Extending clopidogrel therapy to two years instead of traditional one year prevents very late thrombosis in DES recipients: TYCOON

The American College of Cardiology/American Heart Association/Society for Cardiac Angiography and Interventions guidelines recommend at least nine to 12 months of dual antiplatelet drug therapy following intervention with a drug eluting stent (DES) to prevent thrombosis, unless the patient is at high-risk for bleeding complications. These recommendations are not supported by adequate data. However, recently results of a four-year follow-up from the Two-Year Clopidogrel Need (TYCOON) registry published online on September 28, 2009 in the American Journal of Cardiology showed that patients who stopped taking clopidogrel a year after coronary intervention with a DES are still at risk for a stent thrombosis for at least another year.

The registry enrolled 897 patients implanted with a coronary stent in 2003 and 2004. Around half of the patients had DES while the other half were with bare-metal stents. All patients received aspirin indefinitely. Patients with bare-metal stent were given clopidogrel for a month. On the other hand, patients treated with a DES in 2003 stayed on clopidogrel for 12 months, and patients given a DES in 2004 stayed on the drug for 24 months. Both groups had similar baseline characteristics. The overall rates of cardiac death, target vessel revascularization, and myocardial infarction were similar for both the groups. However, of the 173 DES patients who stopped clopidogrel after a year, four had a very late thrombosis; while none of the patients who stayed on clopidogrel after one year experienced very late thrombosis (Table 1).

The authors of the current paper, Dr. Gaetano Tanzilli, San Filippo Neri Hospital, Rome and his colleagues, pointed out that the present findings contradict with the past data which showed that cessation of the clopidogrel regimen at 12 months did not predict stent thrombosis, suggesting that the optimal duration of therapy for the prevention of stent thrombosis is six to 12 months & another study which showed that reduction in stent thrombosis was not associated with clopidogrel continuation beyond one year after DES implantation.

The coinvestigator, Dr Vincenzo Pasceri, San Filippo Neri Hospital, said that the main reason for these different results is that all the earlier studies were undersized while very late stent thrombosis is a rare event and would require a very large number of patients in order to detect significant differences. As the current data suggests that longer clopidogrel treatment may be beneficial & the additional risk of longer dual antiplatelet treatment is very small, particularly for patients who had no bleeding problems after one year of dual antiplatelet therapy; authors pointed out the need of larger prospective trial for definitive results.

"Our study provides novel evidence that continued and more protracted clopidogrel therapy well beyond the recommendations of the scientific societies conveys an important prognostic benefit after drug-eluting-stent implantation," the authors concluded.