When a patient has the overt manifestations of the disease including evident right ventricular abnormalities, the MRI can be confirmatory by its unique ability to identify and characterize fatty tissue infiltration in the right ventricular free wall.  However, in patients with ventricular arrhythmias of left bundle branch block morphology who have minimal anatomic abnormalities of the right ventricle, the sensitivity and specificity of the MRI to distinguish normals from ARVD has not been defined.  In addition, there may be variable degrees of penetration of epicardial fat into the medial layer of the right ventricle in normal individuals.  Also the right ventricular free wall is only 4-5 mm thick and the resolution of the MRI to detect thinning of several millimeters is questionable.  Finally, most radiologists have limited experience in the diagnosis of ARVD by MRI.  Until these issues are clarified, cardiologists should be cautioned not to solely rely on the MRI to diagnose ARVD.  The study has a standardized protocol for MRI evaluation and MRIs are sent to the MRI Core Laboratory under the direction of Dr. David Bluemke, Johns Hopkins Hospital.  MRI protocol

It is essential to examine the involvement of the myocardium of the right ventricular free wall with fibrous and /or fatty replacement and validate the clinical diagnosis by pathological examination of right ventricular endomyocardial biopsy samples.  The interventricular septum is usually not involved in ARVD. Myocarditis predominantly affecting the right ventricle can mimic the clinical presentation of ARVD. Structural abnormalities of development of the right ventricle may be difficult to differentiate from ARVD with certainty without histopathology. The Pathology Core Laboratory is under the direction of Dr. Gaetano Thiene, Padua, Italy. 

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