Myocardial extracellular volume fraction estimations using late enhancement CT in patients with atrial fibrillation: a comparative study with cardiac MR.

Myocardial extracellular volume fraction (ECV) measured via MRI serves as a quantitative indicator of myocardial fibrosis. However, accurate measurement of ECV using MRI in the presence of AF is challenging. Meanwhile, CT could be a promising alternative tool for measuring ECV regardless of sinus rhythm or AF. The purpose of this study was to assess the reliability of estimating ECV using CT in patients with AF by comparing it with MRI-derived ECV. Forty-two patients (n = 42) with AF underwent cardiac CT a median of 12 days before catheter ablation, and cardiac MRI a median of 1 day after catheter ablation. Myocardial ECV measured by CT and MRI was compared. Pre-ablation CT scan was performed in the presence of AF in 25 patients, with the remaining 17 in sinus rhythm (SR). All patients were in SR at the time of MRI post ablation. The average of CT-derived ECVs was 0.277 ± 0.022 and that of MRI-derived ECVs was 0.282 ± 0.019 in patients with AF. The average of CT-derived ECVs was 0.268 ± 0.025 and that of MRI-derived ECVs was 0.278 ± 0.025 in patients with SR at the time of the CT scan. CT and MRI were in good agreement with mean differences of -0.0048 ± 0.027 in AF and - 0.0095 ± 0.0354 in SR. CT-derived ECV in the presence of AF measured before ablation showed good agreement with ECV by MRI in SR after ablation. CT-ECV estimations are reliable and feasible in patients with AF.