Do battery depletion indicators reliably predict the need for pulse generator replacement?

Abstract

The aim of this study was to test the validity of battery depletion indicators to forecast end of service (EOS) in dual chamber pulse generators (PG). Two additional approaches for prediction of EOS were evaluated as well: the real-time telemetry of cell impedance and a battery stress test (BST) that used a transitory increase in pacing rate. The study population consisted of 119 patients with Intermedics dual chamber PG models Cosmos II and Relay, in which cell impedance had exceeded 2.5 k omega. The patients were followed in 6-month intervals. If the interrogation of the PG or the BST prompted the appearance of the intensified follow-up indicator (IFI), the next follow-up was scheduled within 2 months. PG replacement was performed on physician's discretion or immediately on appearance of the elective replacement indicator (ERI), regardless of the method of ERI provocation. During a period of 2 years/and 9 months, 33 patients underwent PG replacement. Out of 21 patients with positive ERI indicators, only 5 had positive warning indicators of approaching battery depletion in the preceding follow-up (IFI during BST, n = 4; ERI during BST n = 1). The majority of patients (n = 16, 76%) revealed ERI without prior activation of IFI, neither spontaneous nor during the BST. Four of these 16 ERI-positive patients had cell impedance values far below the ERI limits of the manufacturer. Based on battery depletion indicators, an exact prediction of EOS of dual chamber pacemakers is not possible. Measuring battery impedance allows for a statistical estimation of remaining service life but it may be misleading in the individual case. A BST that is based on a temporary increase of pacing rate is invalid in forecasting battery depletion. As activation of the ERI can trigger an abrupt change to the VVI backup mode, pacemaker dependent patients with low programmed basic pacing rates may be hemodynamically compromised by an unexpected activation of ERI. Close monitoring intervals and PG replacement before appearance of the ERI is recommended in those patients.