IMPLANTABLE SYSTEM FOR CONSTANT CURRENT PACING

An IMD (104, 200, 302) comprises a case (105, 201) including an output (203, 308) configured to be connected at least to a lead (120, 304), a current generator (CG) circuit (280, 306) configured to generate pacing pulses at the output (203, 308), a switching circuit (226, 310) coupled between the CG circuit (280, 306) and the output (203, 308), one or more capacitors (312) coupled in parallel with the CG circuit (280, 306) and the switching circuit (226, 310) and a control circuit (220, 314) coupled to the CG circuit (280, 306) and the switching circuit (226, 310). The control circuit (220, 314) is configured to manage the CG circuit (280, 306) during a low voltage mode to generate the pacing pulses and control the CG circuit (280, 306) and the switching circuit (226, 310) during a high voltage mode to charge the one or more capacitors (312) and use electrical energy stored in the one or more capacitors (312) to deliver one or more shock pulses to the output (203, 308).