Abstract Number: Esoc2026a312 Cardiac Photon-Counting Detector Computed Tomography in Acute Ischemic Stroke: Diagnostic Accuracy for Detection of Left Atrial Appendage Thrombus

Background and aims In up to 1/3 of ischemic stroke patients no cause can be identified. Left atrial appendage (LAA) is the primary anatomical origin of cardiac embolism, yet it is often inadequately assessed in stroke etiological workup. The goal of this study was to analyse the diagnostic accuracy of cardiac photon-counting detector computed tomography (PCD-CT) integrated in the hyperacute stroke imaging protocol for detection of LAA thrombus. Methods We conducted a retrospective diagnostic accuracy study of consecutive patients with acute ischemic stroke or transient ischemic attack undergoing emergent cardiac PCD-CT and transoesophageal echocardiography (TEE) between 2023-2025. Cardiac PCD-CT and TEE were assessed for detection of LAA thrombus. Patients with and without LAA thrombus (defined by PCD-CT) were compared. Diagnostic performance metrics for cardiac PCD-CT for LAA thrombus detection were calculated using TEE as gold-standard. Results We included 101 patients, 42 were female (42%), median age was 59 years, 87 patients had acute ischemic stroke (86%). Median time between cardiac PCD-CT and TEE was 2 days. LAA thrombus defined by PCD-CT was present in 12 patients (12%). Patients with LAA thrombus were older (74 versus 58 years, p<0.001) and more frequently had atrial fibrillation (83.3% versus 23.6%, p<0.001). Diagnostic accuracy of PCD-CT was 96% (95% confidence interval [95%CI]=90-99%), sensitivity was 90% (95%CI=56-100), specificity was 97% (95%CI=91-99%), positive predictive value was 75% (95%CI=49-90%) and negative predictive value was 99% (95%CI=93-100%). Conclusions Cardiac PCD-CT integrated as part of the acute stroke imaging protocol has an excellent diagnostic accuracy for detecting LAA thrombi.