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Drivers in Relation to Duration of Persistent Atrial Fibrillation
Study Questions:
What are the mechanisms and preferential sites of driver activity in patients with persistent atrial fibrillation (AF)?
Methods:
One hundred and five patients undergoing a catheter ablation for persistent AF underwent noninvasive mapping prior to the procedure. Unipolar electrograms were recorded from the torso by means of a high-density vest, which were then projected onto biatrial shell obtained on computed tomography. AF maps were generated using phase mapping to determine putative driver sites. Drivers were categorized as either reentrant or focal, and were further described based on region of origin. Patients were classified based on persistence of arrhythmia: patients with persistent AF but presenting in sinus rhythm, persistent AF for <12 months, and for >12 months.
Results:
Mapping yielded 4,550 reentrant and 1,017 focal drivers. The median number of reentrant sources per patient was four, with the pulmonary veins (PVs) being the most common, followed by the inferoposterior left atrium. Focal sources were also commonly found in the PVs. With increasing persistence of AF, complexity of AF mechanisms increased as manifested by a greater number of rotations for reentrant sources, and a higher likelihood of harboring sources outside the PVs. AF termination during radiofrequency ablation was achieved in 70% of patients, but decreased sharply in patients with longstanding persistent AF (continuous for >12 months).
Conclusions:
Noninvasive mapping reveals that the PV region is a common source of AF, but also that with increasing duration of AF, regions outside the PVs also participate in maintaining AF.
Perspective:
The ideal ablation targets in patients with persistent AF remain unclear, leading to disparate ablation strategies, and outcomes. This study utilizing a novel AF mapping technology found that the PVs are the dominant regions maintaining AF, but also that as AF progresses, regions outside the PVs may also drive the fibrillatory process. These findings help explain why patients with persistent AF may not fully respond to a PV-only strategy. Further, the results of this study also underscore the importance of early intervention before structural and electrical changes take a firmer hold, making it more difficult to eradicate the arrhythmia. Whether the long-term outcomes are superior to those with conventional mapping (e.g., stepwise ablation to terminate AF) remains unknown.
Keywords: Anticoagulants, Arrhythmias, Cardiac, Atrial Fibrillation, Catheter Ablation, Diagnostic Imaging, Early Intervention, Educational, Pulmonary Veins, Tomography, X-Ray Computed
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