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Background: Boston Scientific (Marlborough, MA, USA) implantable cardioverter-defibrillators (ICDs) and cardiac resynchronization therapy defibrillators (CRT-Ds) manufactured between 2008 and 2014 are potentially subject to premature battery depletion through a low-voltage capacitor malfunction occurring as a result of hydrogen buildup within the device. Although some of these devices are currently under advisory, other devices manufactured during this timeframe carry a lower risk of the same malfunction. These same devices are known to have superior longevity in general, and the overall mean lifespan of the devices remains long., Methods: All patients implanted or followed at our two centers who experienced premature battery depletion and had a Boston Scientific ICD or CRT-D potentially at risk for low-voltage capacitor malfunction were studied retrospectively., Results: Nineteen out of 838 patients (2.3%) with devices potentially at risk have had premature battery depletion: 5.7% of those under advisory and 1.1% of those not under advisory. None of our patients had compromised therapy, and all had >27 days of projected battery longevity remaining., Conclusions: Undetected premature battery depletion in this population of ICDs has the potential to expose a patient to an interval of time where the device is unable to provide therapy. However, with enrollment in remote monitoring, regular follow-up, and attention to audible alerts, the risk of therapy loss due to low-voltage state can be effectively mitigated. For these reasons, prophylactic generator replacement is not recommended., (© 2019 Wiley Periodicals, Inc.)

Patients receiving minimally symptomatic shocks from their implantable cardioverter defibrillators were studied prospectively using transtelephonic ECG loop monitoring. The time course to the first subsequent shock was evaluated. Twenty-nine consecutive patients who received a shock preceded by mild palpitations or no symptoms were given a transtelephonic ECG loop monitor and instructed to activate the monitor if a subsequent shock occurred. Kaplan-Meier analysis was used to quantitate the time to first shock during the study period. The point estimate +/- standard error of patients receiving a shock during the study period was 31% +/- 9% at 30 days, 41% +/- 9% at 60 days, and 60% +/- 9% at 120 days. The ECG was successfully transmitted in 7 of 13 patients who had shocks in the 60-day monitoring period, and demonstrated inappropriate shocks in 6 of 7. Determination of the cause of shock led to a change in subsequent management in all 7 patients. We conclude that the incidence of inappropriate shocks may be higher than estimated previously in patients with minimal symptoms prior to the shock. There are thousands of patients with implantable cardioverter defibrillators that have no storage function for treated tachycardias; transtelephonic ECG loop monitoring can determine the cause of implantable cardioverter defibrillator discharge in these patients, and the diagnosis is invaluable in their management.