Atrial Myxoma

Abstract

A 55-year-old woman had an inferior myocardial infarction due to a coronary artery embolus from a large, polypoid, left atrial mass. The mass had an irregular surface and was prolapsing into the mitral valve orifice during diastole. Coronary angiography revealed tumor vascularization next to the right coronary artery. The other coronary arteries were normal. The tumor was removed surgically; pathologic examination confirmed the diagnosis of myxoma. The patient did well after the procedure and was discharged on postoperative day 10.

The most common primary tumor of the heart is the cardiac myxoma, which frequently occurs in the left atrium.¹ The tumor may cause symptoms of left atrial obstruction and systemic embolization.¹ Chest pain from myocardial infarction secondary to coronary artery embolism is rare. We report a case of left atrial myxoma presenting as an inferior myocardial infarction.

Case Report

A 55-year-old woman was admitted to the emergency room of our institution with a 12-hour history of chest pain. She had no risk factors for atherosclerosis. Her pulse rate was 92 beats/min, and her blood pressure was 120/60 mmHg. Electrocardiography (ECG) showed sinus rhythm and a subacute myocardial infarction pattern in leads II, III, and aVF (Fig. 1). The peak creatinine phosphokinase-MB isoenzyme was 52 ng/mL, and the troponin T was 0.31 ng/mL. The patient was given aspirin, heparin, and metoprolol. Thrombolytic therapy was not given, because the ECG showed a subacute myocardial infarction pattern and the patient was not experiencing chest pain at the time of admission. On the same day, echocardiographic examination showed a large, polypoid, left atrial mass with an irregular surface. The mass was prolapsing into the mitral valve orifice during diastole (Fig. 2). The left ventricular function and wall motion were normal. Coronary angiography revealed visible tumor vascularization next to the right coronary artery (Fig. 3).

Fig. 1 Electrocardiogram shows ST elevation and pathologic Q wave in leads II, III, and aVF.

Fig. 2 Echocardiography shows a large, polypoid, left atrial mass with an irregular surface. The mass prolapses into the mitral valve orifice during diastole.

Fig. 3 The tumor vascularization is shown on coronary angiography (arrows).

The patient was transferred to the cardiothoracic department, and the mass was removed completely (Fig. 4). Pathologic examination of the tumor confirmed the diagnosis of atrial myxoma. The patient did well after the procedure and was discharged on postoperative day 10. At her last follow-up visit, she was still well.

Fig. 4 Echocardiographic view after complete removal of the mass.

Discussion

Fifty percent of all primary cardiac tumors are myxomas.² Myxomas occur most often in patients aged 30 to 70, in women, and in families with a tendency to develop myxomas.³

About 85% of myxomas occur in the left atrium, 10% in the right atrium, and 5% in the ventricles.⁴ Five percent of patients have more than 1 myxoma or a polycentric myxoma. A common site of attachment for atrial myxomas is the fossa ovalis region of the septum; another is the posterior atrial wall.³

Atrial myxomas produce 3 types of clinical presentation: obstructive, constitutional, and embolic. Obstruction mimics mitral and tricuspid valve disease and occurs due to blockage of the atrioventricular valves. In such cases, left atrial myxomas can cause dyspnea or left heart failure, leading to the mistaken diagnosis of mitral stenosis.¹

The symptoms of myxomas are not always predictable nor are the laboratory results. Unusual findings most often include weight loss, arthralgias, fever, anemia, elevated erythrocyte sedimentation rate, and protein abnormalities.³ These signs and symptoms may occur because of bleeding and degeneration within the tumor, microembolism, or the release of tumor fragments, triggering an immunologic response in the patient. Most patients have one or more of these symptoms at some stage during the illness, and such symptoms may occur long before obstructive or embolic events.³ The symptoms generally resolve after removal of the tumor.

In about one third of myxomas, systemic embolism occurs.³ The incidence of coronary artery embolization of myxomas is 0.06%,⁵ and death has been reported in such cases.⁶ Panos and colleagues,⁷ noting the low coronary embolization rates, suggested 2 possible explanations. One is that emboli are less likely to enter the coronary arteries because the coronary ostia are perpendicular to the aortic blood flow, and the second is that the the opening aortic valve leaflets shield the coronary ostia during cardiac systole.⁷

In their review of patients with left atrial myxoma, Panos and colleagues⁷ determined that inferior myocardial infarctions have been seen in 63.6% of cases, anterior in 22.7%, and posterior in 9.1%. Coronary angiograms showed normal results in 23.8% of the cases, and right coronary artery embolization in 47.6% of the patients with embolism. Those authors proposed that the high incidence of embolization to the right coronary artery might have been due to the conducive position of the right ostium relative to the aortic blood flow.⁷

Echocardiography is the most reliable method for the diagnosis of myxomas. Two different anatomic types of myxoma have been determined by means of echocardiography: round, which is solid and round with a nonmobile surface; and polypoid, which is soft and irregular in shape with a mobile surface.² The incidence of systemic embolism is higher in tumors with an irregular and friable surface than in those with a smooth surface.¹ Ha and coworkers² showed that prolapsing and polypoid tumors were associated with embolism. The occurrence of embolism rose as the myxoma size decreased. The more irregular and friable the myxomas were, the higher the likelihood was for embolism. In our patient, the left atrial myxoma was polypoid in shape with an irregular surface, and it prolapsed across the mitral valve orifice.

Thrombolytic therapy usually is not recommended for patients with cardiac myxomas because of the risk of embolism.⁸ There are 2 possible explanations of why thrombolytic agents cause embolic events: 1) the agents may cause lysis of accumulated thrombus⁹; and 2) in the presence of hemorrhagic areas and a rich vascular supply, thrombolysis could increase hemorrhage and cause the rupture of small fragments.⁸

In general, resection of the tumor is sufficient to ensure recovery of the patient; however, if there is total or subtotal occlusion of the coronary artery, coronary angioplasty or coronary artery bypass surgery may be necessary.

Although atrial myxomas are very rare, their presence should be considered, particularly in young patients without cardiac risk factors who present with a myocardial infarction. If there is any suspicion of atrial myxoma, echocardiography is reliable and easy for differential diagnosis and decision-making for the treatment of such patients. Surgery should not be delayed in patients with polypoid-type left atrial myxomas because of the high incidence of embolism.