The following are key points to remember about implantable cardioverter-defibrillators (ICDs) at the end of battery life and opportunities for risk (re)-stratification in ICD recipients:

1. Over 100,000 ICDs are placed every year in the United States, mostly for primary prevention. A quarter of those ICDs are generator replacements for end of battery life.
2. While there is an abundance of randomized controlled trial data to support initial implantation of ICDs, there are relative paucity of clinical data focusing on long-term outcomes in patients undergoing generator exchange for end of battery life.
3. About two-thirds to three-fourths of primary prevention ICD recipients can be expected to reach the end of first battery life without receiving appropriate ICD therapy.
4. According to the National Cardiovascular Data Registry for years 2005-2010, the mean left ventricular ejection fraction (LVEF) at the time of initial ICD implant is 28 ± 11%, while the mean LVEF at the time of generator replacement is 33 ± 14%, suggesting that some patients undergoing generator replacement may no longer meet the primary prevention criterion of LVEF ≤35%. Some studies suggest that there is a significantly lower risk of ICD therapies among those with LVEF improvement after initial implant.
5. As patients age, they may accrue nonarrhythmic mortality risks, which could offset the benefits of the ICD. The risk of nonarrhythmic death increases at a much greater rate than arrhythmic mortality with increasing age.
6. While the likelihood of ICD therapies after generator exchange is lower among those with an uneventful first battery life, the incidence of appropriate therapy still appears to be on the order of 5% annually.
7. Even in patients with improved LV function and no appropriate ICD therapy during the life of the first generator, there continues to be a measurable rate of appropriate ICD therapies after generator replacement. Nota bene, the rate of appropriate ICD therapies is not equivalent to the reduction of arrhythmic mortality.
8. In addition to sudden death prevention, advantages of generator replacement may include monitoring for incidence of asymptomatic atrial fibrillation (potentially triggering a decision to initiate anticoagulation), as well as provision of adjunctive data for heart failure management (e.g., thoracic impedance monitoring for impending heart failure exacerbation).
9. The risk of device infection associated with generator replacement is about twofold higher than at the time of initial ICD implant (2.3% vs. 1.4%). Overall, there is a 4% risk of complications related to generator replacement.
10. With advancing age, the development of frailty, physical, cognitive, and functional impairments could alter the individual risk and benefit calculation before generator replacement. An assessment of patient values and goals of care should be made. Up to one half of patients may not be aware that deactivation of ICD therapies is possible. In patients who have improvement in LVEF, a potential replacement with a cardiac resynchronization therapy (CRT)-pacemaker rather than CRT-defibrillator should be considered.
11. Multicenter prospective registries and randomized clinical trials are needed to assess which patients are most and least likely to benefit from generator replacement.

Keywords: Arrhythmias, Cardiac, Defibrillators, Death, Sudden, Electric Countershock, Heart Failure, Electric Impedance, Geriatrics, Pacemaker, Artificial, Primary Prevention, Risk, Stroke Volume

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