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Magnetic Resonance Imaging Prior to Ablation for Atrial Fibrosis Helps Gauge Success of Treatment

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Atrial Fibrosis

According to results of Delayed Enhancement (MRI determinant of successful Catheter Ablation of Atrial Fibrillation (DECAAF) trial),  for patients with atrial fibrillation, a delayed enhancement magnetic resonance imaging (DE-MRI) performed prior to ablative treatment can stage the extent of damaged heart tissue (atrial fibrosis) and help determine whether treatment will be a success or not.

"The DECAAF results show that stage of atrial fibrosis prior to ablation is a new, powerful, independent predictor of outcome," said lead investigatorfrom the CARMA Center at the University of Utah in Salt Lake City, USA, Nasir Marrouche, MD.

"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 percent.”

The DECAAF trial involved 260 atrial fibrillation (AF) patients with atrial fibrosis who were scheduled for ablation. The patients, taken from 15 centers in the USA, Europe and Australia were an average age of 59 years, with 64.6 percent of them had paroxysmal AF.

High resolution Delayed Enhancement MRI (DE?MRI) was performed up to 30 days prior to ablation in all patients to assess the presence and degree of atrial fibrosis, while post- ablation DE-MRI was carried out at 90-days follow-up in 177 of the patients, in an attempt to find out the degree of remaining ablation.

For the 90-day follow-up, return of arrhythmia was apparent in 88 of the 260 patients (33.8 percent) based on Holter monitors and electrocardiograms.

Multidimensional analysis showed two independent indicators of successful ablation or returning symptoms were stage of atrial fibrosis prior to ablation (P<0.001) as well as lingering fibrosis after (P<0.001).

Particularly, patients whose pre-ablation fibrosis was stage 1 (defined as less than 10 percent damaged atrial tissue) had an 85.8 percent success rate, while those with stage 2 (10 to 20 percent damage) had a 63.3 percent success rate. Those with stage 3 (20 to 30 percent damage) had a 55 percent success rate; and those with stage 4 (more than 30 percent damage) had a 31 percent success rate.

“For every increased percentage of fibrosis before ablation, there was 6.3 percent increased risk of recurrent symptoms after ablation (hazard ratio [HR] 1.063), “said Marrouche.

Likewise, for every percentage of enduring fibrosis there was an 8.2 percent increased risk of recurrent symptoms (HR 1.082).

A secondary discovery of the study, based on post-ablation imaging, revealed that the kind of ablation physicians applied also had an affect on success rates.

The choice of procedure was not ordered in the study etiquette and was left up to the judgment of physicians.

“After comparing pre-ablation images of fibrotic tissue, with post-ablation images showing the extent of residual fibrosis, a surprise finding was that pulmonary vein ablation, which is the standard-of-care in atrial fibrillation ablation candidates, is not the best ablative approach, “said 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 careBut 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,” he concluded.

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