The Occurrence of Implantable Cardioverter Defibrillator Therapies After Generator Replacement in Patients Who No Longer Meet Primary Prevention Indications.

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At the time of generator replacement, after ICD implantation for primary prevention, many patients may no longer meet implantation criteria. We investigated the occurrence of ICD therapy after generator replacement in patients initially implanted ICD for primary prevention. Patients from 3 hospitals undergoing ICD generator replacement, who were initially implanted for primary prevention, were retrospectively evaluated for occurrence of appropriate ICD therapy after generator replacement. Patients were categorized as to whether or not they had appropriate ICD therapy during their first battery life, and by their left ventricular ejection fraction (LVEF) before generator replacement. Data from 168 patients were analyzed, with average follow-up after generator replacement of 41.2 ± 26.5 months. Seventy-six (45.2%) patients had ventricular arrhythmia episodes (>180 beats per minutes) and 63 (37.5%) received appropriate ICD therapy during the first battery life. Among 105 patients without ICD therapy before generator replacement, those with an LVEF ≤35% before ICD replacement had higher occurrence of ICD therapy after generator replacement than patients with an LVEF ≥36%. Patients who no longer met primary prevention ICD indications (no ICD therapy and LVEF ≥36% before generator replacement) showed a lower risk for ICD therapy after generator replacement (11.6% over 5-year follow-up). In patients without ICD therapy before generator replacement, low LVEF (≤35%) contributed to future ICD therapy. In patients initially undergoing ICD implantation for primary prevention, history of ICD therapy during the first battery life and LVEF should be utilized for risk stratification at the time of generator replacement.