Development of a 3D patient-specific model for atrial fibrosis assessment in patients with atrial fibrillation

I. INTRODUCTION Atrial fibrillation (AF) is the most common arrhythmia and its treatment remains suboptimal. Catheter ablation is a promising AF therapy whose success is limited by uncertainty in the mechanisms sustaining arrhythmia. Recently, delayed enhancement magnetic resonance imaging (DE–MRI) has been proposed to optimize AF diagnosis and treatment through the assessment of atrial fibrosis, which is considered an arrhythmogenic substrate. Several studies [1,2] report that fibrotic tissue distribution on the atrial wall is an independent predictor of arrhythmia recurrences after the ablation procedure. II. AIM In this study, we developed a fully-automated 3D patient–specific left atrium (LA) model integrating anatomical and structural information derived from magnetic resonance angiography (MRA) and DE-MRI, in order to assist the electrophysiologist in patient selection for the ablation procedure. III. METHODS MRA and DE-MRI in five patients with AF were acquired pre-ablation. A 3D patient-specific anatomical model was derived from the MRA data, applying a fully automated segmentation algorithm based on a level set approach guided by a phase–based edge detector. An affine registration based on mutual information was applied to register MRA into the spatial domain of DE-MRI. Once affine registration parameters were obtained, the grey level intensity from DE-MRI was used as a texture for the 3D LA patient-specific model, allowing the 3D visualization of LA fibrosis location and extent. A thresholding algorithm [3] based on the normalized voxel intensity was optimized and applied for the fibrosis quantification. IV. RESULTS The fully-automated approach was feasible in all patients. Based on fibrosis quantification, one patient was in class Utah 2 (fibrosis percentage: 19.4%; LA volume: 160 ml), two were classified Utah 3 (25.8%, 126ml and 24.3%, 86ml) and two were in class Utah 4 (38.6%, 87ml and 50.2%, 55ml). No patient experienced AF recurrence at four month follow-up. V. CONCLUSION The 3D LA patient-specific model including structural information seems a promising tool for a correct fibrosis localization and quantification, potentially able to optimize patient selection for AF ablation.