Huge Left Atrial Myxoma Obstructs the Mitral Valve and Causes Massive Pleural Effusion

A 57-year-old woman experienced progressive exertional dyspnea and orthopnea, eventually restricting her regular activities and ability to lie down. Physical examination detected a low-pitched grade IV diastolic murmur at the cardiac apex and bilateral basal rales. Elevated levels of N-Terminal Pro–B-Type Natriuretic Peptide (826.1 pg/mL) and high-sensitivity troponin-I (28.80 pg/mL) were noted in lab tests. Chest radiography revealed bilateral pleural effusion, predominantly on the right (Fig. 1A). Transudative pleural effusion was confirmed based on the low ratio of lactate dehydrogenase and total protein in the pleural sample compared to serum. Transthoracic echocardiography disclosed a large, homogenous mass in the left atrium (LA), obstructing the mitral valve, measuring 5.0×4.0×2.9 cm³ (Fig. 1B-1D). Huge myxoma occupied near all LA (Fig. 1E). Transesophagus echocardiography revealed the stalk of myxoma at atrial septum (Fig. 1F). Chest computed tomography showed the mass had a wide-based stalk attached to the atrial septum (Fig. 1G). Surgical resection identified the jelly-like mass as a typical LA myxoma with a thrombus-coated pedicle anchored to the fossa ovalis’s left upper rim (Fig. 1H). The pleural effusion resolved rapidly within three days after surgery (Fig. 1I), with no symptom recurrence over a six-month follow-up.

FIG. 1. (A) Chest radiography: demonstrates a right-sided dominant pleural effusion (indicated by the black arrow). (B, C) Transthoracic echocardiography, parasternal long axis view: shows a huge homogenous mass in the left atrium (highlighted by the white arrow), obstructing the mitral valve. (D) Transthoracic echocardiography, four-chamber view: reveals a large, homogenous mass in the left atrium, with a wide-based stalk attached to the atrial septum. This mass is obstructing the mitral valve (indicated by the white arrow). (E) M-mode: huge myxoma occupied near all LA. (F) Transesophagus echocardiography: the stalk of myxoma locates at atrial septum. (G) Chest computed tomography: exhibits a large myxoma in the left atrium with a wide-based stalk attached to the atrial septum (pointed out by the white arrow). (H) Surgical view: displays a huge mass in the left atrium (marked by black arrows). (I) Chest radiography: shows resolution of bilateral pleural effusion post-tumor resection. LA: left atrium, LV: left ventricle, MV: mitral valve, RA: right atrium.

Atrial myxomas are the most common benign cardiac tumors, often presenting with symptoms like mitral valve disease or embolic phenomena; pleural effusion is an unusual manifestation.1 This case’s LA myxoma resulted in symptoms akin to mitral valve obstruction and pleural effusion. It has been thought that the increase in LA pressure causes transudative pleural effusion because of the mitral valve obstruction.2,3 This presentation of pleural effusion and myxoma is rare and has only been reported in a few other case studies.2,3,4,5 It remains crucial to consider differential diagnoses for transudative pleural effusion, including mitral valve obstruction by myxoma. We are documenting this case due to the patient’s exceptionally rare clinical presentation.

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