Solution proven to have no PTFE
delamination for 34,000,000+ guidewires.
The guidewire coating
delamination problem reached catastrophic proportions late last year. In
October, Medtronic—a major guidewire supplier—recalled over 84,000 units that
had the potential for the PTFE coating to flake off. But Medtronic was not
alone; other manufacturers have recalled guidewires, too.
These were FDA Class 1
recalls, meaning these guidewires and microguidewires represented serious
health risks in which the applied coating—PTFE in this case—had the potential
to delaminate or flake off. If this occurs before or during a medical procedure
and even a microscopic flake enters the patient’s bloodstream, the results can
be serious, including blood clots, stroke, heart attack, tissue necrosis, and
even death. Between January 2014 and November 2015, the FDA received
approximately 500 Medical Device Reports—including reports of nine
deaths—attributed to PTFE coating delaminating from guidewires.
The medical
ramifications to the patient and their family are undeniably devastating. For
the guidewire manufacturer, the results can also be catastrophic. Based on
other comparable recalls, the device manufacturer will take a substantial hit
to their reputation and see their stock prices and market cap often falling 10
percent from a single incident.
Further, there is the
matter of unresolved liability. Defending a lawsuit stemming from blood clots,
stroke, or death resulting from a faulty guidewire would undoubtedly be a
costly endeavor, and the damages available to the patients and their families
can be significant. There is no set benchmark for the types of damages
available in these cases, particularly when the damage done to a patient is
open-ended and requires ongoing treatment or hospitalization, which may make
early resolution more difficult. Litigants and the courts will invariably look
to other defective medical products for guidance. “The lawsuits that stem from
defective catheter guidewires may follow the pattern established for the IVC
filters that were designed to block blood clots,” explained Rachel V. Rose, a
trial lawyer in Houston who is experienced in medical litigation. “In the case
of guidewires, look for ‘bellwether’ cases in different parts of the nation to
set the standard for monetary awards.”
Background
Coating a guidewire
with PTFE is necessary for its smooth operation in the peripheral, coronary,
and neuro vasculature. The coating reduces friction and eliminates the
potential for binding and kinking during a procedure and, from the physician’s
standpoint, the motion of the guidewire needs to be smooth and unhesitating.
The difference in the tactile feel of a guidewire without and with PTFE is
dramatic.
The origin of the problem of PTFE flaking on guidewires appears to
correspond with the Environmental Protection Agency’s mandate earlier in this
decade to eliminate the surfactant—PFOA—from water-borne PTFE formulations
because PFOA is a suspected carcinogen. For 50 years, pure PTFE, with the aid
of PFOA, had been the gold standard coating for guidewires. It is believed that
PFOA improved adhesion to smooth metal surfaces, including guidewires. Without
it, the flaking problem struck with a vengeance, especially when guidewires
were soaked before use in the ever-present saline used in medical procedures.
Saline penetrates the porous coating and, if adhesion is marginal, causes it to
bubble and delaminate. Reports from operating theaters indicated that
guidewires coated with the new PFOA-free PTFE were visibly flaking after being
placed in saline soaking tanks.
An initial “fix” for the delamination problem was to switch from pure PTFE
to resin-bonded PTFE. These early formulations are based on particles of pure
PTFE and other low-friction particles, suspended in a tough polymer resin.
While adhesion was improved, friction became a problem. While the coefficient
of friction of pure PTFE is as low as 0.02 (similar to ice), the original resin-bonded
coatings often had between 1.5 to 4 times more friction. Over time, the
friction of the resin-bonded coatings has been improved, but not to the level
of pure PTFE. This means the smooth operating feel of the old coated guidewires
was lost, and the tactile feedback sensed by a physician operator is heavier,
hesitant, and jerky. Known as “stick-slip,” this phenomenon is the transition
from static friction to dynamic friction. Some physicians reported that they
could not differentiate between a vascular obstruction and a momentary
resistance of the guidewire.
There
is another potential problem with resin-bonded PTFE: an unknown shelf life. If
the substitute coating is not completely cured, it contains solvents that could
adversely affect packaging, while the original water-based coatings had no such
issue. Given all of this information, it appears that PTFE would be the ideal
coating for guidewires as long as the delamination problem could be resolved
once and for all.
Tags:teflon,ptfe teflon,gudiewire
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