Subtle Symptoms of Large Biatrial Myxomas: A Case Study and Surgical Insights

Introduction

Primary cardiac tumors are not as common as metastatic tumors, and the most prevalent type is atrial myxoma, which accounts for approximately 50% of all cases. Most cases are sporadic, but some can be familial and are transmitted in an autosomal dominant fashion [1]. Myxomas are composed of scattered cells within the gelatinous mucopolysaccharide stroma. Almost 75% of myxomas are found in the left atrium, attached to either the mitral annulus or the fossa ovalis of the interatrial septum, 20% are found in the right atrium, and less than 2.5% are found in both atria [2]. They are benign in nature, and the symptoms depend on the primary location of the tumor and the nature and size of the myxoma.

Large-sized smooth tumors present with obstructive symptoms. When present in the right atrium, they produce tricuspid stenosis, hemodynamic compromise, and right-sided heart failure, with peripheral edema, ascites, jugular venous distension, and hepatomegaly. On the other hand, left atrial tumors usually cause symptoms secondary to mitral regurgitation, leading to pulmonary edema, heart failure, hemoptysis, or fatigue. Myxomas have the ability to secrete vascular endothelial growth factors, thereby stimulating the process of angiogenesis and release of various cytokines and growth factors. Myxomas can also be associated with Carney complex and its subsets. These include LAMB (lentigines, atrial myxomas, mucocutaneous myxomas, and blue naevi), NAME (naevi, atrial myxomas, myxoid neurofibroma, and ephelides/freckles), and Carney syndrome (atrial, cutaneous and mammary myxomas, lentigines, blue naevi, endocrine disorders, and testicular tumors) [3].

We describe a case of a patient presenting with large-sized biatrial myxoma, with progressive symptoms of dyspnea on exertion over a short period of time.

Case Report

A 46-year-old previously healthy woman presented to the Emergency Department with palpitations and rapidly worsening dyspnea on exertion. At baseline, she could walk multiple blocks, but she noted that her overall exercise tolerance had been deteriorating over the past year or so. Over the past month, she could barely walk 1 block without stopping to catch her breath. Despite treatment for asthma, her symptoms persisted. She denied any chest pain, headache, dizziness, nausea, vomiting, leg swelling, orthopnea, and paroxysmal nocturnal dyspnea. On examination, she had tachycardia and was otherwise hemodynamically stable, with normal oxygen saturation on room air. The cardiopulmonary examination was within normal limits and was euvolemic. She had past medical history of asthma. The differential diagnoses included asthma exacerbation, pulmonary embolism, pneumothorax, interstitial lung disease, congestive heart failure, pericardial effusion with possible tamponade, severe anemia, and hyperthyroidism. Chest X-ray showed cardiomegaly with trace right pleural effusion (Figure 1). Electrocardiogram showed 2: 1 atrial flutter with rapid ventricular rate, which was later treated with a beta blocker (Figure 2).

With the presentation of tachycardia, worsening dyspnea, and cardiomegaly on chest X-ray, computed tomography pulmonary angiography (CTPA) was performed to rule out pulmonary embolism, which revealed giant biatrial cardiac masses attached to the interatrial septum. Transthoracic echocardiogram showed a left ventricular ejection fraction of 40%, with severely dilated left and right atria. Multiple soft tissue densities, with scattered hyperechodensities filling most of the left atrium, caused functional mitral stenosis. The largest mass was 4.8×5.4 cm. Multiple large soft tissue densities in the right atrium caused functional stenosis of the tricuspid valve (Figure 3). Gated cardiac CT angiogram of chest, abdomen, and pelvis and CT of the head done for staging showed a large biatrial mass with calcifications. The right atrial component measured 8.8×6.8 cm, and the left atrial component measured 5.6×5.2 cm (Figure 4). There was partial obstruction of the inferior vena cava at the cavoatrial junction, with associated dilatation of the inferior vena cava and hepatic veins. The CT scan of the head was normal. Given the large size of the masses and the high concern for malignancy, a right anterior thoracotomy was performed for biopsy of the right atrial mass. During the procedure, transesophageal echocardiogram was done, which revealed massive right and left atrial myxomas, approximately 7 to 8 cm in size at each one. The masses were causing functional tricuspid and mitral stenosis, as they were prolapsing at the origin of each valve. Due to the large size of the masses completely filling the atria, it was difficult to comment on any preexisting atrial septal defect or patent foramen ovale. Subsequently, the pathology report confirmed the diagnosis of atrial myxoma (Figure 5), and the patient was scheduled for elective resection of the myxoma.

With no family history, risk factors of coronary artery disease and functional tricuspid and mitral stenosis, and long standing tachycardia (atrial flutter, treated with amiodarone and beta blockers), the pretest probability of the coronary artery disease was very low; hence, surgical resection was planned. For the surgical resection, a standard median sternotomy was used. Upon opening the right atrium, a massive myxoma filling the entire chamber was encountered. Both the right and left atrial masses were resected, along with a large portion of the interatrial septum. After resection of the right atrial myxoma, a left atriotomy was performed, revealing the myxoma prolapsing from the right atrial to the left atrial side. Both myxomas were removed along with the septum, and the chambers were copiously irrigated with sterile saline to ensure complete removal of residual tissue. The interatrial septum was then repaired (Figure 6).

The patient tolerated the surgery well, although the postoperative course was complicated by atrial fibrillation. Nevertheless, she was eventually discharged successfully. In follow-up, the patient reported marked improvement in her dyspnea and exercise tolerance. Follow-up echocardiograms revealed that the atria were beginning to return to normal sizes, and the left ventricular ejection fraction improved to 61% to 65%.

Discussion

Myxomas are benign cardiac tumors typically found in a single atrium. Biatrial myxomas are extremely rare and need careful differentiation from malignant tumors. Differential diagnoses for bilateral atrial masses include atrial thrombi, liquefied mesenchymal tumors, like heart lymphoma, and malignant heart tumors [4]. Biatrial masses are seldom benign, such as myxomas.

Echocardiography is the first imaging technique for the atrial masses. Myxomas usually appear non-homogeneous with calcifications, due to tissue necrosis and fibroid degeneration. If transthoracic echocardiography fails to provide detailed information, transesophageal echocardiography might be used, as it can detect smaller tumors (1–3 mm) and shunting. Magnetic resonance imaging or CT scans are crucial for surgical planning [5]. Friable myxomas can cause embolic events, leading to systemic or pulmonary arterial embolism. Therefore, once a diagnosis is confirmed, prompt surgical excision is necessary.

In the case discussed, the patient exhibited extremely large masses in both atria, which raised the strong possibility of either a primary malignant tumor or metastatic disease. Hence, an open surgical biopsy was preferred over an endomyocardial biopsy, to obtain a definitive diagnosis. Also, surprisingly, the biopsy revealed the mass to be a myxoma. One of the striking and unique features of our case was the size of the masses, with the right atrial component measuring 8.8×6.8 cm, and the left atrial component measuring 5.6×5.2 cm. These masses were unusually large for benign tumors, especially myxomas, as they typically do not reach this size. It was also unusual for the patient with large atrial masses to have minimal symptoms of dyspnea on exertion. The entire septum was covered by the masses, another feature hinting toward the mass being malignant. A case report published in 2019 showed a benign myxoma extending through an atrial septal defect to both the atria [6]; however, myxomas invading the atrial septal defect are rare.

The ultimate treatment of a myxoma is the surgical resection, which was approached in our patient as well. For complete visualization of both heart chambers, some surgeons advocate a biatrial approach, as used in our patient, to ensure extensive and complete resection [7]. Removing a wider section of the stalk attachment reduces the burden of pre-tumorous cells. In the present case, a large portion of the interatrial septum was removed. Alternatively, laser photocoagulation can destroy pretumorous cells around the stalk, eliminating the need for wide surgical resection. To minimize the risk of tumor fragmentation and embolization, vigorous palpation or manipulation is avoided or performed only after cardioplegia [8].

If heart valves are invaded and cannot be repaired, they should be replaced. Annuloplasty is recommended if annular insufficiency is observed, and a patch repair is necessary if extensive atrial septal resection is unavoidable. After tumor removal, the heart cavity should be thoroughly flushed to prevent residual tumor debris. Recurrence is usually due to incomplete excision, growth from a secondary focus, or intracardiac implantation from the primary tumor. Patients should undergo biannual echocardiograms for early detection of recurrent tumors.

One other aspect of reporting this case, in addition to its large size and biatrial involvement, was the delayed diagnosis. The diagnosis was delayed because her symptoms were initially attributed to her history of asthma, leading to treatment for asthma exacerbation. For the evaluation of shortness of breath, chest X-ray is the cost-effective investigation of choice. In our case, it showed cardiomegaly, which prompted us to rule out pulmonary embolism leading to right ventricle strain or primary cardiac issue as the cause of patient’s worsening dyspnea on exertion. Further investigations to rule out conditions contributing to dyspnea, particularly treatment-resistant asthma, which was the initial diagnosis in our case, fungal or bacterial infections, allergic bronchopulmonary aspergillosis, type 2 asthma, heart failure, and pneumonia, were put off due to the observation of cardiomegaly and normal lung fields on the chest X-ray.

This case also highlights how preexisting conditions can bias differential diagnoses, delaying definitive diagnosis and treatment. Fortunately, despite the giant atrial myxoma, our patient did not experience any life-threatening or morbid thromboembolic complications, which can significantly affect medical care, well-being, and quality of life.

Conclusions

Our case highlights a patient with minimal symptoms of exertional dyspnea who was discovered to have a large atrial mass invading the interatrial septum and extending into both atria. Despite the initial suspicion of a malignant tumor, the biopsy surprisingly revealed a benign atrial myxoma, which is a rare sight. The tumor was successfully removed, and the patient made a full recovery. This case concludes that myxomas, although rare, can be biatrial and can silently grow to a large size while causing minimal symptoms. Hence, echocardiogram or suitable imaging should be used as a guidance for early diagnosis, as delayed diagnosis can sometimes lead to catastrophic complications.