Optical Coherence Tomography Guided Percutaneous Coronary Intervention With Nobori Stent Implantation in Patients With Non ST Segment Elevation Myocardial Infarction

Coronary artery disease is one of the most prevalent diseases in the western countries.

A waxy substance called plaque can build up inside the coronary arteries. Over time, plaque can harden or rupture, and cause narrowing (stenosis) of the arteries and reduce the flow of oxygen-rich blood to the heart.

The standard treatment of symptomatic coronary stenosis is percutaneous coronary intervention (PCI) with balloon dilation followed by stent implantation.

A stent is a small metallic grid that stabilizes the coronary vessel wall after the balloon dilation.

Currently, drug-eluting stents (DES) are the most widely used stent types. DESs consist of a metallic backbone and an antiprolifetive drug-coating bound by a polymer (glue). These devices have reduced the incidence of excessive formation of new tissue (in-stent restenosis) dramatically in comparison with previously used bare-metal stents.

However, there are "safety concerns" with DES, since later thrombotic events have been reported.

On one hand excessive tissue formation inside the stent can cause in-stent restenosis, and on the other hand insufficient coverage of the stent can cause persistently exposed metalllic material that can induce platelet aggregation and thrombus-formation.

The etiology to stent thrombosis is multifactorial. Possible predisposing factors are, among others: 1) hypersensitivity towards the polymer-coating, which may induce delayed healing inside and around the stent, and 2) insufficient contact between the stent and the underlying coronary vessel wall (incomplete stent apposition), which may cause flow-disturbance and delayed healing.

Delayed healing causes persistently exposed metallic material that can induce platelet aggregation and thrombus-formation.

The Nobori stent is a new-generation DES, coated with a thin layer of drug and a bioabsorbable polymer. The drug is localized on the outer side of the stent, and decreases the release of drug to the blood circulation. The bioabsorbable polymer is degraded after 6-9 months after implantation, and decreases the risk of hypersensitivity-reactions in the vessel wall.

The improved pharmacokinetic profile of the stent is thought to improve the healing pattern.

At routine coronary angiography, a small plastic tube is inserted in the femoral artery under local anesthesia. Thin, flexible catheters are then advanced through the artery system (femoral artery and aorta) to the coronary arteries. Contrast is injected in to the blood stream by the catheters, and the arteries are depicted by a special X-ray technique during dye-release. By angiography, the outer sides of the coronary arteries are visualized, and balloon dilations and stent implantations are guided by this standard technique.

Newer studies have documented that stent placement and expansion is superiorly visualized if supplementary intravascular imaging is performed during stent implantation.

Small imaging catheters are wired through the vessel after stent implantation, and film the stent retrogradely through the vessel.

Intravascular ultrasound (IVUS) visualizes the complete vessel wall by use of sound waves, and stent expansion is evaluated in detail.

Optical coherence tomography (OCT) is a newer light-based, high-resolution technology. The technique can depict every thread (strut) from the stent, enabling visualization of both contact between struts and underlying vessel wall immediately after the procedure, and strut coverage at follow-up.

The purpose of this study is to determine whether OCT-guided PCI can improve healing and coverage of the stent in comparison with routine angiographic guidance alone in patients indicating PCI due to myocardial infarction.

If OCT-guidance improves coverage of the stent, this might lower the later thrombotic risk.

Patients hospitalized due to myocardial infarction are randomized either to OCT-guided or angio-guided stent implantation in the present study. In both groups the Nobori stent is implanted according to standard techniques. In the angio-guided group, implantations are guided by angiography alone. OCT- and IVUS analysis are performed after an angiographic optimal result for documentary reasons. The operator is blinded towards the image findings, and analysis is performed offline later.

In the OCT-guided group, both OCT and IVUS analysis is interpreted immediately after the acquisition. If stent apposition and/or expansion is deemed suboptimal, additional balloon dilation and/or stenting is performed. In case of OCT-driven stent optimization, a documentary OCT and IVUS is performed to document the final result.

Patients are readmitted 6 months later for a control angiogram inclusive OCT to assess stent coverage.

Furthermore, patients are readmitted 12 months after the index procedure for a control angiogram including OCT and IVUS to assess dynamic vessel wall responses.