Arrhythmogenic right ventricular cardiomyopathy (ARVC), mostly originating from right ventricular outflow tract, is a recognized cause of sudden cardiac death (SCD).1 On the other hand, idiopathic RVOT-Ventricular tachycardia (RVOT-VT) is considered as benign in entity,2 whereas ARVC is characterized by fibro-fatty infiltration of right ventricular (RV) myocardium from histopathologic findings, predisposes to syncope, ventricular arrhythmias, and sudden cardiac death (SCD).3-5However, clinical presentation of ARVC varies diversely, ranging from concealed phases (as idiopathic RVOT-VT), overt electrical phase, to profound heart failure,3 which leads to difficulties in differential diagnosis, especially for in patients with ARVC at its early stage or in its minor variant.4-6 Though modified Task Force Criteria have been proposed to diagnose ARVC, patients with ARVC could have undetermined diagnosis, and patients without fulfilling the criteria might still carry the possibility of SCD.7 Currently, ARVC is considered mostly to be autosomal dominant inheritance and genetic variations have been found in the desmosomes.8,9 Seven genes, including plakoglobin (JUP),10 desmoplakin (DSP),11 plakophilin-2 (PKP2),12 desmoglein-2 (DSG2),13 desmocollin-2 (DSC2),14,15 transforming growth factor beta-3 (TGFβ3),16,17 and TMEM43,18 have been identified to be associated with ARVC. Through the detection of high risk genetic mutation in familiar ARVC for risk stratification and implantable cardioverter defibrillator (ICD) implantation has been proved to improve survival.19 Although genetic studies have provided important insights into the pathogenesis of ARVC, the anticipated role of genotyping in the clinical area has not yet been realized, especially in Taiwanese patients. The aims of this study are to integrate the clinical assessment of Task force criteria and the genetic mutations in ARVC. Patients with ARVC fulfilling the Task force criteria and who received electrophysiological study and/or catheter ablation will be enrolled for genetic screen for the 7 genes. In this laboratory, we have demonstrated that successful catheter ablation of ARVC patients may reduce the future mortality as compared to patient who did not receive catheter ablation.20 In the future; determination of genetic mutations in patients with RVOT-VT without fulfilling Task Force criteria has pivotal impact on detection of concealed ARVC. This study will focus on detection of genetic mutations and microRNA in patients with RVOT ventricular arrhythmias, incorporation with the assessment of noninvasive study and/or invasive electrophysiological study, to improve the diagnosis of ARVC, risk stratification, clinical management, and prevention of future SCD.