Entrainment is a useful method for locating reentrant atrial tachycardia（AT）circuits, but alterations or termination of the AT can derail this process. AT resetting by the delivery of a scanned atrial extrastimulus at a site of activation downstream from the neighboring electrodes on a multielectrode catheter when the upstream tissue is refractory may be a useful diagnostic maneuver to avoid AT alterations and termination. In this study, we evaluated the diagnostic performance and the frequency of AT alterations and termination in entrainment pacing and the scanned atrial extrastimulus for 48 atrial tachycardias. The positive predictive value for both diagnostic maneuvers was 100％, and the negative predictive value was equivalent for the entrainment pacing and the scanned atrial extrastimulus（96％ vs. 100％, P＝0.25）. The frequency of AT alterations and termination due to diagnostic maneuver was lower with scanned atrial extrastimulus than with entrainment pacing（1％ vs. 10％, P＝0.003）. Scanned atrial extrastimulus using a multielectrode mapping catheter may enable the diagnosis of AT circuits while avoiding AT alterations and termination.

Development of atrial fibrillation（AF）is closely associated with the progression of atrial structural remodeling. Fibrosis is considered a hallmark of structural remodeling, resulting in a substrate vulnerable to AF. Low-voltage areas（LVAs）identified in the left atrium（LA）by bipolar voltage mapping during catheter ablation have been considered local fibrosis. However, we hypothesized that voltage reduction in the atria is a diffuse process and that the presence of LVAs reflects a global voltage reduction. High-density bipolar voltage mapping was performed during high right atrial pacing to evaluate the relationship between bipolar voltage reduction in the whole LA and LVA. The results confirmed that the presence of LVAs reflects diffuse voltage reduction of the whole LA. We also developed atrial biopsy and demonstrated that the extent of fibrosis was inversely correlated with both bipolar voltage at the biopsy site and global LA voltage. Subsequent studies have revealed that histological correlates of atrial structural remodeling include increased intercellular space preceding fibrosis, fibrosis, myofibrillar loss, and decreased nuclear density. Further analysis of the process of atrial remodeling will help to elucidate the pathogenesis of AF and atrial cardiomyopathy and develop new therapeutic targets.

In pediatric patients with a pacemaker（PM）implanted in the abdomen, little is known about specific electromagnetic interference（EMI）from the use of tablet personal computer（PCs）. We investigated the effects of tablet PCs on EMI in 26 pediatric patients who had implanted PM, in which a pulse generator is located in the abdominal wall. Abbott PMs with a residual number of magnet response episodes were investigated. The period investigated was between January 2022 and February 2023. Of the 26 patients, magnetic response was detected in 7, and factors for the cause of EMI were investigated. All of the 7 children, who had documented magnet response with interrogation, were school children with an average age of 8 years. The average number of episodes was 39 per month, with high incidence during school hours. Tablet PCs were determined to be the cause of EMI, because of the episode was allowed at home. It is well known that the inside structure of tablet PCs includes a magnet. After adequate instruction in the use of tablet PCs, the magnet response has disappeared completely. Careful attention should be paid in pediatric patients with pacemakers implanted in the abdomen, especially when using tablet PCs. Patients should be instructed to move the device away from the abdomen when using tablet PCs.