Abstract: A method and apparatus for inducing fibrillation in a patient's heart by delivering an alternating current stimulus to the heart from a DC-to DC converter. The hardware of a conventional implantable cardioverter/defibrillator (ICD) is utilized with a modification to the control algorithms. Particularly, when it is desired to induce fibrillation in a patient's heart, typically during ICD implant defibrillation threshold (DFT) testing, a command is delivered from an external instrument to the ICD to deliver the fibrillation shock. The DC-to-DC converter which is normally used to charge the ICD high voltage capacitors is activated and immediately thereafter a first pair the high voltage output switches of the output stage are closed for about 4 milliseconds. This delivers an initial pulse of one polarity. Following an interval of about 4 milliseconds, a second pair of the high voltage output switches are closed for 4 milliseconds delivering an opposite polarity pulse.

Abstract: A gate driver circuit includes a timing circuit, an anti-Miller surge protection circuit, and charging and discharging circuits for driving an output transistor, such as an IGBT. The anti-Miller surge protection circuit prevents the output transistor from being accidentally turned on. The gate driver circuit provides a high impedance input, so as to allow such a gate driver circuit to be driven by a relatively smaller isolation transformer. Further, the timing circuit in the gate driver circuit of the present invention allows such isolation transformer a relative lower frequency of operation. In one embodiment, the capacitance of the output transistor's gate terminal is used to determine the time constant of the timing circuit.

Abstract: A method and system for testing the integrity of a high voltage output stage and high voltage leads of an implantable cardioverter/defibrillator. The method and system comprises charging one or more high voltage capacitors associated with the high voltage output stage to a predetermined relatively low voltage on the order of 10-20 volts, discharging the high voltage capacitors synchronous with a sensed cardiac event for a predetermined time period, measuring a residual voltage on the high voltage capacitors, and then comparing the residual voltage to a reference voltage to assess the integrity of the output stage and high voltage leads.

Abstract: A method and apparatus for testing the integrity of biphasic and monophasic defibrillator switches in an implantable defibrillator without delivering a shock to the patient. The test circuitry is integrated with and implantable with the defibrillator and provides for the testing of the defibrillator switches without shocking the patient by charging the capacitive defibrillation voltage source to a predetermined level and discharging it through a resistive network and shunting one of the switches to provide an alternate current path to ground, while isolating the test circuitry from the patient. Switch conditions are capable of ascertainment by measuring residual charge, i.e., voltage, on the capacitive voltage source at selected measurement times.