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

摘要

An initial polarization measurement is made by applying two electrical calibration pulses to the heart separated by a first time period. The first pulse is sufficient to generate an evoked response. The second pulse is applied during a refractory period associated with the first pulse. A polarization measurement is made following the second pulse and compared against a predetermined threshold. If the polarization does not exceed the threshold, the evoked response is adjusted using the measured polarization and an automatic capture function of the pacing system is programmed using the adjusted evoked response. However, if the polarization exceeds the threshold, a second pair of pulses are applied to the heart separated by a second time period, different from the first time period. A second polarization measurement is made after the second pulse and, if the second measured polarization does not exceed the predetermined threshold, the evoked response is adjusted using the newly measured polarization and the automatic capture function is programmed using the adjusted evoked response. If the polarization measurement again exceeds the predetermined threshold, the automatic capture function is disabled. Alternatively, a sequence of three pulses are applied to the heart and polarization is measured after the second and third pulses or calibration pulses may be applied after intrinsic depolarization events such as QRS complexes.