Saturday, February 11, 2006

Drug-eluting stents and angioplasty, the good, the not so goodand the really bad news

Undoubtedly, balloon angioplasty had revolutionised treatment of coronary artery disease (CAD). It has allowed us to treat symptomatic CAD easily without the need for GA and opening the chest. I am sure that Dr Andreas Gruntzig (the inventor of angioplasty) would have been very proud to see the number of patients he has helped with his technique of angioplasty.

The good thing about angioplasty is that we can control chest pains very effectively with minimally invasive teachniques. Of cause, plain old balloon angioplasty (POBA) has its problems, namely acute tear (dissection) in the treated artery, and also re-narrowing (restenosis).

The next logical evolution was the use of the bare metal, plain surgical grade stainless steel stent. This was better then POBA and acute artery dissection was a thing of the past. We no longer need a cardio-surgical team on standby. We now have "stent-by".

Bare metal stents (BMS) still had restenosis as a significant problem, running at about 15%. The next step came with the use of drug-eluting stents (DES). Whether this advance is an evolution or revolution depends on how you see the situation. There are two DES that are currently FDA approved, namely the Cypher stent (JnJ Cordis) and the Taxus stent (Boston Scienntific).

There are a few more waiting in the queue to be approved like the Endeavor stent (AVE Medtronic) and the XcentV stent (Guidant Corp). These DES has very low restenosis rates (<5%) even when we use long stents and multiple overlapping stents. We have been known to line the whole artery with 5-6 stents in the whole length of artery (full metal jacket) with good short and longterm results.

Except for certain subsets, angioplasty and stents have not been known to prolong life, but it does control chest pains well.

Now for the not so good news. Balloon angioplasty suffered from a 4-10% risk of acute artery dissection, causing acute heart attacks, which before the stent era, required emergency bypass graft surgery, which carried a 30% chance of dying and almost 100% chance of heart muscle damage.

While balloon angioplasty has a overall success rate of of about 95%, there are a group of CADs, the chronic total blockage, where the angioplasty success rate can be as low as 40-50% in some centers and is limited to 80-90% in the best of hands. Some blockages just cannot be angioplastied.

The nagging problem with POBA is restenosis. It was quite upsetting to see a patient where you performed a good POBA, where the acute angiogram picture was wonderful, and suddenly in 2-3 months, the artery blockage had returned, possibly worse then before.

This was ugly and usually upset the patient. Of course, with the BMS, the acute dissection and acute bypass problem was essentially solved. We no longer needed to send our angioplasty list to the Operation Room, and the cardiac surgical team could have a nice lunch.

However, the BMS brought a new problem of acute and subacute stent thrombosis. The stents are stainless steel and these attract blood clots, if the proper medical regimes are not followed. Procedural techniques also played a part. These happened on average about 1-4% of the time. This could be minimized by technique improvements and also the use of aspirin and ticlopidine as effective anti-thrombosis medications.

Then came the DES that we are still learning more and more about. With DES, the good news is that restenosis is now single digit (<5%). However, acute and subacute stent thrombosis still remain.

With BMS, the subacute stent thrombosis tend to come in the first 30 days. It tends to be more predictable. This enables us to try and figure out who the high risk group is. With the new DES, the subacute stent thrombosis could occur in the first 30days or as late as up to 1-2 years. Therefore the anti-thrombosis medications (aspirin and plavix/ticlopidine) had to be continued for much longer. This brought about the problem of non-cardiac surgery, should that be necessary on an elective or emergent basis following the use of DES. If these become necessary and the aspirin or plavix is stopped, there is an almost 10% chance of acute stent thrombosis. The DES are more costly and certainly more fuzzy stents.

This problem is so worrying to us, that if we know that the patient may need elective surgery after the angioplasty, we would prefer to use the BMS as a way to avoid the problem of acute stent thrombosis should the apirin or plavix had to be stopped for the elective surgery. With the use of DES, we also discovered a new problem of aspirin and plavix resistance (patients who may be taking the aspirin or plavix yet there is no clinical effect of these medication). With the widespread use of DES nowadays (in some centers, almost 95% of angioplasty includes the use of DES) we have learnt that there are cases of stent allergy, either allergy to the drug or the stent, or the polymer that the drug is bonded to. Stent allergy is still new and we are in the process of learning what we can.

While we improve by what is seemingly leaps and bounds, each and every step carries a high price. There is no such thing as a free lunch

And now for the bad news. As DES use becomes more widespread, more complex lesions are undertaken by the interventional cardiologist with greater and greater confidence as restenosis is low and indications for angioplasty become more liberalised. Cardiac surgery numbers drop worldwide. Is this better for our patients?

2 comments:

Jan said...

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.
Thanks!

Suhana Ansari said...

I really impress from Your Blog. for more information about ANGIOPLASTY SIDE-EFFECTS please click on this link below :
ANGIOPLASTY SIDE-EFFECTS
Angioplasty has proved to be a boon for patients suffering from heart diseases in the last 2-3 decades. It is efficient, economical, time-saving and involves less fuss. But in spite of that, there are a few side-effects of angioplasty as well. Let’s have a look at what could be the possible risks involved in and how to overcome them.