Abstract: An extra-cardiovascular implantable cardioverter defibrillator (ICD) having a high voltage therapy module is configured to control a high voltage charging circuit to charge a capacitor to a pacing voltage amplitude to deliver charge balanced pacing pulses. The capacitor is chargeable to a shock voltage amplitude that is greater than the pacing voltage amplitude. The ICD is configured to enable switching circuitry of the high voltage therapy module to discharge the capacitor to deliver a first pulse having a first polarity and a leading voltage amplitude corresponding to the pacing voltage amplitude for pacing the patient's heart via a pacing electrode vector selected from extra-cardiovascular electrodes. The high voltage therapy module delivers a second pulse after the first pulse. The second pulse has a second polarity opposite the first polarity and balances the electrical charge delivered during the first pulse.

Abstract: An extra-cardiovascular implantable cardioverter defibrillator (ICD) having a high voltage therapy module is configured to control a high voltage charging circuit to charge a capacitor to a pacing voltage amplitude to deliver charge balanced pacing pulses. The capacitor is chargeable to a shock voltage amplitude that is greater than the pacing voltage amplitude. The ICD is configured to enable switching circuitry of the high voltage therapy module to discharge the capacitor to deliver a first pulse having a first polarity and a leading voltage amplitude corresponding to the pacing voltage amplitude for pacing the patient's heart via a pacing electrode vector selected from extra-cardiovascular electrodes. The high voltage therapy module delivers a second pulse after the first pulse. The second pulse has a second polarity opposite the first polarity and balances the electrical charge delivered during the first pulse.

Abstract: An extra-cardiovascular implantable cardioverter defibrillator (ICD) having a high voltage therapy module is configured to control a high voltage charging circuit to charge a capacitor to a pacing voltage amplitude to deliver charge balanced pacing pulses. The capacitor is chargeable to a shock voltage amplitude that is greater than the pacing voltage amplitude. The ICD is configured to enable switching circuitry of the high voltage therapy module to discharge the capacitor to deliver a first pulse having a first polarity and a leading voltage amplitude corresponding to the pacing voltage amplitude for pacing the patient's heart via a pacing electrode vector selected from extra-cardiovascular electrodes. The high voltage therapy module delivers a second pulse after the first pulse. The second pulse has a second polarity opposite the first polarity and balances the electrical charge delivered during the first pulse.

Abstract: An extra-cardiovascular implantable cardioverter defibrillator (ICD) having a high voltage therapy module is configured to control a high voltage charging circuit to charge a capacitor to a pacing voltage amplitude to deliver charge balanced pacing pulses. The capacitor is chargeable to a shock voltage amplitude that is greater than the pacing voltage amplitude. The ICD is configured to enable switching circuitry of the high voltage therapy module to discharge the capacitor to deliver a first pulse having a first polarity and a leading voltage amplitude corresponding to the pacing voltage amplitude for pacing the patient's heart via a pacing electrode vector selected from extra-cardiovascular electrodes. The high voltage therapy module delivers a second pulse after the first pulse. The second pulse has a second polarity opposite the first polarity and balances the electrical charge delivered during the first pulse.

Abstract: Techniques are disclosed for modulating the generation of charge current by operational circuitry included in an implantable medical device (IMD) for delivery of an induction stimulation pulse waveform by the IMD. The modulation may include modulating a charging circuit of the operational circuitry to facilitate the regulation of the induction stimulation pulse waveform. The techniques include monitoring an electrical parameter of a charging path during the delivery of the induction stimulation pulse and modulating the charging circuit based on the monitored electrical parameter.

Abstract: An implantable medical device includes a housing, a power source and an operational circuit that is coupled to the power source. The operational circuit includes a first electrode terminal and a second electrode terminal, an output circuit configured to deliver an electrical stimulation therapy through the first and second electrode terminals and a control circuit configured to evaluate an electrical parameter associated with the output circuit and to control generation of the electrical stimulation therapy responsive to a result of the evaluated parameter. Among other things, the implantable medical device may modify a parameter of the therapy delivery in response to a result of the evaluation.

Abstract: An extra-cardiovascular implantable cardioverter defibrillator (ICD) having a high voltage therapy module is configured to control a high voltage charging circuit to charge a capacitor to a pacing voltage amplitude to deliver charge balanced pacing pulses. The capacitor is chargeable to a shock voltage amplitude that is greater than the pacing voltage amplitude. The ICD is configured to enable switching circuitry of the high voltage therapy module to discharge the capacitor to deliver a first pulse having a first polarity and a leading voltage amplitude corresponding to the pacing voltage amplitude for pacing the patient's heart via a pacing electrode vector selected from extra-cardiovascular electrodes. The high voltage therapy module delivers a second pulse after the first pulse. The second pulse has a second polarity opposite the first polarity and balances the electrical charge delivered during the first pulse.

Abstract: Apparatus and methods for generating an induction waveform for performing threshold testing in an implantable medical device are disclosed. Such tests may be performed during the implant procedure, or during a device checkup procedure, or routinely during the lifetime of the device. The threshold test may include induction of an arrhythmia (such as ventricular fibrillation) followed by delivery of therapy at various progressively-increasing stimulation parameters to terminate the arrhythmia. As such, the capability to induce fibrillation within the device is desired. Induction of the arrhythmias may be accomplished via delivery of a relatively low energy shock or through delivery of an induction stimulation pulse to the cardiac tissue timed concurrently with the vulnerable period of the cardiac cycle.

Abstract: An implantable medical device includes a low-power circuit and a multi-cell power source. The cells of the power source are coupled in a parallel configuration. The implantable medical device includes both a low power circuit that is selectively coupled between the first and second cells and a high power output circuit that is directly coupled to the first and second cells in a parallel configuration. An isolation circuit is coupled to the first cell, the second cell and the low power circuit to maintain a current isolation between the first cell and the second cell at least during delivery of current having a large magnitude to the high power output circuit.

Abstract: An implantable medical device includes a low-power circuit, a high-power circuit, and a dual-cell power source. The power source is coupled to a dual-transformer such that each cell is connected to only one of the transformers. Each transformer includes multiple windings and each of the windings is coupled to a capacitor, and the capacitors are all connected in a series configuration. The low power circuit is coupled to the power source and issues a control signal to control the delivery of charge from the power source to the plurality of capacitors through the first and second transformers.

Abstract: An implantable medical device includes a low-power circuit and a multi-cell power source. The cells of the power source are coupled to a transformer in a parallel configuration. The transformer includes multiple secondary windings and each of the windings is coupled to a capacitor that stores energy for delivery of a therapy to a patient. In accordance with embodiments of this disclosure, the low power circuit is configured to control simultaneous delivery of energy from each of the cells to a plurality of capacitors through the transformer.

Abstract: Techniques for controlling charging of a high voltage therapy energy storage component are provided to reduce any undesirable impact from charging during unusual operating conditions. Unusual operating conditions may be caused by any of a number of external factors, including saturation of charging transformer core, circuit failures, capacitor mismatches, or the like, which may result in an unexpected power supply voltage drop or abnormally high currents through device components. An implantable medical device may comprise a power source, a therapy module that includes at least one energy storage component, and a charging module coupled between the power source and the therapy module. The charging module is configured to obtain a measurement representative of an average power drawn from the power source and to terminate charging of the at least one energy storage component based at least on the measurement representative of an average power drawn from the power source.

Abstract: An implantable medical device includes a low-power circuit and a multi-cell power source. The cells of the power source are coupled in a parallel configuration. The implantable medical device includes both a low power circuit that is selectively coupled between the first and second cells and a high power output circuit that is directly coupled to the first and second cells in a parallel configuration. An isolation circuit is coupled to the first cell, the second cell and the low power circuit to maintain a current isolation between the first cell and the second cell at least during delivery currents having a large magnitude that are delivered to the high power output circuit.

Abstract: An implantable medical device includes a low-power circuit, a high-power circuit, and a dual-cell power source. The power source is coupled to a transformer having first and second primary windings, each of which is selectively coupled to the power source and a plurality of secondary windings that are magnetically coupled to the first and second primary windings. The plurality of secondary windings are interlaced along a length of each of the secondary windings. Each of the plurality of secondary transformer windings is coupled to a capacitor, and the capacitors are all connected in a series configuration. The low power circuit is coupled to the power source and issues a control signal to control the delivery of charge from the power source to the plurality of capacitors through the first and second transformers.

Abstract: An implantable medical device includes a low-power circuit, a high-power circuit, and a multi-cell power source. The implantable medical device delivers stimulation therapy to cardiac tissue. The cardioversion energy is delivered across through electrodes that are coupled to terminals of the high-power circuit. A protection circuit for protecting the low-voltage circuit components from high voltage pulses includes a first segment coupled to a first of the electrodes and a second segment coupled to a second of the electrodes, the components of the low-voltage circuit being coupled to the transthoracic protection circuit portion, and a reference potential corresponding to a ground potential, wherein the first and second segments of the transthoracic protection circuit portion are coupled to the reference potential in a parallel configuration.

Abstract: Recent advancements in power electronics technology have provided opportunities for enhancements to circuits of implantable medical devices. The enhancements have contributed to increasing circuit miniaturization and an increased efficiency in the operation of the implantable medical devices. The therapy delivery circuits and techniques of the disclosure facilitate generation of a therapy stimulation waveform that may be shaped based on the patient's physiological response to the stimulation waveform. The generated therapy stimulation waveforms include a stepped leading-edge that may be shaped having a varying slope and varying amplitudes associated with each of the segments of the slope. Unlike the truncated exponential waveform delivered by the conventional therapy delivery circuit which is based on the behavior of the output capacitors (i.e., i=C(dV/dt)), the stimulation waveform of the present disclosure may be dynamically shaped as a function of an individual patient's response.

Abstract: An implantable medical device includes a housing, a power source and an operational circuit that is coupled to the power source. The operational circuit includes a first electrode terminal and a second electrode terminal, an output circuit configured to deliver an electrical stimulation therapy through the first and second electrode terminals and a control circuit configured to evaluate an electrical parameter associated with the output circuit and to control generation of the electrical stimulation therapy responsive to a result of the evaluated parameter. Among other things, the implantable medical device may modify a parameter of the therapy delivery in response to a result of the evaluation.

Abstract: This disclosure provides an implantable medical device comprising a power source a therapy module that includes at least one energy storage component, and a charging module coupled between the power source and the therapy module. The charging module is configured to control charging of the at least one energy storage component of the therapy module. The charging module may be further configured to detect a condition indicative of improper charging, to detect a condition indicative of the implantable medical device being subjected to fields generated by an magnetic resonance imaging (MRI) device, and to terminate charging of the at least one energy storage component when both the condition indicative of improper charging and the condition indicative of the implantable medical device being subjected to fields generated by the MRI device are detected.

Abstract: An implantable medical device includes a low-power circuit, a high-power circuit, and a dual-cell power source. The power source is coupled to a dual-transformer such that each cell is connected to only one of the transformers. Each transformer includes multiple windings and each of the windings is coupled to a capacitor, and the capacitors are all connected in a series configuration. The low power circuit is coupled to the power source and issues a control signal to control the delivery of charge from the power source to the plurality of capacitors through the first and second transformers.

Abstract: An implantable medical device includes a low-power circuit, a high-power circuit, and a multi-cell power source. The implantable medical device delivers stimulation therapy to cardiac tissue. The cardioversion energy is delivered across through electrodes that are coupled to terminals of the high-power circuit. A protection circuit for protecting the low-voltage circuit components from high voltage pulses includes a first segment coupled to a first of the electrodes and a second segment coupled to a second of the electrodes, the components of the low-voltage circuit being coupled to the transthoracic protection circuit portion, and a reference potential corresponding to a ground potential, wherein the first and second segments of the transthoracic protection circuit portion are coupled to the reference potential in a parallel configuration.