After percutaneous implantation of an atrial septal defect (ASD) occluder, a complex healing process leads to the device coverage within several months. However, an unexplained incomplete device coverage increases the risk of device related complications such as thrombosis or infectious endocarditis. The aim of the study was to non-invasively assess the device coverage process of ASD occluders in a chronic sheep model using micro-CT technology.

After percutaneous creation of an ASD, 8 ewes were implanted with a 16-mm Nit-Occlud ASD-R occluder (PFM medical, Germany) and were followed for 1month (n=3) and 3months (n=5) before sacrifice. The device coverage was then assessed using micro-CT and was compared to histological analysis (gold standard). The micro-CT image resolution was 41.7μm, reconstruction was performed in 2D and 3D with Amira® software allowing measurement of the coverage thickness and surface for each disk of the analyzed devices, using a code. Histological study was performed following resin embedding and Richardson blue staining.

ASD creation and device closure was successful in 100% animals without complications. Following sacrifice, macroscopic assessment of devices showed that the coverage was complete for the left-side disk regardless of the duration of the follow-up and variable for the right-side disk, depending of the protrusion of this disk. 2D and 3D micro-CT analysis allowed an accurate evaluation of device coverage of each disk and was overall well correlated to histology slices (Fig. 1). Surface calculation from micro-CT images showed that the median surface of coverage was 93±8% for the left-side disk and 55±31% for the right-side disk.

This preliminary study made the proof of concept that micro-CT is a reliable tool to assess the coverage of intra-cardiac occluders in vitro. The translation to clinical practice is challenging but would allow an individual follow-up.