Background Atrial fibrillation (AF) is associated with diffuse left atrial (LA) fibrosis and a reduction in endocardial voltage. These changes are indicators of AF severity and appear to be predictors of treatment outcome. In this study we report the utility of delayed enhancement MRI (DE-MRI) in detecting abnormal atrial tissue prior to radiofrequency ablation and in predicting procedural outcome. Methods and Results Eighty-one patients presenting for pulmonary vein antrum isolation (PVAI) for treatment of AF underwent 3D DE-MRI of the LA prior to the ablation. Six healthy volunteers were also scanned. DE-MRI images were manually segmented to isolate the LA and custom software was implemented to quantify the spatial extent of delayed enhancement, which was then compared to the regions of low voltage from electroanatomical maps from the PVAI procedure. Patients were assessed for AF recurrence at least six months following PVAI with average follow-up of 9.6 ± 3.7 months (range = 6 to 19 months). Based on the extent of pre-ablation enhancement, 43 patients were classified as having minimal enhancement (average enhancement = 8.0% ± 4.2%), 30 as moderate (enhancement = 21.3% ± 5.8%), and 8 as extensive (enhancement = 50.1% ± 15.4%). The rate of AF recurrence was 6 patients (14.0%) with minimal enhancement, 13 (43.3%) with moderate and 6 (75%) patients with extensive enhancement (p <0.001). Conclusion DE-MRI provides a non-invasive means of assessing LA myocardial tissue in patients suffering from AF and might provide insight into the progress of the disease. Pre-ablation DE-MRI holds promise to predict responders to AF ablation and may provide a metric of overall disease progression.

Background While catheter ablation therapy for atrial fibrillation (AF) is becoming more common, results vary widely and patient selection criteria remain poorly defined. We hypothesized that late gadolinium enhancement magnetic resonance imaging (LGE-MRI) can identify left atrial (LA) wall structural remodeling (SRM) and stratify patients who are likely or not to benefit from ablation therapy. Methods and Results LGE-MRI was performed on 426 consecutive AF patients without contraindications to MRI and before undergoing their first ablation procedure and on 21 non-AF control subjects. Patients were categorized by SRM stage (I–IV) based on percentage of LA wall enhancement for correlation with procedure outcomes. Histological validation of SRM was performed comparing LGE-MRI to surgical biopsy. A total of 386 patients (91%) with adequate LGE-MRI scans were included in the study. Post-ablation, 123 (31.9%) experienced recurrent atrial arrhythmias over one-year follow-up. Recurrent arrhythmias (failed ablations) occurred at higher SRM stages with 28/133 (21.0%) stage I, 40/140 (29.3%) stage II, 24/71 (33.8%) stage III, and 30/42 (71.4%) stage IV. In multi-variate analysis, ablation outcome was best predicted by advanced SRM stage (hazard ratio (HR) 4.89; p<0.0001) and diabetes (HR 1.64; p=0.036) while increased LA volume and persistent AF were not significant predictors. LA wall enhancement was significantly greater in AF patients vs. non-AF controls (16.6±11.2% vs. 3.1±1.9%, p<0.0001). Histological evidence of remodeling from surgical biopsy specimens correlated with SRM on LGE-MRI. Conclusions Atrial SRM is identified on LGE-MRI and extensive LGE (≥30% LA wall enhancement) predicts poor response to catheter ablation therapy for AF.

BACKGROUND Lone atrial fibrillation (AF) is thought to be a benign type or an early stage of the disease. OBJECTIVE This study sought to compare the left atrium (LA) substrate using delayed-enhanced magnetic resonance imaging (DE-MRI) in patients with lone AF versus those with comorbidities. METHODS Forty of 333 included patients met criteria for lone AF. All patients underwent DE-MRI to quantify atrial fibrosis as a marker for structural remodeling (SRM) and underwent catheter ablation. Based on the degree of SRM, patients were staged into 4 groups: Utah I (≤5% LA wall enhancement), Utah II (>5% to ≤20%), Utah III (>20% to ≤35%), or Utah IV (>35%). RESULTS Distribution in Utah I to IV was comparable in patients with lone AF and non–lone AF. In both groups, a number of patients showed extensive SRM. Mean enhancement (14.08 ± 8.94 vs. 16.94 ± 11.37) was not significantly different between the 2 groups (P = .0721). In the lone AF group, catheter ablation was successful in suppressing AF in all of Utah I, 81.82% of Utah II, 62.5% of Utah III, and none of Utah IV patients. Similar results were achieved in the non–lone AF group. Outcome after ablation was significantly dependent on the SRM of the LA (P < .001). CONCLUSION The degree of LA structural remodeling as detected using DE-MRI is independent of AF type and associated comorbidities. Selecting appropriate treatment candidates based on the quality and quantity of atrial fibrosis using DE-MRI would improve procedural outcome and avoid unnecessary intervention.

Introduction Left atrial (LA) fibrosis and ablation related scarring are major predictors of success in rhythm control of atrial fibrillation (AF). We used delayed enhancement MRI (DE-MRI) to stratify AF patients based on pre-ablation fibrosis and also to evaluate ablation-induced scarring in order to identify predictors of a successful ablation. Methods and Results One hundred and forty-four patients were staged by percent of fibrosis quantified with DE-MRI, relative to the LA wall volume: minimal or Utah stage 1; <5%, mild or Utah stage 2; 5–20%, moderate or Utah stage 3; 20–35%, and extensive or Utah stage 4; >35%. All patients underwent pulmonary vein (PV) isolation and posterior wall and septal debulking. Overall, LA scarring was quantified and PV antra were evaluated for circumferential scarring 3 months post ablation. LA scarring post ablation was comparable across the 4 stages. Most patients had either no (36.8%) or 1 PV (32.6%) antrum circumferentially scarred. Forty-two patients (29%) had recurrent AF over 283 ± 167 days. No recurrences were noted in Utah stage 1. Recurrence was 28% in Utah stage 2, 35% in Utah stage 3, and 56% in Utah stage 4. Recurrence was predicted by circumferential PV scarring in Utah stage 2 and by overall LA wall scarring in Utah stage 3. No recurrence predictors were identified in Utah stage 4. Conclusions Circumferential PV antral scarring predicts ablation success in mild LA fibrosis, while posterior wall and septal scarring is needed for moderate fibrosis. This may help select the proper candidate and strategy in catheter ablation of AF.