Relationship between intended sites of RF ablation and post-procedural scar in AF patients, using late gadolinium enhancement cardiovascular magnetic resonance

BackgroundRadiofrequency (RF) ablation of the left atrium (LA) in patients with atrial fibrillation (AF) is guided by electroanatomic mapping systems. The cardiovascular magnetic resonance (CMR) late gadolinium enhancement (LGE) technique can detect scar after ablation. Direct comparisons between the locations of intended RF ablation sites and locations of scar formation in the LA have not been performed.ObjectiveThis study sought to develop and use a method for comparing the sites of RF application with the sites of post-procedural scar formation in the LA.MethodsA method for rigid registration of CMR LGE images with electroanatomic mapping data (Carto data), visualization of the registered data sets, and quantification of the correlations was developed and used in 19 studies of patients with AF. The distance between the Carto points and the CMR LA surface was measured as the mean integration error. The distance between each Carto ablation and the nearest scar was measured. The gaps in sites of LGE and in Carto ablation were also assessed qualitatively, in 6 sectors of each PV.ResultsThe custom registration method provided a mean integration error between Carto and CMR of 2.7 ± 0.7 mm. The average distance between Carto and LGE scar was 3.6 ± 1.3 mm. Qualitatively, 20% of sectors with sites of Carto ablation showed no evidence of LGE.ConclusionThere was a visual and quantitative correspondence between Carto ablation sites and LGE scar, but for 20% of Carto ablation sites there was no visible corresponding LGE.