Background
Myocardial fibrosis is key for atrial fibrillation (AF) maintenance. We aimed to test the efficacy of ablating cardiac magnetic resonance (CMR)-detected atrial fibrosis plus pulmonary vein isolation (PVI).
Methods
- This was an open label, parallel-group, randomized, controlled trial. Patients with symptomatic drug-refractory AF (paroxysmal and persistent) undergoing first or repeat ablation were randomized in a 1:1 basis to receive PVI plus CMR-guided fibrosis ablation (CMR group) or PVI alone (PVI-alone group). The primary endpoint was the rate of recurrence (>30 seconds) at 12 months of follow-up using a 12-lead ECG and Holter monitoring at 3, 6, and 12 months. The analysis was conducted by intention-to-treat.
Results
- In total, 155 patients (71% male, age 59±10, CHA2DS2-VASc 1.3±1.1, 54% Paroxysmal AF) were allocated to the PVI-alone group (N=76) or CMR group (N=79). First ablation was performed in 80% and 71% of patients in the PVI-alone and CMR groups, respectively. The mean atrial fibrosis burden was 12% (only 〜50% of patients had fibrosis outside the pulmonary vein area). 100% and 99% of patients received the assigned intervention in the PVI-alone and CMR group, respectively. The primary outcome was achieved in 21 patients (27.6%) in the PVI-alone group and 22 patients (27.8%) in the CMR group (odds ratio[OR]: 1.01, 95% confidence interval [CI] 0.50-2.04; p=0.976). There were no differences in the rate of adverse events (3 in the CMR group and 2 in the PVI-alone group; p=0.68).
Conclusions
- A pragmatic ablation approach targeting CMR-detected atrial fibrosis plus PVI was not more effective than PVI alone in an unselected population undergoing AF ablation with low fibrosis burden
Aims
Myocardial fibrosis is a hallmark of atrial fibrillation (AF) and its characterization could be used to guide ablation procedures. Late gadolinium enhanced-magnetic resonance imaging (LGE-MRI) detects areas of atrial fibrosis. However, its accuracy remains controversial. We aimed to analyse the accuracy of LGE-MRI to identify left atrial (LA) arrhythmogenic substrate by analysing voltage and conduction velocity at the areas of LGE.
Methods and results
Late gadolinium enhanced-magnetic resonance imaging was performed before ablation in 16 patients. Atrial wall intensity was normalized to blood pool and classified as healthy, interstitial fibrosis, and dense scar tissue depending of the resulting image intensity ratio. Bipolar voltage and local conduction velocity were measured in LA with high-density electroanatomic maps recorded in sinus rhythm and subsequently projected into the LGE-MRI. A semi-automatic, point-by-point correlation was made between LGE-MRI and electroanatomical mapping. Mean bipolar voltage and local velocity progressively decreased from healthy to interstitial fibrosis to scar. There was a significant negative correlation between LGE with voltage (r = −0.39, P < 0.001) and conduction velocity (r = −0.25, P < 0.001). In patients showing dilated atria (LA diameter ≥45 mm) the conduction velocity predictive capacity of LGE-MRI was weaker (r = −0.40 ± 0.09 vs. –0.20 ± 0.13, P = 0.02).
Conclusions
Areas with higher LGE show lower voltage and slower conduction in sinus rhythm. The enhancement intensity correlates with bipolar voltage and conduction velocity in a point-by-point analysis. The performance of LGE-MRI in assessing local velocity might be reduced in patients with dilated atria (LA diameter ≥45).
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