For patients presenting with sustained ventricular tachycardia（VT）originating from structural heart disease, catheter ablation stands as a contemporary imperative therapeutic approach, particularly in scenarios of VT storm or worsening heart failure. Substrate functional mapping delineates the abnormal conduction properties discerned during sinus rhythm and/or ventricular pacing. Areas of decreased conduction velocity are reflected as isochronal crowding（IC）within the three-dimensional electroanatomical mapping system, indicative of the VT circuit substrate, thereby making them optimal sites for ablation. However, in clinical practice, IC may manifest across multiple locations, sometimes appearing as a long-distance band lesion. We have focused on the presence of an area directly above the IC or at the edge of the IC that exhibits an excitation propagation pattern with an inward curvature of 90° or more, which we defined as a rotational activation pattern（RAP）. In a retrospective analysis of 45 VTs in 37 patients who underwent catheter ablation, RAP was found in 70％ of a total of 33 VTs in which the circuit was identified by direct cessation of radiofrequency energy application or by the pace-mapping technique. Notably, in four cases, RAP was absent during baseline rhythm but emerged upon ventricular pacing from different sites, while in six cases, the VT circuit was located in the midmyocardium or epicardium and the VT became inducible following the ablation to the endocardial surface without RAP. Functional substrate mapping plays a pivotal role in catheter ablation procedures targeting VT in patients with structural heart disease, with areas exhibiting RAP potentially representing optimal treatment targets.

Magnetocardiography（MCG）, a diagnostic modality that measures the magnetic field of the heart, has good spatial resolution because transparency of magnetic field signals is generally constant and not influenced by various tissues in the human body, so this modality could potentially help diagnose arrhythmia more accurately than the electrocardiogram（ECG）. The utility of MCG in discriminating premature ventricular contractions（PVCs）originating from the right ventricular outflow tract from those originating from the aortic sinus cusps was previously reported. To further improve the diagnostic accuracy of MCG mapping, we recently developed a method that merges MCG images with computed tomography（CT）images. This study aimed to evaluate our novel non-invasive MCG mapping method merged with computed tomography（MCG-CT）for PVCs. The study included 22 patients referred for catheter ablation of idiopathic PVCs. Radiopaque L-shaped acrylic markers during CT scanning and coil markers generating a weak magnetic field during MCG measurements were used as reference markers to merge the images. Estimated PVC origins determined by using a spatial filter algorithm applied to MCG data were merged with the 3-D CT image by matching the coordinates of each marker. These MCG-CT mapping images were compared with the successful ablation sites obtained from the CARTO system, and diagnostic accuracy was evaluated. The accuracy of MCG-CT mapping was 94％, which was higher than that of ECG algorithms（72％）. The high diagnostic accuracy of this method may allow us to use MCG-CT mapping in clinical practice.

From CARTO3version7.2, TRUEref^Ⓡ can be selected as a reference electrode for unipolar potential. TRUEref^Ⓡ is a function that allows the electrode placed in the shaft of OCTARAY to be used as a unipolar reference electrode. We compared and verified TRUEref^Ⓡ as a unipolar reference electrode with conventional WCT. The electric potential was obtained from an OCTARAY catheter placed in the left atrium posterior wall and the left pulmonary vein in 5 patients with atrial fibrillation. Obtained and evaluated when using TRUEref^Ⓡ（TR group）and when using WCT（WCT group）. Analysis of the posterior wall of the left atrium showed no difference in the far field potential of the ventricle in the bipolar group, but in the unipolar group, the mean of the TR group was 0.22±0.12mV, and the mean of the WCT group was 1.74±0.48mV. A significant difference was observed. In addition, in the left pulmonary vein, no significant difference was observed between the TR group and the WCT group in the far field potential of the atrium or left atrial appendage in the bipolar group, but in the unipolar group, the average of the TR group was 0.24±0.27mV, and the average of the WCT group was 0.42±0.27mV. A statistically significant difference was observed. The results suggest that TRUEref^Ⓡ can greatly reduce ventricular far field potential without affecting bipolar potential. In addition, it was shown that TRUEref^Ⓡ can also reduce the far field potential of the atrial unipolar, suggesting that the unipolar of TRUEref^Ⓡ reflects more local excitation. TRUEref^Ⓡ could reduce the unipolar far field potential, and it may reflect a more accurate local unipolar potential.