Cardiac myxoma

Cardiac myxomas, although uncommon are one of commonest primary cardiac tumours and account for ~ 50% primary benign cardiac tumours ^3,7-8. 

Epidemiology

Cardiac myxomas are the most common primary cardiac tumour in adults, but are relatively infrequent in childhood, where cardiac rhabdomyomas are more frequent ⁸. There is a wide range in the age of presentation (11 - 82 years), with most patients presenting in adulthood (mean ~ 50 years of age) ⁷. There is a recognised female predilection ⁷.

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 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 location of 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.

Distribution within the heart

Patients with atrial myxomas can be divided into two groups : typical (vast majority) and atypical.

In typical cases, cardiac myxomas are almost always single, and there is a striking predilection for the left atrium, with approximately 75 - 86% occurring there ^7,9.

In atypical cases, presentation is usually early and multiple tumours are more common and they are more frequently located on the right side of the heart, or in the left ventricle ⁷. 

Overall distribution ^8,9:

• atria : 95%
  • left : 75%
  • right : 20%
• ventricles : 5%

Pathology

Controversy exists in regards to the true 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 the region of the fossa ovale.

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 film

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

• cardiomegaly : left atrial enlargement
• intracardiac tumoral 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 asses the mobility of the tumor, as it often protrude through valve flaps.

CT

Myxomas, as is the case with other cardiac tumours, appear as intra-cardiac masses, most often in the left atrium and attached to the interatrial septum. They are usually heterogeneously low attenuating ( approximately 2/3 of cases ^2,8). Due to repeated episodes of haemorrhage, dystrophic calcification is common ⁸. 

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 componants; 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)

Complications

• cardiac arrthythmia(s)
• embolic complications - e.g stroke

Treatment and prognosis

Complete resection in typical cases is usually curative with recurrence rates (either locally or elsewhere in the heart) reported in 1-3% of cases. In atypical cases the rate is much higher  (12 - 22%) ⁷.

Differential diagnosis

• intra-cardiac thrombus
• other primary cardiac tumours