Influence of myopotential interference on the Wavelet discrimination algorithm in implantable cardioverter-defibrillator

Background: Wavelet is a morphology-based algorithm for detecting ventricular tachycardia. The electrogram (EGM) source of the Wavelet algorithm is nominally programmed with the Can-RV coil configuration, which records a far-field ventricular potential. Therefore, it may be influenced by myopotential interference. Methods: We performed a retrospective review of 40 outpatients who had an implantable cardioverter-defibrillator (LCD) with the Wavelet algorithm. The percent-match score of the Wavelet algorithm was measured during the isometric chest press by pressing the palms together. We classified patients with percent-match scores below 70% due to myopotential interference as positive morphology change, and those with 70% or more as negative morphology change. Stored episodes of tachycardia were evaluated during the follow-up. Results: The number of patients in the positive morphology change group was 22 (55%). Amplitude of the Can-RV coil EGM was lower in the positive morphology change group compared to that in the negative group (3.9 +/- 1.3 mV vs. 7.4 +/- 1.6 mV, P=0.0015). The cut-off value of the Can-RV coil EGM was 5 mV (area under curve, 0.89). Inappropriate detections caused by myopotential interference occurred in two patients (5%) during a mean follow-up period of 49 months, and one of them received an inappropriate LCD shock. These patients had exhibited positive morphology change. Conclusions: The Wavelet algorithm is influenced by myopotential interference when the Can-RV coil EGM is less than 5 mV