Gwangju, Korea - Results from the first large, randomized controlled trials of the Cypher and Taxus stents in the setting of AMI (the TYPHOON and PASSION trials) will be unveiled at next week's American College of Cardiology meeting in Atlanta, but Korean researchers, writing in the March 7, 2006 issue of the Journal of the American College of Cardiology, propose another strategy. An abciximab-coated stent, they say, is safe and may reduce adverse clinical outcomes in AMI patients undergoing stent implantation.
According to Dr Weon Kim (Chonnam National University Hospital, Gwangju, Korea) and colleagues, abciximab is attractive as a stent coating not only because it blocks platelet aggregation and is proven to improve outcomes in high-risk PCI patients, but also because it has unique inhibitory effects on inflammatory response and smooth-muscle-cell proliferation following vascular injury.
In their study, Kim et al randomized 96 patients undergoing stenting for AMI to either an abciximab-coated stent or a bare-metal stent. They report that angiographic follow-up, completed in approximately 75% of both groups at six months, indicated that percent diameter stenosis, late loss, and in-stent restenosis were significantly lower in the abciximab-coated-stent group than in the bare-metal-stent group. Intravascular ultrasound (IVUS) studies likewise indicated that intrastent lumen area was significantly greater, while intrastent neointimal hyperplasia area was lesser, than that of the abciximab group. Clinically, however, one-year rates of target lesion revascularization (TLR) and total MACE in the abciximab stent-treated patients were not statistically different from rates in patients who received a bare-metal stent.
"These observations warrant further investigation with a large, randomized multicenter study," the authors conclude.
Outcomes with abciximab-coated vs bare-metal stent
| End point | Abciximab stent | Bare-metal stent | p |
| Diameter stenosis (%) | 18.9 | 37.9 | 0.008 |
| Late loss (mm) | 0.39 | 0.88 | 0.045 |
| Intrastent lumen area (mm) | 5.4 | 4.3 | 0.011 |
| Intrastent neointimal hyperplasia (mm) | 2.2 | 3.4 | 0.008 |
| In-stent restenosis rate (%)* | 13.9 | 34.3 | 0.045 |
| MACE (%) | 10.4 | 25.0 | 0.107 |
| AMI (%) | 0 | 4.2 | 0.495 |
| TLR (%) | 10.4 | 20.8 | 0.261 |
*In-stent restenosis was defined as an in-stent luminal diameter stenosis >40%
PCI timing and AMI definition: Clarification needed
A key problem with interpreting the results, particularly with the TYPHOON and PASSION results pending, may come down to the fact that PCI in all patients in Kim et al's study was not performed within six hours of chest pain. As a result, the authors note, "The true effects of abciximab-coated stents in AMI might have been rendered less pronounced." That said, the absence of AMI and subacute thrombosis in the abciximab-stent-treated patients suggests that platelet aggregation was "effectively inhibited," the investigators write, despite the fact that clopidogrel was given only for two months postprocedure. In the pivotal randomized clinical trials using sirolimus- and paclitaxel-eluting stents, clopidogrel was prescribed for three to six months.
Commenting on the study for heartwire, Dr David J Cohen (Harvard Clinical Research Institute, Boston, MA) called the results "striking" but said he was troubled by the fact that more than 50% of the study participants had TIMI 3 flow in the treated artery at the time of their procedures.
"It's not clear to me whether this is truly what we would consider an AMI population by US standards," he told heartwire.
Still, he said, "If the results these investigators saw are reproducible in a much larger trial, then the abciximab-coated stent could be a viable competitor to the current Cypher and Taxus stents, as it should have both antiproliferative (antirestenotic) properties—as demonstrated in the paper—as well as antithrombotic properties. Given previous experience with abciximab, however, I wonder if future studies will show such low levels of neointimal proliferation and similarly low rates of restenosis."
A more "intriguing" concept, he added, would be a combination of abciximab coating, to provide antithrombotic properties, with another drug such as sirolimus or paclitaxel, for their antirestenotic properties. Several next-generation drug-eluting stents, for example, are exploring the possibilities for eluting different drugs at the same time.