J wave syndrome has emerged as a significant cause of Idiopathic ventricular fibrillation (IVF) responsible for sudden cardiac death. A large body of data is now available on genesis, genetics and ionic mechanisms of J wave syndromes. Two of these viz., Early repolarization syndrome (ER) and Brugada syndrome (BrS) are fairly well characterized enabling correct diagnosis in most patients. The first part of repolarization of ventricular myocardium is governed by Ito current i.e., rapid outward potassium current. The proposed mechanism of ventricular fibrillation (VF) and ventricular tachycardia (VT) storms is the faster I"t"o current in the epicardium than in the endocardium results in electrical gradient that forms the substrate for phase 2 reentry. Prevention of Ito current with quinidine supports this mechanism. Majority of ER patterns in young patients are benign. The key issue is to identify those at increased risk of sudden cardiac death. Association of both ER syndrome and Brugada syndrome with other disease states like coronary artery disease has also been reported. Individuals resuscitated from VF definitely need an implantable cardiac defibrillator (ICD) but in others there is no consensus regarding therapy. Role of electrophysiology study to provoke ventricular tachycardia or fibrillation is not yet well defined. Radiofrequency ablation of epicardial substrate in right ventricle in Brugada syndrome is also under critical evaluation. In this review we shall discuss historical features, epidemiology, electrocardiographic features, ionic pathogenesis, clinical features and current status of proposed treatment of ER and BrS.
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