MRI-guided ablation no better than conventional PVI for Atrial Fibrillation

Key Points:                                         

• DECAAF-1 showed that higher volumes of atrial tissue fibrosis on cardiac MRI were associated with higher rates of atrial arrhythmia recurrence after catheter ablation.

• Patients were randomized to undergo MRI-guided ablation in addition to pulmonary vein isolation verses conventional pulmonary vein isolation and followed for 12-18 months to assess for atrial arrhythmia recurrence.

• MRI-guided ablation did not decrease rates of atrial arrhythmia recurrence, and was found to have higher adverse events, including stroke.

The original Delayed-Enhancement MRI Determinant of Successful Radiofrequency Catheter Ablation of Atrial Fibrillation (DECAAF) study (JAMA) found that atrial tissue fibrosis estimated by delayed enhancement cardiac MRI was associated with likelihood of recurrent arrhythmias in patients undergoing catheter ablation for atrial fibrillation (AF). The results showed that the more severe the fibrosis, the more likely AF was to recur, with a cumulative incidence of almost 70% at 18 months in those with stage 4 fibrosis. DECAAF-II, therefore, sought to expand upon those results. The authors postulated that imaging-guided fibrosis ablation in addition to conventional pulmonary vein isolation (PVI) would be superior to PVI alone in patients with persistent AF.

The results of the study were presented in a Hot Line Session at the European Society of Cardiology Congress 2021 by Dr. Nassir Marrouche (Tulane University School of Medicine).

In this industry-sponsored, prospective, multicenter trial, 843 participants with persistent AF underwent a baseline cardiac MRI, after which they were randomized to receive MRI-guided PVI or conventional PVI for treatment of their AF. During the ablation, operators in the investigation group were instructed to cover the more fibrotic areas seen on MRI in addition to the pulmonary veins, and those in the control group were instructed to only encircle the pulmonary veins, as is standard practice. Those in the investigation group also underwent a three-month MRI to assess for new, ablation-mediated fibrosis that may have occurred.

The primary endpoint of the study was time to atrial arrhythmia recurrence after the standard 90 day blanking period. Participants were followed for 12 to 18 months using a variety of ambulatory monitoring: smartphone ECGs (given to all participants), Holter monitor recordings, and standard 12-lead ECGs.  Safety outcomes were assessed as well, and included stroke, pulmonary vein stenosis, bleeding requiring transfusion, heart failure, death and cardiac tamponade. Participants were mostly male (78.9%) with a mean age of 62 years. Most participants had either Stage II (47%) or Stage III (34.2%) fibrosis.

In the intention to treat analysis, there was no significant difference between MRI-guided and conventional PVI when it came to the primary outcome of atrial arrhythmia recurrence or repeat ablation (43% vs. 46.1%, HR 0.95 [95% CI 0.77 – 1.17], p =0.63). A subgroup analysis of those with Stages I and II fibrosis, however, showed a trend toward lower rates of arrhythmia recurrence. There were 6 stroke events in the MRI-guided ablation group, 4 of which were in those with higher stages of fibrosis, compared to 0 in the conventional group (p = 0.013). Rates of other complications were also numerically higher for the investigational group.

The as-treated analysis, which assessed atrial arrhythmia recurrence according to the proportion of covered fibrosis on the three month follow up MRI also confirmed a benefit of image-guided ablation in patients with Stage I or II fibrosis (HR 0.839 [95% CI 0.732–0.961; p<0.05]).

Dr. Gerhard Hendricks, in discussing the results after the presentation, called this the most important atrial fibrillation study since CABANA, as it gains information that was previously unavailable by linking ablation data to serial MRI data. Regardless, when asked about these findings, Dr. Marrouche said they indicate that “PVI should remain the mainstream ablation strategy in AF patients with high levels of fibrosis”.