Cardiac rhabdomyoma

A cardiacCardiac rhabdomyoma is type of benign myocardial tumour and is a most common fetal cardiac tumour ⁷. 

Epidemiology

Cardiac rhabdomyomas are often multiple and can represent up to 90% of cardiac tumours in the paediatric population¹. The majority are diagnosed before the age of 1 year.  The estimated incidence is at ~ 1~1 in 20,000 births ⁸.

Clinical presentation

The majority of cardiac rhabdomyomas are asymptomatic although there can be wide clinical spectrum. On occasion 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). They grossly the appear as yellow-tan solid, circumscribed, unencapsulated lesions. Microscopically, a characteristic spider cell is seen which is a large clear cell with cytoplasmic strands composed of glycogen extending to the plasma membrane.

Location

• they may arise anywhere in the myocardium but are commoner in the ventricles (may involve the left ventricle more) ⁶

Associations

• there is a well known association with tuberous sclerosis, with over 50% of all cardiac rhabdomyomas found in patients with later confirmed tuberous sclerosis ^1,2.
• congenital renal anomalies ⁸

Radiographic features

Ultrasound / Echocardiography/Echocardiography

May be seen as one or more solid hyper echoic mass(es) located in relation to the myocardium. Small lesions can mimic diffuse myocardial thickening. They frequently occur in relation to the ventricles. The size for lesion detected in utero may range from ~ 10 - 50~10-50 mm ⁶.

MRI

• T1: relatively well defined mass(es) iso intense isointense to adjacent myocardium 
• T2:  : relatively relatively well defined mass(es) hyper intense hyperintense to adjacent myocardium

Potential complications

• development of cardiac arrhythmias
• intra cavitatory growth may cause
  • ventricular outflow tract obstruction
  • valvular compromise
  • disruption of intra-cardiac blood flow leading to congestive heart failure and hydrops

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 dependant on the number, size and location of the lesions as well as the presence or absence of associated anomalies.  

Differential diagnosis

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

• fetal hypertrophic cardiomyopathy