Silent but Obstructive: A Left Atrial Myxoma Incidentally Identified During Cardiac Decompensation.

Cardiac myxomas are rare benign tumors, most commonly located in the left atrium. Despite their benign histology, they may present with serious clinical consequences due to obstruction, embolism, or systemic symptoms. Their presentation can mimic valvular heart disease or heart failure, often delaying diagnosis. We report the case of a 72-year-old woman with a history of diabetes and hypertension who presented with progressive exertional dyspnea, New York Heart Association (NYHA) class III, evolving over two weeks. Clinical examination revealed signs of pulmonary congestion and pulmonary hypertension. Transthoracic echocardiography demonstrated a large, heterogeneous, mobile mass in the left atrium prolapsing into the mitral valve with a transmitral gradient of 14 mmHg and an estimated pulmonary artery pressure of 60 mmHg. Coronary angiography ruled out associated coronary artery disease. Surgical excision of the mass was performed successfully the following day. The postoperative course was uneventful, with resolution of symptoms. Histopathological examination confirmed the diagnosis of a left atrial myxoma with no features of malignancy. This case highlights the obstructive presentation of a left atrial myxoma mimicking mitral stenosis, leading to elevated left atrial pressure and pulmonary hypertension. Echocardiography was essential for diagnosis and surgical planning, particularly given the risk of embolization and hemodynamic deterioration. Clinicians should maintain a high index of suspicion for structural cardiac tumors in elderly patients presenting with unexplained dyspnea and preserved ejection fraction. Early recognition and surgical management are essential to prevent serious complications and ensure favorable outcomes.