DECAAF: Targeting MRI-Identified Fibrosis During Ablation Improves Outcomes

September 01, 2013

AMSTERDAM — Delayed enhancement MRI prior to ablation of patients with atrial fibrillation is able to detect the degree of atrial fibrosis and predict ablation success, according to the results of a new study.

Presenting the results of the Delayed Enhancement-MRI Determinant of Successful Catheter Ablation of Atrial Fibrillation (DECAAF) trial here at the European Society of Cardiology (ESC) 2013 Congress, the investigators also reported that ablation of the pulmonary veins was not a significant predictor of treatment success.

"As you all know, today in atrial fibrillation, we're still debating what the best strategy is and where to ablate," said lead investigator Dr Nasir Marrouche (University of Utah, Salt Lake City) during a morning press conference announcing the results. "With this study, what we're trying to see is what the operators are really doing with the heart."

In total, 260 patients with atrial fibrillation, including 65% with paroxysmal atrial fibrillation, were included in the study. All patients underwent a preablation MRI up to 30 days before the procedure and 90 days following the ablation. Based on the degree of atrial remodeling/fibrosis, patients were classified into four groups: stage 1 (<10% fibrosis), stage 2 (>10% to <20% fibrosis), stage 3 (>20% to <30% fibrosis), and stage 4 (>30% fibrosis).

After adjustment for multiple variables, including age, gender, hypertension, comorbidities, type of atrial fibrillation, left atrial volume, and left ventricular ejection fraction, the extent of atrial disease was the only significant predictor of atrial-fibrillation recurrence. Each 1% increase in the extent of atrial fibrosis was associated with a significant 5.8% increased risk of recurrence postablation. For patients classified with stage 1 scarring, 84.6% were free from the arrhythmia at one year compared with just 31% of patients with stage 4 fibrosis. Overall, 64% and 54% of patients with stage 2 and 3 fibrosis were arrhythmia-free at one year.

"The extent of atrial disease was the only predictor of outcomes," said Marrouche. "When you look at the MRI, you can predict the chance of the patient having a recurrence, independent of the operator, experienced centers, and type of lesions. And as you all know, for the past 15 years we've been targeting the pulmonary veins to isolate and treat atrial fibrillation. This is another major finding, that encircling the veins with lesions as seen on the MRI was not important in terms of treatment success."

Speaking with the media, Marrouche said the more fibrotic tissue ablated during the procedure, the better the outcome. To heartwire , he said that he no longer targets the pulmonary veins during every procedure, instead ablating only the MRI-identified fibrosis in the atrium. "I would like everybody to look at the hearts before doing the ablation procedure."

To heartwire , Dr Douglas Zipes (Indiana University School of Medicine, Indianapolis, IN), a past president of the American College of Cardiology, said he was impressed by the data, saying they will help physicians identify good candidates for atrial-fibrillation ablation. "Currently, we don't really screen, and consequently many patients end up undergoing many procedures before a successful outcome," he said. "This helps determine which patients might be more effectively treated with ablation."

Zipes, who was not involved in the trial, said that the pulmonary veins are important triggers for arrhythmia in patients with paroxysmal atrial fibrillation. As the disease progresses, however, the atria remodel, and as they remodel, fibrosis develops. When this happens, the atrial body itself can be responsible for the perpetuation of atrial fibrillation. "Isolating the pulmonary veins at that stage is not going to be as successful as early on," said Zipes. "And that's basically what they're telling us with this study."

Marrouche has received honoraria from Biotronik, Siemens, Boston Scientific, and Boehringer Ingelheim; consulting fees from Sanofi and eCardio; research grants from eCardio and estech; and equipment from Siemens. He also has stock options with MRI-Interventions and holds stock in Marreck.

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