Less than three years ago, my article in this publication¹ (“MR Imaging: New Techniques for the Treatment of Atrial Fibrillation,” November 2008) noted that, “as advanced techniques for scar imaging become available, MRI will be an indispensable tool within the catheter lab itself.” Since then, research involving delayed enhancement magnetic resonance imaging (DE-MRI) has accelerated at an ever-quickening pace.

A number of studies conducted by the Comprehensive Arrhythmia Research and Management (CARMA) Center at the University of Utah have shown that MRI has tremendous potential to improve the diagnosis and treatment of atrial fibrillation (AF). MR angiograms of the left atrium (LA) help to improve anatomical maps, which are used in conjunction with other imaging modalities to determine optimal sites to target during ablation. In addition to the pre-procedure assessment, MRI has been used post-ablation to detect and quantify the extent of scarring in the LA. Scar formation and the location of that scar within the LA are indicators of procedural success and the prevention of AF recurrence. Without this technology, such assessments could only be made using invasive methods.

The most promising new development, however, is the application of DE-MRI as a pre-ablation investigative tool into the structural remodeling of LA wall tissue. When used with custom software tools and computer algorithms (Figure 1), DE-MRI not only calculates the extent of non-healthy LA tissue, but also predicts the success of first-time ablations as well as assists with the selection of optimal rate/rhythm control strategies. Given the costs of ablation procedures and heightened demands for replicable, measurable methods that ensure efficacy, such a prognostic tool has incalculable value. As Cardiovascular Business reported in its January 2011 cover story, “Delayed enhancement MRI could be a game changer.”²

Personalizing AF Management

An innovative DE-MRI visualization technique and analysis protocol developed at the CARMA Center personalizes AF management. By using custom-made, high-resolution DE-MRI sequences, CARMA researchers define areas of enhancement within the atrial wall, which correspond to intramyocardial fibrosis and/or ablation scar. This information is the basis for staging disease progression based on the amount of pre-ablation delayed enhancement (fibrosis) as a percentage of the volume of the LA wall. This clinical staging system includes four stages: Utah I (≤5% enhancement) Utah II (>5–20%), Utah III (>20–35%) and Utah IV (>35%) (Figure 3).