The FDA has updated its alert regarding Boston Scientific’s call for providers to check the connections of their patients’ implanted defibrillators, where calcification growth over time can prevent the system from delivering its full electric shock to the heart.
The company’s Endotak Reliance leads are used to wire the implanted pulse generator to the cardiac muscle. Certain models with coils covered in expanded polytetrafluoroethylene—or ePTFE, a nonstick coating similar to Teflon—may require an earlier replacement procedure.
The FDA previously alerted the public to the issue in early August, following Boston Scientific’s first letters to healthcare providers and patients sent out in late July. At that time, the agency said the company had reported 386 serious injuries and 16 deaths associated with the problem.
Now, the FDA’s recommendations have become more explicit: It says that leads demonstrating an electrical resistance of more than 150 ohms should be replaced to avoid failures in defibrillation. The agency said any impedance over that level has been tied to a 1 in 10 risk of blocking potentially lifesaving shocks.
However, the FDA cautioned that, based on how long the device has been implanted and the amount of calcification, otherwise routine extraction procedures could pose serious complications, and patients should be made aware of the risks. The agency recommended that providers reach out to Boston Scientific for technical assistance if needed.
In Boston Scientific’s July 24 letter (PDF), it urged providers to continue with scheduled follow-ups of defibrillation systems with ePTFE leads—through in-person appointments as well as remote monitoring—to note measurements including a 28-day average of low voltage shock impedance. Gradually increasing readings have been linked to growing calcification over a period of years.
In addition to seeking replacements after reaching 150 ohms, the company recommended programming devices to deliver all shocks at maximum energy in single-coil leads with an average impedance greater than 90 ohms and in dual-coil leads with an average higher than 70 ohms.
Reliance leads were first introduced with the nonstick coating in 2002 in order to make the replacement procedure easier. Boston Scientific said it stopped manufacturing ePTFE-coated leads in 2021, following advancements in extraction tools and techniques in addition to ePTFE supply constraints at the time.
According to the FDA’s Class I recall notices, about 247,000 of the devices have been distributed within the U.S., plus another 344,000 internationally.