Enhancing left atrial thrombus

Case contributed by Jayanth Keshavamurthy
Diagnosis certain


The patient was admitted for atrial fibrillation and rapid ventricular response. 1 week later she had sudden loss of vision in her right eye and left lower extremity pain.

Patient Data

Age: 65 years
Gender: Female

Electrocardiogram (ECG)


Atrial fibrillation, ventricular rate between 61-149 bpm.

She underwent CT angiogram of abdomen and pelvis with run-off protocol. There is a large filling defect in the left atrium abutting the interatrial septum measuring approximately 4.5 x 3.1 x 4.4 cm. (with HU equal 44, 88, 66, and 50 during the non-contrasted, arterial, portal venous, and delayed GU phases respectively, HU of non-opacified left atrial blood equal 61).


Echocardiogram conclusion was showed severe concentric LVH with hyperdynamic LV systolic function.   

LA mass suggestive of LA myxoma and normal mitral valve. 

Coronary angiogram


Coronary angiogram findings as above.


The patient underwent median sternotomy to resect the mass as myxoma was considered based on imaging characteristics. LA was entered via the right atrium. A large fresh and organized thrombus was found attached to the interatrial septum via a thin cord. Multiple fragments of red-tan-brown soft clot measuring 6.5 x 6.5 x 3.0 cm in aggregate. A lamellated organized clot was also removed by vascular surgeons from the right popliteal artery using a Fogarty balloon technique. There was no PFO on TEE. There was a small organized left atrial appendage thrombus also. A Maze procedure and a 45 mm Atriclip was applied to the base of the left atrial appendage. There was no atrial myxoma on pathology.



There is a left atrial appendage clip in place.

Sternotomy changes and intact sternal suture wires.

Case Discussion

Thrombus formation can be caused by hypercoagulable states, systolic dysfunction with wall motion abnormalities, atrial fibrillation, valvular abnormalities, or artificial devices. Thrombi are the most common cause of an intracardiac mass. These are most common in LA and LV. They are at increased risk for systemic embolism.

It typically appears as a hypodense, low-attenuation filling defect in a contrast pool within a cardiac chamber and may be differentiated from primary and secondary tumors by knowledge of predisposing risk factors, attachment location, shape, and lack of mobility. But it is not without false positive and false negative diagnosis.

Chronic thrombi may develop spotty calcifications. Unfortunately, this feature has not been shown to significantly differentiate thrombus from atrial myxoma. The left atrial appendage (LAA) is the main location of thrombus formation, predominantly in patients with nonvalvular AF. Atrial thrombi, also commonly occur along the posterior wall of the LA. There are now cases of atrial thrombi arising from inter-atrial septum in the newly described left atrial septal pouch as another potential location of atrial thrombus.

Although useful imaging characteristics of myxomas and thrombi can be found on CT, potential overlap in the imaging findings may result in persisting uncertainty in the differentiation of the two disorders. Therefore, alternative imaging approaches such as MRI with superior tissue characterization with higher temporal resolution should also be considered.

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