Reference right atrial function determined by steady-state free precession cardiovascular magnetic resonance

Background: There is agreement that measurements of atrial volumes and ejection fraction (EF) are superior to atrial diameters for accurate determination of atrial size, follow up studies and prognosis. However, reference values for right atrial volumes and EF for cardiovascular magnetic resonance (CMR) have not been established but are crucial to identify patients with impaired right atrial function. Methods and Results: Atrial function was studied in 70 healthy subjects (52 ± 16 years, 38 male) with both the standard short axis method (SA) and the area-length method (AL) using steady-state free precession gradient-echo cine imaging (SSFP). Intraobserver, interobserver (n = 70) and interstudy (n = 10) variability was assessed for both methods. Maximal volumes, minimal volumes and EF for SA and AL were 101.0 ± 30.2 mL, 50.3 ± 19 mL and 47.2 ± 8.3%, and 103.2 ± 32.6 mL, 50.8 ± 20.2 mL and 51.4 ± 9.2%, respectively. Maximal volumes, minimal volumes and EF were higher with AL than with SA (mean difference: 2.2 ± 4.6 mL, 3.5 ± 3.5 mL and 2.8 ± 2.8%, respectively). Atrial function measurements were not related to gender (p ≥ 0.387) and age (rho ≤ 0.16) with either method. Intraobserver, interobserver and interstudy variability for volumes and EF was lower for SA compared to AL, with narrower limits of agreement. Analysis was faster with AL than with SA (62 ± 18 s versus 7 ± 2 minutes). Conclusion: Normal ranges for right atrial function vary significantly between methods. AL is faster, but less reproducible than SA. Appropriate reference ranges should be used to differentiate normal from abnormal right atrial function.