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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developed stents (metal wire-mesh scaffoldings) that could be left behind to hold the artery open once the balloon was withdrawn.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 1980s 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)