Corrosive behaviour of Amplatzer® devices in experimental and biological environments

Abstract

Nitinol wire of Amplatzer septal occlusion devices is resistant to corrosion when exposed to physiologic saline solution, and in experimental animals as well as humans. A device in contact with a platinum pacemaker electrode developed minimal pitting of the titanium oxide layer, believed to be galvanic in nature and of no structural or clinical significance. There is no increase of concentrations of nickel in the blood of patients who have received Amplatzer nitinol devices. These favorable testing results reveal that nickel-titanium is an inert, corrosion resistant alloy.

Corrosion of Shape Memory and Superelastic Alloys

“…Biochemical studies showed no significant elevation of Ni levels after implantation. These test results imply that fretting corrosion did not occur in these devices in vitro or in vivo during fatigue loading [96].…”

“…He describes an explanted NiTi Amplatzer septal occluder in direct contact with the Pt leads of a pacemaker for 18 months. The occluder showed minor pitting of the passive layer and is believed to be galvanic in nature [96].…”

“…For instance, such situations can occur with NiTi used in vivo as a stent and the stent is a woven structure or is rubbing against another stent [2,38,61,72,96]. The regeneration of a passive surface layer on the Ti surface in in vivo environments is generally slow and Ti-corrosion product has been found in the tissue adjacent to some Ti implants [38,67,72].…”

“…The U.S. Food and Drug Administration (FDA) required an evaluation of stents that might experience fretting corrosion [98]. Kong examined NiTi Amplatzer septal occluders and no wire fractures were found in vitro after cycle testing with 400 million cycles or in devices taken from the animals and humans [96]. Biochemical studies showed no significant elevation of Ni levels after implantation.…”

Explantation of Patent Foramen Ovale Closure Devices

“…There is disagreement as to the optimal method of testing for nickel allergy, which occurs in 10% to 15% of the population, and whether a cutaneous reaction to a patch test corresponds to an allergic reaction within the bloodstream (8 -10). Some studies also suggest that the rise of nickel levels in the blood can only be observed for a few weeks after implantation; therefore, associated symptoms persisting for several months cannot reliably be linked to nickel allergy (11)(12)(13). However, the mechanism of nickel allergy to an indwelling device is not well-understood and might not depend only on the solubility of nickel ions.…”