arrhythmogenic right ventricular cardiomyopathy

Arrhythmogenic right ventricular cardiomyopathy (ARVC), also referred to as arrhythmogenic right ventricular dysplasia (ARVD) or simply arrhythmogenic cardiomyopathy, is a cardiomyopathy that is one of the more common causes of sudden cardiac death in young patients.

Epidemiology

The estimated population prevalence is thought to range around 1 in 1000-5000 . It typically presents in young individuals. There is a recognized male predilection, with a male-to-female ratio of 2.7:1. Several reports suggest that there is a familial occurrence of ARVC of about 30-50%, with mainly autosomal dominant inheritance, various penetrance, and polymorphic phenotypic expression.

Clinical presentation

Patients with ARVC commonly present with palpitations, syncope, or sudden cardiac arrest due to their propensity for ventricular ectopy arising from the structurally abnormal right ventricle. Exertion is a common trigger for the causative ventricular tachyarrhythmias. Patients may also present with the clinical hemodynamic "congestion" component of CHF, including;

• jugular venous distension
• hepatic congestion
• symmetric, pitting pedal edema
• exercise intolerance

ECG

• conduction abnormalities
  • features most pronounced in the right precordial leads (V1-3)
    • epsilon wave 
      • subtle positive "notch" after the J point and before the T wave
    • localized widening of QRS complex (V1-3)
      • prominent, broad S wave with slurred upstroke
    • inversion of T waves (V1-3)
• ventricular tachyarrhythmias
  • usually regular, wide (QRS duration >0.12) complex rhythms with rates between 140-250 beats per minute
    • typical of monomorphic ventricular tachycardia (VT)
  • deviation of the QRS axis in the frontal plane
  • often demonstrates a morphology consistent with an ectopic origin in the right ventricular outflow tract (RVOT VT)
    • major QRS vector travels from the base to the apex, roughly leftward and inferiorly, thus appearing predominantly positive in leads aVL (high lateral) and II, III and aVF (inferior)
  • may also demonstrate a left bundle branch morphology

Associations

Diagnosis is based on the presence of structural, histologic, electrocardiographic, arrhythmic, and genetic factors . This involves a combination of characteristic abnormalities in family history, electrocardiography, cardiac imaging as well as an endomyocardial biopsy.

Diagnostic 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 arrhythmogenic right ventricular cardiomyopathy .

Pathology

Two morphologic variants of ARVC 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 fibro-fatty variant is associated with significant thinning of the right ventricular wall, and the left ventricular myocardial wall may also be involved

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

As the name implies, it classically involves the right ventricle although, on autopsy studies, a sizable number of cases also show a degree of left ventricular involvement. Left dominant arrhythmogenic cardiomyopathy is a separate entity.

Radiographic features

Plain radiograph

Chest radiographic findings are non-specific and can often be normal. May show evidence of right ventricular dilatation (best seen on a lateral view).

Echocardiography

Echocardiography has inconsistent sensitivity and specificity for the diagnosis of ARVC and is not considered a primary modality in the final diagnosis .

The major echocardiographic criteria consistent with ARVC are:

• regional right ventricular dyskinesia or aneurysm (required)
• right ventricular outflow tract diameter (measured in the parasternal long-axis) of 36 mm or larger
• a fractional area change of 33% or less

The minor criteria are:

• regional right ventricular akinesia or dyskinesia (required)
• right ventricular outflow tract diameter (measured in the parasternal long-axis) between 29 and 35 mm
• a fractional area change between 34-39%

The aforementioned wall motion abnormalities are required. Disproportionate enlargement of the basal right ventricle, severe functional TR may occur in the presence of RV dilatation and dysfunction while visualization of an intensely echogenic moderator band are supportive features in the presence of major or minor criteria .

CT

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

MRI

Cardiac MRI is the most sensitive diagnostic imaging modality. Major cardiac MRI diagnostic criteria are:

• regional RV akinesia or dyskinesia or dyssynchronous RV contraction and 1 of the following:
  • ratio of RV end-diastolic volume to BSA ≥110 mL/m (male) or ≥100 mL/m (female)
  • RV ejection fraction ≤40%

Minor cardiac MRI diagnostic criteria are:

• regional RV akinesia or dyskinesia or dyssynchronous RV contraction and 1 of the following:
  • ratio of RV end-diastolic volume to BSA ≥100 to <110 mL/m (male) or ≥90 to <100 mL/m  (female)
  • RV ejection fraction >40% to ≤45%

MRI may show fatty infiltration in the right ventricle (and occasionally in the left ventricle) , but this can also be seen in normal myocardium  and is no longer part of the diagnostic criteria . A corrugated pattern to the right ventricular wall may be seen, known as the “accordion sign.”

Focal left ventricular dyskinesia may be present with fatty infiltration within the left ventricle. MRI is also helpful in the evaluation of myocardial fibrosis and scarring.

Treatment and prognosis

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

Therapy is focused on prevention of arrhythmogenesis by either pharmacologic (amiodarone or beta-blockade) or interventional (e.g. endocardial-epicardial radiofrequency ablation) means. An implantable cardioverter-defibrillator (ICD) is often placed to prevent degeneration of any future paroxysms of the abovementioned tachyarrhythmias.

Differential diagnosis

Imaging differential considerations include:

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

Siehe auch:

• Kardiomyopathie
• SSFP - steady state free precession
• diagnostic criteria for arrthymogenic right ventricular dysplasia

und weiter:

• cardiomyopathy 1995 WHO classification