The HELEX™ Septal Occluder device is a purpose designed device for atrial septal defect closure. The purpose of this study was to evaluate the biologic response of this device in the canine heart.

Thirty-four animals had percutaneous implantation of a HELEX™ device. Animals were sacrificed at intervals from 2 days to 2 years post implantation (PI). Gross and histological assessment of the extent and type of tissue coverage was performed. Complete fibrous connective tissue coverage was seen in 2 of 5 devices examined 14 days PI. Fibrous connective tissue completely covered the left atrial component in 13/14 devices implanted > 30 days. One device at 6 months PI had complete coverage of the right atrial side with extensive coverage of the left atrial side. Endothelial-like cell coverage ranged from multifocal to complete in 10/13 devices implanted > 30 days. One device examined by scanning electron microscopy and immunohistochemistry confirmed that the endothelial-like cells seen with light microscopy were true endothelial cells. The lungs, brain and kidneys of each dog implanted longer than 30 days were examined for thrombo-embolism and no infarction was seen.

The biologic response following implantation of the HELEX™ device is progressive with an initial fibrous connective tissue coverage followed by endothealisation. There was complete coverage of the left atrial side of the device with fibrous connective tissue by 30 days post implantation in almost all animals. These data provide evidence of the biocompatibility of the HELEX™ Septal Occluder.