Background: Addition of cardiac CT (CCT) to the acute stroke brain imaging set is potentially useful at determining aetiology of stroke. In dual-phase CCT, left atrial filling defects (LAFD) in the early phase and not the late phase represent slow mixing of contrast and blood in the left atrium, giving the false appearance of thrombus. The significance of this finding is uncertain. We aimed to assess if early phase LAFD in acute stroke imaging is associated with cardioembolic stroke aetiology.
Methods: We performed a retrospective review of prospectively collected clinical and radiological data of patients undergoing non-ECG gated dual-phase CCT with confirmed stroke at a comprehensive stroke centre from November 2020 to April 2024.
Results: A total of 774 patients were identified. After excluding patients with incomplete imaging (n= 18) or filling defect in the late phase (n=31), 725 patients were included, with 69 (9.5%) patients having LAFD in the early phase of CCT. Patients with early phase LAFD were more likely to have history of atrial fibrillation (72.5% vs 23.5%, p<0.01), develop atrial fibrillation during inpatient admission (42.0% vs 19.4%, p<0.01) and have larger left atrial size (median 30 cm2 vs 20 cm2, p< 0.01). Early phase LAFD was associated with cardioembolic stroke (69.5% vs 33.1%, p<0.01).
Conclusions: Patients with early phase LAFD detected on acute CCT are more likely to have a cardioembolic stroke aetiology and this finding may prompt an extended cardiac evaluation. Future studies may evaluate if early phase LAFD independently confers increased stroke risk.