Detailed Analysis of the Relation Between Bipolar Electrode Spacing and Far- and Near-Field Electrograms
Résumé
OBJECTIVESThis study sought to evaluate the relation between bipolar electrode spacing and far- and near-fieldelectrograms.BACKGROUNDThe detailed effects of bipolar spacing on electrograms (EGMs) is not well described.METHODSWith a HD-Grid catheter, EGMs from different bipole pairs could be created in each acquisition. This studyanalyzed the effect of bipolar spacing on EGMs in 7 infarcted sheep. A segment was defined as a 2-mm center-to-centerbipole. In total, 4,768 segments (2,020 healthy, 1,542 scar, and 1,206 in border areas, as defined by magnetic resonanceimaging [MRI]) were covered with an electrode pair of spacing of 2 mm (Bi-2), 4 mm (Bi-4), and 8 mm (Bi-8).RESULTSA total of 3,591 segments in Bi-2 were free from local abnormal ventricular activities (LAVAs); 1,630 segmentswere within the MRI-defined scar and/or border area. Among them, 172 (10.6%) segments in Bi-4 and 219 (13.4%)segments in Bi-8 showed LAVAs. In contrast, LAVAs were identified in 1,177 segments in Bi-2; 1,118 segments were withinthe MRI-defined scar and/or border area. Among them, LAVAs were missed in 161 (14.4%) segments in Bi-4 and in 409(36.6%) segments in Bi-8. In segments with LAVAs, median far-field voltage increased from 0.09 mV (25th to 75thpercentile: 0.06 to 0.14 mV) in Bi-2, to 0.16 mV (25th to 75th percentile: 0.10 to 0.24 mV) in Bi-4, and to 0.28 mV (25thto 75th percentile: 0.20 to 0.42 mV) in Bi-8 (p<0.0001). Median near-field voltage increased from 0.14 mV (25th to75th percentile: 0.08 to 0.25 mV) in Bi-2, to 0.21 mV (25th to 75th percentile: 0.12 to 0.35 mV) in Bi-4, and to 0.32 mV(25th to 75th percentile: 0.17 to 0.48 mV) in Bi-8 (p<0.0001). The median near-/far-field voltage ratio decreased from1.67 in Bi-2, to 1.43 in Bi-4, and 1.23 in Bi-8 (p<0.0001).CONCLUSIONSCloser spacing better discriminates surviving tissue from dead scar area. Although far-field voltagesystematically increases with spacing, near-field voltages were more variable, depending on local surviving muscularbundles. Near-field EGMs are more easily observed with smaller spacing, largely due to the reduction of the far-field effect.(J Am Coll Cardiol EP 2019;5:66–77) © 2019 by the American College of Cardiology Foundation.
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