Background: Accurate mapping of the compact atrioventricular (AV) node is critical during ablation of a range of arrhythmias.
Objective: The purpose of this multicenter prospective study was to test the hypothesis that microelectrode (ME)-embedded catheters more accurately define the near-field compact AV node compared to conventional catheters.
Methods: For the mapping phase, detailed AV junction maps were created in 47 patients using an ME-embedded catheter. His electrograms (EGMs) detected by conventional electrodes (Hisc) and by ME (Hisμ) were annotated. For the ablation phase, AV nodal ablation (Qmode 50 W) was performed in 10 patients after pacemaker implantation, with initial Hisc-only ablation in group 1 (n = 6) and initial Hisμ ablation in group 2 (n = 4). For the clinical phase, a prospective registry of parahisian tachycardia using QDOT was obtained.
Results: In the mapping phase, 7.0 ± 5.4 Hisc and 8.0 ± 5.6 Hisμ points were acquired per map (n = 47). Hisμ cloud was smaller and more proximally located than Hisc cloud: (99.4 ± 74.7 mm2 vs 197.6 ± 110.6 mm2; P = .0008). Hisμ EGMs had larger amplitudes than Hisc EGMs (0.40 ± 0.38 mV vs 0.16 ± 0.1 mV; P = .0002). In the ablation phase, for group 1: Hisc-only ablation never resulted in AV block, whereas Hisμ ablation resulted in AV block after limited ablation in all patients (after 13.3 ± 9.2 s); and for group 2: Hisμ ablation always resulted in AV block after 1 application (after 14.3 ± 10.3 s). In the clinical phase, a Hisμ-avoidance strategy could avoid AV block in a prospective registry of 11 patients.
Conclusion: ME more accurately defines the region of the compact node, and ablation in this region is associated with a high risk for AV block. ME-based mapping has the potential to significantly enhance ablation safety and efficacy.
Keywords: Ablation; Atrioventricular nodal region; High-density mapping; Mapping; Microelectrodes.
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