Evaluation of Endothelial ProGenitor Cell Capture Sirolimus-Eluting Stent by Optical Coherence Tomography: the COMBO Stent angiographic extension Study (EGO-COMBO angiographic extension Study)

The Genous Stent (the EPC Capture R-stent, OrbusNeich Medical Inc., Fort Lauderdale, FL) is commercially available and has been used extensively in standard coronary intervention in the treatment of more than 200 patients with critical coronary stenoses at Queen Mary Hospital. The COMBO Stent (OrbusNeich Medical Inc., Fort Lauderdale, FL) is an improved version of the Genous Stent and has been implanted in 60 patients at Queen Mary Hospital. All patients have remained in good condition since the treatment.

The Genous Stent is a bio-engineered 316L stainless steel coronary stent with a biocompatible coating having specific CD34 antibody on the inner surface. CD34 is a surface antigen present on circulating endothelial progenitor cell (EPC). It will be bonded to the CD34 antibody, resulting in capturing of the EPC onto the stent surface and differentiation into endothelial layer. Animal model has demonstrated that a functional endothelial layer could be formed as soon as 24 to 48 hours after Genous stent implantation (1). The HEALING-FIM registry has shown that Genous stent is clinically safe and effective in the treatment of coronary stenosis (2). Recent reports have further confirmed its efficacy in patients with acute coronary syndrome requiring urgent revascularization (3,4).

The COMBO Stent is developed basing on the GENOUS stent platform, and in addition, it also delivers a drug called sirolimus to the treated coronary blood vessel. The stent's original CD34 antibody coating is designed to promote healing of the coronary artery by catching circulating endothelial progenitor cells as they pass through the stent. These cells are naturally flowing in the circulation and are responsible for endothelial healing. This is intended to help the blood vessel wall heal over the stent more quickly and restore normal tissue function in the stented area. The combination of these two technologies in this new COMBO stent is expected to produce even better clinical results, which have been investigated in the previous REMEDEE Study.

Animal study has shown the COMBO Stent promotes endothelialization and reduces neointima formation, as assessed by both optical coherence tomography (OCT) and histopathology (5). Even though COMBO Stents have been used and found to be safe in over 210 patients world-wide and in about 61 patients at Queen Mary Hospital under the EGO-COMBO Study Protocol, such beneficial endothelial coverage as assessed by OCT has never been documented in human subjects.

This current EGO-COMBO angiographic extension study protocol is designed based on the approved protocol EGO-COMBO Study (IRB: UW 10-342). This current study mainly focuses on the time frame, degree of endothelialization, and the subsequent neointimal proliferation after COMBO Stent implantation from 2 years, as assessed by intracoronary optical coherence tomography (OCT).

Intracoronary optical coherence tomography (OCT) is a simple catheter-based imaging technique using optic fibre to achieve very detailed assessment (resolution down to 100 microns) in intra-coronary stent apposition, early stent coverage (endothelialization) and late stent neoinitmal growth (restenosis). It is performed as part of routine cardiac catheterization procedure and provides high-resolution cross sectional images of the coronary arteries. OCT has been shown to be safe in clinical practice (6, 7). The C7XR OCT system (Frequency Domain OCT) is a commercial available product with CE Mark and FDA approval. The OCT catheter is just a non-occlusive optic fibre which is extremely small and flexible and will pose no additional risk to the patient other than those inherent risks of a standard angioplasty procedure.

Inclusion Criteria:

• Patient aged 18-85 years old
• Patient who agrees to have follow-up coronary angiograms
• Patient who were previously enrolled in EGO-COMBO study

Exclusion Criteria:

• Patient who refuses to consent to coronary angiogram or coronary angioplasty