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

Background

Radiofrequency (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.

Objective

This 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.

Methods

A 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.

Results

The 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.

Conclusion

There 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.

Keywords: Carto, Late gadolinium enhancement, Left atrium, RF ablation, Pulmonary vein isolation, Delayed enhancement, MRI, Contrast agent

Abbreviations: AF, atrial fibrillation, CMR, cardiac magnetic resonance, EAM, electroanatomic mapping, LA, left atrium, LGE, late gadolinium enhancement, LIPV, left inferior pulmonary vein, LSPV, left superior pulmonary vein, LV, left ventricle/ventricular, MIE, mean integration error, MRA, magnetic resonance angiogram, PV, pulmonary veins, PVI, pulmonary vein isolation, RF, radiofrequency, RIPV, right inferior pulmonary vein, ROI, region of interest, RSPV, right superior pulmonary vein