Discussion
LAAA is an extremely rare cardiac abnormality. Since its first report by Parmley in 1962, there have been no more than 200 cases reported so far. LAAA can be classified into congenital and postnatal according to the etiology, or intrapericardial and extrapericardial according to the presence or absence of pericardial defect. This case is a congenital and intrapericardial LAAA2.
The etiology of LAAA remains unclear, although the anomaly is probably due to congenital dysplasia of the atrial pectinate muscles3. Acquired LAAA is often secondary to conditions that lead to chronically elevated left atrial pressures (such as mitral regurgitation or stenosis), or conditions that result in weakness of the left atrial wall (such as syphilitic or tuberculous myocarditis)4. Intrapericardial LAAA is hypothesized to be due to an inherent atrial wall weakness, while extrapericardial LAAA is associated with a secondary protrusion of the LA due to a congenital defect of the pericardium5.
Based on previous case reports, only a small number of patients are incidentally diagnosed and remain asymptomatic. Most patients are diagnosed after symptoms, which mainly include palpitation, dyspnea and chest pain. The life-threatening complication is mural thrombosis caused by slow blood flow and vortex formation in LAAA, which can lead to systemic embolism once shedding off3.
As a noninvasive examination, TTE is the most important screening tool for LAAA, but its value in diagnosis is limited. To clarify the relationship between the LAAA and the surrounding tissue structure, transesophageal echocardiography (TEE), CT and MRI can be performed, and cardiography can also be used to help make a clear diagnosis5.
According to previous study by Aryal, the proposed definition of LAAA was a LAA which has dimensions at the diameter of the orifice, width of the body, and the length of the LAA larger than 27, 48, and 68 mm, respectively6. And the proposed imaging diagnostic criteria are: (1) origin from an otherwise normal LA, (2) clearly-defined communication with the LA, (3) location within the pericardium, and (4) distortion of the free wall of the LV by the aneurysm5.
Once LAAA is diagnosed, surgical resection is always recommended even in asymptomatic patients to prevent fatal complications. In our patient, the large size of this LAAA made us choose resection via median sternotomy and cardiopulmonary bypass. Patients who undergo surgical resection usually have a great prognosis. To our knowledge, there are no reports of aneurysm or symptom recurrence.