Arrhythmogenic right ventricular dysplasia

Clinical History

A 4 year old boy was referred to our hospital for cardiac examination with a history of familial sudden cardiac death.

Imaging Findings

A 4 year old boy admitted to our paediatric cardiology department for cardiac examination. Since his 14 year old brother died suddenly with an unknown cardiac problem, he was taken to detailed examination although he did not have any complaint. In chest radiography, there was moderate cardiomegaly without pulmonary vascular redistribution (Fig 1). Due to bilateral ventricular dilatation and decrease in right ventricular ejection fraction in echocardiography, cardiac MRI study was done to characterize the pathology which led to dilated cardiomyopathy. Bright-blood gradient echo images (SSFP) in cine mode revealed dyskinesia in the free wall of the right ventricle and hypokinesia in the left ventricular wall (Fig 2). There was diffuse dilatation of the chamber of the right ventricle without aneurysm formation. Right ventricular outflow tract was also dilated (Fig 3). In the functional MR studies, ejection fractions of both ventricles were decreased. Diffuse contrast enhancement of the right ventricular free wall was demonstrated in the delayed enhancement phase sensitive inversion recovery flash sequences (Fig. 4). Diagnosis of arrhythmogenic right ventricular dysplasia (ARVD) was made according to clinical and radiological findings.

Discussion

Arrhythmogenic right ventricular dysplasia (ARVD) is a major cause of death in young adolescents which is characterized by progressive fibro fatty replacement of the right ventricular wall. Patients usually present with arrhythmias with left bundle branch block due to right ventricular dysplasia. Therefore, an early and accurate diagnosis followed by appropriate therapy for this condition is increasingly important to prevent lethal arrhythmias. Some patients have some degree of left ventricular involvement accompanying right ventricular involvement.

30-50% of ARVD patients have a familial inheritance which is mostly autosomal dominant [1]. So family history with a clinical diagnosis of ARVD or family history of a sudden death before 35 years caused by suspected ARVD; forms criteria in the diagnosis. The most important diagnostic modalities for the detection of ARVD include conventional angiography, echocardiography, radionuclide angiography, ultrafast computed tomography (CT), and magnetic resonance (MR) imaging.

Two morphologic variants of ARVD have been reported: fatty and fibro-fatty. 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 fibro-fatty variant is associated with significant thinning of the right ventricular wall, and the left ventricular myocardial wall may also be involved. Early ARVD shows predilection for the regions of heart with relatively thinner walls and high shear stress – the subtricuspid portion, outflow tract, apex and mid-free wall of the RV ("triangle of dysplasia") and the inferior wall septal junction and infero-lateral wall of the LV [2].

MR imaging allows a three-dimensional evaluation of ventricular anatomy and volumes, and recognition of myocardial fatty and fibro-fatty replacement. The typical criteria that can be demonstrated with MR imaging are (a) fatty infiltration of the right ventricular myocardium with high signal intensity on T1-weighted images; (b) fibro-fatty replacement, which leads to diffuse thinning of the right ventricular myocardium; (c) aneurysms of the right ventricle and right ventricular outflow tract; (d) dilatation of the right ventricle and right ventricular out-flow tract; (e) regional contraction abnormalities; and (f) global systolic dysfunction and global diastolic dysfunction [3]. Significant fatty infiltration can be observed in more that 50% of normal elderly hearts but the presence of total transmural fatty infiltration with diffuse thinning of the right ventricle and dyskinetic areas on cine images are highly suggestive of ARVD. Recently, the role of delayed enhancement of the right ventricle in the diagnosis of ARVD is demonstrated by some authors and this finding may support the inflammatory theory meaning fibro-fatty infiltration as a healing process in the context of myocarditis [4].

Differential diagnosis of ARVD consists of idiopathic dilated cardiomyopathy and the Uhl anomaly, which is characterized by a paper-thin right ventricle due to almost complete absence of myocardial muscle fibres. Therapeutic options include antiarrhythmic medication, catheter ablation, implantable cardioverter defibrillation, and surgery.

Differential Diagnosis List

Final Diagnosis

Arrhythmogenic right ventricular dysplasia

URL:	https://www.eurorad.org/case/7700
DOI:	10.1594/EURORAD/CASE.7700
ISSN:	1563-4086