Atrial Fibrosis and Re-Entrant Activity in Atrial Fibrillation
What is the relationship between fibrosis and re-entrant activity in persistent atrial fibrillation (AF)?
The investigators evaluated 41 patients with persistent AF (age 56 ± 12 years; 6 women). High-resolution electrocardiographic imaging (ECGI) was performed during AF by using a 252-chest electrode array, and phase mapping was applied to locate re-entrant activity. Sites of high re-entrant activity were defined as re-entrant regions. Late gadolinium-enhanced (LGE) cardiac magnetic resonance (CMR) was performed at 1.25 × 1.25 × 2.5 mm resolution to characterize atrial fibrosis and measure atrial volumes. The relationship between LGE burden and the number of re-entrant regions was analyzed. Local LGE density was computed and characterized at re-entrant sites. All patients underwent catheter ablation targeting re-entrant regions, the procedural endpoint being AF termination. Clinical, CMR, and ECGI predictors of acute procedural success were then analyzed.
Left atrial (LA) LGE burden was 22.1 ± 5.9% of the wall, and LA volume was 74 ± 21 ml/m2. The number of re-entrant regions was 4.3 ± 1.7 per patient. LA LGE imaging was significantly associated with the number of re-entrant regions (R = 0.52; p = 0.001), LA volume (R = 0.62; p < 0.0001), and AF duration (R = 0.54; p = 0.0007). Regional analysis demonstrated a clustering of re-entrant activity at LGE borders. Areas with high re-entrant activity showed higher local LGE density as compared with the remaining atrial areas (p < 0.0001). Failure to achieve AF termination during ablation was associated with higher LA LGE burden (p < 0.001), higher number of re-entrant regions (p < 0.001), and longer AF duration (p = 0.008).
The authors concluded that the number of re-entrant regions during AF relates to the extent of LGE on CMR, with the location of these regions clustering to LGE areas.
This study reports that the amount of LGE is related to the number of regions exhibiting re-entry, re-entrant activity clusters to LGE areas, and the extent of LGE and re-entrant activity both affect procedural outcome during ablation. Furthermore, the relationship with the number of re-entrant regions suggests that, beyond ablation targeting, the quantification of AF complexity by electrocardiographic imaging may be an interesting noninvasive tool to select ablation candidates. Additional studies are needed to validate the findings of this multimodality noninvasive approach.
Keywords: Arrhythmias, Cardiac, Atrial Appendage, Atrial Fibrillation, Catheter Ablation, Diagnostic Imaging, Electrocardiography, Fibrosis, Gadolinium, Magnetic Resonance Imaging
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