Background: The efficacy of ablation targeting low-voltage areas (LVAs) is controversial, although LVA presence is well known to be associated with AF recurrence after ablation. Atrial fibrillation (AF) substrate may not localize within LVAs. Methods and results: This observational study enrolled 405 consecutive patients who underwent an initial AF ablation procedure. The left atrial voltage map was obtained after pulmonary vein isolation. LVAs were defined as areas with voltage < 0.5 mV. To estimate whole atrial electrophysiological degeneration, mean regional voltage at each of 6 regions and left atrial total conduction velocity were measured. LVAs existed in 143 of 405 (35.3%) patients. Patients with LVAs demonstrated lower mean regional voltages throughout all 6 regions than those without LVAs (1.3 [1.8, 0.8] vs. 0.6 [1.0, 0.2] for anterior wall, p<0.001). On the other hand, left atrial conduction velocity was lower in patients with LVAs than in those without (0.89 [1.01, 0.74] vs. 0.93 [1.03, 0.87] m/s, p<0.001). Multivariate analysis revealed that low left atrial total conduction velocity and a higher number of regions with mean voltage reduction were independently associated with AF recurrence, although LVA presence was not. Conclusion: Patients with localized left atrial LVAs were characterized by whole left atrial electrophysiological degeneration as assessed by mean regional voltage and conduction velocity. In addition, whole left atrial electrophysiological degeneration parameters were well associated with AF recurrence.

Introduction: The randomized controlled VOLCANO trial demonstrated comparable 1-year rhythm outcomes between patients with and without ablation targeting low-voltage areas (LVAs) in addition to pulmonary vein isolation among paroxysmal atrial fibrillation (AF) patients with LVAs. To compare long-term AF/atrial tachycardia (AT) recurrence rates and types of recurrent-atrial-tachyarrhythmia between treatment cohorts during a > 2-year follow-up period. Methods: An extended-follow-up study of 402 patients enrolled in the VOLCANO trial with paroxysmal AF, divided into 4 groups based on the results of voltage mapping: Group A, no LVA (n=336); group B, LVA ablation (n=30); group C, LVA presence without ablation (n=32); and group D, incomplete voltage map (n=4). Results: At 25 (23, 31) months after the initial ablation, AF/AT recurrence rates were 19% in group A, 57% in group B, 59% in group C, and 100% in group D. Recurrence rates were higher in patients with LVAs than those without (group A vs. B+C, p<0.0001), and were comparable between those with and without LVA ablation (group B vs. C, p=0.83). Among patients who underwent repeat ablation, ATs were more frequently observed in patients with LVAs (Group B+C, 50% vs. A, 14%, p<0.0001). In addition, LVA ablation increased the incidence of AT development (group B, 71% vs. C, 32%, p<0.0001), especially biatrial tachycardia (20% vs. 0%, p=0.01). Conclusion: Patients with LVAs demonstrated poor long-term rhythm outcomes irrespective of LVA ablation. ATs were frequently observed in patients with LVAs, and LVA ablation might exacerbate iatrogenic ATs.

Introduction Some patients fail to respond to persistent atrial fibrillation (PeAF) catheter ablation in spite of multiple procedures and ablation strategies, including low voltage area (LVA)-guided, linear, and complex fractionated atrial electrogram (CFAE)-guided ablation procedures. We hypothesized that LVA extent could predict non-response to PeAF catheter ablation in spite of multiple procedures. Methods This study included 510 patients undergoing initial ablation procedures for PeAF. LVAs were defined as regions with bipolar peak-to-peak voltages of <0.50 mV after PVI during sinus rhythm. Patients were categorized by LVA size into groups A (0-5 cm2), B (5-20 cm2), and C (over 20 cm2). The primary endpoint was AF-free survival after the last procedure. Results During a median follow-up of 25 (17, 36) months, AF recurrence was observed in 101 (20%) patients after 1.4±0.6 ablation procedures (maximum 4). A Kaplan-Meier analysis showed the AF-free survival rate significantly differed by LVA size. Conclusion Extensive LVA after initial PVI was associated with a poor clinical outcome even following multiple procedures.

Introduction: A novel ablation catheter that can measure local impedance (LI) was recently launched. We aimed to explore target LI measurements at each radiofrequency application (RFA) for creating sufficient ablation lesions during pulmonary vein (PV) isolation. Methods: This prospective study included 15 consecutive patients scheduled to undergo an initial ablation of paroxysmal atrial fibrillation (AF). Circumferential ablation around both ipsilateral PVs was performed using a 4-mm irrigated ablation catheter with an LI sensor. Point-by-point ablation was used with a 4-mm inter-ablation-point distance. Operators were blinded to LI measurements during the procedure. Creation of sufficient ablation lesions was assessed by the absence of a conduction gap. Results: After first-pass encircling PV antrum ablation, left atrium to PV conduction remained in 12 of 30 (40%) ipsilateral PVs. Mapping using the mini-basket catheter identified 48 ablation points through which the propagation wave entered the PV. At ablation points with a gap, the LI drop during RFA was half that at points without a gap (12 ± 7 vs. 23 ± 12 ohm, p<0.001). The GI drop did not differ between ablation points with and without a gap (12 ± 7 vs. 14 ± 10 ohm, p=0.10). An LI drop of 15 ohm predicted sufficient lesion formation without a gap with a sensitivity of 0.71, specificity of 0.81, and predictive accuracy of 0.75. Conclusion: A target LI drop of 15 ohm at each RFA with a 4-mm distance between adjacent ablation points may facilitate creation of sufficient ablation lesions during PV isolation