March 27, 2006
In a presentation at the 2006 Scientific Sessions of the American College of Cardiology this month, investigators reporting on the results of the BASKET-LATE trial suggested that drug-coated stents may present a higher risk of late, sudden restenosis. In this trial, 746 patients with complex coronary artery blockages were randomized to receive either bare metal stents, or drug coated stents (coated with either sirolimus or paclitaxel). Patients were treated with the anti-platelet drug clopidogrel (Plavix) for 6 months after receiving their stents. The aim of the trial was to show whether, in complex artery disease, drug coated stents resulted in less restenosis than bare metal stents.
They found that, as in many other trials comparing the two kinds of stents, those receiving the bare metal stents had more classic restenosis and required either re-stenting or bypass surgery more often than those treated with drug coated stents. However, the restenosis events for bare metal stents appeared to plateau at about 8 months after stent placement, whereas the rate for drug coated stents continued to climb. Furthermore, the kind of late restenosis seen with the drug coated stent tended to be more sudden, and possibly more likely to be fatal. The investigators estimated that approximately 3 late deaths would occur for every 100 patients treated with drug coated stents, given current treatment guidelines. (They hastily added, however, that their trial did not have the statistical power to enable them to be very sure of this kind of estimate.) More prolonged use of Plavix appears to significantly reduce this risk.
DrRich Comments:
DrRich reported on this phenomenon in 2004, but it has not received much public notice since then. However, cardiologists have been concerned enough about sudden, late restenosis to begin extending the use of anti-platelet drugs after inserting drug-coated stents from 3 months to at least 12 months, and some worry they will need to use Plavix indefinitely in these patients. The fact that the restenosis is sudden (instead of gradual, as with the typical restenosis that occurs with stenting) makes this phenomenon behave more like an acute heart attack than a gradual return of symptoms - and makes it all the more worrisome.
Drug coated stents prevent restenosis by inhibiting abnormal cell growth within the stent. However, the drugs used to coat these stents also inhibit the growth of a layer of normal cells (called endothelial cells) that would prevent the bare metal of the stent from being exposed to the blood. So, when anti-platelet drugs are stopped, platelets in the bloodstream may be more likely to "stick" to the stent, and to begin forming a clot that could block blood flow within a matter of several minutes. At this point, late occlusion of drug coated stents still has not been carefully studied, so its actual incidence is not known. Even with this "new" phenomenon, however, the overall risk of stent restenosis still appears substantially lower with drug coated stents than with bare metal stents.
Odds are that cardiologists will now feel obligated to continue the use of Plavix almost indefinitely in patients with drug coated stents, at least until more is known about the risk of sudden, late restenosis. This late risk is something cardiologists should begin to discuss with their patients who need stenting, along with the "risk" of having to buy Plavix (a very expensive drug) for a very long time. For some patients, the risk of bare metal stents may make more sense than it did a short time ago.
Click here for an update on the issue of late problems with drug-coated stents
