Introduction: Atrial fibrillation (AF) is the most common arrhythmia in the clinical setting. Structural atrial remodeling has been observed in clinical and experimental AF models and proved to play a major role in the AF substrate. The relationship between left atrial (LA) structure and function is not fully elucidated.
Patients and methods: Thirty four patients with AF who underwent pulmonary vein isolation (cryo- or radiofrequency ablation) were included between April 2016 and May 2017. They were subjected prior to the Ablation to a 3-dimensional delayed-enhancement MRI and the degree of LA wall fibrosis was detected and quantified using a semi-automated quantification algorithm (Marrek). All patients underwent an echocardiography with tissue Doppler measurements as well as left atrial strain rate obtained by speckle tracking.
Results: Five patients were excluded due to suboptimal echocardiographic images. 29 eligible patients with mean age of 62± 11 years old (42% women) were enrolled for further analysis. 76 % of our cohort had paroxysmal AF prior to the ablation. Mean fibrosis was 14.45 ± 5.63%. Ten patients revealed a Utah-score 1 in MRI whereas 55% of the patients showed a Utah-score 2. Left atrial fibrosis detected with cardiac-MRI showed a strong positive correlation with pA-TDI interval (r=0.84, p<0.0001) and was inversely correlated to left atrial strain rate (r= -0.521, p= 0.005). Moreover, a significant correlation between the left atrial fibrosis obtained in MRI and echocardiographic left atrial volumes was found (r=0.450, p=0.019) irrespective of the paroxysmal or persistent nature of AF.
Conclusion: LA wall fibrosis by delayed-enhancement MRI correlates with a prolonged atrial electromechanical coupling (PA-TDI interval). The disturbed left atrial compliance accompanying AF was revealed through both techniques. Echocardiographic evaluation of LA functional remodeling is feasible and can improve the assessment.