Algorithmic detection of the beginning and end of bipolar electrograms: Implications for novel methods to assess local activation time during atrial tachycardia

摘要

Activation mapping is required to effectively ablate atrial tachycardia (AT). Conventional tools to assess local activation time (LAT) are based upon the peak of the bipolar electrogram (B-EGM, LAT_(Peak)) and the maximal negative slope of the unipolar electrogram (U-EGM, LAT_(Slope)). Bipolar electrograms are influenced by wavefront direction, bipole orientation, and inter-electrode spacing causing ambiguity in peak detection, whereas unipolar electrograms are disturbed by the presence of far-field signals. We developed a new algorithm to detect the beginning and end of bipolar electrograms (t_(begin) and t_(end))- Then, we introduced new LAT methods related to the onset of B-EGMs (LAT_(Onset)). the center of mass of B-EGMs (LAT_(CoM)), and the slope of U-EGMs within a pre-defined window (LAT_(Slope-hybnd)).In total 3752 recordings from 31 AT patients were retrospectively analyzed. The signal-to-noise ratio (SNR) for B-EGMs was calculated to differentiate algorithmically high from low quality electrograms (HQ and LQ). In a subset of 328 B-EGMs, five experts validated the r_(begin) as determined by the algorithm by visual rating. The newly developed LAT methods were compared to the conventional LAT methods and to one another (Bland-Altman plots) in both HQ (n = 3003) and LQ EGMs (n = 749). The t_(begin) algorithm was accurate (deviation < ±10 ms) in 96 ± 4% of HQ and 91 ± 8% of LQ B-EGMs. BA plots revealed the following difference (bias) and variation in HQ and LQ EGMs respectively: (1) LAT_(Onset) vs. LAT_(Peak): 27±30 ms and 24±62 ms; (2) LAT_(CoM) vs. LAT_(Peak): 0±16ms and 2 ±38 ms; (3) LAT_(Slope-hybrid) vs. LAT_(Slope): 1±32 ms and 15± 110 ms; (4) LAT_(Onset) vs. LAT_(CoM): 22±24 ms and 18±22 ms; (5) LAT_(Onset) vs. LAT_(Slope-hybrid): 16 ± 18 ms and 13 ±22 ms; and (6) LAT_(CoM) vs. LAT_(Slope-hybrid): 5 ±20 ms and 4± 18 ms. In the present study, we introduced three new methods to assess local activation time in AT, based upon an algorithm detecting accurately the beginning and end of the B-EGM complex. BA analysis of the new methods showed similar variation in high and low quality EGMs, suggesting that they introduce less ambiguity than the conventional peak method. LAT_(Onset) consistently yielded an earlier activation moment. LAT_(Slope-hybrid) - by blanking far-field potentials - seems to be the optimal method for detection of the maximal negative slope in U-EGMs. Interestingly, LAT_(CoM) in B-EGMs coincided with the maximal negative slope in U-EGMs, suggesting its physiological sense and future use. The new LAT methods can be implemented in real-time mapping applications.