Clinical History A 46 year old man presented with middle cerebral artery (MCA) territory cerebral infarct, thought to be of embolic origin. After receiving thrombolytic therapy, the patient was referred for a transesophageal echocardiography to exclude a left atrial thrombus. Approximately one week later, the patient was referred for CT angiography (CTA).
Findings Transesophageal echocardiography demonstrated a dilated left atrium, with spontaneous echo contrast (Figure 1), showing reduced emptying velocities within the left atrial appendage, but no definite evidence of thrombus was identified. One week later, a cardiac CTA revealed incomplete opacification of the left atrial appendage, suggestive of thrombus. A delayed image was obtained, demonstrating persistent poor opacification of the left atrial appendage, most consistent with the presence of a thrombus that most likely developed in the interim between the ultrasound study and the cardiac CTA.
(Click on images to enlarge)
Figure 1. Transesophageal echocardiography (mid-esophageal view) of the left atrium demonstrates swirling echoes in the left atrial appendage.
Figure 2.Paraseptal longaxis MIP images of CTA at arterial phase and delayed equilibrium phase highlight the persistent filling defect in the LAA.
Figure 3. Axial arterial-phase CTA demonstrates an expanded left atrial appendage with a filling defect. This could represent either slow mixing, or thrombus.
Figure 4.Equilibrium-phase (delayed) axial CTA image demonstrates persistence of the filling defect in the expanded left atrial appendage, confirming the presence of thrombus in the appendage.
Discussion 64-detector-row CTA is a noninvasive and sensitive modality for detecting thrombi in the left atrial appendage of stroke patients. Currently, transesophageal echocardiography is considered the gold-standard for the detection of left atrial appendage thrombi, but multidetector cardiac CTA with delayed phase imaging has the potential to become a useful clinical modality for the detection of left atrial thrombus in patients who cannot undergo a transesophageal examination. This important cause of embolic stroke should be considered in cases of ischemic embolic neurologic events.
Hur J, Kim YJ, Nam JE, et al. Thrombus in the left atrial appendage in stroke patients: detection with cardiac ct angiography - a preliminary report. Radiology 2008;249:81-7.
Tang RB, Dong JZ, Zhang ZQ, et al. Comparison of contrast enhanced 64-slice computed tomography and transesophageal echocardiography in detection of left atrial thrombus in patients with atrial fibrillation. J Interv Card Electrophysiol 2008;22:199-203.
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Editors: Suhny Abbara, MD MGH Department of Radiology Wilfred Mamuya, MD, PhD MGH Division of Cardiology