Giant biatrial myxoma in an atrial septal defect

Abstract

Myxomas account for a majority of the reported primary cardiac tumors that are relatively rare, and biatrial myxomas in an atrial septal defect are extremely rare. Here, we present the case of a healthy 79-year-old woman who was referred to our hospital after a giant mass in the left atrium was incidentally detected by transthoracic echocardiography. Although she was asymptomatic, we surgically resected the mass soon after admission, considering the risk of embolism. During the surgery, we observed the giant bilateral tumor in an atrial septal defect, which was, on pathological evaluation, found to be a myxoma.

<Learning objective: Differential diagnosis of intra-cardiac tumors is sometimes difficult because they are relatively rare. Cardiac magnetic resonance imaging is the most useful imaging modality for the differential diagnosis of intra-cardiac tumors. We describe a case wherein a large myxoma was detected in an atrial septal defect. It is useful to know that myxoma in an atrial septal defect can grow to a large size as it tends to grow in the direction of blood flow.>

Introduction

Cardiac myxoma is a well-known benign primary cardiac tumor. It usually occurs in the left atrium, although it can originate in any cardiac chamber [1]. On the other hand, biatrial myxomas (BAMs) are rare and account for less than 2.5% of all myxomas [2]. Most cases involve independent masses, followed by myxomas interconnected by a thin pedicle or through the foramen ovale. BAMs that grow through atrial septal defects (ASDs) are extremely rare.

Case report

A previously healthy 79-year-old woman with a medical history of hypertension underwent medical check-up. Chest radiography revealed calcifications in the cardiac shadow. Additional chest computed tomography (CT) and transthoracic echocardiography (TTE) revealed a giant mass (>5 cm) in her left atrium (Fig. 1a and b). Considering coronary risk, we performed a coronary angiogram (CAG), which revealed that the feeding arteries to the mass branched from right and left coronary artery (Fig. 1c and d). In addition, we performed cardiac magnetic resonance imaging (CMR) to evaluate the cardiac mass.

Fig. 1.

(a) Trans thoracic echocardiography showing a big mass (>5 cm) in the left atrium (LA). (b) Chest enhanced computed tomography (CT) showing a low-density mass with calcification inside it (yellow arrow). (c) Feeding artery from the right coronary artery to the mass in the LA (yellow arrow). (d) Feeding artery from the left coronary artery to the mass in the LA (yellow arrow).

The CMR showed a well-circumscribed, non-infiltrative mass with a broad-based attachment to the interatrial septum (IAS). This mass was heterogeneously enhanced and isointense on T1-weighted imaging, high intensity on T2-weighted imaging, and did not show any change in fat suppression imaging (Fig. 2a–c). These imaging tests were unable to appropriately describe the relationship between the mass and the IAS.

Fig. 2.

Cardiac magnetic resonance imaging showing: (a) isointensity on T1-weighted images (yellow arrow). (b) High intensity on T2-weighted images (yellow arrow). (c) No change on fat suppression images (yellow arrow).

Although she exhibited no symptoms, considering the risk of embolism, we urgently performed cardiac surgery to remove the mass. The surgery was performed through a mid-sternal incision. After initiating a cardiopulmonary bypass, the ascending aorta was clamped, and cardiac arrest was achieved by ante-grade cardioplegia. Through extended bilateral atriotomy, we found a large mass in an ASD (Fig. 3a and b). After the removal of the mass (60 × 52 × 35 mm) arising from the IAS and attaching to the lower edge of the ASD, we repaired the ASD using autologous pericardium (Fig. 3c and d). The surgery was completed and the patient was discharged on post-operative day 16 (POD16). The post-operative period was uneventful. We used anti-coagulant drug for three months after surgery to prevent thromboembolic events. On pathological evaluation, the mass was found to be a myxoma.

Fig. 3.

(a) Operative photograph showing biatrial myxoma through atrial septal defect (ASD). (b) Operative schema showing biatrial myxoma through ASD (black arrow). (c, d) Resected myxoma (60 × 52 × 35 mm) appears gelatinous, dark brown, and partly calcified. RA, right atrium; LA, left atrium; MV, mitral valve; TV, tricuspid valve.

Discussion

Intracardiac tumors, both benign and malignant, require early imaging work up and treatment because they can cause obstructive or embolic events. In this case, we were able to promptly perform serial imaging tests such as chest CT, ultrasonic cardiogram, CAG, CMR, and perform surgery. This patient's tumor showed some interesting radiographic features.

Usually, the main differential diagnosis of a left cardiac mass are primary benign tumors (e.g. myxoma, lipoma, cardiac fibroma, and angioma), primary malignant tumors (e.g. angiosarcoma, fibrosarcoma, and rhabdomyosarcomas in children), metastatic tumor and “pseudotumors” (e.g. thrombus, anatomic variants).

Chest CT of her cardiac tumor showed it to be well-circumscribed, calcified, non-infiltrative, and heterogeneous, indicating a primary cardiac tumor. Myxomas other than cardiac fibroma and lipoma present with calcification inside the tumor [1]. CMR is currently a useful imaging test for the differential diagnosis of cardiac tumors. Actually, it was useful to distinguish myxoma from cardiac fibroma and lipoma because the findings of CMR in our case corresponded with those of myxoma.

Coronary angiography showed feeding arteries from right coronary artery (RCA) and left coronary artery (LCA) to the mass in the left atrium. Although there are a few reports describing cases with myxoma fed by arteries from the coronary artery, vascular supply from both the RCA and LCA is rare [3].

Preoperative imaging tests were unable to clarify the relationship between the mass and IAS, because we did not detect ASD flow by echocardiogram, and based on CT and CMR findings, we thought that the IAS was displaced by the tumor toward the right atrium. BAM associated with an ASD is very rare. One report states that BAM associated with an ASD can cause right heart functional impairment [4]. In our case, ASD was completely occluded by BAM. Considering the calcifications inside the tumor and the absence of symptoms of right heart functional impairment, the tumor seemed to have grown through the ASD over the years because myxoma tends to grow in the direction of the flow.

Lastly, to repair the ASD properly post myxoma resection, we confirmed the anatomical position between the IAS and myxoma through ASD with an extended bilateral atriotomy and marked the point of IAS to cut starting.

We report an extremely rare case of BAM associated with an ASD, which was fed by arteries from both the RCA and LCA. In such cases, timely diagnosis and appropriate management is essential to avoid worsening of the condition.

The authors have nothing to disclose with regard to commercial support.