MRI may help identify best candidates for ablation

Physicians managing atrial fibrillation patients may get a hand from delayed enhancement MRI. A study published Feb. 5 in JAMA found that MRI helped predict the likelihood of recurrent arrhythmia in patients treated with catheter ablation based on the degree of detected atrial tissue fibrosis.

DECAAF (Delayed-Enhancement MRI Determinant of Successful Radiofrequency Catheter Ablation on Atrial Fibrillation) study researchers, led by Nassir F. Marrouche, MD, of University of Utah Health Sciences Center in Salt Lake City, wanted to evaluate the feasibility of using delayed enhancement MRI in a broader setting than has been reported in single-center studies. DECAAF involved 15 centers from six countries that had varying degrees of expertise in cardiac MRI and that used a variety of ablation approaches.

DECAAF enrolled 329 patients between 2010 and 2011 with atrial fibrillation who underwent catheter ablation and were followed for at least one year. Less than 30 days before the procedure, patients underwent delayed enhancement MRI of the left atrium to quantify the degree of atrial fibrosis. Small studies suggested that extensive fibrosis was associated with recurrent arrhythmia.

After excluding patients for poor quality imaging or loss to follow-up, they evaluated 260 patients. Based on MRI findings, patients were categorized as stage 1 (detected fibrosis of less than 10 percent of the atrial wall, 18.9 percent of the patients); stage 2 (10 percent or greater but less than 20 percent, 41.2 percent of the patients); stage 3 (20 percent or greater but less than 30 percent, 30.8 percent of the patients); and stage 4 (30 percent or greater, 9.2 percent of the patients).

The percent of atrial fibrosis was strongly associated with recurrent arrhythmia in adjusted analyses. They defined recurrence as any episode of atrial fibrillation, atrial flutter or tachycardia of at least 30 seconds that occurred after the 90-day blanking period.

The unadjusted overall hazard ratio per 1 percent increase in fibrosis was 1.06. By day 325, the unadjusted cumulative incidence of recurrent arrhythmia was 15.3 percent for stage 1, 32.6 percent for stage 2, 45.9 percent for stage 3 and 51.1 percent for stage 4. By day 475, it was 15.3 percent, 35.8 percent, 45.9 percent and 69.4 percent, respectively.

The results suggest that delayed enhancement MRI may be a useful tool in a spectrum of clinical settings for selecting patients for catheter ablation therapy, Marrouche and colleagues wrote. “[I]t would be clinically useful if patients likely to respond could be identified and selected for ablation while other patients not likely to respond to ablation could be counseled against this procedure. The DECAAF study demonstrates the feasibility and potential clinical value of such a concept by evaluating atrial fibrosis noninvasively using MRI prior to the ablation procedure in a multicenter setting.”

They acknowledged that 17.3 percent of DECAAF patients were not evaluated because of poor quality MRI imaging, primarily due to technologist error. They proposed that insights gained from identifying the reasons for poor quality could be used to improve image quality in the future.