Wednesday, March 01, 2006

Stent Thrombosis with Drug-eluting stents

A reader who did not leave an email asked

Where did you get your data re: 10% chance of thrombosis if ASA and Plavix are stopped after DES? I have only seen anecdotal reports and not firm numbers. I am curious because I frequently have patients needing to stop antiplatelet therapy for elective procedures such as EGD or colonoscopy. I'd like to be able to quote a percentage rather than just tell them there is a risk of subacute thombosis.

Short answer?

This data comes from the work of Dr Antonio Colombo of Milan, Italy, a personal friend of the author.

Long answer?

I have just returned from the Singapore Live demo course, where I was part of the guest faculty. At this meeting, DES stent thrombosis was extensively discussed. We must understand that many studies have been done on this subject, because, when stents thrombose, the patient will suffer a heart attack. Since drug eluting stents are usually implanted in large arteries with a large region of myocardium at risk, should the stent thrombose, the heart attack is likely to be massive. In fact, all of them will suffer a Q-wave myocardial infarction, and the mortality from this could be as high as 30%, depending on which study you quote. It is also important to note that stent thrombosis can occur over different time phases.

0-24hrs after implantation

Acute stent thrombosis: important risk factors on this include - techniques and procedural factors, whether aspirin and plavix was given early enough and also co-morbidity factors like diabetes and renal failure.

1-30 days

Subacute stent thrombosis: invariably due to anti-platelet regiments, aspirin or plavix resistance. Technical factors play a smaller role here, although stent malapposition is a factor. Co-morbidities like previous brachytherapy is important. Accidental cessation of plavix is also a factor here.

1-up to 2 years

Late stent thrombosis. Usually due to anti-platelet regimes mismanagement, and co-morbidities. Almost unheard of with bare metal stents.

Obviously, stent thrombosis is potentially a bigger problem with drug eluting stents because the drugs eluting from the stents delay healing and delay endothelisation, so exposing the thrombogenic stainless steel and polymer coating on the stent, for longer. Therefore, the thrombosis can come later.

If you look at Dr Antonio Colombo's experience (Centero Cuoro Colombo at Milan) and Dr Eberhard Grube's experience (Seigburg Heart Centre, Germany) over 9 months, the stent thrombosis is about 1.3 % (29/2229pts) overall with 29% (10/29pts), of these occuring because of premature stoppage of plavix. In the acute phase, as high as 10% of the overall 1.3% (3 out of the 29 stent thrombosis pts) could be due to premature stoppage of plavix, for very many reasons, coupled with technical reasons. Please note that the absolute number of stent thrombosis is small (29pts out of 2229patients under study). We are making this point because, this cause for stent thrombosis can easily be avoided, if we share this information with our family doctors and surgeons.

This problem is so important to us that there is a new stent (genous stent) discovered, that uses normal tissue healing to cover the stents very quickly after implantation, so that there is no need for plavix, thereby lessening the problem of stent thrombosis. However this stent (genous stent) is still very much under clinical study, and we await their long term safety data anxiously.

Hopefully this explanation, has helped clarify things. Please do keep the questions coming.

1 comment:

Jan said...

Thanks for the response.
Will bookmark this at work.
Have just found your blog and really appreciate the way you summarize clinical data.
Very helpful to me, a cardiology nurse practitioner. I miss being at a large medical center - I previously was at a large tertiary care VA in LA with a cardiology fellowship. Now I am at a small VA facility in Northern CA that does not have cardiology grand rounds.

I will be going to Atlanta for ACC and hope to soak up lots of info!

My email - lehcimj AT comcast DOT net