Delayed Enhancement-MRI Scanning Before Atrial Fibrosis Ablation Helps Predict Treatment Effectiveness

The use of delayed enhancement magnetic resonance imaging (DE-MRI) in patients with atrial fibrillation, performed before ablative treatment, can help assess the degree of injured heart tissue (atrial fibrosis) and predict whether treatment will be effective or not.

The recent findings were an outcome of the DE-MRI determinant of successful Catheter Ablation of Atrial Fibrillation (DECAAF) trial. “The DECAAF results show that stage of atrial fibrosis prior to ablation is a new, powerful, independent predictor of outcome,” said lead investigator Nasir Marrouche, MD, from the CARMA Center at the University of Utah (Salt Lake City, USA). “By performing this imaging before ablative treatment we can triage patients according to likelihood of treatment success, and avoid ablative procedures in those patients for whom it is unlikely to work. If a patient has late stage 3 or stage 4 fibrosis their chance of being cured is only 30%–35% which is really low, but if they’re in an early stage, their chance of cure is 60%–80%,” he said.

The DECAAF trial included 260 atrial fibrillation (AF) patients with atrial fibrosis who were in the process of undergoing ablation. The patients, from 15 centers in United States, Australia, and Europe were an average age of 59 years, and 64.6% of them conducted up to 30 days before ablation in all patients to determine the presence and extent of atrial fibrosis, whereas postablation DE-MRI was performed at 90-days follow-up in 177 of the study participants, to determine the extent of residual ablation. At the 90-day follow-up, recurrence of arrhythmia was observed in 88 of the 260 patients (33.8%), based on Holter monitors and electrocardiograms (ECGs).

Multivariate analysis showed two independent predictors of successful ablation or recurrent symptoms were stage of atrial fibrosis before ablation therapy (p < 0.001) as well as residual fibrosis after (p < 0.001). Patients whose preablation fibrosis was stage 1 (defined as less than 10% damaged atrial tissue) had an 85.8% success rate, those with stage 2 (10%–20% damage) had a 63.3% success rate, those with stage 3 (20%–30% damage) had a 55% success rate and those with stage 4 (more than 30% damage) had a 31% success rate.

For every increased percentage of fibrosis before ablation, there was 6.3% increased chance of recurrent symptoms after ablation (hazard ratio [HR] 1.063), according to Dr. Marrouche. Correspondingly, for every percentage of residual fibrosis there was an 8.2% increased risk of recurrent symptoms (HR 1.082).

Based on postablation imaging, a secondary finding of the study revealed that the kind of ablation clinicians used also had an impact on the rate of success. The choice of approach was not dictated in the study protocol and was left to the discretion of individual treating physicians.

After comparing preablation images of fibrotic tissue, with postablation images showing the extent of residual fibrosis, an unexpected finding was that pulmonary vein ablation, which is the standard-of-care in atrial fibrillation ablation candidates, is not the best ablative technique, according to Dr. Marrouche. “We do ablation around the pulmonary veins because we have assumed for years that the trigger for AF comes from the vein—that’s the standard of care,” he said. “But what we found in DECAAF is that ablation of the veins did not predict outcome. In fact, the most important predictor of outcome, along with stage of atrial fibrosis, was the degree of ablation of the fibrotic tissue. Rather than targeting the pulmonary veins, procedures which ablated fibrotic tissue produced better outcomes—the more that was targeted, the better the outcome.”

Related Links:
CARMA Center at the University of Utah