DISCUSSION
LA size greater than 6.5 cm is considered as giant LA [1]. Giant LA
can be caused by numerous etiologies shown in Table 1. The most common
etiology is from long-standing rheumatic mitral valve regurgitation or
mixed mitral valve disease with predominant regurgitation [2]. The
exact pathophysiology causing giant LA, only in a subset of RHD
patients, is not well understood. However, two factors that may
contribute are increased LA pressure and weakening of LA wall by
rheumatic pancarditis [2,3]. When mitral valve disease is a
long-standing process, it leads to LA enlargement as a compensatory
mechanism to ease the markedly increased LA pressure which could lead to
pulmonary congestion due to back-pressure hemodynamics, hence protecting
the lung from the development of pulmonary hypertension [4]. While
these compensatory mechanisms help the patient remain asymptomatic for a
long time, he or she gradually deteriorates due to progressive increase
in LA pressure leading to an inevitable increase in pulmonary venous
pressure.[3]. LA enlargement can lead to the development of atrial
fibrillation which can lead to further enlargement of the LA [5].
Giant LA can lead to various complications including the increased
propensity of thrombus formation and thromboembolic events, pulmonary
edema, and pulmonary hypertension. Furthermore, it can lead to
compressive symptoms because of compression of the esophagus and airway
by the enlarged posterior wall of the LA resulting in dysphagia and
respiratory dysfunction [1,6]. Despite all the complications, in
rare instances, patients may be completely asymptomatic [7]. The
chest radiography is a useful modality for diagnosing LA enlargement.
However, it may be difficult to interpret when the left atrium reaches
massive proportions. In our case, the chest radiography did not
visualize the enlarged cardiac chamber but was revealed by the
echocardiogram. It is important to note that the size of the LA does not
change after mitral valve replacement (MVR) because of irreversible
changes in the atrial muscles by fibrosis [6]. Symptomatic giant LA
can be repaired by atrial plication at the time of MVR [8]. However,
this procedure can lead to various complications like circumflex
coronary artery injury, pulmonary vein obstruction, and esophageal
stricture formation [9]. Our case was unusual because the giant LA
distorted the cardiac structures with striking cardiomegaly on the chest
radiograph and it clouded our interpretation of the cause of the
enlarged cardiac silhouette; however, echocardiogram was very helpful in
demonstrating the severe MS and the giant LA.