Objective: Contrast-enhanced computed tomography (CT) is a convenient method to visualize left atrial appendage (LAA) thrombi. We determined whether diagnostic accuracy improves by including dual-energy as compared to transesophageal echocardiography (TEE). Furthermore, the influence of protocol parameters on radiation dose were quantified.
Methods: Patients were assigned to the different CT protocols. All CTs were assessed qualitatively for presence of LAA thrombi and dual-energy CT scans quantitatively for iodine concentration. TEE was assessed qualitatively for the presence of thrombi.
Results: Of 32 enrolled patients, 6 had a thrombus in TEE. Qualitative CT assessment yielded 83% sensitivity and 88% specificity. In the 26 patients who underwent dual-energy CT, median iodine concentration was 8.6 mg/cm3 and significantly lower in patients with than without LAA thrombi ; furthermore, it provided value for detecting LAA thrombi (AUC: 0.950 vs 0.867 for combined vs. only qualitative assessment, p = 0.04). The median radiation dose was 1.83 mSv; independently lower in scanning only LAA and with prospective gating , while arrhythmia and dual-energy did not contribute independently.
Conclusion: CT provides good diagnostic accuracy for detecting LAA thrombi, which can further be improved if iodine density measurements by dual-energy are incorporated. With an optimized protocol, reasonably low radiation dose can be achieved.
Keywords: Computed tomography; Dual-energy imaging; Intracardial thrombus; Iodine concentration; Transesophageal echocardiography.