Structural and functional properties of the left atrium in healthy volunteers and patients with atrial fibrillation: Data of magnetic resonance imaging

Abstract

Background. In the recent years, there has been an increasing number of publications postulating that data on left atrial (LA) structure obtained by late gadolinium enhancement magnetic resonance imaging (LGE MRI) can improve the management of patients with atrial fibrillation (AF). At the same time, similar data regarding healthy LA myocardium is limited. Aim. To assess structural and functional properties of LA in healthy volunteers (HV) using cardiac magnetic resonance (CMR) (including LGE MRI); to compare these properties in patients with AF and HV. Materials and methods. We included in this study 53 patients with AF (28 without signs of cardiovascular disease, 28 with hypertension) and 23 HV of similar age. All enrolled persons underwent MRI. Cine-MRI was used to assess end diastolic volume of LA (LA EDV), LA ejection fraction (LA EF), left ventricular diastolic index (LV DI). High resolution LGE MRI was performed 15–20 min after gadoversetamide injection using IR 3D gradient echo pulse sequence with fat saturation (TI 290–340 ms, TE 2.44 ms, TR 610–1100ms). On obtained images LA was segmented semiautomatically. LA fibrosis quantification was performed using developed software LGE Heart Analyzer. The extent of fibrosis was represented as percent of LA myocardium volume. Fibrosis location was determined on reconstructed rotating 3D LA model. Results. Compared with patients HV had lower LA EDV (59 [54; 78] ml and 79 [65.5; 86.6] ml, р=0.043, respectively), higher LA EF (56.1 [49; 63.2] % and 44.5 [34.5, 54.5] %, р=0.03, respectively), and lower extent of LA fibrosis (0.7 [0.05; 3.5] % and 9.1 [1.7; 18] %, р<0.001). In HV sparse foci of fibrosis were located predominately in the inner part of LA posterior wall. In AF predominant fibrosis location was pulmonary vein ostia region. In HV the extent of LA fibrosis correlated with LA EDV (r=0.4, р=0.04), age (r=0.66, p<0.001) and LV DI (r= –0.5, p=0.015). In AF the extent of LA fibrosis correlated with LA EDV (r=0.37, p<0.001), LA EF (r= – 0.4, р<0.001) and grade of hypertension (r=0.35, p=0.01). Conclusions. In HV LA is characterized by normal EDV and EF. Minor LA fibrosis which can be found in HV is located predominantly in inner part of LA posterior wall adjacent to the mitral valve. Patients with AF are characterized by LA dilatation, LA EF reduction and pronounced LA fibrosis (compared to HV) predominantly located near ostia of pulmonary veins.