(P252) DIAGNOSTICALLY CHALLENGING MYXOMA PRESENTING AS ACUTE MYOCARDIAL INFARCTION

Case background: Patient Demographics:
31-year-old female with a past medical history significant for acute myeloid leukemia treated as a child, splenectomy, and enlarged thyroid.

Clinical Presentation:
While at home, the patient developed sudden-onset chest pain and syncope. Electrocardiogram by emergency responders detected self-terminating ventricular tachycardia and inferior ST-segment elevation. She was brought urgently to the hospital for acute ST-elevation myocardial infarction.

Diagnostic

Methods:
Emergent cardiac catheterization showed abrupt tapering of the left anterior descending artery, its diagonal branches, and the obtuse marginal branch of the left circumflex, findings consistent with embolic phenomenon with differential diagnoses of spasm post-cardiac arrest and spontaneous coronary artery dissection. The right coronary artery was normal, but its mid portion gave rise to a small branch that perfused multiple left atrial microvessels suspicious for a feeding vessel for a cardiac myxoma. Left ventriculography showed mildly reduced LV systolic function and apical regional wall motion abnormalities (Figure 1). Transthoracic echocardiogram showed LVEF 54.4%, segmental LV dysfunction with severe hypokinesis of the lateral and inferolateral walls, an irregular left atrial mass (4 x 3 x 2 cm) arising from the interatrial septum (IAS) with contour suggestive of a villiform myxoma prolapsing across the mitral annulus. The diagnosis of left atrial (LA) cardiac myxoma with embolization causing acute myocardial infarction was made.

Treatment:
Given the ischemic presentation with arrhythmia, there was concern for ongoing embolic potential and the patient was taken for emergency resection of LA myxoma. The procedure was performed via a median sternotomy with bicaval cannulation and trans-septal incision with extension onto the left atrial dome. The tumour was pedunculated, villiform, and friable. It was removed en-bloc and the resulting defect in the IAS was repaired with autologous pericardium. Surgical pathology examination revealed a villiform cardiac myxoma (3.0 x 2.1 x 1.5 cm) with multifocal areas of recent surface rupture covered by platelets and fibrin, consistent with systemic arterial myxoma embolization (Figure 2).

Outcomes:
The patient’s post-operative course was uncomplicated. She was discharged home on post-operative day 12 as she lived out of province and had to arrange transport home.

Management Challenges:

Discussion:
Primary cardiac tumours are rare, with an incidence of approximately 0.02% (1). Myxomas are the most common primary cardiac tumour. They are most often sporadic (with a subset associated with the Carney complex) and the vast majority originate in the left atrium (2, 3). LA myxomas cause mitral valve obstruction or regurgitation, left-sided heart failure, and secondary pulmonary hypertension, leading to symptoms such as exertional dyspnea, orthopnea, paroxysmal nocturnal dyspnea, and pulmonary edema. They can also be associated with constitutional symptoms or with systemic embolization and resulting complications. We present a case of LA myxoma that presented as acute myocardial infarction.

This was a diagnostic challenge and thus can serve as a learning opportunity. Typically, an acute myocardial infarction in a young female would lead to a differential of stress cardiomyopathy or spontaneous coronary artery dissection (SCAD) (4,5). Stress cardiomyopathy is characterized by transient regional systolic dysfunction, typically of the left ventricle. It mimics myocardial infarction but is differentiated by the absence of obstructive coronary artery disease or acute plaque rupture on angiography (4). Meanwhile, SCAD is a coronary artery epicardium wall tear not caused by atherosclerotic plaque rupture, iatrogenic disease, or trauma. It is characterized by intimal tear, intramural hematoma, and false lumen formation, which can obstruct coronary blood flow and cause myocardial ischemia. SCAD is an emerging cause of acute coronary syndrome (ACS) in young females without any known cardiovascular risk factors (5).

The diagnosis of stress cardiomyopathy was ruled out by echocardiography. Meanwhile, the angiography was more difficult to exclude, as the abrupt change in vessel diameter between normal and diseased segments could suggest type 2 SCAD. However, the abnormal left atrial feeding vessel in association with coronary angiographic findings suggested an embolic phenomenon from a cardiac tumour, which was confirmed by echocardiography in the cardiac catheterization laboratory. In conclusion, this is unusual presentation of an embolizing LA myxoma presenting as an acute myocardial infarction in a young woman. We should keep this in our differential when working up young females presenting with ACS.