Feasibility and Diagnostic Yield of Left Atrial Appendage Imaging in Comprehensive CT Stroke Protocols

Background/Objectives: Cardioembolic sources account for a substantial minority of ischemic strokes, and in non-valvular atrial fibrillation nearly all left atrial thrombi form in the left atrial appendage (LAA). We asked whether extending a standard CT stroke protocol caudally to cover the LAA would add diagnostic yield for LAA thrombus. Methods: We retrospectively reviewed 616 consecutive patients imaged using a revised CT stroke protocol at a single academic center between March 2018 and March 2020. The acquisition was single-phase, arterial and non-gated. Two cardiothoracic radiologists reassessed every study for adequacy of LAA opacification and for thrombus. Acute stroke was confirmed in 418 patients, of whom 342 had adequate opacification and formed the analysis cohort. Clinical characteristics, stroke etiology, echocardiographic results and dose-length product were abstracted. Results: LAA thrombus was identified on CT in 10 of 342 patients (2.9%). Seven underwent transthoracic echocardiography (TTE), and all were negative; none underwent transesophageal echocardiography (TEE). Atrial fibrillation was more frequent in the thrombus cohort (60% vs. 21.1%, p = 0.010). Among the 332 patients without CT thrombus, 265 of 266 TTE and 17 of 18 TEE studies were also negative, and two patients had positive echocardiography despite a negative CT. Mean dose-length product for the extended protocol was 5054.8 ± 2772.5 mGy·cm and did not differ significantly from the standard protocol (p = 0.66). Conclusions: Extending the CT stroke protocol to the LAA was technically feasible and did not significantly increase radiation dose, but added little diagnostic yield. CT-detected thrombus was not confirmed on subsequent echocardiography. Because no patient in the thrombus cohort underwent TEE, these findings are reported as unconfirmed rather than false-positive and no estimate of diagnostic accuracy can be derived. On current evidence, the extended protocol should complement rather than replace echocardiography.