Recall is the last word a medtech business wants to hear. But in 2015, the guidewire industry experienced recalls due what might be considered a combination of best intentions and unintended consequences.
In March 2015, there was a voluntary recall for stainless steel guidewires going back to April 2013, which FDA classified as Class 1. The problem was poor adhesion of an aqueous PFOA-free PTFE coating that resulted in flakes of coating being dislodged from guidewires during in vitro procedures. According to FDA, coating flakes that get lodged in the intravascular system can cause cardiac arrest.
This problem was first noticed when flakes of aqueous green PTFE were discovered in saline tanks of operating rooms during procedures using guidewires to install stents and balloons. FDA reported that in at least one of these instances, the coating flakes resulted in patient injury, although not fatal. This triggered the first recall alarm. Later reports of green flakes in sterilized packages of guidewires caused more concern. Solvent-based PFOA-free PTFE coatings were not involved in any recalls by the FDA.
A major factor of the delamination was a ban on PFOA, a potential carcinogen. EPA had required that PFOA be removed from PFTE in any form by 2015. PFOA is used for its surfactant quality to apply the coatings. Removing it made the guidewires more vulnerable to electro-chemical attack. Saline already degrades the hydrophobicity of PTFE and without PFOA, the immersion into saline made parts even more sensitive. When immersed in even mild saline solutions – similar to those found in surgeries (0.5-0.9%) or body fluids – the coatings tend to blister, wrinkle and peel off.
Surface Solutions Group has solved the problem of delamination using a proprietary adhesion process, FluoroBond-PT. The process, says the company, offers adhesion equal to the coating that used PFOA.
“We started to do some research when the recalls first began,” says Mike Osterhout, a technical consultant at SSG. “One thing we knew immediately was that we needed to clean the wire better. We found through extensive research that we had to remove the iron oxide from the surface of the guidewires.”
FlouroBond-PT is an environmentally friendly process that starts with hypercleaning the wire surface. Then a PFOA-free PTFE coating is applied to the wire, in a closely controlled aqueous formulation with extremely tight tolerances. For testing, the company uses an aggressive saline soak and tape test to ensure adhesion.
“This has become a new industry standard for all wires coated with aqueous-based PTFE coatings,” says Osterhout.
Osterhout says he is still seeing the after effects of the recall.
“Although SSG has coated millions of medical devices with no delamination in the field, OEMs still don’t trust PTFE.” He says the company is seeing a lot of change going on, and particularly with suppliers, as they are held to an even higher standard. “We now are able to prove gating work to meet the stricter coating requirements from OEMs.”