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.