Left atrial active contractile function parameters assessed by cardiac MR are sensitive to myocardial iron

Purpose To determine the impact of myocardial iron overload on left atrial (LA) volume and function using MR in patients with systemic iron overload. Materials and Methods Thirty-eight patients with systemic iron overload disease and 10 controls underwent 1.5 Tesla MR performing steady state free precession short-axis cine-series of the LA. Three-dimensional-volumetry was assessed to calculate LA volumes and function. Parameters were indexed (i) to body surface area. The myocardial transverse relaxation rate R2* was determined in the ventricular septum using a multi-echo GRE sequence (breathhold; electrocardiography triggered; 12 echoes; echo time = 1.3-25.7 ms). Results Significantly decreased active atrial emptying fraction (AAEF) (23% 95%-range, 7–34 versus 36% 95%-range, 14–49, P = 0.009), active atrial emptying volume (AAEVi) (5.5 mL/m2 95%-range, 2–11 versus 11.9 mL/m2 95%-range, 3–23, P = 0.008), and active peak emptying rate (APERi) (46 mL/s/m2 95%-range, 29–69 versus 75 mL/s/m2 95%-range, 45–178, P 40 s-1) compared with patients with normal myocardial iron levels (R2* < 40 s−1). Receiver operating characteristics (ROC) analysis revealed higher potential to indicate myocardial iron overload for the AAEF (area under the ROC curve AUC = 0.84; P < 0.0001), APERi (AUC = 0.87; P < 0.0001), and AAEVi (AUC = 0.80; P < 0.0001) compared with LA ejection fraction (LAEF) (AUC = 0.68; P = 0.02) with equal sensitivities and specificities of 82% (AAEF), 79% (APERi), 73% (AAEVi), and 57% (LAEF). Conclusion MR parameters of active LA contractile function were associated with myocardial iron overload. This cross-sectional study suggests impaired active LA contractile function to be sensitive to myocardial iron toxicity. Level of Evidence: 3 J. Magn. Reson. Imaging 2017;45:535–541.