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Introduction: Few studies have demonstrated a high degree of atrioventricular (AV) synchrony with a new leadless pacemaker called Micra AV. Our group previously reported a new and unique sensing method. We believe that this novel sensing method, "Simplified A3 method," might facilitate better AV synchrony than a conventional sensing method in almost all cases with Micra AV implantation. Methods: We conducted a non‐randomized retrospective study comparing the two pacing methods at two centers. From December 1, 2021 to October 31, 2022, Micra AV was implanted for 32 patients at the two centers. Twenty of the 32 patients with sinus rhythm and complete AV block were included in this study. In Group 1, the conventional setting was programmed as follows: auto A3 threshold, auto A3 window‐end (WE), and auto A4 threshold turned on during hospitalization. In Group 2, the "Simplified A3 method" was programmed as follows: auto A3 threshold and auto A3WE turned off. Instead, an intentionally prolonged A3WE (850–1000 ms) and low A3 threshold (A3 signal amplitude + 0.5–1.0 m/s2) were programmed. Results: Twenty patients were analyzed. In Group 2, AV synchrony (%AMVp) was significantly higher at the first outpatient clinic (63.0 ± 5.7% vs 81.0 ± 4.2%, p =.03). A3 threshold was significantly lower in Group 2 (5.9 ± 0.7 m/s2, p <.05 vs 2.3 ± 0.5 m/s2, p <.05). Conclusion: Our novel sensing method might be a more feasible sensing method for obtaining higher AV synchrony than the conventional algorithm. [ABSTRACT FROM AUTHOR]

Background: The mechanism of typical slow‐fast atrioventricular nodal re‐entrant tachycardia (AVNRT) and its anatomical and electrophysiological circuit inside the right atrium (RA) and Koch's Triangle (KT) are not well known. Objective: To identify the potentials of the compact AV node and inferior extensions and to perform accurate mapping of the RA and KT in sinus rhythm (SR) and during AVNRT, to define the tachycardia circuit. Methods: Consecutive patients with typical AVNRT were enrolled in 12 Italian centers and underwent mapping and ablation by means of a basket catheter with small electrode spacing for ultrahigh‐density mapping and a modified signal‐filtering toolset to record the potentials of the AV nodal structures. Results: Forty‐five consecutive cases of successful ablation of typical slow‐fast AVNRT were included. The mean SR cycle length (CL) was 784.1 ± 6 ms and the mean tachycardia CL was 361.2 ± 54 ms. The AV node potential had a significantly shorter duration and higher amplitude in sinus rhythm than during tachycardia (60 ± 40 ms vs. 160 ± 40 ms, p <.001 and 0.3 ± 0.2 mV vs. 0.09 ± 0.12 mV, p <.001, respectively). The nodal potential duration extension was 169.4 ± 31 ms, resulting in a time‐window coverage of 47.6 ± 9%. The recording of AV nodal structure potentials enabled us to obtain 100% coverage of the tachycardia CL during slow‐fast AVNRT. Conclusion: Detailed recording of the potentials of nodal structures is possible by means of multipolar catheters for ultrahigh‐density mapping, allowing 100% of the AVNRT CL to be covered. These results also have clinical implications for the ablation of right‐septal and para‐septal arrhythmias. [ABSTRACT FROM AUTHOR]