Safety Notice Regarding Medtronic Cobalt XT, Cobalt, and Crome Implantable Cardioverter Defibrillators (ICDs) and Cardiac Resynchronization Therapy Defibrillators (CRT-Ds)

Publication Date: June 23, 2022

Impacted Models

Background

During high-voltage (HV) therapy for Cobalt and Crome implantable cardioverter defibrillators (ICDs) and cardiac resynchronization therapy defibrillators (CRT-Ds), there is the potential for reduced shock energy (~79% of programmed energy). Medtronic has identified 27 devices (0.03% of devices distributed worldwide) that have experienced a reduced-energy shock, which is accompanied by a Short Circuit Protection (SCP) alert. To date, there have been no reports of permanent harm or death due to this issue. The likelihood of these events increases over time, and Medtronic projects 0.18% of devices may experience such an event within 24 months of service life, with a risk of patient mortality estimated to be 0.002%. A device software update is anticipated to be available beginning the third/fourth quarter of calendar year 2022. Once installed, this software update, in addition to the programming recommendations, should resolve occurrences of these events.

Issue Summary

The potential for reduced shock energy is the result of a safety feature, Short Circuit Protection (SCP), that was designed to truncate delivered energy to protect the device when unexpected current is detected during high-voltage (HV) therapy; this feature was originally created to address potential lead integrity issues. A value of exactly zero (0) ohms for an RV Defib lead impedance alert is an indication that an SCP event has occurred. These alerts occur simultaneous with HV delivery, and the device will issue an audible tone and wireless CareAlert.

If truncation occurs as a result of a device-related SCP event in this advisory, the resulting therapy would be a monophasic shock, due to elimination of the second phase of the biphasic shock, and delivered energy during the episode would be ~79% of the programmed energy (~32J if programmed for 40J). This is NOT a lead issue.

For comparison, SCP events due to a lead integrity issue are typically evidenced by <10J delivered. In both device-related and lead-related SCP events, the episode text for a treated episode will report lead impedance <20 ohms (see Table below).

*SCP CareAlerts are available only in the Cobalt/Crome family of devices

Potential harms related to device-related Short Circuit Protection event include:

1. Failure to terminate the arrhythmia due to reduced delivered HV energy
2. Theoretical risk (not clinically seen) of pro-arrhythmia – higher in the AX>B configuration or if Active Can is disabled due to possible current leak at the RV coil (minimized with programming changes – see below)
3. Provider misinterpretation of the SCP alert as a lead integrity issue, with subsequent unindicated lead replacement

Medtronic has also released a white paper illustrating defibrillation efficacy estimates related to this advisory.

Medtronic Recommendations

• Prophylactic device replacement is NOT recommended.
• Remote monitoring with normal frequency of follow-up per clinic protocol, with patients' next follow-up scheduled in-clinic to allow for device reprogramming (if necessary):
  • Programming all HV therapies to 40J with a B>AX pathway and Active Can/SVC Coil set with Active Can enabled across all therapy zones.
• Contact Medtronic Technical Services (1-800-723-4636) or your local representative if an RV Defib Lead Impedance Alert reporting zero (0) ohms is observed – as this is an indicator that an SCP event was detected during HV therapy.
  • Consider device replacement only after observing and confirming the cause of an SCP event with a Medtronic representative, with the understanding a device has an ~81% probability of delivering subsequent reduced-energy shocks, and with the understanding an update for implanted devices is anticipated to be available beginning third quarter/fourth quarter of calendar year 2022.
    
    Note: The software update will require an additional in-clinic follow-up in order for it to be installed into a patient's device.
  • After an SCP event, pacing, sensing, episode detection, and anti-tachycardia pacing (ATP) therapies are not impacted; additionally, HV charging, battery longevity and Bluetooth telemetry are not impacted.

HRS Recommendations

HRS strongly encourages its members to read the Medtronic Safety Notification. The associated white paper provides details regarding how defibrillation efficacy estimates were obtained. If an SCP event occurs, HRS recommends careful analysis of benefits and risks if device replacement is considered (with the expectation that the planned software update with recommended programming should resolve the issue).

Reporting Adverse Reactions or Quality Problems

Adverse reactions or quality problems experienced with the use of this product may be reported to the FDA's MedWatch Adverse Event Reporting program either online, by regular mail or by fax.

• Complete and submit the report Online: www.fda.gov/medwatch/report.htm.
• Regular Mail or Fax: Download form www.fda.gov/MedWatch/getforms.htm or call 1-800-332-1088 to request a reporting form, then complete and return to the address on the pre-addressed form or submit by fax to 1-800- FDA-0178.

For additional questions, contact your local Medtronic Representative or Medtronic Technical Services at 1-800-723-4636.