Use of the Elective Replacement Indicator in Predicting Time of Automatic Implantable Cardioverter-Defibrillator Battery Depletion

The elective replacement indicator (ERI) of an automatic implantable cardioverter-defibrillator (AICD) is intended to be utilized as strict criteria for the appropriate timing of pulse generator replacement. The manufacturer's newest recommendations suggest replacement within 3 months post-ERI attainment and this applies to both AID-B units and the latest Ventak models currently being implanted with expectations or increased battery longevity. Twelve patients with the AID-B model were prospectively evaluated in regard to (a) time from attainment of ERI to generator exchange and (b) total battery life with respect to the presence or absence of spontaneous discharges. In the overall group, the ERI was reached at 18.9 +/- 3.9 months (mean +/- standard deviation). The time from ERI attainment to generator exchange due to battery depletion was 8.1 +/- 5.1 months, and total battery life was 27.3 +/- 3.1 months. In the group with spontaneous discharges, the duration of time (months) post-ERI to generator exchange was 5.7 +/- 2.6 but was 11.4 +/- 6.1 in the others (P = 0.052); battery life was 25.7 +/- 2.4 and 29.4 +/- 2.7, respectively (P = 0.03). We conclude that the current ERI recommendation seems overly conservative in planning generator exchange for patients without the occurrence of spontaneous discharges and appropriate for patients with such discharges.