Idiopathic right ventricular tachycardia or arrhythmogenic right ventricular cardiomyopathy?

History: While cycling a 38-year-old man suddenly experienced palpitations associated with marked weakness. 90 min later his general practitioner, hav ing diagnosed a ventricular tachycardia (VT) with a rate of 218/min, termin ated it by a drug injection. Investigations: Electrocardiography (ECG), echocardiography and biventricul ar cardiac catheterization with right ventricular contrast injection failed to provide any evidence of structural abnormality. However, ergometry and EPS with programmed ventricular stimulation induced VT of identical morphol ogy (left bundle branch bloc [LBBB] with right axis deviation [RAD]). Treatment and course: Idiopathic right-ventricular outflow tract tachycardi a (IRVT) having been diagnosed, the patient was put on a maintenance dose o f 50 mg/d atenolol. After 6 months without symptoms he again experienced se veral attacks of tachycardia. Resting ECG merely revealed an epsilon potent ial and negative T waves in V1-V3. Right ventricular contrast injection rev ealed inferolateral dyskinesia. EPS demonstrated both the known VT and a se cond, morphologically different one (LBBB with LAD). These findings indicat ed arrhythmogenic right-ventricular cardiomyopathy (ARCV). A cardioverter/d efibrillator was implanted (ICD) and over the subsequent 8 months he had si x episodes of VT which were quickly terminated by the ICD. Conclusion: At first presentation of right-ventricular outflow tract tachyc ardia it is often not possible to differentiate between IRVT and arrhythmog enic RV cardiomyopathy. The two being significantly different in prognosis and treatment, follow-up monitoring is essential to establish the definitiv e diagnosis.