Patent ID: 8244349

Claim:
An implantable cardioverter-defibrillator (ICD) system including a lead system coupled to a canister, the canister housing operational circuitry, the ICD comprising: a plurality of stimulus delivery electrodes consisting of a first electrode disposed on the lead system and a second electrode that takes the form of an electrically conductive surface that makes up all or a portion of the surface of the canister; implantable operational circuitry coupled to the first and second electrodes such that first and second selectable stimulus delivery configurations are available for use by the operational circuitry; the improvement comprising: the operational circuitry being configured to determine whether stimulus is currently needed and if so, delivering the currently needed stimulus by: determining whether a successful stimulus has previously been delivered; and, if so, using a stimulus delivery configuration for a most recent successful stimulus delivery to deliver the currently needed stimulus; otherwise delivering the currently needed stimulus using a predetermined stimulus delivery configuration chosen from the first and second configurations; wherein: the operational circuitry is configured to provide therapy as a biphasic waveform having first and second phases; the first configuration uses the first electrode as the positive electrode during the first phase of the biphasic waveform and as the negative electrode during the second phase of the biphasic waveform; and the second configuration uses the second electrode as the positive electrode during the first phase of the biphasic waveform and as the negative electrode during the second phase of the biphasic waveform.