New Magnetic Resonance Imaging-Based Method for Defining the Extent of Left Atrial Wall Injury After the Ablation of Atrial Fibrillation
Christopher J. McGann, MD*,
Eugene G. Kholmovski, PhD*,
Robert S. Oakes, BS , ,
Joshua J.E. Blauer, BS,,
Marcos Daccarett, MD,
Nathan Segerson, MD,
Kelly J. Airey, MD,
Nazem Akoum, MD,
Eric Fish,,
Troy J. Badger, MD,
Edward V.R. DiBella, PhD*,,
Dennis Parker, PhD*,,
Rob S. MacLeod, PhD, and
Nassir F. Marrouche, MD,*
* Radiology Department, University of Utah School of Medicine, University of Utah, Salt Lake City, Utah
Division of Cardiology, Internal Medicine, University of Utah School of Medicine, University of Utah, Salt Lake City, Utah
Bioengineering Department, University of Utah, Salt Lake City, Utah
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Figure 1 Left Atrial Injury Before PVAI and 3 Months After PVAI on 3D DE-CMRI
Left panels show LA wall slices at baseline (A) and 3 months after PVAI (B) on 3D navigated DE-CMRI in 4 different patients. Right panels show 3D rendering of LA in Patient #1 before and after PVAI in multiple views (posterior, right, left, and superior) reconstructed from MRI slice data. Post-PVAI hyperenhancement of LA wall is clearly seen (yellow arrows) in regions subjected to RF ablation and suggests scarring. 3D = three-dimensional; DE-CMRI = delayed-enhancement cardiac magnetic resonance imaging; LA = left atrial/atrium; MRI = magnetic resonance imaging; PVAI = pulmonary vein antrum isolation; RF = radiofrequency.
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Figure 2 Automated Quantification of Chronic LA Injury 3 Months After PVAI
Left atrial wall injury was determined using a threshold based on the defined normal wall regions. Panels 1 to 16 show extent of injury at 5 standard deviations in a subset of slices from the 3D DE-CMRI from Patient #1 (Fig. 1). Reconstruction in 3D of the full set of data is shown in the right panels (3D PA and RL views). Using these methods, LA injury volume can be determined and calculated as a percentage of total LA wall volume. PA = posterior-anterior; RL = right-left; other abbreviations as in Figure 1.
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Figure 3 Overlay Images of LA Wall Injury
Panels 1A to 1D are 4 example LA slices from the 3D DE-CMRI from Patient #1 (Fig. 1) that show close correlation of LA injury as determined by automated methods using a 3-SD cutoff value (blue transparency) overlaying MRI. Right panels show 3D overlay of full data set (3D PA and RL). LA injury mask (blue) determined by automated methods should match and overlay hyperenhanced areas (white) of true injury on DE-CMRI. Although the left pulmonary veins are white on MRI, this enhancement is attributable to navigator interference, not injured tissue, as we position the navigator over the right hemidiaphragm. The PVs are shown here only to help with anatomical orientation and are excluded from raw data used to produce injury mask by automated methods. Abbreviations as in Figures 1 and 2.
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Figure 4 Association Between Atrial Fibrillation Recurrences and Clinical Success According to LA Wall Injury After Catheter-Based PVAI
Patients with minimal scar formation at 3 months after the procedure (>13% of LA myocardial volume enhancement on DE-MRI) had low procedural success and a high recurrence of atrial fibrillation, whereas patients with moderate scar formation at 3 months had very high procedural success and a low recurrence of atrial fibrillation. Abbreviations as in Figure 1.
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Figure 5 Delayed-Enhancement MRI Scans Acquired 3 Months After a First (Failed) Procedure and a Second (Successful) Procedure
Incomplete scar formation located near the antrum of the pulmonary veins after failed isolation was noted in both patient examples. The gap in RF lesions at the pulmonary vein antrum (purple) correlated with incomplete electrical isolation of the left superior pulmonary vein. Delayed-enhancement MRI at 3 months after the repeat PVAI shows complete scar formation (white/orange) isolating the pulmonary veins. Both patients were free of AF at follow-up. Posterior and left lateral views are shown. Abbreviations as in Figure 1.
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