Cardiac rhabdomyomas are a type of benign myocardial tumour and are considered the most common fetal cardiac tumour. They have a strong association with tuberous sclerosis.

Epidemiology

Cardiac rhabdomyomas are often multiple and can represent up to 90% of cardiac tumours in the paediatric population ¹. The majority are diagnosed before the age of 1 year. The estimated incidence is at ~1 in 20,000 births ⁸.

Associations

• there is a well-known association with tuberous sclerosis, with >50% of all cardiac rhabdomyomas found in patients with later confirmed tuberous sclerosis ^1,2

• congenital renal anomalies ⁸

Clinical presentation

The majority of cardiac rhabdomyomas are asymptomatic although there can be a broad clinical spectrum. Occasionally, they may present with left ventricular outflow tract obstruction or refractory arrhythmias.

Pathology

It is a hamartomatous lesion consisting of cardiac muscle tissue (derived from embryonal myoblasts).

Location

They may arise anywhere in the myocardium but are more common in the ventricles (may involve the left ventricle the most) ⁶.

Macroscopic appearance

Macroscopically, they appear as yellow-tan solid, circumscribed, unencapsulated lesions.

Microscopic appearance

Microscopically, a characteristic spider cell is seen which is a large clear cell with cytoplasmic strands composed of glycogen extending to the plasma membrane.

Radiographic features

Ultrasound/echocardiography

May be seen as one or more solid hyperechoic masses located in relation to the myocardium. Small lesions can mimic diffuse myocardial thickening. They frequently occur in relation to the ventricles. The size of a lesion detected in utero may range from 10-50 mm ⁶.

MRI

• T1: isointense to adjacent myocardium 

• T2: hyperintense to adjacent myocardium

Treatment and prognosis

In most cases, no treatment is required, and these lesions regress spontaneously. Patients with left ventricular outflow tract obstruction or refractory arrhythmias respond well to surgical excision. The overall prognosis is dependent on the number, size and location of the lesions as well as the presence or absence of associated anomalies.  

Complications

• development of cardiac arrhythmias

• intracavitary growth may cause

  • ventricular outflow tract obstruction

  • valvular compromise

  • disruption of intracardiac blood flows leading to congestive heart failure and hydrops

Differential diagnosis

For the in-utero sonographic appearance of diffuse myocardial thickening, consider:

• fetal hypertrophic cardiomyopathy