Mean follow-up was 1.0 ± 0.1 years, and 35.4% of the cohort experienced recurrent atrial fibrillation or atrial tachycardia. Recurrence occurred in 46.2% of the 13 patients with one topological obstacle and 44.4% of the 27 with four or more, compared with 23.5% of 17 patients with two and 34.4% of 180 with three. The comparison between any recurrence and no recurrence across the four groups was not statistically significant (p = 0.433), while the overall distribution of no recurrence, atrial fibrillation and atrial tachycardia also did not differ significantly (p = 0.584).

Multivariable logistic regression adjusted for age, clinical type of atrial fibrillation, left atrial diameter, left ventricular ejection fraction, CHA2DS2-VASc score and low-voltage area burden; no obstacle-count group was significantly associated with recurrence relative to the three-obstacle group, and the overall likelihood-ratio p value was 0.194. The research was conducted at Seoul National University Hospital among patients who underwent radiofrequency catheter ablation between January 2023 and January 2024. Of 336 people initially considered, the investigators excluded 78 with a history of prior ablation, 13 without a complete left atrial voltage map, four without post-ablation follow-up and four whose recurrence was typical atrial flutter.

The final sample included 42.6% with paroxysmal atrial fibrillation, 43.5% with persistent disease and 13.9% with long-standing persistent disease. High-density electroanatomic maps acquired before ablation were used to identify low-voltage myocardium, with bipolar thresholds below 0.5 mV in sinus rhythm or pacing and below 0.2 mV during atrial fibrillation. Maps were acquired during sinus rhythm or pacing in 166 patients, or 70.0%, and during atrial fibrillation in 71, or 30.0%.

Low-voltage area burden was calculated as the percentage of the total mapped left atrial surface meeting the applicable voltage threshold. The investigators modeled the atrium as a closed two-dimensional surface and defined topological obstacles as non-conductive regions that interrupt electrical propagation. Each map initially contained three fundamental obstacles: the left pulmonary vein antrum, the right pulmonary vein antrum and the mitral valve.

Discrete low-voltage regions were then added when they met a size criterion, while extensive scar connecting anatomical structures could merge separate barriers into a single continuous obstacle. Incorporating the actual ablation lines completed the topological representation. To avoid counting negligible low-voltage spots as functional barriers, the researchers derived a minimum area from the wavelength required to support a macroreentrant circuit.

They used an estimated minimum atrial action potential duration of 150 milliseconds and a conduction velocity of 0.5 meters per second, producing a wavelength of 75 millimeters. Under an assumed circular geometry, that circumference corresponded to a radius of approximately 11.9 millimeters and an area of 4.45 square centimeters, rounded to 4.5 square centimeters for classification. Low-voltage regions smaller than 4.5 square centimeters were therefore not treated as independent obstacles.

The threshold was based on literature-derived rather than patient-specific physiological estimates, and the circular assumption could underestimate the boundary length of small, irregularly shaped regions. Obstacle count was related to low-voltage burden, but the relationship was not linear. Patients with one obstacle had the highest mean burden at 36.6% ± 24.8%, and all 13 had a burden of at least 5%, compared with 24.9% of the overall cohort.

The largest group, containing 180 patients with three obstacles, had a mean burden of only 2.1% ± 3.5%. Counts differed significantly across burden quartiles (p < 0.001). The highest-burden quartile, with a mean burden of 18.9% ± 17.6%, was the only quartile containing patients from all four obstacle groups, demonstrating that extensive low-voltage tissue can form either one large confluent barrier or several discrete ones.

The lowest quartile contained only patients with three obstacles. Patients with a single obstacle also differed clinically from the rest of the cohort. They were older, with a mean age of 67.8 years, and had a larger left atrium, lower left ventricular ejection fraction and higher CHA2DS2-VASc score.

Their mean left atrial diameter was 50.1 ± 5.2 mm, compared with 44.6 ± 7.0 mm in the three-obstacle group, while mean ejection fraction was 51.7% ± 12.6% and 57.6% ± 6.5%, respectively. Valvular heart disease was the only comorbidity that differed significantly across obstacle groups (p = 0.021). These imbalances limit attempts to separate the influence of topology from that of underlying remodeling: a lone obstacle was simultaneously associated with a greater burden of low-voltage tissue and less favorable cardiac measurements.

Most patients received pulmonary vein antrum isolation alone as the standard strategy, although 81, or 34.1%, also received additional lesions at the operator’s discretion; cavotricuspid isthmus ablation was the most common. The primary outcome was atrial fibrillation or atrial tachycardia lasting at least 30 seconds, documented on a 12-lead electrocardiogram or Holter monitor, after a three-month blanking period. Atrial tachycardia was less common than atrial fibrillation among recurrent cases, and the mean cycle length in patients with atrial tachycardia was 235 milliseconds.

Across low-voltage-area quartiles, recurrence was 20.0% in the lowest quartile, 41.7% in the second, 34.5% in the third and 45.8% in the highest; the overall quartile-level comparison was statistically significant (p = 0.018). Comparisons among obstacle groups within individual quartiles were limited by small subgroups and did not show a consistent pattern of increasing recurrence with obstacle count. The investigators also examined whether the structural differences were reflected in electrocardiographic measures of fibrillatory organization.

They analyzed lead V1 from 12-lead recordings obtained at recurrence, separated QRS and T waves with NeuroKit2, extracted and preprocessed fibrillatory-wave segments, and used fast Fourier analysis to calculate dominant frequency and organization index. Dominant frequency ranged from 5.04 ± 0.87 Hz in the single-obstacle group to 5.66 ± 1.51 Hz among patients with four or more obstacles. Organization index was highest in the single-obstacle group at 0.49 ± 0.09 and lowest in the three-obstacle group at 0.45 ± 0.07.

Neither measure differed significantly by obstacle count or low-voltage-area quartile, so the global signal-derived measures did not reproduce the distinctions identified by voltage mapping. The study’s retrospective, single-center design and small extreme-count groups limit generalizability. Operator-dependent additional ablation and incompletely documented comorbidities may also have influenced outcomes.

Voltage measurements can vary with mapping rhythm, wavefront direction and electrode configuration, while low-voltage area remains an imperfect surrogate for fibrosis. The fixed action-potential-duration and conduction-velocity assumptions and circular geometry make the 4.5-square-centimeter classification method-dependent. Threshold sensitivity against alternative cutoff values was not formally tested, although a supplementary shape-based analysis suggested that the circular assumption may have a modest effect for mildly elongated regions and a greater effect for markedly elongated ones.

Taken together, the results support further investigation of atrial substrate geometry, but they do not establish obstacle count as a recurrence predictor or clinical ablation target.

Subject of Research: Association of left atrial topological obstacles and low-voltage burden with atrial fibrillation recurrence after pulmonary vein antrum isolation

Article Title: Impact of low-voltage area burden and topological obstacles on atrial fibrillation recurrence after pulmonary vein antrum isolation

Article References: Choi, J., Go, Y.-H., Kwon, S., Lee, K.-Y., Ahn, H.-J., Lee, S.-R., Kim, T., Lee, J. C., Choi, E.-K., & Oh, S. (2026). Impact of low-voltage area burden and topological obstacles on atrial fibrillation recurrence after pulmonary vein antrum isolation. Frontiers in Network Physiology, 6, 1945351. https://doi.org/10.3389/fnetp.2026.1945351

Image Credits: AI Generated

DOI: 10.3389/fnetp.2026.1945351

Keywords: atrial fibrillation, pulmonary vein antrum isolation, topological obstacles, low-voltage area, cardiac ablation, arrhythmia recurrence, atrial substrate, left atrium, electrical conduction, network physiology, Impact, low-voltage