Method and device for delivering multi-phase defibrillation therapy

An implantable medical device, comprising:

• electrodes configured to sense cardiac events;
• a battery and a single charge storage capacitor;
• one or more processors configured to:
• declare a ventricular fibrillation (VF) episode based on the cardiac events;
• charge a single charge storage capacitor utilizing the battery;
• deliver a multi-phase VF therapy that includes phase I and II therapies, wherein:
• a) during the phase I therapy, a combination of two or more medium voltage (MV) shocks are delivered entirely from the single charge storage capacitor;
• and
• b) during the phase II therapy, a low voltage pulse train is delivered at least partially from the single charge storage capacitor.

An output control system for use in an implantable medical device, comprising:

• an output configured to be connected to a lead;
• a charging circuit;
• a capacitor switchably coupled to the charging circuit;
• a switching circuit coupled between the capacitor and the output;
• an output control circuit configured to generate a control signal that includes control pulses that control the switching circuit to switchably connect the capacitor to the output, the output control circuit configured to vary a duty cycle of the control pulses in a manner that defines a shape of an effective waveform for one or more shocks.

An implantable medical device, comprising:

• electrodes configured to sense cardiac events;
• a charging circuit;
• a capacitor switchably coupled to the charging circuit;
• a switching circuit coupled between the capacitor and the output;
• an output control circuit configured to generate a control signal that includes control pulses that control the switching circuit to switchably connect the capacitor to the electrodes, the output control circuit configured to vary a duty cycle of the control pulses in a manner that defines a shape of an effective waveform for one or more shocks.

A method, comprising:

• sensing cardiac events of a heart;
• utilizing one or more processors to declare a ventricular fibrillation (VF) episode based on the cardiac events and initiate charge of a capacitor based on the declaration of the VF episode;
• switchably connect the capacitor to the output based on a control signal;
• generate the control signal to includes control pulses having a duty cycle;
• varying the duty cycle of the control pulses in a manner that defines a shape of an effective waveform for one or more shocks.

An implantable medical device, comprising:

• electrodes configured to sense cardiac events;
• a charging circuit;
• a reconfigurable capacitor bank that includes capacitors;
• a switching circuit coupled between the reconfigurable capacitor bank and the output;
• and
• a parallel/series reconfiguration (PSR) circuit that interconnects the capacitors in parallel and series configurations, the PSR circuit configured to switch between the parallel and series configurations during delivery of a shock to define an ascending stepped waveform.

A method, comprising:

• sensing cardiac events of a heart;
• utilizing one or more processors to declare a ventricular fibrillation (VF) episode based on the cardiac events and initiate charge of a reconfigurable capacitor bank based on the declaration of the VF episode;
• switchably connect capacitor of the reconfigurable capacitor bank to the output to deliver a shock;
• and
• during delivery of the shock, connecting the capacitors in a parallel configuration and switching from the parallel configuration to a series configuration to define an ascending stepped waveform for the shock.