Method and apparatus for reducing the effect of evoked responses on polarization measurements in an automatic capture pacing system

A system for determining an amount of polarization occurring following generation of electrical pulses in heart, the system comprising:

• an implantable cardiac stimulation device to stimulate the heart tissue;
• a first pair of electrical pulses separated by a first amount of time, the first pair of electrical pulses delivered by the implantable cardiac stimulation device;
• means for measuring a magnitude of electrical polarization occurring within the heart tissue resulting from the first pair of electrical pulses;
• means for determining whether the magnitude of electrical polarization exceeds a predetermined threshold;
• if the magnitude of electrical polarization exceeds the predetermined threshold, a second pair of electrical pulses separated by a second amount of time, different than the first amount of time, the second pair of electrical pulses delivered by the implantable cardiac stimulation device;
• and
• means, responsive to a determination that the magnitude of electrical polarization exceeds a predetermined threshold, for re-measuring the magnitude electrical polarization delivered by the second pair of electrical.

A system for determining an amount of polarization occurring following generation of electrical pulses in heart tissue, the system comprising:

• an implantable cardiac stimulation device to stimulate the heart tissue;
• a first pair of electrical pulses separated by a first amount of time, the first pair of electrical pulses delivered by the implantable cardiac stimulation device;
• an electrical polarization measurement unit for measuring a magnitude of electrical polarization occurring within the heart tissue by delivering the first pair of electrical pulses;
• a threshold comparison unit for determining whether the magnitude of electrical polarization exceeds a predetermined threshold,
• if the magnitude of electrical polarization exceeds the predetermined threshold, a second pair of electrical pulses separated by a second amount time, different than the first amount of time, the second pair of electrical pulses delivered by the implantable cardiac stimulation device;
• a control unit, responsive to a determination that the magnitude of electrical polarization exceeds a predetermined threshold, for controlling the electrical polarization unit to re-measure the magnitude electrical polarization resulting from the second pair of electrical pulses.

A method comprising:

• delivering a first pair of electrical pulses to heart tissue, the first pair of electrical pulses separated by a first amount of time;
• measuring a magnitude of electrical polarization resulting from the first pair of electrical pulses;
• if the magnitude of electrical polarization exceeds a predetermined threshold, delivering a second pair of electrical pulses to the heart tissue, the second pair of electrical pulses separated by a second amount of time, the second amount of time being different from the first amount of time;
• re-measuring the magnitude of electrical polarization resulting from the second pair of electrical pulses;
• and
• if the magnitude of electrical polarization resulting from the second pair of electrical pulses is within the predetermined threshold, adjusting an evoked response in accordance with the magnitude of electrical polarization resulting from the second pair of electrical pulses.