Saturday, April 01, 2006

The problems of Drug Eluting Stents

In this series on Drug Eluting Stents we have covered what DES are and the different types of DES.

Today we consider the problems of DES.

Like everything man made, there are problems and adverse reactions. Since we embed DES' in vital heart arteries for life, we must make it as safe as possible. The truth of the matter is that there are problems. In 2003, there were market reports that the Cypher stent, after being implanted, had a high rate of acute stent blood clot. However, on closer examination, JnJ cordis (the makers of Cypher) produced post-market survey information to show that the acute stent blood clot rate in the Cypher stent was the same as that in Bare Metal Stents. This is now accepted to be true, that DES has the same acute blood clot rate as BMS.

In yr 2004, Boston Scientific voluntarily recall their Taxus stent because of market reports of some cases of their Taxus stent balloons not deflating well, causing death in some cases. Being a responsible company, they voluntarily recalled their Taxus stent for inspection and corrected the problem quickly. Presently, the Taxus stent is okay.

Then we learnt that blood thinning medications (aspirin and plavix) prescribed after DES implantation is very important to avoid acute, subacute and late DES blood clotting in them. Sometimes, for very many reasons, the blood thinning medication is discontinued. There is then a high chance of blood clotting in the DES, causing acute heart attacks and in some instances, death. In fact, 20-25% of acute blood clotting in the DES is due to accidental discontinuation of the blood thinning medications. Medical, dental and other health personnels must remember this fact, and of course, the patients too.

There has also been cases (on necropsy studies) of allergic reaction in the artery wall around the DES. Whether it is allergy to the polymer coating (likely) or the stainless steel (unlikely) or the drug (maybe) or all of the above, we are not certain. Therefore, continued observation and close monitoring is necessary. Long-term post marketing surveillance is important. Overall, DES does much, much more good then harm. It is a major evolution in the treatment of CAD. Some even call it a revolution, a quantum leap.

I would like to re-emphasize that we must always be vigilant and monitor our patients closely. Of course using well studied DES by responsible, reputable companies helps a lot as we always have the benefit of their post-market surveillance, in case some of the reactions come late. Please do bear in mind that since 28th May 2002 (when the first DES was implanted in Malaysia), over 2 million DES' have been implanted annually worldwide, by the category 1 stents. We cannot say the same for the smaller companies.


It is important to note that not all DES are the same. The Cypher, Taxus and Endevour are good DES stents. They are also a little costly. The cheaper generic stents may not work the same as the well studied ones. It may be wise, if you need a DES, to ask which one is being recommended by your doctor. DES are very good as they are safe and effective. We only hope that the cheap imitators do not spoil the good results of the real DES.

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