Background Atrial fibrillation (AF) is associated with diffuse left atrial (LA) fibrosis and a reduction in endocardial voltage. These changes are indicators of AF severity and appear to be predictors of treatment outcome. In this study we report the utility of delayed enhancement MRI (DE-MRI) in detecting abnormal atrial tissue prior to radiofrequency ablation and in predicting procedural outcome. Methods and Results Eighty-one patients presenting for pulmonary vein antrum isolation (PVAI) for treatment of AF underwent 3D DE-MRI of the LA prior to the ablation. Six healthy volunteers were also scanned. DE-MRI images were manually segmented to isolate the LA and custom software was implemented to quantify the spatial extent of delayed enhancement, which was then compared to the regions of low voltage from electroanatomical maps from the PVAI procedure. Patients were assessed for AF recurrence at least six months following PVAI with average follow-up of 9.6 ± 3.7 months (range = 6 to 19 months). Based on the extent of pre-ablation enhancement, 43 patients were classified as having minimal enhancement (average enhancement = 8.0% ± 4.2%), 30 as moderate (enhancement = 21.3% ± 5.8%), and 8 as extensive (enhancement = 50.1% ± 15.4%). The rate of AF recurrence was 6 patients (14.0%) with minimal enhancement, 13 (43.3%) with moderate and 6 (75%) patients with extensive enhancement (p <0.001). Conclusion DE-MRI provides a non-invasive means of assessing LA myocardial tissue in patients suffering from AF and might provide insight into the progress of the disease. Pre-ablation DE-MRI holds promise to predict responders to AF ablation and may provide a metric of overall disease progression.

Background-Atrial fibrillation (AF) is a progressive condition that begins with hemodynamic and/or structural changes in the left atrium (LA) and evolves through paroxysmal and persistent stages. Because of limitations with current noninvasive imaging techniques, the relationship between LA structure and function is not well understood. Methods and Results-Sixty-five patients (age, 61.2Ϯ14.2 years; 67% men) with paroxysmal (44%) or persistent (56%) AF underwent 3D delayed-enhancement MRI. Segmentation of the LA wall was performed and degree of enhancement (fibrosis) was determined using a semiautomated quantification algorithm. Two-dimensional echocardiography and longitudinal LA strain and strain rate during ventricular systole with velocity vector imaging were obtained.

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