Comparison of native versus ablation-induced scar on left atrial magnetic resonance imaging
Introduction: Previous studies have demonstrated that the extent of left atrial (LA) myocardial native and ablation-induced scar is associated with post-ablation atrial fibrillation (AF) recurrence. However methodologies to distinguish native versus ablation-induced scar have not been defined. We sought to define the characteristics of native versus ablation-induced LA scar on late gadolinium enhanced (LGE) magnetic resonance imaging (MRI). Methods: LGE-MRI was performed before and at least 3 months after initial pulmonary vein antral isolation in 9 patients. The intra-cardiac locations of ablation points on electro-anatomic mapping were co-registered using custom software with the corresponding sites on the axial planes of post-procedural LGE-MRI. The image intensity ratio (IIR) defined as LA myocardial MRI signal intensity divided by the mean LA blood pool intensity was calculated for native scar on pre-procedural images and ablation-induced scar sites on post-procedural images. Results: Pre- and post-procedural LGE-MRI planes were successfully co-registered with electro-anatomic map data in all cases. IIR values of 2988 ablation-induced scar sites and 1196 native scar sites collected from all patients were calculated. The mean IIR of ablation-induced scar sites on post-procedural images was 14.3% higher than that of native scar sites on the pre-procedural MRI (1.28+/-0.26 vs. 1.12+/-0.11 p\textless0.001). Conclusion: Ablation-induced scar has higher intensity than native scar on LGE-MRI suggesting greater uptake and/or reduced washout of gadolinium compared to regions with native scar.