Isolated Large Right Atrial Myxoma Manifested by Syncope

A 65-year-old woman had been diagnosed with congestive heart failure at another hospital and was started on medication. Three months later, in February 2003, she was admitted to our department with syncope on mild exertion. Her pulse and blood pressure were normal at admission. Physical examination revealed arrhythmia. On cardiac auscultation, a diastolic murmur of grade 1–2/6, maximal at the lower left sternal border, was audible. There was mild edema in the lower extremities. All other organ systems were normal. Electrocardiography demonstrated atrial fibrillation, and chest radiography revealed an enlarged cardiac silhouette. Transthoracic echocardiography (TTE) showed a large echo-dense mass in the right atrium, 6.3 × 5.2 cm in diameter, which was immobile and clearly separated from the atrial septum (Fig. 1). The hemoglobin was 10.7 g/dL, and the erythrocyte sedimentation rate was 105 mm/hr. Other hematologic and biochemical laboratory results were within normal limits. Magnetic resonance imaging showed a dense mass filling the right atrium (Fig. 2). Surgery was performed, and the mass, which was attached to the lateral side of the right atrium, was removed. The macroscopic diagnosis of myxoma was confirmed by microscopic evaluation (Fig. 3). The patient's condition was stable postoperatively, and she was discharged from the hospital 2 days later. Three months after surgery, the patient was asymptomatic and doing well; her follow-up TTE was normal.

Fig. 1 Transthoracic echocardiogram: apical 4-chamber view shows a large right atrial myxoma almost completely occupying the right atrium.

LA = left atrium; LV = left ventricle; MASS = myxoma; RA = right atrium

Fig. 2 Magnetic resonance image shows a myxoma in the right atrium with speckled calcification inside.

Fig. 3 Microscopic appearance of the myxoma (H&E, ×400).

Comment

Myxoma is the most frequently occurring primary tumor of the heart and arises from the endocardium as a pedunculated mass. Most often, myxomas are found in the left atrium (82%). Only about 15% to 20% of cardiac myxomas are situated in the right atrium; most of these are attached to the interatrial septum. Right atrial myxomas are sometimes asymptomatic; however, they can manifest with a variety of signs and symptoms, including fever, weight loss, and arthralgias. In some cases, symptoms arise from distal embolization. Myxoma can mimic tricuspid stenosis, and a large tumor can cause a temporary, complete obstruction of the tricuspid valve, which results in syncope or sudden death.^1,2

About 10% of myxomas are calcified, in which case they may be considered as a degenerative, age-related phenomenon caused by hemodynamic factors. If areas of metaplastic bone tissue or massive calcification are seen, the mass is called a lithomyxoma^2,3—a rare pathologic entity, first described by Strouse⁴ in 1938, of which the pathogenesis remains unknown.

The best treatment for myxoma is surgical removal of the mass, which is generally curative.