Assessing left atrial size and pump function in ischemic stroke patients: Is cardiac MRI superior to transthoracic echocardiography?

Objectives: Current guidelines recommend transthoracic echocardiography (TTE) following an ischemic stroke as the primary technique to identify cardiac abnormalities associated with an increased risk of cerebral embolism. It is unclear whether cardiac magnetic resonance imaging (cMRI), a technique shown to provide increased imaging resolution, may also enhance the cardiac assessment of ischemic stroke patients. We compared cMRI with TTE in the evaluation of Left Atrial (LA) size and pump function in a cohort of 44 patients with ischemic stroke. Materials and methods: The biplane method was utilized to acquire LA diameters as well as area measurements in both TTE and cMRI. We calculated LA volume (LAV), LAV index (LAVI), LA Global Longitudinal Strain (GLS) and LA pump function. Results were compared using paired two sample for means t-test. Lin's concordance correlation coefficient (CCC) and Bland-Altman methods quantified the agreement of measurements obtained by TTE and cMRI. Results: LAVI measurements by cMRI were significantly larger (34.97 v. 28.81; p = 0.001) than by TTE. The concordance correlation demonstrated only a weak agreement between LA size measured by cMRI and TTE (rho c = 0.397; p= 0.001, 95% CI 0.16 - 0.59), and the Bland-Altman plot demonstrated that LAVI measured by cMRI averaged 6.3 ml/m2 larger magnitude than those obtained by TTE. Conclusions: Using TTE alone leads to an underestimation of LA abnormalities important in the evaluation of ischemic stroke patients. Nearly one in every five ischemic stroke patients evaluated based on the current guidelines may have a missed potential source of cardiac embolism.