Correlation between AF Substrate Ablation Difficulty and Left Atrial Fibrosis Quantified by Delayed‐Enhancement Cardiac Magnetic Resonance

Abstract

Studies have shown that the presence of left atrial (LA) fibrosis can be assessed by LA delayed-enhancement cardiac magnetic resonance (LA DE-CMR) and may be predictive of outcome after ablation for atrial fibrillation (AF). We sought to test the hypothesis that the amount of LA fibrosis evaluated by DE-CMR correlates with the difficulty of complex fractionated atrial electrograms (CFAE) ablation. Twenty-two consecutive patients (86.4% nonparoxysmal AF) underwent substrate CFAE radiofrequency (RF) ablation (±Pulmonary veins isolation) with AF termination as the endpoint. LA DE-CMR was performed prior to ablation. A global index of DE was defined by an average of six LA segmental scores based on a four-grade scale (no enhancement to maximum enhancement). Time between first RF application and AF termination, and RF duration until AF termination, was recorded. CFAE area/total LA surface was also measured on CARTO maps (Biosense Webster, Diamond Bar, CA, USA). These measures served to evaluate ablation difficulty, and were correlated with CMR images by double-blinded analysis. Ablation restored sinus rhythm in 20 of 22 patients (91%), with a time to terminate AF of 140 ± 91 minutes. There was a significant correlation between the global averaged DE-CMR fibrosis grade and the electrophysiological substrate indexes such as "time to terminate AF" (Rho = 0.70, P = 0.0003), "RF duration until AF termination" (Rho = 0.65, P = 0.001), and a trend toward correlation with "CFAE area/LA surface" (Rho = 0.47, P = 0.03). LA DE-CMR can predict increased difficulty of CFAE ablation in AF. This tool may be beneficial in both selection of patients and ablation strategy.