MRI of the left atrium at 3T: Evaluation of measurement reproducibility in healthy volunteers and patients with cardiovascular disease

Background Left ventricular (LV) function has traditionally been the focus for cardiac magnetic resonance imaging (MRI) investigations, but similar methods can also be applied to the left atrium (LA). Previous studies elsewhere have almost entirely involved the use of 1.5T systems, but 3T MRI can provide faster data acquisition with thinner image slices, and may be more suitable for quantifying the structure and function of the LA. Purpose To evaluate 3T-MRI for LA volume assessments in: (i) healthy volunteers (HV); (ii) patients with LV-hypertrophy and ischemia (LVHI); and (iii) patients with LV-hypertrophy and diabetes (LVHD). Material and Methods Participants were imaged using a balanced steady-state free precession sequence. Healthy volunteers were scanned twice and patients were scanned on one occasion. Volumes were segmented by two observers, and coefficients of repeatability (CoR) were derived. Results For LA volumes (indexed to body surface area), CoRs were in the range of 1.3-4.6 mL/m². The LVHI patients had enlarged LA volumes (diastolic, 46.4 mL/m²; systolic, 25.9 mL/m²) and reduced ejection fraction (EF) (44.9%) relative to the HV (diastolic, 39.0 mL/m²; systolic, 17.8 mL/m²; EF, 54.5%) and LVHD groups (diastolic, 41.4 mL/m²; systolic, 20.2 mL/m²; EF, 50.7%). LA volumes were moderately correlated with LV mass in the HV group (R²= 0.59 for LA end-systolic volume), but became weaker (R²≤ 0.17) for patient groups. Conclusion 3T-MRI derived LA volume measurements are simple and repeatable, and can elicit clear differences between LVHI patients and HVs. These MRI endpoints provide scope for improved radiological interpretation of LA structure and function, and the high degree of repeatability validates their use for longitudinal investigations where precision work is essential.