Abstract 3798: Intravascular Ultrasound Findings Four Months’ Post Absorbable Metal Stent Implantation in Human Coronary Arteries
Background: Conventional metal stents are used to support the vessel wall during percutaneous coronary intervention (PCI). These stents carry the potential risk of late thrombosis, chronic inflammation, late restenosis, and associated with artifact in non-invasive imaging of CT or MRI. Absorbable metal stent (AMS) have the potential to overcome these drawbacks. PROGRESS-I is the first human trial to evaluate the safety of the AMS (BIOTRONIK AG, Switzerland) for the treatment of coronary artery stenosis. The aim of this analysis was to use serial area and volumetric intravascular ultrasound (IVUS) to evaluate the effects of AMS on in-stent neointima formation and vascular remodeling.
Methods: PROGRESS-I is a multicenter registry of 63 patients. Angiographic inclusion criteria were lesion length ≤13 mm and vessel diameters between 3.0–3.5 mm. All lesions underwent pre-dilatation while post-dilatation was performed (at the discretion of the physician) in 66.7% of the lesions. IVUS was conducted immediately post AMS implantation and at 4 months. Using computerized planimetry, the reference segment external elastic membrane (EEM), stent, and lumen were measured every mm within the stent. Neointima was calculated as stent minus lumen measures and volumes were calculated using Simpson’s rule.
Results: The AMS was well expanded immediately post PCI. Although the stents were completely biodegraded at 4 months, a reflection of the stents were visible by IVUS in all patients. AMS was associated with lower neointima (20.38 ± 14.40 mm3) compared to historical data of conventional bare metal stents. The net volume obstruction at follow-up was 20.08 ± 14.74%. Thus, the main contributor for restenosis of AMS could be attributed to the negative remodeling effect of the vessel post PCI vessel CSA 14.64 ± 4.25 mm2, versus follow-up vessel CSA 12.56 ± 4.40 mm2, (p <0.001).
Conclusions: AMS implantation in human coronaries was safe and associated with good stent apposition. Overall the AMS was absorbed at 4 months and resulted in low neointima formation but with excess of late remodeling compared to bare metal stents. Change in stent design and development of drug-eluting AMS are currently under development as is testing to overcome these contributors of restenosis.