A differential diagnosis to be considered when evaluating patients with right ventricular outflow tract tachycardia is arrhythmogenic right ventricular dysplasia which occurs in the presence of a diseased right ventricle. The right ventricle is dilated and covered by fatty tissue and the musculature of the right ventricle is replaced with fatty infiltration and fibrous tissue. Most patients experience arrhythmias before the fourth decade of life. A history of exercise-related tachycardia is common in arrhythmogenic right ventricle dysplasia. Sudden cardiac death is associated with exertion in this syndrome.
Most cases are sporadic, although familial forms exist.
Also the signal average EKG is often abnormal in patients with arrhythmogenic right ventricular dysplasia. Right ventricular angiography often reveals global dilatation of the right ventricle with a marked decrease in contractility, as well as deep fissuring and delayed emptying of contrast material from the right ventricle. Intravenous verapamil will often terminate ventricular tachycardia originating from the right ventricular outflow tract. The mechanism of these tachycardias is presumed to be abnormal automaticity in the case of repetitive monomorphic ventricular tachycardia or triggered automaticity in the case of tachycardia originating from the right ventricular outflow tract. A variety of treatments have proved successful in these patients, such as beta blockers, verapamil, and Class I and Class III antiarrhythmic agents.