
vessel revascularization when compared with bare metal
stents.
The DES category of
angioplasty tools is currently experiencing extensions in
clinical indications and organ coverage, use of varied
biocompatible metals (stainless steel, cobalt chromium,
platinum), advance in polymer/drug carrier technologies
and the foray into multiple drug coatings. All these
efforts are geared towards ensuring
greater user-friendliness, managing thrombosis and
avoiding restenosis.
A steady rate of development
in coronary stent technology, producing an equally steady
stream of new stent market introductions, is focused on
shifting the concentration of stent sales to the DES
variety. DES is the world market leader in turnover with
an equal position compared to BMS. Around 1,50,000 stents
were used in India last year and DES contributed to around
50% of them.
However, due to the
requirement for longer dual anti-platelet therapy and late
in-stent thrombosis – two important factors forced to be
considered post implantation of a DES, clinicians
and stent companies innovated on treatments that can open
up an occluded artery and deliver the drug without use of
a metal stent. This concept is now called the Drug Eluting
Balloon or DEB wherein a balloon is coated with a drug,
avoiding the use of a metal (that can cause restenosis) or
a polymer (that can cause thrombosis).
(Source : Chronicle
Pharmabiz , December 16 , 2010)
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