In vivo delamination of coronary guidewire polytetrafluoroethylene layer – A dreaded complication

Abstract

Coronary guidewires are coated with polytetrafluoroethylene (PTFE) layer to decrease resistance and enhance trackability. Delamination and embolization of PTFE material can be detrimental during percutaneous coronary interventions. We report an occurrence of such delamination and discuss the implications and possible mechanism of this dreaded complication.

A 65-year-old male patient with acute anterior wall MI was taken for coronary angiogram which revealed proximal LAD 90% lesion. The lesion was crossed with Galeo J tipped floppy guidewire and predilatation was planned with a 2.0 mm × 10 mm complaint balloon. While passing the balloon catheter over the guidewire, the operator felt some resistance and the balloon could not be pushed further.

As there was high resistance, which could not be overcome with moderately high force, the entire assembly consisting of guiding catheter, guidewire and balloon was withdrawn. The tip of the balloon catheter showed heaped-up green-colored material which was peeled off from the guidewire while the stainless steel core of the guidewire was seen exposed (Fig. 1).

Fig. 1.

Galeo wire with green colored PTFE layer peeling.

As the most common cause of such guidewire peeling might have been improper storage or handling during the procedure, we decided to repeat the test in vitro by soaking another new Galeo guidewire from the same lot in 0.9% normal saline for 30 min at room temperature (similar to how the manufacturing companies test after production). To our surprise the test showed similar peeling of the polytetrafluoroethylene (PTFE) material (Fig. 2).

Fig. 2.

In vitro saline soak test showed delamination of PTFE material when a PTCA balloon was passed over it.

1. Discussion

Guidewire generally consists of three components – central core, distal flexible tip coils and a coating such as silicone, PTFE, or hydrophilic polymers. Galeo F guidewire (BIOTRONIK SE & Co. KG, Germany) is a flexible hydrophobic guidewire made of stainless steel core with distal 30 cm having silicone coating and proximal 145 cm having PTFE coating. PTFE coating generally is used to decrease friction, enhance guidewire movement and optimize device tracking.

PTFE was traditionally coated over stainless steel core using PFOA (perfluorooctanoic acid) as a surfactant. But PFOA has recently been declared to be a potential carcinogen and the EPA (Environmental Protection Agency, USA) insisted in 2006 that it should be eliminated from all PTFE used on any products in USA by 2015 (2010/2015 PFOA Stewardship Program).¹ All PTFE coatings used on medical devices must comply with the EPA mandate. PFOA free PTFE has less firm adhesion to underlying stainless steel so that hydrophobic guidewire becomes “less hydrophobic” and vulnerable to delamination. This problem was first noticed when flakes of aqueous green PTFE were discovered in saline tanks of operating rooms during procedures using guidewires for passing stents, balloons, etc. Later on PTFE flaking was observed in some new packaged guidewires while using them in vivo.

One such adverse event of Galeo F guidewire PTFE coating flaking was reported to FDA in December 2014² and peeling of PTFE has already been noticed with other guidewires in last few years. The problem led some coronary guidewire manufacturing companies (Medtronic Vascular, Medline, and Covidien) to publish firm-initiated recalls for all affected models and lots of guidewires.3, 4, 5 Similar events have also been reported to FDA in neurovascular intervention devices which led FDA to publish Class I Medical Device Recall in 2014 for “Potential for the PTFE coating to delaminate and detach from the delivery wire”.⁶

These recalls have led to some changes in the manufacturing process of the guidewires coatings like hyper cleaning of the wire surface, application of a closely controlled aqueous formulation of PFOA-free PTFE coating to the wire and more aggressive testing to ensure adhesion.⁷ However PFOA-free PTFE still remains vulnerable to delamination and poses risk of embolization of PTFE material.

Our report herein highlights the fact that guidewire PTFE coating can be detrimental to the patient if it peels off in vivo and embolizes to coronaries. If any unexpected resistance is met with during passing of any catheter over guidewire, the operator should not use force to push the catheter; rather withdraw the entire assembly to inspect the guidewire and balloon. High index of suspicion in such scenario can avert catastrophic consequences of PTFE embolization.

Conflicts of interest

The authors have none to declare.