Presentation
Easy fatigability, occasional palpitations, dyspnea for 2 years.
Patient Data
The heart shows marked asymmetric enlargement, more on the left side.
No double density is appreciated and the carinal angle shows normal angulation (less than 90 degrees). On the lateral view, the left main stem bronchus is not displaced posteriorly. These findings make an enlarged left atrium and pericardial effusion, a less likely diagnosis.
The left hemidiaphragm and costophrenic sulcus are obscured. Vertical density in the left retrocardiac area may represent atelectasis.
Non-contrast CT scan of the chest in the axial plane shows a large non-calcified, soft tissue mass that is isodense to the heart, occupying the left hemithorax. This mass appears to be contiguous with the left atrial wall. Within is an ovoid structure of relatively lower density.
Axial lung window shows focal ground glass densities in the apicoposterior segment of the left upper lobe may represent compressive atelectasis due to focal compression by the mass, or by compressive changes to vascular structures causing focal edema. An inflammatory process cannot totally be ruled out.
The arterial phase confirms the presence of a thin-walled sac-like structure that is contiguous with an otherwise normal looking left atrium. This sac-like structure arises from the area of the left atrial appendage and is within the pericardial sac.
A pedunculated non-calcified ovoid intraluminal filling defect is seen within this aneurysm favoring a thrombus over a myxoma by virtue of its origin since thrombi in the left atrium most commonly originate in the left atrial appendage.
Local mass effects are seen in the left inferior pulmonary vein, as well as the anteromedial and lingular segments of the left lower lobe. The large atrial appendage aneurysm also compresses the heart medially causing it to have a tubular appearance.
Intraoperatively an aneurysmal left atrial appendage was seen measuring approximately 7 x 7 cm with a hardened thrombus measuring 5 x 4 cm. Resection of the aneurysm and primary closure was done.
Histopathology showed a left atrial appendage aneurysm with moderate myocyte hypertrophy and an intralesional thrombus. Brown and Brenn special staining did not show bacterial colonies.
Case Discussion
Key learning points:
left atrial appendage aneurysms are extremely rare with about 150 cases reported in literature 1
studies show that the most common finding in plain radiographs is a prominent left cardiac border, as is seen in this case 2
CT scan has a role in defining the anatomy of the lesion, investigating mass effects on surrounding structures and detecting alternative diagnoses 2
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the aneurysm described in this case has features that satisfy the diagnostic criteria for congenital aneurysms of the left atrium, as follows:
the atrial cavity and the aneurysm must show clearly defined communication
the aneurysm must originate from a normal atrial chamber
the aneurysm should be intrapericardial in location with resultant compression and distortion of the left ventricle 3