2剤併用抗血小板薬療法は6ヵ月で十分である

EXCELLENT：薬剤溶出ステントを使用した場合の抗血小板薬使用期間はガイドラインの勧告よりも短縮できる可能性がある
EXCELLENT: When drug-eluting stents are used, length of antiplatelet treatment could be shorter than guidelines suggest
EXCELLENTスタディから得られた新たなデータの結果、抗血小板薬を内服している薬剤溶出ステント使用患者に対する抗血小板療法の期間は、6ヵ月とガイドラインが推奨する12ヵ月とでステント血栓リスクは同等であるとの無作為化コントロールトライアルから得られたはじめてのエビデンスが示されたと第60回American College of Cardiology学会で発表された。この19施設のトライアルにおいて1,443人の患者が、エベロリムスまたはシロリムス溶出ステント植え込みとともに2剤併用抗血小板療法6ヵ月または12ヵ月を行う群に無作為に割り付けられた。標的血管不全（心臓死、心筋梗塞または標的血管再血行再建術施行）は6ヵ月群において716人中34人（4.7%）に認められたのに対し、12ヵ月群においては712人中31人（4.4%）であった。この一次エンドポイントに関して6ヵ月群の12ヵ月群に対する、予め規定された40%の非劣性マージンを伴う非劣性が認められた（p=0.0031）。安全性のエンドポイント－死亡、心筋梗塞、脳血管事故、ステント血栓および重大な出血の合計（TIMI）－に関しては6ヵ月群では24人（3.4%）であり12ヵ月群では22人（3.1%）であった。これら2群における主要な脳－心血管イベントはそれぞれ54人（7.5%）および60人（8.4%）であった。
Full Text

Patients with drug-eluting stents take antiplatelet drugs to reduce the risk of late stent thrombosis, but questions exist about how long the therapy should last. New data from the EXCELLENT study provide the first evidence from a randomized controlled trial that show six-month antiplatelet therapy is equivalent to the 12-month regimen prescribed by current guidelines, according to research presented at the American College of Cardiology's 60th Annual Scientific Session.

Although drug-eluting stents (DES) outperform bare metal stents, data suggest they have a slightly higher risk of late stent thrombosis, a common cause of myocardial infarction and sudden death. The most important risk factor for late thrombosis has been stopping dual antiplatelet therapy (DAPT) too soon, but alternatively, long durations of DAPT can increase the risk of bleeding.

"The recommended duration of DAPT was three to six months in the early introduction period of drug-eluting stents," said Hyeon-Cheol Gwon, M.D., Ph.D., Department of Cardiology, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, South Korea. "Current American College of Cardiology/American Heart Association guidelines recommend 12 months or longer without solid scientific evidence."

In this 19-center trial, 1,443 patients were randomly assigned to six or 12 months of DAPT with a stent that released either everolimus or sirolimus; 12-month data are available for 1,428 patients and results of the stent trial have been presented. This is the first presentation of findings for a comparison of six-month and 12-month DAPT with the standard combination of aspirin and clopidogrel. Patients will be followed for at least two more years.

Results for target vessel failure - defined as cardiac death, myocardial infarction and target vessel revascularization - were 34 of 716 patients (4.7 percent) in the six-month group and 31 of 712 patients (4.4 percent) in the 12-month group. For this primary endpoint, the six-month group was non-inferior to the 12-month group, with a pre-specified non-inferiority margin of 40 percent (p=0.0031). For the safety endpoint - a composite of death, myocardial infarction, cerebrovascular accident, stent thrombosis and a type of major bleeding (TIMI) - results were 24 (3.4 percent) in the six-month group and 22 (3.1 percent) in the 12-month group. Major adverse cerebro-cardiovascular events for these groups were 54 (7.5 percent) and 60 (8.4 percent), respectively. The subgroup analysis by stent type showed very even numbers by outcome for the everolimus stent at six and 12 months, but the study was underpowered to compare the two regimens reliably for death, myocardial infarction and stent thrombosis.

"Our results may be very reassuring for many physicians who may need to discontinue clopidogrel before the routinely recommended 12-month duration for various reasons," Gwon said. "However, we need to remember that this study was underpowered to test the non-inferiority of the shorter duration for hard endpoints. A larger-scale randomized controlled trial is needed."

The study was funded by the Ministry of Health, Welfare, and Family Affairs of Korea, Abbott Vascular Korea and Boston Scientific Korea. Gwon has no financial relationship with either company.