Electrophysiological characteristics of the earliest activation site in idiopathic right ventricular outflow tract arrhythmias under mini‐electrode mapping

Abstract Introduction Right ventricular outflow tract ventricular arrhythmias (RVOT VAs) often originate in the voltage‐transitional zone. The target electrogram could be compromised by the architecture of the roving catheter. Mini‐electrodes could improve the mapping resolution, especially in low‐voltage areas. The aim was to assess the electrophysiological characteristics of the earliest activation site (EAS) of RVOT VAs during mapping using mini‐electrodes. Methods and Results Twenty‐seven patients with RVOT‐type VAs were mapped using Orion mini‐electrodes and the Rhythmia mapping system. Bipolar and unipolar electrograms were analyzed and compared with conventional ablation catheter recordings. Twenty‐five patients (25 of 27) were successfully mapped and ablated at the RVOT. At the EAS, all 25 (100%) patients exhibited local sharp potentials (spiky potential) at the VAs, and 88% (22 of 25) individuals showed reverse late potentials in adjacent sinus beats on the bipolar mini‐electrode recordings. Related unipolar electrograms manifested 20% “q‐plateau‐QS,” 76% “gross QS,” and 4% “late QS” patterns related to spiky potential voltages and advanced times. Compared with electrograms recorded by ablation catheter, bipolar mini‐electrode recordings exhibited significantly shorter spiky potential durations ( P = 0.001) and a significantly increased incidence of the reverse late potentials ( P = 0.041). Unipolar mini‐electrode recordings had a lower incidence ratio of “late QS” patterns ( P = 0.039). Conclusion Compared with ablation catheter mapping, mini‐electrodes improved the mapping resolution of the EAS of RVOT VAs and exhibited shorter spiky potential durations and reduced incidence of “later QS” unipolar patterns.