アスピリンにクロピドグレルを併用しても有意な有益性は認められない

CASCADE：アスピリン単独と抗血小板薬併用療法のバイパス術後の静脈グラフト疾患予防効果は同等である

CASCADE: Aspirin alone as effective as dual antiplatelet therapy in preventing vein graft disease one year after bypass surgery

冠動脈バイパスグラフトの開存維持率はアスピリン単独とアスピリンとクロピドグレルの併用とでは同等である、と2009年American Heart Association学会のレイトブレイキング臨床試験のセッションで発表された。冠動脈疾患術後のクロピドグレル（Clopidogrel After Surgery For Coronary Artery DiseasE ：CASCADE）無作為化コントロールトライアルは、クロピドグレルをアスピリンに追加することで冠動脈バイパス術（CABG）後の伏在静脈狭窄およびグラフト閉塞が軽減するか否かを評価した初めての前向き試験である。研究者らは初回の多枝CABGを2本以上の伏在静脈グラフト（SVGｓ）を用いて施行された患者113人を、アスピリン162mgとクロピドグレル1日75mgまたはアスピリンとプラセボを1年間内服する群に無作為に割り付けた。1年後の静脈グラフトの開存率はアスピリン単独群で93.2%であったのに対し、アスピリンとクロピドグレルを内服した群で94.3%であり統計学的有意差はなかった。二次エンドポイントである静脈グラフトの開存率、主要な心血管イベント、または大出血に関しても有意差はなかった。

Aspirin alone is as effective as aspirin and clopidogrel in keeping coronary artery bypass grafts open during the first year after surgery, researchers reported in a late-breaking clinical trial presentation at the American Heart Association's Scientific Sessions 2009.

The Clopidogrel After Surgery For Coronary Artery DiseasE (CASCADE) Randomized Controlled Trial is the first prospective randomized study to evaluate whether the addition of clopidogrel to aspirin reduces saphenous vein graft narrowing and graft occlusion after coronary artery bypass grafting (CABG).

"We found no significant difference in the amount of vein graft thickening, or the number of blocked bypasses, cardiovascular events or bleeding events for the 113 CABG surgery patients treated with either aspirin and clopidogrel or aspirin alone," said Alexander Kulik, M.D., M.P.H., lead author of the study and a cardiovascular surgeon at the Boca Raton (Fla.) Community Hospital.

Researchers randomly assigned the patients to one year of 162 milligrams (mg) a day of aspirin plus 75 mg/day of clopidogrel or 162 mg/day of aspirin plus placebo. More than 90 percent of patients in the CASCADE trial were also taking cholesterol-lowering statin drugs.

"I think this study presents both good news and bad news," said Kulik, who was a cardiac surgery resident at the University of Ottawa Heart Institute in Ontario, Canada, where the study was based, during most of CASCADE's May 2006 through July 2008 enrollment period.

"The good news is that patients and their doctors can expect more than 90 percent of vein grafts to remain open one year after surgery with the use of aspirin and statins," Kulik said. "In this study there was no statistical difference in the vein graft patency rate between the 93.2 percent for the aspirin only group vs. 94.3 percent for those who received aspirin plus clopidogrel. However, it is bad news for the advancement of the cardiac surgery field. It has been more than 10 years since the last advance in medical therapy for bypass grafts, which was a study showing that statin therapy helps keep vein grafts open."

Aspirin is the standard antiplatelet therapy for post-CABG patients, while dual antiplatelet therapy with aspirin and clopidogrel is routinely used during and after angioplasty and during acute heart attacks. Some surgeons have recently begun using clopidogrel instead of or in addition to aspirin after bypass surgery, believing that it might improve outcomes. The study didn't validate that belief, Kulik said.

The CASCADE trial was funded by research grants from Physicians' Services Inc. Foundation, Boston Scientific Inc. and the Bristol-Myers Squibb Sanofi Canada Partnership.

Co-authors are: Michel Le May, M.D.; Jean-Claude Tardif, M.D.; Robert De Larocheliere, M.D.; Sarika Naidoo, B.Sc.; George A. Wells, Ph.D.; Thierry G. Mesana, M.D., Ph.D.; Pierre Voisine, M.D.; and Marc Ruel, M.D., M.P.H.

Disclosures: Michel Le May - Sanofi-Aventis Canada and Bristol Myers Squibb Canada, Research Grant; Marc Ruel - Bristol-Myers Squibb Sanofi Canada Partnership, Research Grant