Atrial Myopathy in Persistent Atrial Fibrillation: Three-Dimensional Quantification of Atrial Fibrosis by High-Density Electro-Anatomic Mapping and Its Association with Arrhythmia Duration.

Background: Progressive atrial myopathy marked by fibrotic remodelling drives the transition from paroxysmal to persistent atrial fibrillation (AF), yet the temporal dynamics of fibrosis within persistent AF remain poorly defined.

Objective: To quantify dense scar and borderline fibrotic zones using high-density electro-anatomic mapping (HD-EAM) in patients with persistent AF, and to compare fibrotic burden between early persistent (>7 days-<3 months) and persistent (≥3 months-<1 year) AF.

Methods: Retrospectively analysed 78 consecutive patients (59 ± 15 years, 59% men) undergoing first-time pulmonary vein isolation for persistent AF. Atrial voltage maps (CARTO 3 CONFIDENSE™) acquired in sinus rhythm classified tissue as healthy (>0.5 mV), borderline (0.3-0.5 mV), or dense scar (<0.2 mV). Echocardiographic left atrial diameter (LAD) and volume (LAV) were compared with mapping data. The primary endpoint was dense scar point count; secondary endpoints included AF/atrial tachycardia recurrence and correlation between imaging modalities.

Results: Twenty-two patients had early persistent and 56 persistent AF. Mapping resolution was similar (5 193 ± 459 vs 5 399 ± 601 points, p = 0.83). Dense scar points were significantly higher in persistent AF (2 807 ± 336 vs 1 634 ± 236; p < 0.001). LAD and LAV from HD-EAM correlated moderately with echocardiography (r = 0.45 and 0.48; both p < 0.01) but did not differ between groups. After 7.2 ± 3.7 months, recurrence occurred in 16% of persistent versus 8% of early persistent AF (p = 0.11).

Conclusions: Fibrotic burden increases markedly after three months of uninterrupted AF despite stable atrial size. HD-EAM enables intra-procedural quantification of atrial myopathy and may guide personalised ablation strategies.