Patent ID: 7877139

Claim:
An implantable cardiac stimulation device comprising: a first electrode; a second electrode; a housing containing operational circuitry including: a power capacitor for storing stimulation energy; charging circuitry for charging the power capacitor; control circuitry configured to direct a stimulus operation including charging the power capacitor to a predetermined stimulus voltage and discharging the power capacitor to deliver therapy using at least the first and second electrodes, the control circuitry including a delivery circuit having a high side and a low side, the high side coupling the power capacitor to the first and second electrodes and the low side coupling the first and second electrodes to the testing resistor, the high and low sides each comprising first and second electric switches; and a testing resistor placed such that, when in a testing configuration, a testing current applied between the first and second electrodes passes through the testing resistor; wherein the control circuitry is further configured to direct a testing operation including charging the power capacitor to a testing voltage and closing a high side switch and a low side switch of the H-bridge to apply current from the power capacitor through the first and second electrodes such that at least some current passing between the first and second electrodes also passes through the testing resistor, the testing voltage being less than the stimulus voltage.