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A circuit for determining lead impedance during the time a pacing or other stimulating electrical pulse is being delivered measures current and voltage simultaneously to check for open circuits or short circuits based on different thresholds. The detection of a bad lead can force a double pulse to b

A circuit for determining lead impedance during the time a pacing or other stimulating electrical pulse is being delivered measures current and voltage simultaneously to check for open circuits or short circuits based on different thresholds. The detection of a bad lead can force a double pulse to be delivered in real time in a unipolar configuration. Switching from unipolar to bipolar configuration based on detecting a bad bipolar circuit can be supported.

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[ What is claimed is:] [1.] A medical electrical lead measurement circuit for use inside a hermetically sealed housing of an implantable pulse generator(IPG), said IPG having a connector member for electrically connecting a medical electrical lead conductor to a discharge circuit element, said eleme

[ What is claimed is:] [1.] A medical electrical lead measurement circuit for use inside a hermetically sealed housing of an implantable pulse generator(IPG), said IPG having a connector member for electrically connecting a medical electrical lead conductor to a discharge circuit element, said element for providing current through said lead conductor to tissue in a body with which said lead is designed to be electrically connected by an electrode to be associated with said tissue, and also having means for connecting said lead conductor and said discharge means to said medical electrical lead measurement circuit said circuit further comprising:Voltage amplifier (VA) means for amplifying a voltage variation found on said lead conductor during a stimulating pulse delivered through said lead conductor from said discharge circuit element,Derivative Detector circuit means for receiving an output from said VA amplifier and generating at a Derivative Detector's output a current proportional to a slope in the variation found on said VA amplifier output over a time determined by and substantially commensurate with the length of said pacing pulse,Current Amplifier circuit connected to said discharge means across a resistor circuit member for generating a current proportional to the voltage on said discharge means during said stimulating pulse, andcircuit comparator means for producing a signal indicating a condition of said lead conductor based on a comparison of the outputs of said Derivative Detector and said Current Amplifier.