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J Am Coll Cardiol, 2005; 45:1574-1579, doi:10.1016/j.jacc.2005.01.048 © 2005 by the American College of Cardiology Foundation |



* Thoraxcenter, Erasmus Medical Center, Rotterdam, the Netherlands
OrbusNeich, Fort Lauderdale, Florida
Terrence Donnelly Heart Centre, St. Michaels Hospital, University of Toronto, Toronto, Canada
Manuscript received December 9, 2004; revised manuscript received January 22, 2005, accepted January 25, 2005.
* Reprint requests and correspondence: Dr. Patrick W. Serruys, Thoraxcenter, Bd 406, Erasmus Medical Center, Dr. Molewaterplein 40, 3015 GD Rotterdam, the Netherlands (Email: p.w.j.c.serruys{at}erasmusmc.nl).
| Abstract |
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BACKGROUND: A "pro-healing" approach for prevention of post-stenting restenosis is theoretically favored over the use of cytotoxic or cytostatic local pharmacologic therapies. It is believed that the central role of the vascular endothelium is to maintain quiescence of the underlying media and adventitia.
METHODS: Sixteen patients with de novo coronary artery disease were successfully treated with implantation of endothelial progenitor cell (EPC) capture stents.
RESULTS: Complete procedural and angiographic success was achieved in all 16 patients. The nine-month composite major adverse cardiac and cerebrovascular events (MACCE) rate was 6.3% as a result of a symptom-driven target vessel revascularization in a single patient. There were no other MACCE despite only one month of clopidogrel treatment. At six-month follow-up, mean angiographic late luminal loss was 0.63 ± 0.52 mm, and percent stent volume obstruction by intravascular ultrasound analysis was 27.2 ± 20.9%.
CONCLUSIONS: This first human clinical investigation of this technology demonstrates that the EPC capture coronary stent is safe and feasible for the treatment of de novo coronary artery disease. Further developments in this technology are warranted to evaluate the efficacy of this device for the treatment of coronary artery disease.
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Recently, the existence of circulating endothelial progenitor cells (EPCs) has been identified as a key factor for re-endothelialization (4). The early establishment of a functional endothelial layer after vascular injury has been shown to assist in the prevention of neointimal proliferation and thrombus formation (5,6). The EPC capture stents have been developed using immobilized antibodies targeted at EPC surface antigens. The HEALING-FIM (Healthy Endothelial Accelerated Lining Inhibits Neointimal Growth-First In Man) registry is the first clinical investigation using this technology.
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Study device: EPC capture stent. The EPC antibody surface consists of a covalently coupled polysaccharide intermediate coating with murine monoclonal anti-human CD34 antibodies, attached to a stainless steel stent (R stent, OrbusNeich, Fort Lauderdale, Florida) (Fig. 1). This antibody specifically targets CD34+ cells (endothelial progenitor cells are CD34 positive) in the vascular circulation. This device was supplied in aqueous sodium azide solution as a preservative to maintain bioactivity and required hand crimping by the operator onto a percutaneous transluminal coronary angioplasty balloon catheter before implantation.
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Intravenous boluses of heparin were administered to maintain an activated clotting time >300 s during the implantation. Treatment with aspirin, at a dose of at least 80 mg/day, was initiated at least 12 h before the procedure and continued for one month. In addition, a loading dose of 300 mg of clopidogrel was administered before the procedure, followed by 75 mg daily for 28 days. Glycoprotein IIb/IIIa inhibitors were used at the operators discretion. Angiographic success was defined as the successful implantation of the study device, with a stenosis of <20% of the vessel diameter with TIMI flow grade 3.
Follow-up. All patients were scheduled for a clinical follow-up at one, six, and nine months following the implantation procedure to assess the anginal status and the occurrence of major adverse cardiac and cerebrovascular events (MACCE). An electrocardiogram was obtained at each visit, and an angiographic and intravascular ultrasound (IVUS) study was performed at a mean of 185 ± 14 days.
Quantitative angiographic and IVUS analysis. Coronary angiograms were obtained in multiple views after an intracoronary injection of nitrates. Offline quantitative analyses of preprocedural, postprocedural, and six-month follow-up angiographic data were performed. Restenosis was defined as a reduction of 50% or more of the luminal diameter. Late luminal loss was defined as the difference between the minimal luminal diameter after procedure and at six months. The target lesion was defined as the stented segment plus the 5-mm segments proximal and distal to the stented segment.
Intravascular ultrasound was performed with an automated pullback at 0.5 mm/s to examine the target lesion at postprocedure and six-month follow-up. Lumen, stent, and external elastic membrane contours were detected with the use of CUARD QCU analysis software (CUARD BV, Wijk Bij Duurstede, the Netherlands), applying a three-dimensional reconstruction as described elsewhere (7).
Study end points. The primary safety end point of this study was the absence of stent thrombosis up to six months. The second end point was a composite of MACCE, defined as cardiac death, stroke, Q-wave or non-Q-wave myocardial infarction (MI), and target vessel revascularization. Stroke was defined as a focal neurologic deficit resulting from a vascular cause involving the central nervous system. Q-wave MI was defined as development of new abnormal Q waves not present on the patients baseline. Non-Q-wave MI was defined as a creatine kinase of more than twice the upper limit of normal with an abnormal level of the MB isoenzyme of creatine kinase. The efficacy end point was late luminal loss as determined by quantitative coronary angiography and % stent volume obstruction by IVUS at six months. Stent thrombosis was angiographically documented as a complete occlusion (TIMI flow grade 0 or 1) or a flow-limiting thrombus (TIMI flow grade 1 or 2) of a previously successfully treated artery.
Detection of human antimurine antibody (HAMA).
Human antimurine antibody testing was not added to the study until several patients had already returned for follow-up. Testing with baseline data was conducted on 4 of 16 patients. The HAMA was determined by a commercially available enzyme-linked immunosorbent assay kit (MEDAC, Hamburg, Germany) (8). A positive assay was defined as
10 ng/ml. Significant levels of HAMA were defined as
150 ng/ml.
Histology. One specimen was retrieved by directional atherectomy (Flexi-cut, Guidant Europe SA, Diegem, Belgium), fixed in 4% buffered formaldehyde with metal stent fragments removed and embedded in paraffin.
Sections were stained with hematoxylin eosin and an elastin stain (Resorcin Fuchsin) for general assessment of the tissue. Cellular characterization was performed with immunocytochemistry, using antibodies against smooth muscle (specific alpha-actin), leukocytes (CD45), macrophages (mac 387), proliferation cells (Mib 1), and EPC (CD34). All antibodies except anti-CD34 were obtained from DAKO (DakoCytomation, Produktionsvej, Denmark).
Statistical analysis. Because of the size of the patient population in this nonrandomized registry, no formal statistical analysis was conducted to determine the efficacy of the device. Continuous variables are expressed as mean ± SD. Comparisons between postprocedure and six-month follow-up values were performed with a two-tailed paired t test. A p value <0.05 was considered statistically significant.
| Results |
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| Discussion |
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This clinical registry was preceded by several experimental studies. In an in vivo study, at 1 h after deployment the EPC capture stent showed a >90% cell coverage, while the bare stainless steel stents were almost completely devoid of cells. Histologic analysis at 31 days showed that percent area luminal stenosis was significantly reduced with the EPC capture stents compared with stainless steel stents (15.49 ± 4.54% vs. 23.96 ± 7.70%, p = 0.01) (9).
These preclinical and preliminary clinical results have to be interpreted carefully, considering the recent emergence of new technologies such as drug-eluting stents. Drug-eluting stents inhibit the inflammatory and proliferative process of the normal healing response, including the formation of a confluent endothelial layer on the stent (3). The EPC capture stents induce the rapid establishment of a functional endothelial layer early in the healing response. In this registry, the atherectomy specimen indicated a well-healed artery with minimal inflammation.
Of note, the neointimal hyperplasia in the EPC capture coating stents was not significantly reduced when compared with the usual late loss seen after conventional bare metal stent implantation. It has been argued that EPC capture coating covers only the stent struts, and theoretically no early functional endothelial lining can be expected in the interstrut space, although the interstrut area in the animal model (healthy coronary artery undergoing direct stenting) was covered with functional endothelium within 48 h; this situation differs substantially from a human pathologic atherosclerosis vessel after balloon injury. In addition, the bioactivity of these prototype EPC capture stents used in HEALING-FIM registry was unstable and was easily reduced by sterilization with gamma irradiation. It was subsequently discovered through the use of a bioassay that gamma irradiation lessened the immunoaffinity of EPC capture prototype stents used in this trial. Therefore, it is likely that the reduced bioactivity of EPC capture stents in the HEALING-FIM registry may not have been enough to inhibit neointimal hyperplasia after stent implantation.
The technology behind the creation of an EPC affinity surface is achieved by attaching murine monoclonal antihuman CD 34 antibodies to the stent. An immunoreaction against the murine monoclonal antibody may occur in patients who have human ant-murine antibody (HAMA). In addition, production of HAMA may result in the neutralization of the EPC capture surface. In this registry, increased HAMA levels were not observed in the four patients who underwent serial HAMA testing, and no patients exhibited systemic symptoms of immunoreaction. This safety issue was in agreement with other trials, evaluating immunologic treatment using murine antibody for ovarian cancer (10).
Because of the small sample size and single-center enrollment, the present study did not fully evaluate the efficacy of this device. However, further developments in this technology, such a providing a dry stent premounted on a delivery system and maintaining good activity post-sterilization, are currently being evaluated in the HEALING-II registry (Table 4). The technology for preserving antibody structure and bioactivity has advanced, resulting in a higher capture of EPCs (Fig. 3). As a result of these improvements, further clinical investigation of this technology is warranted to evaluate the efficacy of this device for the treatment of coronary artery disease.
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| Footnotes |
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| References |
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