Background-The measurement of late gadolinium enhanced MRI (LGE-MRI) intensity in arbitrary units (au), limits the objectivity of thresholds for focal scar detection and inter-patient comparisons of scar burden.
Objectives
We sought to a) use a novel method of late gadolinium enhancement (LGE) quantification that utilizes normalized intensity measures to confirm the association between LGE extent and atrial fibrillation (AF) recurrence following ablation, and b) examine the presence of interaction and effect modification between LGE and AF persistence.
Background
Recurrent AF after catheter ablation has been reported to associate with the baseline extent of left atrial (LA) LGE on cardiac magnetic resonance (CMR). Traditional methods for measurement of intensity lack an objective threshold for quantification and interpatient comparisons of LGE.
Methods
The cohort included 165 participants (60.0±10.2 years, 77% men, 57% persistent AF) that underwent initial AF ablation. The association of baseline LGE extent with AF recurrence was examined using multivariable Cox proportional hazard models. Multiplicative and additive interaction between AF type and LGE extent were examined.
Results
During 10.2±5.7 months of follow-up, 63 (38.2%) patients experienced AF recurrence. Baseline LGE extent was independently associated with AF recurrence after adjusting for confounders [hazard ratio (HR) 1.5 per 10% increased LGE, P<0.001]. The HR for AF recurrence progressively increased as a function of LGE. The magnitude of association between LGE >35% and AF recurrence was greater among patients with persistent AF (HR 6.5, P=0.001 versus HR 3.6, P=0.001); however, there was no evidence for statistical interaction.
Conclusions
Regardless of AF persistence at baseline, participants with LGE ≤ 35% have a favorable outcome, whereas those with LGE > 35% have a higher rate of AF recurrence in the first year after ablation. These findings suggest a role for a) patient selection for AF ablation using LGE extent, and b) substrate modification in addition to pulmonary vein isolation in patients with LGE extent exceeding 35% of LA myocardium.
Catheter ablation is an important treatment modality for patients with atrial fibrillation (AF). Although the superiority of catheter ablation over antiarrhythmic drug therapy has been demonstrated in middle-aged patients with paroxysmal AF, the role the procedure in other patient subgroups-particularly those with long-standing persistent AF-has not been well defined. Furthermore, although AF ablation can be performed with reasonable efficacy and safety by experienced operators, long-term success rates for single procedures are suboptimal. Fortunately, extensive ongoing research will improve our understanding of the mechanisms of AF, and considerable funds are being invested in developing new ablation technologies to improve patient outcomes. These technologies include ablation catheters designed to electrically isolate the pulmonary veins with improved safety, efficacy, and speed, catheters designed to deliver radiofrequency energy with improved precision, robotic systems to address the technological demands of the procedure, improved imaging and electrical mapping systems, and MRI-guided ablation strategies. The tools, technologies, and techniques that will ultimately stand the test of time and become the standard approach to AF ablation in the future remain unclear. However, technological advances are sure to result in the necessary improvements in the safety and efficacy of AF ablation procedures.
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