Palpitations, syncope, and sudden death, the hallmark manifestations of cardiac arrhythmias, are encountered by all cardiologists and other clinicians. In the United States alone, more than 2 million people are affected with atrial arrhythmias. Annually more than 250 000 are victims of sudden death, most often from ventricular arrhythmias. Heart rhythm abnormalities are common comorbidities in many cardiac diseases, and a significant number of people have primary electrophysiological diseases without structural or functional heart disease.The field of interventional cardiac electrophysiology began more than 20 years ago, when Melvin Scheinman and John Gallagher's work demonstrating that an electric shock applied to a temporary pacing catheter could be used to selectively damage a portion of the cardiac electrical system, establishing the feasibility of catheter ablation in humans. Almost simultaneously, Michel Mirowski's dream of an implantable defibrillator was becoming a clinical reality, with the first cardioverter defibrillator implantation in 1980. These technologies rapidly developed to the point of replacing antiarrhythmic drug therapy and arrhythmia surgery as treatments for many arrhythmias. As cardiac rhythm management devices evolved, they provided diagnostic insights into the pathophysiology of arrhythmias that apply directly to diagnosis and treatment. Articles in the Interventional Cardiac Electrophysiology series will provide an up-to-date review and assessment of the field.Depressed ventricular function from any cause and an increasing number of genetic diseases are associated with a risk of sudden arrhythmic death that can be dramatically reduced by an implantable defibrillator. Implantable arrhythmia devices now treat ventricular dysfunction in an increasing number of patients with heart failure. Challenges remain in the identification of patients who benefit and in optimal implementation of the therapy. Articles on Sudden Death Prevention With Implantable Devices, Electrophysiological Interventions for Inherited Arrhythmia Syndromes, and Cardiac Resynchronization Therapy for Heart Failure will address current use and challenges.Catheter ablation provides effective therapy for many arrhythmias and has also advanced our understanding of conduction system anatomy, physiology, and arrhythmia mechanisms. Articles on catheter ablation of supraventricular tachycardias, atrial fibrillation, and interventions for ventricular tachycardias will review physiological insights and practical issues relevant to invasive procedures for treatment of these arrhythmia substrates.All cardiologists and primary-care providers manage patients for whom interventional electrophysiological therapies can be curative, life changing, or life saving. As with any intervention, potential risks as well as benefits are important considerations when recommending these therapies or referring for interventional electrophysiology procedures. We hope that this series will provide a framework for integrating new pathophysiological an...