A Left Atrial Myxoma Masquerading As Acute Coronary Syndrome

Acute coronary syndrome is caused by a rupture of atherosclerotic plaque with superimposed thrombus formation. Non-ST-segment elevation acute coronary syndrome (NSTE-ACS) occurs when occlusion of the epicardial coronary artery by a thrombus causes partial thickness myocardial ischemia and an ischemic cascade downstream. Cardiac masses are known to produce symptoms predominantly by local obstruction or systemic embolism. Coronary artery tumor embolism causing acute coronary syndrome is a rare presentation of cardiac mass. We report NSTE-ACS as the initial presentation of the left atrial myxoma in a 62-year-old woman. She presented to the emergency department with acute onset severe anginal chest pain, diaphoresis, and dizziness. Her serial electrocardiograms (ECGs) were normal, and serial troponins were elevated, consistent with non-ST-segment elevation acute coronary syndrome. Cardiac catheterization revealed insignificant coronary artery disease, and transthoracic and transesophageal echocardiograms showed a left atrial mass attached to the interatrial septum consistent with myxoma. The patient underwent surgical excision, and histopathology was consistent with myxoma. Her symptoms subsided after surgery. Primary cardiac tumors are very uncommon and can present with myriad symptoms, from tumor embolism, local cardiac effects, to constitutional symptoms. Although embolism to other organs has been reported, left atrial myxoma presenting as an acute coronary syndrome is very uncommon.


Introduction
Primary cardiac neoplasms are very rare, with an incidence rate of about 0.2% at autopsy [1]. Cardiac tumors can be classified into benign, malignant (primary malignant, and secondary), and tumor-like masses (Lambl's excrescences, papillary fibroelastoma, endocarditis, and blood cysts). About 90% of primary cardiac neoplasms are benign and arise from the myocardium, heart valves, and pericardium [2]. Studies have shown that secondary cardiac neoplasms are about 100 times more common than primary cardiac tumors [3]. Common primary benign cardiac tumors are myxoma, lipoma, papillary fibroelastoma, rhabdomyoma, fibroma, and cardiac paraganglioma [2]. Commonly encountered malignant cardiac tumors are angiosarcoma, leiomyosarcoma, rhabdomyosarcoma, osteosarcoma, undifferentiated sarcoma, primary cardiac lymphoma, and mesothelioma [2]. The tumors known to metastasize to the heart in order of decreasing frequency are primary lung cancer, breast cancer, hematological malignancy, pleural mesothelioma and, melanoma, ovarian and renal cancers [4]. Cardiac masses can have a myriad of clinical presentations, commonly present with local cardiac effects and constitutional/ systemic symptoms by releasing inflammatory cytokines and embolic phenomenon. Although pulmonary and systemic embolism with cardiac myxoma is common, coronary artery embolism is very rare. We describe a case of acute coronary syndrome as an atypical presentation of left atrial myxoma.

Case Presentation
A 62-year-old woman with a past medical history of hyperlipidemia, hypothyroidism, a family history of coronary artery disease, and a current smoker presented to the emergency department with sudden onset of left-sided crushing chest pain. Chest pain was pressure-like, 9/10 in intensity, radiated to the left arm and jaw, and associated with diaphoresis. Physical examination revealed normal first and second heart sounds without any murmur or rales. An ECG showed premature ventricular and atrial complexes and was negative for ST-segment changes ( Figure 1).  Transthoracic echocardiogram showed a normal left ventricular systolic function, no regional wall motion abnormalities, and a large sessile heterogenous globular echodensity 2.9 x 2.6 cm in the left atrium attached to the interatrial septum suggestive of myxoma (Video 7-8, Figure 2). The anatomic extent of the tumor was further studied by transesophageal echocardiography, which did not show the involvement of any other cardiac chambers. The mass was localized to the interatrial septum and did not cause mitral valve obstruction (Figure 3, Videos 9-11). Cardiac surgery was consulted and planned on surgical excision after a clopidogrel washout. Midline sternotomy and left atriotomy were performed under cardiopulmonary bypass. The sessile tumor measuring about 4.5 cm had the appearance of myxoma and was seen attached to the area of the fossa ovalis. The right atriotomy was performed, and the tumor was removed completely, along with a full-thickness piece of septum measuring 2 cm. The iatrogenic atrial septal defect was closed with sutures. The gross specimen showed an ovoid, well-defined, yellow-red soft tissue mass with diffuse hemorrhage and a gelatinous appearance (Figures 4-5).

FIGURE 4: Gross specimen shows a 4.4 x 3.2 x 2.8 cm ovoid, yellow-red
rubbery soft tissue mass. The surface was glistening and gelatinous.

FIGURE 5: The cut surface reveals a yellow-red diffuse hemorrhagic and gelatinous appearance
Histology was consistent with myxoma ( Figures 6-8). She was discharged home in stable condition. Surveillance echocardiography after six months showed no recurrence.

Discussion
The primary cardiac tumor is very rare, and myxoma is the most common primary cardiac tumor, constituting about 50% [5]. Most of them used to be diagnosed at autopsy in the past, but with the evolution of multimodality imaging, cardiac masses are being diagnosed more frequently now [2]. Myxoma arises from multipotent mesenchymal cells and is more common in women and in the third and sixth decades of life [1]. It may occur sporadically or as an autosomal dominant condition called Carney complex, where it presents in combination with other neoplasms like skin myxomas, cutaneous lentiginosis, pituitary neoplasm, testicular tumors, and primary adrenocortical tumors [6]. Myxomas typically arise from the interatrial septum adjacent to fossa ovalis. Valvular myxomas are very rare. It may rarely arise from the posterior and anterior atrial wall, left atrial appendage, left ventricle and right ventricle, and combined atrial and ventricular walls [1]. Multiple myxomas and myxomas with atypical locations are common in familial myxomas. Myxomas are commonly polypoid in gross appearance, often attached with a pedicle to the interatrial septum, and have spherical or oval shapes with smooth or bossellated surfaces [1]. The symptom triad commonly consists of systemic embolic manifestations, intracardiac obstructive symptoms like dyspnea on exertion, pulmonary edema, right heart failure, and constitutional symptoms like fever, weight loss, myalgia, and arthralgia. About 40% of patients with myxoma present with systemic embolism, and the central nervous system is involved in about 50% of them; coronary arteries involvement has been reported in only 0.06% [7,8].
Our patient presented with non-ST-segment elevation myocardial infarction due to coronary artery embolism from left atrial myxoma. Physical examination commonly reveals a diastolic murmur in the mitral area due to left ventricular inflow obstruction. Late diastolic tumor "plop'' occurs after the second heart sound when the tumor protrudes into the left ventricle. Our patient did not have any murmur as myxoma was sessile and localized to the interatrial septum only. Two-dimensional transthoracic echocardiography is diagnostic and has a sensitivity of about 95%. Transesophageal echocardiography has a sensitivity of about 95-100%, can detect tumors as small as 1-3 mm, and further demonstrate the site of attachment, mobility, concurrent involvement of the other chambers, and typical gross pathologic features like calcification, necrotic foci, and intratumor hemorrhage. Multimodality imaging like cardiac computed tomography scan (CT) and magnetic resonance imaging (CMR) can be used to evaluate extracardiac involvement and evaluate tissue components [1]. The tumor is benign and most of the time diagnosed by transthoracic and transesophageal echocardiography only, and multimodality imaging is not pursued for a typical myxoma with characteristic echocardiographic appearance and location, like in our patient. Surgery with sternotomy and atriotomy with resection of the tumor is curative with an excellent long-term prognosis. The recurrence rate of myxoma ranges from 5-14% [9]. Careful and complete resection should be performed as intraoperative fragmentation of the mass can cause embolism, and incomplete resection may lead to a recurrence [10]. Semi-annual surveillance echocardiography is recommended for four years after surgery to