Abstract
OBJECTIVE: Noninvasive Electrocardiographic Imaging (ECGI) was used to define the mechanisms of atrial fibrillation (AF) in mitral regurgitation (MR), which remain poorly understood. METHODS: Seventeen patients with degenerative MR and AF undergoing were studied. Thirteen age-matched patients with lone AF provided a control group. Epicardial electrograms were constructed noninvasively with ECGI using 256 body surface electrocardiograms and patient-specific heart-torso geometry from delayed-enhancement magnetic resonance imaging (DE-MRI) or computed tomography (CT) scans. Bi-atrial epicardial activation time maps and phase maps were generated. AF drivers were classified as focal (radial activation) or rotors (high curvature wavefront rotating about a center). Left atrial (LA) fibrosis was quantified from the DE-MRI scans in 5 MR patients. RESULTS: The LA and right atrium (RA) harbored 61% and 36% of drivers, respectively and the anterior inter-atrial groove had 3% of the sources. 51% of the drivers were mapped in the posterior LA. One third of drivers occurred repeatedly. The left PV and LA appendage regions had the most repetitive drivers. Activation patterns varied from single macro-reentry to simultaneous wavelets resulting in wave breaks and collisions. Driver distribution and activation patterns remained similar between MR and lone AF groups, except stable rotors were not observed in MR. DE-MRI maps showed bi-atrial fibrosis. Drivers and discontinuous wavefront propagation were often localized in fibrotic regions. CONCLUSIONS: AF activation patterns in MR were complex and exhibited spatio-temporal variability. Bi-atrial drivers were present. The posterior LA harbored the highest percentage of drivers. This region also exhibited fibrosis in a subset of patients, suggesting that it may play a role in creating the AF substrate.