NEW YORK (Reuters Health) – Overall outcomes of drug-eluting coronary stent (DES) implantation are statistically no worse with 6 months of dual antiplatelet therapy than with 12 months, based on the results of a comparison trial reported in Circulation online December 16.

“However, noninferiority margin was wide, and the study was underpowered for death or myocardial infarction,” the authors note, “Our results need to be confirmed in larger trials.”

Dr. Hyo-Soo Kim, at Seoul National University Hospital, Korea, and colleagues note that 12 months of dual antiplatelet therapy (DAPT) is currently recommend for patients undergoing percutaneous coronary intervention with a DES, unless they are at high risk for bleeding.  On the other hand, some studies have indicated that there is no additional benefit of DAPT after 6 months.

To investigate, the team randomly assigned 1443 patients having a DES implanted to receive 6 or 12 months of DAPT — aspirin 100 to 200 mg/day plus clopidogrel 75 mg/day.  In the 6-month group, aspirin alone was continued after clopidogrel was stopped.

The primary endpoint of target vessel failure at 12 months was defined as a composite of MI, cardiac death or revascularization.  The investigators expected that the endpoint incidence would be 10%, and they set the non-inferiority margin at 4 percentage points “based on historical data, clinically acceptable relevance, and the feasibility of study recruitment.”

They found that the actual rates of target vessel failure at 12 months were 4.8% and 4.3% on the 6-month and 12-month DAPT groups, respectively, thus demonstrating non-inferiority of the shorter protocol.

Regarding the components of the endpoint, the stent thrombosis rate trended higher in the 6-month than the 12-month arm (0.9% vs 0.1%; p=0.10), but the rate of MI or death was similar (2.4% vs 1.9%; p=0.58), the investigators found.

They also discovered that diabetes influenced the treatment effect.  Target vessel failure occurred more frequently among diabetic patients with 6-month DAPT than with 12-month treatment (hazard ratio 3.16; p=0.005), while the reverse was true among patients without diabetes (hazard ratio 0.44; P=0.03).

Bleeding rates were not statistically different in the two arms (p=0.40), but numerically there were fewer events in the 6-month group (4) than the 12-month group (10).

Overall, Dr. Kim and colleagues conclude, “The safety of short duration of DAPT regarding stent thrombosis or in diabetic patients should be studied in larger randomized trials.”

The authors of a related editorial suggest that there is no one-size-fits-all for antiplatelet therapy, and recommend a tailored approach.

Drs. Matthias Pfisterer, Christoph Kaiser, and Raban Jeger of University Hospital Basel, Switzerland, discuss the pros and cons of the newer P2Y12 inhibitors, prasugrel and ticagrelor, and examine the findings of the current study.  They conclude that 6 months of DAPT with clopidogrel and aspirin seems sufficient to prevent stent thrombosis in most patients given a DES.

SOURCE:

Six-Month versus Twelve-Month Dual Antiplatelet Therapy after Implantation of Drug-Eluting Stents: ‘EXCELLENT’ Randomized, Multicenter Study

Circulation 2011.