Teaching Case

A frail 85-year-old lady was admitted with raised JVP and peripheral oedema. Echo revealed a large right atrial mass. CT chest defined this as a 9cm by 6cm tumour herniating into the right ventricle and causing back pressure.

A frail 85 year old female was admitted with peripheral oedema. She had a 6cm JVP, with mild arm and moderate leg oedema. BNP was 825 (normal< 100), haemoglobin = 11.0 g/dl, ESR= 58 mm/hr. Liver function tests showed hepatic congestion.

Echocardiography was difficult, but a rounded heterogeneous mass of > 6cm was seen in the right atrium (RA) (Fig. 1). The left heart seemed displaced and could not be assessed.

64-MDCT of thorax confirmed the presence of a large rounded mass measuring 9 by 6cm, which seemed to arise from the inter-atrial septum. It occupied most of the right atrium and the basal right ventricle. Left heart structures were seen to be displaced laterally (Fig. 2). In coronal views, dilatation of the superior vena cava could be seen in keeping with the raised JVP and arm oedema (Fig. 3a). The right ventricle and pulmonary artery were normal (Fig. 4a). Several small flecks of calcification were seen in the tumour mass (Fig. 4b). The remainder of the study was normal. Ultrasound of abdomen showed dilated hepatic veins consistent with back pressure but no evidence of malignancy. The patient was started on loop diuretic therapy.

Surgery and follow-up were declined. A presumptive diagnosis of giant right atrial myxoma was made based on:

1. Rounded appearance of the tumour arising from the atrial septum
2. Spotty calcification
3. Raised ESR and mild anaemia, without other cause.
4. No evidence of malignant disease elsewhere
5. Lack of contrast enhancement

Atrial myxomas are relatively uncommon with only one discovered in 4553 consecutive cardiac CT studies. [1] They are the commonest primary cardiac tumour. Mean age at presentation is 50 years and approximately two thirds occur in females. Only 10% occur in the RA, where presentation is often coincidental or with dyspnoea but pulmonary emboli and right heart failure secondary to tricuspid obstruction can occur. Smooth rounded tumours are more likely to cause obstruction whilst polypoid and myxoid ones embolise. [2] Anaemia and a raised ESR are common findings.
In this case, where a tissue diagnosis is not possible, other causes of a RA mass and their characteristic features must be considered:

1. Myxomas are characteristically attached to the fossa ovalis by a stalk, here the tumour lay adjacent to most of the inter-atrial septum and a stalk is not seen but the tumour is smooth and rounded and contains flecks of calcification which is more typical of RA myxoma. [2]

2. Angiosarcomas are the commonest malignant cardiac tumours and may also present as well defined RA tumours but they tend to enhance strongly with contrast due to their vascular nature. Invasion of the atrial wall and pericardial effusion may be seen. [2]

3. Cardiac lymphomas are often seen in disseminated disease, primary cardiac lymphomas are rare. The RA is the most frequent site, followed by the pericardium and right ventricle. Cardiac lymphomas appear as an ill-defined mass with infiltration of chamber walls. [3]

4. Metastases represent about 14% of resected cardiac tumours, often right-sided and tend to be either cavoatrial extensions of abdominal tumours or haematogenous spread. [2]

5. Lipomatous hypertrophy of inter-atrial septum. This benign mass of brown fat extending across to the crista terminalis can appear sinister on echocardiography but exhibits characteristic fat density on CT and spares the fossa ovalis.

In conclusion, cardiac myxomas are uncommon with a RA location seen in only 10% of cases. The RA myxoma has the same general characteristics as the left but sometimes shows more calcification. Although most often asymptomatic or causing dyspnoea, its location means that embolisation and obstruction will produce pulmonary emboli and right heart failure with oedema.
Several other RA masses, some with poor prognosis, can resemble RA myxoma so careful assessment must be made especially if tissue diagnosis is delayed or not possible.