Failure of the GORE HELEX atrial septal defect occluder to treat membranous VSDs in swine.

OBJECTIVE: We tested the suitability of the GORE HELEX septal occluder for closure of membranous ventricular septal defect in three Yucatan minipigs that had naturally-occurring membranous ventricular septal defects. METHODS: The animals were studied in the Gore Science Center Laboratory in Flagstaff, Arizona. In all of the device implantations, seating of the right disk along the right ventricular septum was problematic with resultant entanglement of one device in the chordae tendinae during attempted removal, implantation of one device onto the tricuspid valve papillary muscle and unlocking of one device occurring after implantation. CONCLUSIONS: A new occluder design appears to be needed to minimize the risk of disk entanglement with cardiac structures, particularly within the right ventricle. These studies did establish that the Yucatan mini swine are an acceptable and appropriate model for evaluating occluders intended for closure of membranous ventricular septal defects.

Fracture of the GORE HELEX septal occluder: associated factors and clinical outcomes.

OBJECTIVES: This study examines factors associated with, and clinical effects of, wire frame fractures (WFF) of the GORE HELEX Septal Occluder (HELEX). METHODS: Investigator-reported data from every HELEX implanted in the United States between 4/2000 and 4/2005 were reviewed. Clinical and procedural data from patients who experienced WFF were compared with data from patients who did not. The echocardiographic and fluoroscopic images for HELEX with WFF were reviewed for predictors of WFF and alterations in HELEX function. RESULTS: With 90% of subjects followed for >12 months, 19/298 (6.4%) HELEX implanted were found to have WFF. Thirty WFFs were observed, with multiple WFFs occurring in 8/19 HELEX. Univariate predictors of WFF were large device size (P = 0.0003) and balloon defect size (P = 0.001); however, large device size (P = 0.0003) was the only significant predictor of WFF by multivariate analysis. WFF of the 30-mm and 35-mm HELEX accounted for 84% (16/19) of all WFFs. Review of HELEX images with WFF revealed all WFF occurred along the circumferential wire, except one (straight portion of locking loop). Seventeen of 29 (59%) circumferential WFFs were on the right disk. Residual defect status remained clinically insignificant (6/19) or became completely occluded (13/19) during follow-up. There were no clinical sequelae due to WFF; however, secondary to right atrial disk mobility, the HELEX with locking loop WFF was percutaneously removed 6 weeks after implantation. CONCLUSIONS: WFF occurred in 6.4% of HELEX and were most common in large devices. With the exception of one device removed for theoretical risks, no clinical sequelae were related to WFF. WFF did not alter the function of the HELEX.

Countercurrent blood vessel arrangement in beaver (Castor canadensis).

The vascular anatomy of five beavers (Castor canadensis) was studied by dissection and injection of arteries and veins with vinyl acetate. There is extensive countercurrent arrangement of arteries and veins distal to and including the common iliac artery and veins. Two types of countercurrent vessels occur (1) a venae comitantes type in which two or three veins surround a central artery, and (2) a modified rete type. The retia are located proximal to the large flat tail and the webbed hind feet. Two bypass veins are described for the feet and tail and the significance of these structures in temperature regulation is stressed.