Abstract: In an implantable cardioverter-defibrillator and/or pacemaker, each having DDD pacing capabilities, an improved method of operation is described which dramatically increases the longevity of the implanted device by conserving battery power. The method comprises deactivating at least one unnecessary, power-consuming feature of the device until such feature is needed and then reactivating said feature only for so long as it is required by the patient. In a particular embodiment, the atrial sense amplifier is deactivated during normal operation of the implantable device, resulting in single-chamber sensing and pacing. Upon the occurrence of a predefined event, indicative of a need for dual-chamber sensing and pacing, the atrial sense amplifier is reactivated, the need for DDD pacing confirmed, and if appropriate, DDD pacing is begun. Once the patient's heart rate has returned to an acceptable level, the atrial sense amplifier is again deactivated and single-chamber sensing/pacing continued.

Abstract: The implant guiding programmer is configured to automatically determine the defibrillation threshold (DFT) for a particular patient and to further determine an optimal implantation configuration for an implantable cardioverter fibrillator (ICD). In one implementation, to determine the DFT for the patient, the programmer correlates patient specific data with a predictive data base containing DFT information for an entire population of patients. The patient specific data includes the age, gender, heart size, chest size and medical history of the patient. The predictive database provides information correlating patient DFT with various ranges of the patient specific data for an entire population of data. In this manner, the programmer quickly approximates the DFT for the particular patient based upon the age, gender, heart size and medical history of the patient.