About UHMwPE Fibers
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the balloon was withdrawn.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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