Significant Discrepancy Between Estimated and Actual Longevity in St. Jude Medical Implantable Cardioverter‐Defibrillators

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Longevity of a cardiovascular implantable electronic device (CIED) may be defined as the interval between device implantation and detection of the end‐of‐service indicator (or elective replacement indicator [ERI]).1 Longevity of implantable cardioverter‐defibrillators (ICDs) has important clinical implications for patient care and outcomes. Manufacturers specify the expected longevity of various models based on a specific set of nominal conditions and programmed parameters. Various factors affect the actual longevity of implanted ICDs (device survival) including bradycardia parameters such as pacing mode, outputs, lead impedances, and pacing percentage and tachycardia therapies such as number of high‐voltage charges and shocks. Several recent studies have reported on the real‐life longevity of different types of ICDs of various manufacturers.2
Specific algorithms in implantable devices can calculate the estimated time remaining in the life of the device by incorporating device factors such as battery voltage and charge time, and patient factors such as pacing percentages and pacing outputs. Such patient‐specific real‐time longevity estimates have been available in pacemakers for several years. They have recently been introduced in ICDs by most manufacturers. The specific algorithm for longevity calculation in ICDs is manufacturer‐specific and proprietary. Real‐time longevity estimates are most useful as the battery of the device approaches depletion, and, if accurate, can assist physicians in making clinical decisions such as frequency of follow‐up, planning for generator replacement, and conveying expectations to patients. There have been no studies evaluating the accuracy of real‐time longevity estimates in devices. We sought to evaluate the accuracy of the real‐time longevity estimate in St. Jude Medical (SJM) ICDs, especially as the device battery approaches depletion.
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