(HealthDay News) — Magnetic resonance imaging (MRI) measurements of left atrial scarring in patients with atrial fibrillation (AF) are associated with poor outcomes of first AF catheter ablation, according to a study published in the February 5 issue of the Journal of the American Medical Association.

Nassir F. Marrouche, MD, from the University of Utah School of Medicine in Salt Lake City, and colleagues quantified fibrosis in patients diagnosed with paroxysmal and persistent AF between August 2010 and August 2011 at 15 centers internationally. Blinded assessors characterized fibrosis as stage 1 (<10% of the atrial wall), 2 (≥10 to <20%), 3 (≥20 to <30%), and 4 (≥30%). Delayed enhancement MRI images were taken up to 30 days before ablation.

The researchers found that, for recurrent arrhythmia, the unadjusted overall hazard ratio per 1 percent increase in left atrial fibrosis was 1.06 (P<0.001). The estimated unadjusted cumulative incidence of recurrent arrhythmia by day 325 for stage 1 fibrosis was 15.3%; stage 2, 32.6%; stage 3, 45.9%; and stage 4, 51.1%. Results were similar when adjusting for covariates. Utilizing a recurrence prediction model with traditional clinical covariates resulted in an improved predictive accuracy, with the C statistic increasing from 0.65 to 0.69 (risk difference of 0.05) with the addition of fibrosis.

“Among patients with AF undergoing catheter ablation, atrial tissue fibrosis estimated by delayed enhancement MRI was independently associated with likelihood of recurrent arrhythmia,” the authors write.

Several authors disclosed financial ties to the medical device industry.

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