Condition monitoring pacer

An autodiagnostic pacer for cardiac condition monitoring comprising a generating means for providing cardiac stimulation signals, said generating means including a pulse generator and a constant current driver, the output of said constant current driver being coupled between first and second terminals to cardiac tissue along a single current path, means for sensing cardiac condition across said two terminals along said single current path, said means including a differential amplifier means coupled across said first and second terminals, sampling means for generating first and second time displaced sampling intervals at expected response time of a properly responding cardiac tissue for sampling the cardiac condition signals sensed by said differential amplifier, comparing means for comparing the output of said sampling means to predetermined threshold levels, said sampling conditions occurring between successive stimulation pulses in accordance with expected biphasic cardiac response, said comparing means providing an output pulse in the event said comparison indicates the input signal exceeds said threshold levels, a multistage counter, said multistage counter preset to provide an output when said counter reaches a predetermined count condition, means coupling said stimulating signals to said counter for causing said counter to step in accordance with each of said stimulating signals, means coupling the output of said comparator to said counter for resetting said counter, means responsive to said counter achieving said predetermined stage for providing an output signal, said output signal representative of failure of said comparison threshold to be met for a predetermined number of times thereby indicating a specific failure condition of said pacer, and means responsive to said output signal for injecting a supplemental signal into said constant current driver for appearance on said output electrodes, said signal being observable on an EKG trace.

A pacer for cardiac stimulation and cardiac condition monitoring comprising electrode means for both stimulation and sensing, generating means coupled to said electrode means for generating a cardiac stimulation signal, sensing means coupled to said electrode means for sensing cardiac events, said cardiac events including a stimulated cardiac signal produced in response to said stimulation signal, said sensing means including means for generating sampling signal coincident with at least a portion of said stimulated cardiac signal produced in response to said stimulation signal, a gating means for producing an output signal in response to said coincidence, and a monitoring means coupled to said gating means and responsive to a lack of coincidence between said sampling signals and said cardiac signal for providing a clinically discernible first warning signal, said cardiac events further including a spontaneous response, produced by a natural heartbeat, said sensing means including means inhibiting the generation of said stimulating signal for a predetermined period of time after the occurrence of a natural heartbeat, means for detecting the presence of said stimulation signal within at least a portion of said predetermined period, indicative of a malfunction, said monitoring means responsive to said means for detecting for generating a second warning signal, said second warning signal being time displaced from said stimulation signal and said first warning signal and thus time discernible on said electrocardiogram.

A pacer for cardiac stimulation and cardiac condition monitoring comprising a single current path for both stimulation and sensing, generating means coupled to said single current path for generating a cardiac stimulation signal, sensing means coupled to said signle current path for sensing cardiac events, said cardiac events including a biphasic cardiac signal produced in response to said stimulation signal, said sensing means including means for generating sampling signals coincident with at least a portion of both phases of a biphasic cardiac signal produced in response to said stimulation signal, gating means for producing an output signal in response to said coincidences, and a monitoring means coupled to said gating means responsive to a lack of coincidence between both said sampling signals and the respective phase signals of said biphasic signal for providing a first warning signal time displaced from said stimulation signal and thus clinically discernible, said cardiac event further including a spontaneous response, produced by a natural heartbeat, and said sensing means included means inhibiting the generation of said stimulating signal for a predetermined period of time after the occurrence of a natural heartbeat, means for sensing the presence of said stimulation signal within at least a portion of said predetermined period, indicative of a malfunction, said monitoring means responsive to said means for sensing for generating a second warning signal, said second warning signal time displaced from said first warning signal and thus time discernible on said electrocardiogram, said monitoring means including a multistage counting means having a preset maximum counting level, means for applying said stimulating signals to said counter for stepping said counter from one stage to the next, means for introducing the output of said gating means to said counting means for reset, and switching means responsive to the achievement of said level prior to resetting said counting means for introducing said first warning signal to said generating means, said switching means being a bistable component set into a first condition by said counting means achieving said level, further means for generating said first warning signal in predetermined timed spacing from said stimulation signal, and further gating means responsive to the set output of said bistable component for passing said first warning signal to said generating means, said stimulating signal and said first warning signal then appearing at the output of said generating means.