A Right Atrial Mass, Patent Foramen Ovale, and Indwelling Central Venous Catheter in a Patient With a Malignancy: A Diagnostic and Therapeutic Dilemma

A 33-year-old woman with a history of gestational trophoblastic disease presented for investigation of a right atrial mass. She had been receiving chemotherapy administered via a Port-a-Cath system for 2 months prior to presentation. On transesophageal echocardiography and magnetic resonance imaging, she was found to have a mass attached to the right atrial free wall, with a segment projecting across a patent foramen ovale. Because of the risk for an embolic event, the mass was surgically removed and the patent foramen ovale repaired. Pathology showed an organized thrombus. This case emphasizes the need for high suspicion for thrombus when a right atrial mass is found in a patient with a hypercoagulable state due to underlying malignancy who has a central venous catheter.

Case Report

A 33-year-old woman was hospitalized 11 months prior to this admission with gestational trophoblastic disease. The molar pregnancy was terminated, and the patient was started on methotrexate therapy. However, because of an inadequate response after 9 months on methotrexate, she was switched to an actinomycin D regimen, which was administered via a Port-a-Cath (Smiths Medical, Keene, NH) system inserted in her right subclavian artery.

Two months after the placement of the Port-a-Cath system, the patient presented to an outside hospital with progressive dyspnea on exertion and 2 episodes of syncope. Transthoracic echocardiography revealed a mobile, globular, echo-dense mass in the right atrium, which had not been present on transthoracic echocardiography performed 10 months previously. The patient was trans ferred to our institution for further workup.

Upon arrival, the patient’s vital signs were stable except for a resting oxygen saturation of 91% on room air. She had normal results on cardiac physical examination and chest x-ray. Transesophageal echocardiography (TEE) was performed ( Video 1 ), revealing a 3.2 × 3.5 × 2.9 cm mass attached to the right atrial free wall. The mass was directly opposite the indwelling central venous catheter (CVC), which projected 2.5 cm into the right atrium ( Video 2 ). The mass did not appear to extend from the superior or inferior vena cava, both of which were visualized. However, the mass appeared to partially occlude the orifice of the tricuspid valve, and a patent foramen ovale (PFO) with right atrial–to–left atrial flow was detected by color Doppler ( Video 3 ). Because of both the appearance of the mass and its broad-based attachment, as well as a lack of any evidence of extension via the superior vena cava or inferior vena cava, it was felt that the mass most likely represented an organized thrombus, but because of the possibility of metastatic malignant gestational trophoblastic disease, biopsy of the mass under echocardiographic guidance was considered. However, a β–human chorionic gonadotropin level was obtained and was found to be normal at 1 mIU/mL, suggesting that the mass was not a tumor. Because of suspicion that the mass was a thrombus, the catheter was removed, and the patient was started on low–molecular weight heparin for anticoagulation.

The patient remained stable, and magnetic resonance imaging (MRI) performed on hospital day 7 showed that the mass was still attached to the right atrial free wall, measuring 3.7 × 3.9 cm ( Video 4 ). The mass was not bright on T1 or T2 imaging ( Figures 1 A and B). The mass did not perfuse on first-pass perfusion imaging and was homogenously dark on delayed enhancement imaging ( Figure 2 ). The PFO was noted to have a new small mass projecting across it, with the largest part located in the left atrial side of the septum ( Video 5 ).

Repeat TEE with three-dimensional imaging was obtained on hospital day 12, showing the right atrial mass to be unchanged in size and confirming the presence of a tear-shaped mass attached at the PFO and projecting 1.4 cm into the left atrium ( Videos 6 and 7 ). The foraminal mass had a lucent center, suggesting that it could be a cast evulsed from the previous Port-a-Cath.

Because of the concern about the potential for an embolic event from the structure projecting across the PFO and concern that the right atrial mass had not decreased in size on adequate anticoagulation, it was felt that surgical intervention was needed. A standard median sternotomy was performed, and cardiopulmonary bypass was instituted. The right atrial mass was removed via a right atriotomy. The PFO was then closed in 2 layers with a running 3-0 Prolene suture (Ethicon, Inc, Somerville, NJ). The patient tolerated the procedure well, and her in-hospital recovery was uneventful. Pathologic examination revealed an organized thrombus with no evidence of neoplasia ( Figure 3 ).

Discussion

CVCs are routinely used for a variety of therapeutic interventions. Eight percent of hospitalized patients receive CVCs, and >5 million CVCs are inserted in the United States each year. Although catheter tip location is routinely confirmed after placement by chest radiography, it is not fixed and can migrate 2.0 to 3.0 cm with head and arm movement, as well as with changes in body position. Because CVCs are often used in patients with hypercoagulable states, such as malignancies or blood dyscrasias, migration of the catheter tip into the right atrium could lead to irritation of the endothelium of the right atrial free wall opposite the entrance of the superior vena cava, with the formation of a thrombus at the site of irritation. A prospective transesophageal echocardiographic study in adult bone marrow transplantation patients showed abnormal masses consistent with thrombi in 12.5% of patients, all of whom were in a group with the CVC tip in the right atrium. Our echocardiography lab has seen 25 patients in the past 2 years for CVC-related right atrial thrombi, all of whom were being treated for either malignancies or blood dyscrasias.

In this case, the differential diagnosis of a right atrial mass included thrombus, metastatic tumor, and primary benign or malignant tumor. Because of both the location of the mass and the patient’s history of malignancy, it was felt that this mass most likely represented a broad-based thrombus attached to the right atrial free wall. There was no evidence that this patient had direct extension of malignant neoplasm via either the superior or inferior vena cava. Although our patient did have a history of gestational trophoblastic disease, which can rarely cause cardiac metastasis, the patient’s normal β–human chorionic gonadotropin level decreased the suspicion of a metastatic choriocarcinoma. Although the possibility of a benign cardiac tumor, such as a myxoma, remained in the differential diagnosis, given the appearance and location of the mass, it was felt most likely to represent a thrombus.

Differentiating an intracardiac thrombus from a tumor is not always straightforward, because cardiac thrombi may have diverse appearances on imaging studies and may mimic neoplastic processes. TEE was the first imaging modality used because it is the best diagnostic tool to elucidate the cause of a right atrial mass. This patient’s mass was not associated with invasion of the right atrial wall, a pericardial effusion, or extension from the inferior vena cava, suggesting that it was benign. Three-dimensional echocardiography has been reported to be superior to 2-dimensional echocardiography for accurately sizing intracardiac masses and discerning their locations and sites of attachment. This modality helped determine that the mass was located on the right atrial free wall, which is usually the case with CVC-related right atrial thrombi because the catheter is in contact with this area.

Cardiac MRI has been reported to be helpful in the characterization of intracardiac masses. On delayed enhancement imaging, thrombi typically appear as dark structures surrounded by bright blood. The lack of enhancement on dynamic first-pass perfusion and on delayed images did not suggest a tumor, which often enhance because of prominent vascularity. The MRI findings in this patient provided additional support for thrombus over tumor and revealed the presence of a mass entrapped in the PFO, which was later confirmed on repeat TEE.

In our patient, the size of the right atrial mass caused partial obstruction of the tricuspid valve inflow. This likely led to an increase in right atrial pressure with opening of the PFO and persistent right atrial–to–left atrial flow. The patient’s admission oxygen saturation of 91% suggested this phenomenon. Case reports of right-to-left shunts caused by right atrial thrombi are very rare in the literature.

Our case underscores the need for a high index of suspicion for thrombus when a right atrial mass is discovered in a patient with a CVC who has a hypercoagulable state due to underlying malignancy or blood dyscrasia. Even more important, proper catheter placement with appropriate imaging such as chest x-ray or repeat transthoracic echocardiography and repositioning are essential in preventing this complication. The standard treatment for thrombus formation is removal of the catheter and concomitant anticoagulation with follow-up imaging to see if the mass resolves. In our patient, the thrombus did not resolve with anticoagulation, probably because of organization leading to a chronic course. Serial imaging with TEE and the additional use of MRI helped rule out neoplastic processes and detect structural cardiac changes that could have led to thromboembolism.