Assessment of Atrial Fibrillation Substrate: Correlation between Left Atrial Function and Myocardial Fibrosis by Non-Invasive Imaging

Purpose The atrial fibrillation (AF) substrate can be characterized by left atrium (LA) fibrosis assessed by delayed-enhancement cardiac magnetic resonance (CMR), potentially guiding therapeutic strategies and predicting outcomes in patients with AF undergoing the catheter ablation (CA) procedure. Two-dimensional speckle tracking echocardiography (2D-STE) can assess LA function and has been shown to be predictive of CA success. This study evaluated the correlation between LA function by 2D-STE and LA fibrosis by delayed-enhancement CMR in patients with paroxysmal AF before the CA procedure. Methods This was a single-centre, prospective study of patients undergoing the CA procedure due to symptomatic drug-refractory paroxysmal AF. LA function was assessed by 2D-STE. Strain (S) and strain rate (SR) curves were obtained for the assessment of reservoir (LASs, LASRs), conduit (LASe, LASRe) and booster pump (LASa, LASRa) phases. Quantification of LA fibrosis was obtained using delayed-enhancement CMR according to the Utah classification. LA fibrosis was defined as Utah stage > 1 (≥ 10%). Results Eighty-six patients were studied. LASa and LASRa were abnormally low in all Utah fibrosis stages. LASs, LASe, LASRs and LASRe significantly decreased as the burden of fibrosis increased. LASRe proved to be an independent predictor of LA fibrosis by delayed-enhancement CMR with a cut-off point of -1.6 s -1 , AUC of 0.72, sensitivity of 80% and specificity of 75% with PPV 0.52 and NPV 0.89. Conclusions LASRe was the strongest independent predictor of LA fibrosis by delayed-enhancement CMR. Further investigations are needed to assess to long-term the ablation success / freedom from arrhythmia after catheter ablation, which should be correlated with the potential of LASRe to predict LA fibrosis.