Arrthymogenic right ventricular dysplasia

An arrythmogenic right ventricular dysplasia (ARVD) is classified as type of cardiomyopathy seen particularly in young males, and is one of the more common cause of sudden death in these patients. 

Epidemiology

Typically presents in young individuals. There is a recognised male predilection, with a male-to-female ratio of 2.7:1. Several reports suggest that there is a familial occurrence of ARVD of about 30%–50%, with mainly autosomal dominant inheritance, various penetrance, and polymorphic phenotypic expression.

Clinical presentation

ARVD is characterized clinically by ventricular arrhythmias with left bundle branch block (LBBB) that may lead to cardiac arrest. As such it may present as a sudden onset collapse or syncopal episode and should be a consideration in a young fit individual with such a presentation. 

Associations

• as the name implies this is associated with fatal arrhythmias and sudden cardiac death.
• other non fatal arrhythmias include
  • left bundle branch block : LBBB
  • ventricular tachycardia

Diagnosis is based on the presence of structural, histologic, electrocardiographic, arrhythmic, and genetic factors ⁴. Criteria have also been developed, of which patients must have either two major criteria, one major and two minor criteria, or four minor criteria. See diagnostic criteria for arrthymogenic right ventricular dysplasia ². 

Pathology

Two morphologic variants of ARVD have been reported: fatty and fibrofatty.

The fatty form is characterized by almost complete replacement of the myocardium without thinning of the ventricular wall, and it occurs exclusively in the right ventricle.

The fibrofatty variant is associated with significant thinning of the right ventricular wall, and the left ventricular myocardial wall may also be involved ^1,2.

Both idiopathic and familial aetiologies have been proposed (see epidemiology above) ².  

As the name imples it classically involves the right ventricle although on autopsy studies a sizeable number of cases also show a degree of left ventricular involvement.

Radiographic features

Chest radiograph

Non specific and can be normal. May show evidence of right ventricular dilatation (best seen on a lateral view)

Echocardiography

The right ventricle is often dilated and hypokinetic

MRI

Most sensitive imaging modality for diagnosis although image interpretation can still be difficult due to a degree of RV wall focal fatty infiltration (high signal on T1) in normal individuals ³. Classically demonstrates fibrofatty diposition in right ventricular free wall as well as morphological features of right ventricular dilation. The ventricular wall may be thinned as a result. The left ventricle is typically spared. SSFP sequences may provide additional information on functional wall impairment. 

Other associated features include

• right ventricular aneurysm formation
• diffuse right ventricular wall thinning resulting in severe global dilatation
• segmental hypokinesia.

CT

May show right ventricular dilation and fatty low attenuation to the right ventricular wall.

Treatment and prognosis

ARVD is a progressive disease and will probably lead to right ventricular failure in the long term unless sudden cardiac death occurs beforehand.

The four therapeutic options in patients with ARVD include antiarrhythmic agents, catheter ablation, implantable cardioverter defibrillators, and surgery.

Differential diagnoses

• large right ventricular infarction 
• idiopathic dilated cardiomyopathy
• Uhl anomaly
  • paper-thin right ventricle due to almost complete absence of myocardial muscle fibers
  • no gender predilection or familial occurrence