The multiple facets of right ventricular cardiomyopathies.

Arrhythmogenic right ventricular dysplasia (ARVD) was the term originally used to identify a new cardiac entity characterized by right ventricular arrhythmias and juvenile sudden death. Recognition of this disease was the result of the investigation of a group of patients who had no cardiac abnormalities on physical examination but developed episodic right ventricular tachycardia. Treatment by open chest ventriculotomy was successful in preventing recurrent ventricular tachycardia. Other terminology has subsequently been used to describe this disease, including ARVC/D, which was included in the new classification of cardiomyopathies in 1996. Arrhythmogenic right ventricular cardiomyopathy (ARVC) is also employed to describe this entity. The original term of arrhythmogenic right ventricular dysplasia (or dystrophy) was chosen because sections of the right ventricle during surgery showed a marked decrease in muscle thickness covered by a large amount of fat, suggesting a defect in development. This inference was also made by Henry Uhl in his description of his eponym case. It was impossible for pathologists to identify the disease with certainty because fat without fibrosis is frequently observed in the free wall of the right ventricle, a feature unique to the human species. Due to advances in molecular biology, this developmental defect consisting of an increased amount of adipocytes and interstitial fibrosis replacing cardiomyocytes starting in the embryo (Figure 1) and progressing during adolescence and adulthood has been partially elucidated. This pathological process may produce sustained ventricular arrhythmias. Atrial arrhythmias can also be the first presentation of the disease, suggesting a more generalized cardiomyopathy. Subsequently, other entities have been included that primarily affect the right ventricle, such as some cases of Brugada syndrome or some cases of right ventricular outflow tachycardia, in addition to Uhl’s anomaly and Naxos disease, resulting in a wide spectrum of right ventricular cardiomyopathies. However, right ventricular outflow tract tachycardia and right ventricular dysplasia remain the most common forms of right ventricular cardiomyopathies. Some patients with ARVD treated with antiarrhythmic drugs and/or an implantable defibrillator may have an uneventful course over decades. More frequently, over a long-term follow-up there is progressive right ventricular enlargement as well as a later expression of left ventricular disease. An