Background: Pulmonary vein isolation (PVI) lesions after cryoballoon ablation (CBA) are characterized as a wider and more continuous than that after conventional radiofrequency catheter ablation (RFCA) without the contact force (CF)-sensing technology. However, the impact on the lesion characteristics of ablation with a CFsensing catheter has not been well discussed. We sought to assess the lesions using late-gadolinium enhancement magnetic resonance imaging (LGE-MRI) and to compare the differences between the two groups (CB group vs. RF group). Methods: A total of 30 consecutive patients who underwent PVI were enrolled (CB group, 18; RF group, 12). The RF applications were delivered with a target lesion size index (LSI) of 5. The PVI lesions were assessed by LGE-MRI 3 months after the PVI. The region around the PV was divided into eight segments: roof, anteriorsuperior, anterior carina, anterior inferior, bottom, posterior inferior, posterior carina, and posterior superior segment. The lesion width and visual gap of each segment were compared between the two groups. The visual gaps were defined as no-enhancement site of >4 mm. Results: The mean LSI was 4.7 ± 0.7. The lesion width was significantly wider but the visual gaps were more frequently documented at the bottom segment of right PV in the CBA group (lesion width: 8.1 ± 2.2 vs. 6.3 ± 2.2 mm; p = .032; visual gap at the bottom segment or right PV: 39% vs. 0%; p = .016). Conclusions: The PVI lesion was wider after CBA, while the visual gaps were fewer after RFCA with a CF-sensing catheter.

Introduction Pulmonary vein isolation (PVI) lesions after cryoballoon ablation (CBA) are wide and continuous, however, the distribution can depend on the pulmonary vein (PV) size. We sought to assess the relationship between the lesion distribution and PV size after CBA and hotballoon ablation (HBA). Methods and Results A total of 80 consecutive patients who underwent PVI were enrolled (40 with CBA). The lesions were visualized by late‐gadolinium enhancement magnetic resonance imaging. The lesion width, lesion gaps, and distance from the PV ostium (PVos) to distal lesion edge (DLE) were assessed. If the DLE extended inside the PV, the value was expressed as a negative value. Although the lesion width was significantly wider in the CB group (7.8 ± 2.0 vs 4.9 ± 1.0 mm, P < .001), the number of lesion gaps was significantly less in the HB group (2.9 ± 2.4 vs 1.3 ± 1.4 gaps, P = .001). The distance from the PVos to DLE was a negative value in both groups, but the impact was significantly greater (−1.5 ± 1.8 vs −0.2 ± 1.2 mm, P < .001) and negatively correlated with PV size in the CB group, but not in HB group (r = −0.27, P = .007). The AF recurrence 12 months after the procedure did not differ (5 [12.5%] of 40 in the CB group vs 4 [10%] of 40 in the HB group, P = .695). Conclusions The PVI lesions after HBA were characterized by (a) narrower, but (b) more continuous, (c) smaller lesion inside the PV, and (d) irrespective of PV size as compared to that after CBA.

Background A computational model demonstrated that atrial fibrillation (AF) rotors could be distributed in patchy late‐gadolinium enhancement (LGE) areas and play an important role in AF drivers. However, this was not validated in humans. Objective The purpose of this study was to evaluate the LGE properties of AF rotors in patients with persistent AF. Methods A total of 287 segments in 15 patients with persistent AF (long‐standing persistent AF in 9 patients) that underwent AF ablation were assessed. Non‐passively activated areas (NPAs), where rotational activation (AF rotor) was frequently observed, were detected by the novel real‐time phase mapping (ExTRa Mapping). The properties of the LGE areas were assessed using the LGE heterogeneity and the density which was evaluated by the entropy (LGE‐entropy) and the volume ratio of the enhancement voxel (LGE‐volume ratio), respectively. Results NPAs were found in 61 (21%) of 287 segments and were mostly found around the pulmonary vein antrum. A receiver operating characteristic curve analysis yielded an optimal cutoff value of 5.7% and 10% for the LGE‐entropy and LGE‐volume ratio, respectively. The incidence of NPAs was significantly higher at segments with an LGE‐entropy of >5.7 and LGE‐volume ratio of >10% than at the other segments (38 [30%] of 126 vs. 23 [14%] of 161 segments; p = .001). No NPAs were found at segments with an LGE‐volume ratio of >50% regardless of the LGE‐entropy. Of five patients with AF recurrence, NPAs outside the PV antrum were not ablated in three patients and the remaining NPAs were ablated, but their LGE‐entropy and LGE‐volume ratio were low. Conclusion AF rotors are mostly distributed in relatively weak and much more heterogenous LGE areas.

Introduction:The ablation index (AI) and lesion size index (LSI) are novel markers for predicting the ablation lesion quality, however, collateral damage is still a concern.This study aimed to compare the lesion characteristics and tissue temperature profiles between 20 W (20 Ws) and 40 W (40 Ws) ablation settings under the same AI and LSI.Methods: An ex vivo model consisting of swine myocardium (5-6 mm thickness) in a circulating, warmed saline bath was used. Twenty-one tissue temperature electrodes were used. Radiofrequency applications with different power settings were performed with a 10 to 12 g contact force until the AI and LSI reached 350 and 4.5, respectively.Results: A total of 120 radiofrequency (RF) applications and 2520 tissue temperature profiles were analyzed. The speed of the tissue temperature rise with 40 Ws was significantly faster than that with 20 Ws. However, the maximum tissue temperature did not significantly differ between 20 and 40 Ws with the same AI (44.6°C ± 3.9°C vs 45.1°C ± 6.4°C, P = .73), and was significantly lower for 40 Ws with the same LSI (42.8°C ± 3.4°C vs 40.0°C ± 3.4°C, P = .003). For both the AI and LSI, the number of electrodes exhibiting high temperatures (≥39°C) was significantly larger and the duration of high tissue temperatures was significantly longer with 20 Ws. The thermal latency with 40 Ws was greater.Conclusions: Although the targeted AI and LSI were the same for both 20 and 40 Ws, the tissue temperature profiles differed greatly depending on the RF power setting. A high power setting based on the AI and LSI may reduce the collateral thermal damage. K E Y W O R D S ablation index, catheter ablation, lesion size index, tissue thermodynamics 1 | INTRODUCTION Pulmonary vein isolation (PVI) is a cornerstone of radiofrequency (RF) catheter ablation of atrial fibrillation. Transmural and continuous ablation lesions are essential factors for preventing reconduction of the PVs, however, an excessive contact force and overheating of the tissue can cause steam pops, cardiac perforations, and collateral damage. Low power long duration RF settings (20-25 W × 20-30 seconds) have been used for the posterior wall of the left atrium (LA) especially in areas adjacent to the esophagus.

Background Medium‐dose (25 gray) x‐ray radiation therapy has recently been performed on patients with refractory ventricular tachyarrhythmias. Unlike x‐ray, carbon ion and proton beam radiation can deliver most of their energy to the target tissues. This study investigated the electrophysiological and pathological changes caused by medium‐dose carbon ion and proton beam radiation in the left ventricle (LV). Methods and Results External beam radiation in the whole LV was performed in 32 rabbits. A total of 9 rabbits were not irradiated (control). At the 3‐month or 6‐month follow‐up, the animals underwent an open‐chest electrophysiological study and were euthanized for histological analyses. No acute death occurred. Significant LV dysfunction was not seen. The surface ECG revealed a significant reduction in the P and QRS wave voltages in the radiation groups. The electrophysiological study showed that the local conduction times in each LV site were significantly longer and that the local LV bipolar voltages were significantly lower in the radiation groups than in the control rabbits. Histologically, apoptosis, fibrotic changes, and a decrease in the expression of the connexin 43 protein were seen in the LV myocardium. These changes were obvious at 3 months, and the effects were sustained 6 months after radiation. No histological changes were seen in the coronary artery and esophagus, but partial radiation pneumonitis was observed. Conclusions Medium‐dose carbon ion and proton beam radiation in the whole LV resulted in a significant electrophysiological disturbance and pathological changes in the myocardium. Radiation of the arrhythmogenic substrate would modify the electrical status and potentially induce the antiarrhythmic effect.