ステント留置後で抗血小板薬内服中の患者におけるアスピリン中止は安全である

WOEST study：ステント留置後に抗血小板薬を内服している患者において抗血小板薬からアスピリンを除外することにより安全性が低下することなく出血が軽減する
WOEST study: Omission of aspirin from antiplatelet regimen reduces bleeding without compromising safety in patients taking oral anticoagulants following stent placement
WOEST（What is the Optimal antiplatElet and anticoagulant therapy in patients with oral anticoagulation and coronary StenTing）スタディの結果から、抗凝固薬にクロピドグレルのみを追加（そしてアスピリンを中止）することにより出血は減少しステント血栓などの血栓性および血栓塞栓性合併症予防の点では安全であることが示されたと2012年European Society of Cardiology学会で発表された。このスタディは、2008年11月から2011年11月の間に施行された。573人の患者は心房細動または機械弁に対し既に抗凝固薬を内服しており、冠動脈内ステント留置を施行され、前向きに2群：1つ目の群はクロピドグレルのみを追加（2剤併用療法群）に、もう1 つの群はクロピドグレルとアスピリンを追加（3剤併用療法群）に無作為に割り付けられた。各々の群は1年間追跡された。冠動脈内ステント留置後1年の経過 観察の時点で、2剤併用群は3剤併用群よりも出血が少なく全死亡率が低かった。さらに、心筋梗塞、脳卒中またはステント血栓も3剤併用群よりも少なかった。WOESTは抗凝固薬で治療されている冠動脈内ステント留置後患者においてアスピリン中止が安全であることを示した初めてのスタディである。
Full Text

Lifelong anticoagulation is necessary for the prevention of stroke in patients with rhythm disturbances and with mechanical valves. Patients who have a coronary stent implanted also need the antiplatelet drugs aspirin and clopidogrel to prevent the rare but lethal complication of stent thrombosis. For patients taking oral anticoagulant drugs (for atrial fibrillation or mechanical valve) who also have to undergo coronary stenting, the optimal antithrombotic treatment is still unknown, even though the use of all three drugs (oral anticoagulants, aspirin and clopidogrel) seems logical for the prevention of stroke and stent thrombosis. However, treatment with all three drugs often causes serious bleeding complications and the frequent need to discontinue the aspirin and clopidogrel.

Now, results from the WOEST study (What is the Optimal antiplatElet and anticoagulant therapy in patients with oral anticoagulation and coronary StenTing) show that a strategy of adding clopidogrel only to anticoagulants (and omitting aspirin) causes less bleeding and is safe with respect to preventing thrombotic and thromboembolic complications such as stent thrombosis. The results were presented at ESC Congress 2012 by Dr. Willem Dewilde, TweeSteden Hospital, Tilburg, the Netherlands, who said that "WOEST is the first study demonstrating that the omission of aspirin in patients treated with oral anticoagulants and having a coronary stent is safe".

He explained that the WOEST study was designed to resolve this specific dilemma of cardiology - the optimal antithrombotic treatment for patients taking oral anticoagulant drugs who also have to undergo coronary stenting. The study hypothesis was that aspirin could be omitted. "This would possibly lead to less bleedings," said Dr. Dewilde, "but hopefully would not increase the risk of thrombotic complications such as stent thrombosis."

The study took place between November 2008 and November 2011, when 573 patients already treated with oral anticoagulants for atrial fibrillation or mechanical valves and undergoing coronary stenting were prospectively randomized to two groups: one given additional clopidogrel only (double therapy group), or a second given additional clopidogrel and aspirin (triple therapy group). Each was followed for one year. The investigator-driven study was conducted in 15 hospitals in the Netherlands and Belgium, and was sponsored by the St Antonius Hospital, Nieuwegein, the Netherlands.

Results showed that at one-year follow-up after coronary stenting, the dual therapy group had less bleeding and a lower overall mortality rate than the triple therapy group. Furthermore, there was no increase in the occurrence of myocardial infarction and stent thrombosis as compared with the triple therapy group.

"Thus," said Dr. Dewilde, "the WOEST study demonstrates that omitting aspirin leads to less bleedings but does not increase the risk of stent thrombosis, stroke or myocardial infarction. Although the number of patients in the trial is limited, this is an important finding with implications for future treatment and guidelines in this group of patients known to be at high risk of bleeding and thrombotic complications."