Cardiac myxoma

Cardiac myxomas, although uncommon are one of the commonest primary cardiac tumours and account for ~50% primary benign cardiac tumours. 

Epidemiology

Cardiac myxomas are the most common primary cardiac tumour in adults (~50%) but are relatively infrequent in childhood, where cardiac rhabdomyomas are more frequent ^8,11. The incidence of cardiac myxomas is approximately 0.5 per million population per year ¹². There is a broad range in the age of presentation (11-82 years), with most patients presenting in adulthood (mean ~50 years of age) ^7,13. There is a recognised female predilection ^7,13.

Clinical presentation

Approximately 20% of patients are asymptomatic, with myxomas being found incidentally on imaging of the heart ⁷. Presumably, as the amount of imaging increases, so will this figure.

Clinical features are variable and depend on the location and other associated pathology, e.g. valve destruction. However, a triad of symptoms is recognised ^7-8:

1. valvular obstruction
   • left sided: dyspnoea, orthopnoea, pulmonary oedema
   • right sided: symptoms of right heart failure
2. embolic event
   • distribution will depend on the location of the tumour
   • most are left sided, and, therefore, most are systemic (brain or extremities)
3. constitutional symptoms
   • weight loss, fatigue, weakness
   • may resemble infective endocarditis (fever, arthralgia, lethargy)

In ~20% of patients, arrhythmias may be identified ⁷.

On auscultation, a cardiac murmur is usually present. A characteristic finding in patients with pedunculated and prolapsing myxoma is the so-called "tumour plop" ⁷.

Pathology

Controversy exists in regards to the exact nature of these masses, but in general, they are considered benign neoplasms. Some authors believe that they represent organised thrombus. 

Morphologically they are often haemorrhagic and are of variable firmness. They can be sessile or pedunculated (commoner) and of variable size (1-10 cm). They most frequently arise in the left atrium, attached to the interatrial septum in the region of the fossa ovale.

Location

Patients with atrial myxomas can be divided into two groups: typical (vast majority) and atypical ^7,9:

• typical: solitary with ~75% located in the left atrium
• atypical: earlier presentation; multiple tumours are common and are more frequently located in the right heart or left ventricle

Overall distribution ^8,9:

• atria (95%)
  • left (75%)
  • right (20%)
• ventricles (5%)

Associations

An uncommon but well-described association with multiple endocrine neoplasia syndromes has been described, and is known as Carney complex ^7-8.

Radiographic features

Plain radiograph

Chest radiographs can be normal ². Abnormalities, if present, are non-specific and include:

• cardiomegaly: left atrial enlargement
• intracardiac tumoraltumoural calcification
• evidence of mitral valve obstruction
• evidence of elevated left atrial pressure, e.g. pulmonary oedema

Ultrasound

Echocardiography is usually the initial modality used for identification and evaluation of cardiac myxomas. They appear as hyperechogenic lesions with a well-defined stalk. Moreover, echocardiography can be useful to assess the mobility of the tumour, as it often protrudes through valve flaps.

CT

Myxomas, as is the case with other cardiac tumours, appear as intracardiac masses, most often in the left atrium and attached to the interatrial septum. They are usually heterogeneously low attenuating (approximately two-thirds of cases ^2,8). Due to repeated episodes of haemorrhage, dystrophic calcification is common ⁸.  calcification is more common in right atrial myxoma.

If the mass is pedunculated, the motion within the heart can be demonstrated, including prolapse through the mitral valve.

MRI

MRI appearances are heterogeneous, reflecting the non-uniformity of these masses. They are typically spherical or ovoid masses which may be sessile or pedunculated ^2,3. 

• T1: tend to be low to intermediate signal, but areas of haemorrhage may be high ³
• T2: can be variable due to heterogeneity in tumour components; e.g. calcific components > low signal; myxomatous components  > high signal 
• GE (gradient echo): may show blooming of calcific components
• T1 C+ (Gd): shows enhancement (important discriminator from a thrombus)

Treatment and prognosis

Complete resection in typical cases is usually curative with recurrence rates (either locally or elsewhere in the heart) reported in 0-5% of cases^11,14. In atypical cases or those with Carney complex, the rate is much higher (12-22%) ^7,11.

Complications

• cardiac arrhythmia(s)
• embolic complications, e.g. stroke, hemorrhagehaemorrhage from neoplastic intracranial aneurysm

Differential diagnosis

On imaging consider

• intracardiac thrombus
• other primary cardiac tumours