Importance of bipolar electrode orientation on local electrogram properties

Background The direct effect of bipolar orientation on electrograms (EGMs) remains unknown. Objective The purpose of this study was to examine the variation of EGMs with diagonally orthogonal bipoles. Methods The HD-32 Grid catheter (Abbott, XXXX, MN) can assess the effect of bipolar orientation while keeping the interelectrode distance and center unchanged. Seven sheep with anterior myocardial infarction were analyzed using diagonally orthogonal electrode pairs across splines by comparing local EGMs from each pair of opposing electrodes {ex. A1-B3 (southeast direction [SE]) vs A3-B1 (northeast direction [NE])}. Results A total of 4084 EGMs (1 in each direction) were analyzed for 2042 sites (544 in the infarcted area, 488 in the border area, and 1010 in the normal area). The higher and lower voltages measured using each pair of opposing electrodes significantly differed (1.10 mV [0.43–2.56 mV] vs 0.69 mV [0.28–1.58 mV]; P P 1.5 mV in NE stayed in the same voltage range as those in SE. However, only 348 of 624 (55.8%) sites with the voltage 0.5–1.5 mV in NE stayed in the same range as those in SE. Local ventricular abnormal activities (LAVAs) were detected in 592 of 2042 (29.0%) sites in total, frequently distributed in the border area. A total of 177 (29.9%) LAVAs were missed in one direction and 180 (30.4%) in the other. When the LAVAs detected in NE (n = 415) are defined as the reference, 235 of 415 (56.6%) matched with those detected in SE. Conclusion The bipolar voltage and distribution of LAVAs may differ significantly between diagonally orthogonal bipolar pairs at any given site.