The Food and Drug Administration (FDA) said on Wednesday it is monitoring a potential safety issue involving Boston Scientific Corporation’s ENDOTAK RELIANCE defibrillation leads, following a letter from the company alerting healthcare providers of possible reduced shock efficacy.

Boston Scientific’s ENDOTAK RELIANCE leads are used with implantable cardioverter-defibrillators (ICDs) to deliver pacing and shock therapy to prevent sudden cardiac death.

The affected leads are coated with expanded polytetrafluoroethylene (ePTFE), which the company has linked to issues that could lead to early device replacement and, in severe cases, patient death.

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Boston Scientific ( BSX ) alerted healthcare providers on July 24, warning that calcification of the defibrillation lead coils may gradually increase low-voltage shock impedance (LVSI), potentially impairing the effectiveness of life-saving shocks.

The company emphasized that while the calcification doesn’t compromise physical or electrical lead integrity, the insulation effect can still reduce shock performance.

The company advised continued routine follow-up of patients with affected leads, either in-person or via remote monitoring.

During these checks, clinicians are instructed to examine the 28-day average LVSI, unaffected by shocks, and review all high-voltage shock impedance (HVSI) measurements. Monitoring for rising LVSI patterns may help detect early signs of coil calcification.

If replacement of the lead is considered, Boston Scientific ( BSX ) urged healthcare professionals to carefully weigh the risks of extraction versus abandonment. Leads implanted for over eight years may carry higher risks of complications due to coil calcification.

Complex clinical decision-making may be required in certain scenarios, like defibrillator replacement, and Boston Scientific’s technical services can assist with that.

The company’s investigation found that reversed polarity (RV+) shocks are significantly more prone, 4.5 times more likely, to trigger a high shock impedance alert than initial polarity shocks. This condition also correlates with reduced defibrillator-determined success in delivering therapeutic shocks.

As of July 24, Boston Scientific ( BSX ) reported 386 serious injuries and 16 patient deaths linked to this issue. The FDA has categorized this as a potentially high-risk device problem and is actively reviewing data to assess further regulatory action.

Price Action: BSX stock is trading higher by 1.13% to $104.13 at last check Friday.

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