Left Atrial Myxoma Masquerading as Acute Heart Failure

A 68-year-old woman with hypertension, dyslipidemia, and hypothyroidism arrived at the emergency department with severe progressive dyspnea and bilateral leg swelling. On exam she had jugular venous distention, diffuse pulmonary crackles, and pitting edema — a picture immediately consistent with acute decompensated heart failure. What was not immediately apparent was the cause.

An urgent echocardiogram changed everything. It revealed a large pedunculated mass in the left atrium, attached to the interatrial septum, prolapsing through the mitral orifice during diastole — creating a functional mitral stenosis. Coronary angiography was normal, ruling out ischemia as the driver.

Figure 1

Echocardiographic images of the left atrial myxoma

Transthoracic echocardiography (TTE) short-axis (A) and four-chamber views in systole (B) and diastole (C). Transesophageal echocardiography (TEE) views in systole (D, E) and diastole (F). The tumor (arrow) can be seen prolapsing through the mitral valve in diastole — the mechanism of dynamic obstruction that produced the clinical picture of acute mitral stenosis and heart failure. Note the heterogeneous echotexture characteristic of myxomas, which helps distinguish them from thrombi.

The patient was referred emergently to cardiac surgery. Via full cardiopulmonary bypass (CPB time 156 minutes, cross-clamp 92 minutes), the myxoma was excised through a right atriotomy. Intraoperatively, with the obstructing mass removed, the true underlying valve disease became apparent: severe mitral regurgitation that had been completely masked by the myxoma's presence. Multiple repair attempts were unsuccessful, necessitating mitral valve replacement with a biological prosthesis, plus tricuspid annuloplasty (DeVega technique) for coexisting severe tricuspid regurgitation.

Figure 2

Intraoperative image of the excised left atrial myxoma

The resected myxoma after removal from the left atrium. Cardiac myxomas have a characteristic gelatinous, lobulated gross appearance. Complete excision — including the base of attachment at the fossa ovalis — is essential to minimize recurrence risk, which ranges from 2–13% in reported series.

Weaning from bypass was complicated by severe right heart failure. The patient required extracorporeal life support (ECLS) via the right femoral vein and ascending aorta. A tracheotomy was performed on postoperative day 7 for prolonged ventilator dependence. She was gradually weaned from ECLS by day 11 and from mechanical ventilation by day 15. Intraoperative transesophageal echocardiography (TEE) documented the progression from pre-repair severe regurgitation to the post-replacement result.

Figure 3

Intraoperative TEE images after myxoma excision

Sequential TEE views: (A) after myxoma removal, (B) severe tricuspid regurgitation exposed, (C) severe mitral regurgitation — both valvulopathies had been concealed by the obstructing tumor, (D) persistent significant regurgitation after attempted mitral repair, (E) result after mitral valve replacement, (F) residual mild tricuspid regurgitation after annuloplasty. This sequence illustrates how a large obstructing mass can mask coexisting valvular disease until the obstruction is relieved.

Histopathology confirmed cardiac myxoma. The patient was transferred to the ward on postoperative day 17, discharged ambulatory on day 28, and was asymptomatic with no evidence of recurrence or cardiac decompensation at one- and six-month follow-up.

Discussion

This case is a reminder that not all acute decompensated heart failure is what it appears to be. Cardiac myxomas account for up to 75% of primary cardiac tumors and are most commonly located in the left atrium, attached to the fossa ovalis. Their clinical presentation varies from incidental finding to sudden death, with 28% presenting with acute decompensated heart failure from mechanical obstruction. The critical diagnostic pitfall here was that the myxoma was not only causing functional mitral stenosis but was also concealing severe pre-existing mitral regurgitation — a dual mystery that only echocardiography and surgical exploration could unravel. Echocardiography is first-line; TEE provides superior resolution for tumor characterization and surgical planning. Cardiac MRI can further differentiate myxomas (heterogeneous T1/T2 signal, gadolinium enhancement) from thrombus (homogeneous hypointense, no enhancement) when diagnostic uncertainty remains.

The management lesson extends beyond diagnosis to surgical planning. When a large obstructing cardiac tumor is identified, the operative team must be prepared for unexpected valvular disease that becomes apparent only after tumor removal. In this patient, intraoperative discovery of severe bi-valvular disease required valve replacement and repair in the same sitting, substantially increasing complexity. Postoperative right heart failure leading to ECLS dependence is a recognized hazard after combined procedures and should be anticipated in the pre-surgical risk assessment. Despite a prolonged ICU course, full recovery was achieved — underscoring that early diagnosis and complete excision remain the keys to favorable prognosis, with post-surgical survival rates approaching those of the general population when resection is complete.