Background - Achieving bidirectional mitral isthmus (MI) block using radiofrequency catheter ablation (RFCA) alone is challenging, and MI reconnection is common. Adjunctive vein of Marshall (VOM) ethanol infusion (VOM-Et) can facilitate acute MI block. However, little is known regarding its long-term success. This study sought to evaluate the impact of adjunctive VOM-Et on MI block achievement and durability compared to RFCA alone. Methods - Patients undergoing a first attempt of posterior MI ablation were grouped according to their MI block index strategy: adjunctive VOM-Et and RFCA alone. Rates of acute MI block and MI reconnection observed during repeat procedures were compared between the two groups. Results - The VOM-Et group consisted of 152 patients (63.8 ± 9.4 years) undergoing adjunctive VOM-Et for MI block. The RFCA group consisted of 110 patients (60.9 ± 9.2 years) undergoing MI ablation using RFCA alone. Acute MI block was more frequently achieved in the VOM-Et group (98.7% [150/152] vs. 63.6% [70/110]; p < 0.001) with shorter RFCA duration (5.00 [3.00-7.00] vs. 19.0 [13.6-22.0] mins; p < 0.001). Of the 220 patients with MI block achieved during the index procedure, 81 underwent a repeat procedure during follow-up (VOM-Et group: 23.3% [35/150] vs. RFCA group: 65.7% [46/70], respectively; p < 0.001). A significantly greater number of patients exhibited durable MI block in the VOM-Et group (62.9% [22/35] vs. 32.6% [15/46], respectively; p = 0.008). Conclusions - Beyond facilitating acute MI block, VOM-Et is associated with greater lesion durability as evidenced by higher rates of MI block during repeat procedures.

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Background-The post-second-generation cryoballoon (CB) ablation isolation area during the chronic phase has not been described. The aim of this study was to quantitatively evaluate the chronic-phase isolation area after 28-mm secondgeneration CB ablation and compare it to the estimated conventional radiofrequency circumferential pulmonary vein isolation (CPVI) line. Methods and Results-Thirty-two patients with paroxysmal atrial fibrillation underwent pulmonary vein (PV) isolation using second-generation CB. After a median of 6.0 (4.0-9.0) months, the PV isolation area was evaluated using highresolution mapping (1-mm electrode, 2-mm interelectrode spacing; 527±99 points per map) and pacing techniques in all patients (17 with and 15 without arrhythmia recurrence beyond blanking period) and compared with estimated conventional radiofrequency CPVI area. PV reconnections were observed in 34 of 126 PVs (27.0%) among 21 of 32 patients (65.6%), which were eliminated by a median of 1.0 (1.0-3.0) focal radiofrequency application. The left-and right-sided PV antrum isolation area and nonablated posterior wall areas were 9.8±1.7, 8.1±2.3, and 17.0±6.1 cm 2 , respectively. The cryoablated areas were significantly smaller than the estimated conventional radiofrequency CPVI areas in all but the right inferior PV. The difference was highest in the left superior PV. In 2 patients (6.3%), recurrent atrial fibrillation originated from the foci identified at the left superior PV antrum outside the CB isolation area but inside the estimated conventional radiofrequency CPVI line. Conclusions-Although the PV isolation areas during the chronic phase after the second-generation CB ablation were generally wide, they were significantly smaller than the area encircled by the CPVI line except at the right inferior PV antrum. Recurrent atrial fibrillation could originate from the left superior PV antrum and could be isolated by a CPVI but not by a CB. (Circ Arrhythm Electrophysiol. 2016;9:e003879.

Aims Pulsed field ablation (PFA), a non-thermal ablative modality, may show different effects on the myocardial tissue compared to thermal ablation. Thus, this study aimed to compare the left atrial (LA) structural and mechanical characteristics after PFA vs. thermal ablation. Methods and results Cardiac magnetic resonance was performed pre-ablation, acutely (&lt;3 h), and 3 months post-ablation in 41 patients with paroxysmal atrial fibrillation (AF) undergoing pulmonary vein (PV) isolation with PFA (n = 18) or thermal ablation (n = 23, 16 radiofrequency ablations, 7 cryoablations). Late gadolinium enhancement (LGE), T2-weighted, and cine images were analysed. In the acute stage, LGE volume was 60% larger after PFA vs. thermal ablation (P &lt; 0.001), and oedema on T2 imaging was 20% smaller (P = 0.002). Tissue changes were more homogeneous after PFA than after thermal ablation, with no sign of microvascular damage or intramural haemorrhage. In the chronic stage, the majority of acute LGE had disappeared after PFA, whereas most LGE persisted after thermal ablation. The maximum strain on PV antra, the LA expansion index, and LA active emptying fraction declined acutely after both PFA and thermal ablation but recovered at the chronic stage only with PFA. Conclusion Pulsed field ablation induces large acute LGE without microvascular damage or intramural haemorrhage. Most LGE lesions disappear in the chronic stage, suggesting a specific reparative process involving less chronic fibrosis. This process may contribute to a preserved tissue compliance and LA reservoir and booster pump functions.