Automatic stimulus artifact reduction for accurate analysis of the heart's stimulated response

A method of electrically stimulating a patient's heart and analyzing the heart's stimulated response, comprising the steps of:

• generating triphasic cardiac stimulation pulses having first and third phases of one polarity and a second phase of the opposite polarity,
• timing the generation of said triphasic cardiac stimulation pulses so that at least one pulse occurs during the refractory period of the heart in each of a plurality of cardiac cycles,
• measuring a stimulation polarization artifact resulting from the generation of said triphasic cardiac stimulation pulses during the refractory period of the heart, and
• adjusting the amplitude and polarity of the current flow during at least one phase of said triphasic cardiac stimulation pulses to reduce the amplitude of said stimulation polarization artifact.

An apparatus, adapted to be implanted in a patient, for electrically stimulating the heart and analyzing the heart's stimulated response, comprising:

• means for generating triphasic cardiac stimulation pulses having a first and third phase of one polarity and a second phase of the opposite polarity,
• means for timing the generation of said triphasic cardiac stimulation pulses so that at least one pulse occurs during the refractory period of the heart in each of a plurality of cardiac cycles,
• means operative during the refractory period of the heart for measuring a stimulation polarization artifact resulting from the generation of said triphasic cardiac stimulation pulses, wherein during a period lasting from ten to fifty milliseconds following said stimulation pulse, said measuring means derives a parameter characterizing the polarity of the stimulation polarization artifact,
• means operative to adjust the amplitude and polarity of the current flow during at least one phase of each of said triphasic cardiac stimulation pulses for reducing the amplitude of said stimulation polarization artifact,
• means for measuring the values of underlying physiological signals occurring concurrently with said stimulation polarization artifact during the refractory period, and
• means for correcting said stimulation polarization artifact to remove said underlying physiological signal values therefrom.

A method of electrically stimulating a patient's heart and analyzing the heart's stimulated response, comprising the steps of:

• generating triphasic cardiac stimulation pulses having first and third phases of one polarity and a second phase of the opposite polarity,
• timing the generation of said triphasic cardiac stimulation pulses so that at least one pulse occurs during the refractory period of the heart in each of a plurality of cardiac cycles,
• measuring a stimulation polarization artifact resulting from the generation of said triphasic cardiac stimulation pulses during a period lasting from ten to fifty milliseconds following said stimulation pulse within the refractory period of the heart,
• deriving a parameter characterizing the polarity of the stimulation polarization artifact, and
• adjusting the amplitude and polarity of the current flow during at least one phase of each of said triphasic cardiac stimulation pulses to reduce the amplitude of said stimulation polarization artifact.