CASE:

We present the case of a 58yo woman, with a history of rheumatic mitral valve disease and Atrial Fibrillation (AF), who underwent mitral valve replacement surgery with bioprosthesis implanted in 1992. Since 2021, she presented symptoms of heart failure, with evidence of severe tricuspid valve insufficiency, mitral prothesis dysfunction (insufficiency) and biatrial enlargement; echocardiography showed left atrium (LA) indexed volume of 178 ml/m² and anteroposterior measurement of 64mm. Due to COVID-19 pandemic related delays, she awaited surgery until 2024, when cardiac magnetic resonance (CMR) was performed to interoperative programming. CMR showed an increase in LA measures, with an anteroposterior diameter of 75 mm and indexed volume of 263 ml/m² by the biplanar method and 333 ml/m² by volumetry. No thrombi were visualized at the LA.

DISCUSSION:

A giant left atrium (GLA) is a rare condition, more commonly related to rheumatic mitral valve disease. The most used definition is an anteroposterior size of 65mm in the parasternal long axis view on echocardiogram; this view is mimicked in the CMR, with higher space resolution, as a 3-chamber scan. At CMR, the estimation of the total volume of the LA using the biplanar method in scenarios of great deformation of the cavity is less accurate, hence volumetry is a more reliable measurement. However, when less accurate methods are implemented, GLA can be mistaken with tumors and pericardial effusion, leading to interventions such as biopsies or pericardiocentesis, that can be particularly dangerous in this setting. The consequences of GLA involve symptoms related to extra-cardiac compression, refractory thrombus formation and AF. The main indication to perform LA volume reduction surgery is generally related to the occurrence of such complications; otherwise, the mitral valve replacement itself showed to be capable of eventual reduction of the LA size.

CONCLUSION:

GLA is a rare condition that can be mistaken with a few possible differential diagnoses when less accurate methods are implemented, which may lead particularly dangerous procedures in this setting. Advanced cardiovascular imaging methods such as CMR can be useful in this differentiation and offer high spatial resolution, enabling the correct diagnosis and surgical programming. Furthermore, GLA quantitative evaluation by volumetry instead of the biplanar method in these cases of large deformity ensures better accuracy of the values obtained.