Introduction: Independent groups now show that paroxysmal and atrial fibrillation (AF) is sustained by rotors or focal impulses that are stable when mapped using Focal Impulse and Rotor Mapping (FIRM), where FIRM-guided ablation substantially improves patient outcomes. We hypothesized that sources would be stable across a wide range of AF patient populations.
Methods: In a multicenter prospective clinical trial we mapped AF in 210 patients (28% paroxysmal) using 64 pole electrode baskets in both atria, with AF analyzed using phase mapping (RhythmViewTM, Topera Inc). FIRM-Guided ablation was performed in n=132 consecutive patients (n=33 paroxysmal, LA diameter 54±10 mm; n=73 first ablation) by targeting each source for abolition prior to pulmonary vein isolation.
Results: Sources were identified in 129/130 mapped patients (99.2%), for 2.6±1.2 sources/patient (all cases) and 2.7±1.2 sources/patient (1st ablation cases). Sources were distributed in RA/LA 64/36% (all cases) and 65/35% (1st ablation). On FIRM mapping, sources were stable (see figure) for 5961±9650 cycles (all cases), and 5906±7499 cycles (1st ablation; p=0.96). Stability was equivalent between patients with paroxysmal or persistent AF (p>0.50), or right and left atrium (p>0.50).
Conclusions: Rotors and Focal sources for human AF present evidence for a consistent mechanism across patients, in which paroxysmal or persistent AF differ primarily in the number and locations of sources. These results provide the first mechanistic explanation for why localized ablation can terminate AF, and further motivate source-based AF ablation.