RESUMO
Polarization artifacts that result from pacing may interfere with analysis of paced evoked responses during, e.g., automatic threshold tracking. We have developed a method for reduction of such artifacts that relies on the introduction of pacing stimuli during the refractory period of unipolar or bipolar paced captured beats after previous identification of a refractory period "template" or baseline. The refractory pacing stimuli cannot capture the heart, and thus any deviation from the template is due to polarization artifact alone. The artifact amplitude is measured and the precharge duration of the triphasic stimulus waveform is changed each time until artifact is minimized, as detected by repeated reversals in the polarity of the polarization artifact. In a series of 11 patients with unipolar and bipolar permanent pacing leads, mean initial artifact before balancing was 1.44 +/- 0.84 mV, which was reduced to 0.44 +/- 0.30 mV after balancing (P = 0.001). Initial precharge duration was 3.2 msec by design; mean final precharge duration was 3.30 +/- 0.34 msec. This algorithm is universally applicable in permanent pacing systems, as it is valid in unipolar and bipolar pacing and it does not require an intrinsic cardiac rhythm.
