Pulmonary Embolism and Acute Heart Failure as the Initial Manifestation of Right Atrial Myxoma: A Case Report and Review of the Literature

Abstract
Cardiac myxomas are noncancerous primary tumors of the heart. The majority of cardiac myxomas are found in the left atrium and arise in the interatrial septum. Right atrial myxomas tend to be more solid and sessile, and have a wider attachment to the interatrial septum. Myxomas can lead to multiple complications resulting in obstruction, embolization, and constitutional symptoms. Right atrial myxomas are rare. We report the case of a massive round right atrial myxoma removed in a young male presenting with acute heart failure and embolism to the pulmonary vasculature. This 49-year-old male presented to an outpatient cardiology clinic with severe dyspnea on excretion and worsening pedal edema over a two-week period. Transesophageal echocardiogram demonstrated a 6 x 4 cm large mobile mass in the right atrium arising from the interatrial septum. He was found to be in acute congestive heart failure. A computed tomography angiogram of the chest demonstrated small pulmonary emboli in the right middle lobe, right lower lobe, and left lower lobe. He was subsequently anticoagulated and transferred to a tertiary care center. He underwent excision of the mass and the pathologic report was consistent with myxoma. Primary tumors of the heart are extremely rare. Right atrial myxomas are uncommon, and have not been previously reported to present with pulmonary embolism and congestive heart failure. In order to avoid complications from atrial myxoma, early diagnosis and surgical intervention is necessary. Clinicians should consider right atrial myxoma in their differential diagnosis of a patient presenting with pulmonary embolism and acute congestive heart failure.

Introduction
Primary tumors of the heart are extremely rare and contribute to approximately 5% of all cardiac tumors.¹ Cardiac myxomas are noncancerous primary tumors of the heart and constitute around 50% of all primary heart tumors.² They are polypoid, round, or oval, are yellow, brown, or white in color, and are usually gelatinous, with a smooth or lobulated surface. About 90% of myxomas are pedunculated and solitary. Cardiac myxomas can be found in any of the 4 chambers of the heart. The majority of cardiac myxomas are found in the left atrium and arise in the interatrial septum at the border of fossa ovalis.^3,4 Seventy-five percent of myxomas arise in the left atrium, 20% arise in the right atrium, and around 8% arise in the ventricles. Right atrial myxomas tend to be more solid and sessile than left atrial myxomas, and have a wider attachment to the interatrial septum and atrial wall. The average age onset of cardiac myxomas is during the 6th decade of life and approximately 75% occur in females.^5,6 Myxomas can lead to multiple complications that may result in obstruction (67%), embolization (29%), and constitutional symptoms (34%).⁷ Peripheral embolization commonly occurs in about 35% of left atrial myxomas, and most embolize to the central nervous system and retinal arteries.⁸ Embolization can also occur in the kidneys, adrenals, spleen, viscera, and proximal lower extremities. Approximately 80% of left atrial myxomas present with dyspnea on exertion, followed by orthopnea, paroxysmal nocturnal dyspnea, and pulmonary hypertension. Patients can also present with transient ischemic attack, hemiplegia, syncope, palpitations, and chest pain. In contrast, right atrial myxomas are mostly asymptomatic, but can rarely present with obstructive symptoms that can result in intracardiac flow disturbance. This can lead to systemic embolization or pulmonary artery embolism if there is an atrial septal defect or patent foramen ovale.⁹ Systemic and pulmonary embolization is more frequent in polypoid tumors as compared to round tumors.² Involvement of the tricuspid valve can result in tricuspid regurgitation. Over time, right-sided heart failure can develop, which can present as pedal edema, hepatic congestion, exertion shortness of breath, and ascites. Left atrial myxomas produce symptoms when they are approximately 75 gm in weight versus right atrial myxomas, which grow to approximately twice this size before becoming symptomatic. Myxomas have a large variation in size, ranging from 1 cm to 15 cm in diameter. Atrial myxomas can be successfully treated with surgical resection. The mortality is low, but may rarely cause sudden cardiac death.

There are few reports on right atrial myxoma complicated with either pulmonary embolism or acute congestive heart failure documented in the literature. We report the first case of a massive, round, right atrial myxoma that was surgically removed in a young male who presented with acute congestive heart failure and embolism to the pulmonary vasculature.

Case Study
A 49-year old male presented to an outpatient cardiology clinic with severe dyspnea on excretion and worsening pedal edema over a two-week period. Family history at the time was negative for thromboembolic disorders or cardiac myxoma. His past medical history was significant for coronary artery disease, with a coronary stent placed in the first diagonal artery of the left anterior descending artery. Recent cardiac catheterization confirmed patency of the first diagonal stent, with minimal luminal irregularities involving the dominant right coronary artery and left circumflex artery. A transesophageal echocardiogram demonstrated a 6 x 4 cm large mobile mass in the right atrium arising from the interatrial septum (Figure 1). Other findings included abnormal left ventricular diastolic filling, concentric left ventricular hypertrophy, and mild dilatation of the right atrium and inferior vena cava. The patient was admitted to a community hospital for a further workup.

Thorax radiography revealed cardiomegaly and a right lower lobe infiltrate and effusion. Electrocardiogram showed normal sinus rhythm with diffuse low voltage. Laboratory testing showed ALT 34 U/liter; D-Dimer 4.06 μg/ml; NT-proBNP 758 pg/mL; troponin I 0.05 ng/ml. A computed tomography angiogram of the chest demonstrated small pulmonary emboli in the right middle lobe, right lower lobe, and left lower lobe. It also indicated a 6.4 x 4.5 x 4.6 cm filling defect in the right ventricle and right atrium. The patient was subsequently anticoagulated. No venous thrombosis was detected. Given the possibility of myxomatous emboli, the patient was transferred to a tertiary care hospital for further treatment. He underwent surgical excision of the right atrial myxoma by median sternotomy under circulatory arrest. He was found to have a large distinct focus of right atrial tumor (Figure 2). The right ventricle, left atrium, and left ventricle did not have any additional foci upon careful inspection. A 6 x 4 cm surgical specimen was excised (Figure 3). Pathologic evaluation was consistent with the diagnosis of cardiac myxoma.

Discussion
Primary tumors of the heart are extremely rare¹ and account for only 5% of all cardiac tumors.¹⁰ The reported prevalence of cardiac tumors found on autopsy is also extremely rare, being discovered in only 0.05% of autopsies.¹¹ Cardiac myxomas are the most common type of primary cardiac tumors, constituting 50% of all primary tumors of the heart.¹² They are described as a benign primary cardiac neoplasm of the primitive mesenchymal cells found in sub-endocardial tissue.¹³ Myxomas have the potential to arise in any chamber of the heart but are most often located in the left atrium.^11,12 Myxomas have a greater prevalence among the female population and have tendency to occur in the middle-aged patients who are between 30 and 60 years old.^12,13 Cardiac myxomas can be clinically silent, or present with symptoms such as dyspnea, syncope, distention of jugular neck veins, and clinical evidence of mitral stenosis or insufficiency.¹² Mortality due to atrial myxoma is low;¹⁴ however, clinical manifestations exhibited by patients can be attributed to valvular or flow obstructions caused by the mass of the tumor or embolism of myxomatous fragments.¹⁰

We present a case of a patient with confirmed cardiac myxoma associated with pulmonary embolism and congestive heart failure. While any embolic event resulting in dissemination to the pulmonary or systemic circuit can be a life-threatening phenomenon, frequent, repeated embolic episodes of the pulmonary vasculature have shown to lead to pulmonary hypertension.¹⁵ A study that investigated the risk factors associated with embolism in patients with known cardiac myxomas highlighted the following predictors that make embolism more likely: atrial fibrillation, irregularity of the tumor surface, and increased left atrial diameter.¹⁶ In order to avoid complications from atrial myxoma, early diagnosis and surgical intervention are very important. The diagnostic test of choice is 2D echocardiogram. Transesophageal echocardiogram has shown to be superior in diagnosing right atrial myxoma when compared to transthoracic echocardiogram.¹⁷ Treatment with surgical excision is curative, and is associated with excellent survival rates and low rates of re-operation.⁵ The patient presented in this case study underwent successful surgical excision of a 6 x 4 cm myxomatous mass with the diagnosis confirmed by histopathological evaluation of the surgical specimen. We hope that our case will remind clinicians to consider right atrial myxoma in their differential diagnosis of a patient presenting with pulmonary embolism and acute congestive heart failure.

Conclusion
Right atrial myxomas are extremely rare and clinically are silent. Clinical manifestations can be attributed to embolism of fragments, or flow and valvular obstructions caused by the tumor size. Concurrent acute congestive heart failure and pulmonary hypertension from right atrial myxoma have not yet been reported. Early diagnosis and surgical excision is vital to prevent complications. Surgery is usually curative and associated with excellent survival rates. Healthcare providers should consider right atrial myxomas in their differential diagnosis of a patient presenting with features of acute heart failure and pulmonary embolism.

Disclosures: The authors report no conflicts of interest regarding the content herein.

The authors can be contacted via Sheharyar Minhas, MD, at sminhas7@yahoo.com.

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