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.