Abstract 16668: Characterisation of the Structural Phenotype in Atrial Fibrillation by Combined Cardiac Computed Tomography and Atrial Magnetic Resonance Imaging: Towards a Differentiated Approach to Patients With Atrial Fibrillation

Abstract

Rational: Atrial remodelling (AR) is the persistent change in atrial structure and/or function and contributes to the initiation, maintenance and progression of AF. Left atrial (LA) size, geometry, fibrosis, wall thickness (LAWT) and ejection fraction (LAEF) have all been shown to vary with pathological AR. The association of these global remodelling markers with each other for differentiating structural phenotypes in AF is not well investigated. Method: Patients referred for first-time AF ablation and controls without AF were prospectively recruited to undergo cardiac CT and MRI with 3D atrial LGE sequences. LAWT based on the eikonal equation, atrial myocardial mass, LA volume and sphericity were calculated from CT. Biplane LA EF and LA fibrosis burden (IIR method) were derived from atrial MRI. Results were compared between patients with AF and controls. Statistical significance was set at α 0.05. Results: 42 AF patients (64.3% male, age 64.6+/- 10.2 , CHA2DS2-VASc 2.48+/- 1.5, 69.0% paroxysmal AF, 31% persistent AF, LVEF 57.9+/-10.5%) and 37 controls (64.9% male, age 56.6+/-7.2, CHA2DS2-VASc 1.54 +/-1, LVEF 60.4 +/- 4.9%) were recruited. Patients with AF had a significantly higher LAWT, mass, fibrosis burden, left atrial size and lower LAEF compared to controls. There was no significant correlation between % fibrosis with LAWT (p 0.573), mass (p 0.775), volume (p 0.407) or sphericity (p 0.855). LAWT had a weak positive correlation with LA volume (p=0.041), but not with sphericity (p 0.86). LAEF had a weak negative correlation with fibrosis (p 0.025) and LAWT (p 0.017) Conclusion: AF is associated with significant quantifiable structural changes yet individual remodelling markers do not or only weakly correlate with each other suggesting different remodelling subtypes exist (e.g. fibrotic, hypertrophic, dilated). Structural phenotyping may provide insight in the individual AF mechanism and inform a more differentiated approach to the heterogenous AF population.