By Deborah Brauser
ORLANDO, Fla -- November 23, 2009 -- Adding clopidogrel to aspirin after patients have undergone coronary artery bypass grafting (CABG) does not significantly reduce saphenous vein graft (SVG) intimal hyperplasia or significantly improve graft patency, according to a study presented at the American Heart Association (AHA) Scientific Sessions 2009.
Results of the Clopidogrel After Surgery for Coronary Artery Disease (CASCADE) study were presented on November 16 during a Late-Breaking Clinical Trial session by lead author Alexander Kulik, MD, currently at Boca Raton Community Hospital, Boca Raton, Florida, formerly with the University of Ottawa Heart Institute, Ottawa, Ontario, where the study was primarily based.
"In animal models of thrombosis, clopidogrel inhibits the process of intimal hyperplasia, the first step in SVG stenosis and failure," explained Dr. Kulik. "We therefore hypothesised that individuals might benefit from the addition of clopidogrel to standard aspirin antiplatelet therapy following CABG."
For the study, 113 patients (mean age, 66.9 years; 88.3% male) undergoing primary multivessel CABG with at least 2 SVGs were enrolled at 2 centres from May 2006 to July 2008. After surgery, they were randomised to receive aspiring 162 mg daily plus either clopidogrel 75 mg daily or a matching placebo for 1 year.
The primary outcome was mean SVG intimal area at the 1-year follow-up, with secondary outcomes including SVG patency and the incidence of major adverse cardiovascular events at 1 year.
Results showed no statistical difference between the combination-therapy group and the aspirin-alone group in the vein graft intimal area at 1 year (4.1 +- 2.0 mm2 vs 4.9 +- 3.3 mm2, respectively).
"We saw a 14.8% reduction in the intimal area in the clopidogrel group but this did not reach significance, as we were powered for a 20% clinically relevant reduction," explained Dr. Kulik.
In addition, there was no statistical difference in the vein graft patency rate between those treated with the combination therapy and those with aspirin alone (94.3% vs 93.2%, respectively).
There was no significant difference between the groups in the amount of vein graft thickening, the number of blocked bypasses, or the number of cardiovascular or bleeding events.
"Basically, aspirin alone was as effective as adding in clopidogrel in keeping the grafts open during the first year after surgery," said Dr. Kulik. "In other words, we do not support the use of dual antiplatelet therapy for the prevention of vein graft disease after CABG."
He said that these results represent both good and bad news. "The good news is that patients can expect more than 90% of vein grafts to remain open after surgery. However, it's bad news for the advancement of the cardiac surgery field -- where it's been more than 10 years since the last advance in medical therapy for bypass grafts."
Funding for this study was provided by Physicians' Services Incorporated Foundation, Boston Scientific, and the Bristol-Myers Squibb Sanofi Canada Partnership.
[Presentation title: Clopidogrel and Aspirin Versus Aspirin Alone After Coronary Bypass Surgery: Results From the Clopidogrel After Surgery for Coronary Artery Disease (CASCADE) Randomized Controlled Trial. Abstract LBCT-20022]
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