Thursday, March 12, 2015

Arrhythmogenic right ventricular dysplasia (ARVD)

Arrhythmogenic right ventricular dysplasia (ARVD) is a disorder characterized by progressive replacement of the right ventricular myocardium by fibrofatty tissue.




Although this disorder usually involves the right ventricle, the left ventricle and septum also may
be affected. This dysplasia can lead to extensive wall thinning, atypical arrangement of
trabecular muscles, dilatations or aneurysms having paradoxical systolic motion, and,
in rare cases, right-sided congestive heart failure.


Although the exact prevalence of ARVD is unknown, it has been estimated to occur in
one in 5000 individuals from the general population. Several reports suggest that there
is a familial occurrence of ARVD of about 30%?0%, with mainly autosomal dominant
inheritance. It represents the second cause of sudden cardiac death in young persons,
especially athletes, after hypertrophic heart disease.


Patients with ARVD are usually men younger than 35 years who complain of chest pain
or tachycardia. In some cases, sudden cardiac death can be the fi rst presentation.
The diagnosis of ARVD is based on the presence of major and minor criteria encompassing
genetic, electrocardiographic, pathophysiologic, and histopathologic factors.


Fifty to 90 percent of persons with ARVD will have characteristic fi ndings on a resting
electrocardiogram (ventricular tachycardia with LBBB, originating from the right ventricle).
The imaging modalities used to evaluate right ventricular abnormalities include
conventional angiography, echocardiography, radionuclide angiography, ultrafast computed
tomography, and magnetic resonance (MR) imaging.


Right ventricular angiography has usually been regarded as the standard of reference
for the diagnosis of ARVD, especially for discerning abnormalities such as akinetic or
dyskinetic bulging in the infundibular, apical, and subtricuspid regions.
Echocardiography can detect regional or global changes in myocardial contractility,
enlargement of the right ventricle, and right ventricular systolic dysfunction during a
routine study. However, visibility of the apex and the right ventricular outfl ow tract is
limited, areas of wall thinning may be very diffi cult to detect, and echocardiography
lacks spatial resolution in depicting the typical fatty and fi brofatty changes in the right
ventricular myocardium.


MR imaging allows visualization of ventricular cavities and walls with an excellent
depiction of myocardial anatomy. Cine sequences detect regional motion changes such
as global or local hypokinesia, localized early diastolic bulging, or circumscribed saccular
outpouchings. T1-weighted sequences are able to detect intramyocardial fat in
some cases. MR images obtained with the delayed-enhancement technique may reveal
fi brous replacement of the right-ventricular free wall.

Because MR imaging depicts both functional and structural abnormalities, positive MR imaging fi ndings should be used as important additional criteria in the clinical diagnosis of ARVD. CMR appears to be the optimal technique for the detection and follow-up of clinically suspected ARVD.


Balanced fast fi eld-echo cine MR images performed in the 4-chamber (Fig. 2.3.1) and short-
axis (Fig. 2.3.2) projections show severe dilation of the right ventricle, along with wall thinning,
increased trabeculation, multiple bulges with dyskinetic areas, and severe global dysfunction.
The left ventricle is normal in size with mildly reduced global systolic function.
Black-blood T1-weighted MR images obtained in the 4-chamber (Fig. 2.3.3) and shortaxis
(Fig. 2.3.4) planes show the absence of areas of fatty replacement of the right ventricular
wall.

On the basis of these fi ndings, ARVD was diagnosed even though no fatty replacement
of the RV wall was observed.

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