DECAAF: Delayed-Enhancement MRI (DE-MRI) Determinant of Successful Radiofrequency Catheter Ablation of Atrial Fibrillation

Atrial fibrillation (AF) is an electrophysiological condition characterized by a
disorganized electrical activity in the atria of the heart. AF is associated with structural
heart disease including hypertension, systolic and diastolic ventricular dysfunction and
valvular heart disease. It represents a significant public health problem with the
increasing longevity of the general population. A major determinant of the progression of AF
is structural remodeling or fibrosis that occurs in the left atrium. A more extensively
remodeled atrium represents the substrate needed for the arrhythmia to persist. Structural
remodeling is also a major determinant for success of rhythm control strategies in AF. While
catheter ablation has been reproducibly shown to be superior to anti-arrhythmic drug therapy
for rhythm control in AF, the success of this procedure is significantly affected by the
extent of structural remodeling present at the time of catheter ablation.

Delayed-Enhancement Magnetic Resonance Imaging (DE-MRI) has been demonstrated to be a very
effective modality in identifying fibrotic and scarred cardiac tissue with excellent
correlation with autopsy findings. This is related to the characteristics of Gadolinium, an
extracellular contrast agent that is very effective in identifying regions of fibrotic
non-viable myocardium. DE-MRI technology can be a very powerful, non-invasive method, of
identifying the extent and the distribution of structural remodeling or fibrosis associated
with AF.

Applying DE-MRI technology to the atrium causes significant technical challenges. The atrial
wall is often a few millimeters thick which requires high spatial resolution to obtain
adequate and useful images. In addition, image acquisition has to be gated to the diastolic
phase of the atrial contraction cycle, which may be difficult to do when the patient is in
AF. The ongoing research at the University of Utah has shown significant progress and very
promising results overcoming the challenges mentioned. Specific image acquisition sequences
have allowed for reproducible identification of high pixel intensity regions within the
2-dimensional images of the atrial wall. Three-dimensional reconstruction of the entire left
atrium then provides a quantification of the overall volume occupied by these hyper-enhanced
regions relative to the entire left atrial wall volume. Used prior to catheter ablation,
DE-MRI can therefore identify regions of significant structural remodeling or fibrosis. The
same technology has also been shown to be very useful in examining the amount and
distribution of ablation related scarring.

Clinical patient characteristics will be collected for this study from clinic visits and
chart reviews.

Imaging Protocol: All patients will undergo a DE-MRI within 30 days prior to the AF ablation
procedure using a DE-MRI protocol. The purpose of the initial MRI is to quantify the degree
of atrial structural remodeling or fibrosis pre-ablation. Following ablation, DE-MRI will be
obtained at 3, 6, and 12 months follow-up to detect and quantify ablation-related scar
formation (Figs. 4-5).

Clinical Follow-up: The institution where the ablation was performed will continue
post-procedural care following standard of care procedures. Monitoring and definition of
atrial arrhythmia AF recurrences will be guided by the HRS consensus document on ablation of
atrial fibrillation.

Clinical and MRI data will be stored using the IRB-approved University of Utah database.
De-identified clinical data and MRI images from participating institutions will also be
submitted to the database, and will be processed at the University of Utah for pre- and
post-ablation fibrosis and scar quantification. The ablation strategy utilized and
procedural endpoint will be left to the discretion of the operators at the participating
sites. This data will also be collected and included in the final analysis. MRI image
processors at the University of Utah will be blinded to the ablation technique and mother
institution using a unique de-identified study participant ID number.

Atrial arrhythmia recurrences will be catalogued up to one year post-ablation and predictors
of recurrences determined by multivariate/survival analysis. The specific mechanism and
electrophysiological characteristics of atrial arrhythmia recurrence will also be analyzed.

Inclusion Criteria:

- Patients who underwent an AF ablation as per recent Heart Rhythm Society (HRS)
consensus document, as per the University of Utah AFIB Database (IRB_00020347)

- Patients who have had an MRI post-ablation.

- Age ≥18 years.

Exclusion Criteria:

- Contraindication for DE-MRI with a full dose of Gadolinium-based contrast agent.

- Previous left atrial ablation or surgical procedure

- Renal failure with CrCl <60 ml/min

- Women currently pregnant, breastfeeding, or of childbearing age not currently taking
or not willing to use a reliable form of contraception

- Mental or physical inability to take part in the study

- Uncontrolled hypertension

- Morbid obesity (BMI > 35), or inability to be placed in MRI due to body mass.

- Patients who have not had a DE-MRI post-ablation.