Methods to identify and treat patients at high indi- vidual risk for SCD who are not identified by cur- rent ICD eligibility criteria, including those who are within 40 days of an MI. Defining the role of the ICD in patients with HCM, arrhythmogenic right ventricular cardiomyopathy, cardiac sarcoidosis, and inherited cardiac chan- nelopathies in prospective studies (preferably RCT). Determining the best approach to patients due for elective ICD generator replacement due to battery depletion, but who may now be at low risk for SCA, such as if significant LVEF improvement has occurred. Obtaining more data on the efficacy and effec- tiveness of the subcutaneous implantable cardio- verter-defibrillator, compared with transvenous ICDs and on the extent of testing required, and its use with other novel technologies, including lead- less pacemakers. Conducting RCTs on catheter ablation of VT in ischemic heart disease and cardiomyopathies that evaluates procedural end points, mortality, arrhythmia suppression, QoL, and costs. Improving identification of individuals without sig- nificant ventricular dysfunction who are at risk of SCD. Identifying mechanisms and risk factors for SCD in patients with HFpEF. Improving emergency response to out-of-hospital cardiac arrest. Developing better methods for identifying and ablating the arrhythmia substrate in structural heart disease. Developing better risk stratification of diseases and syndromes associated with sudden death, includ- ing ischemic heart disease, NICM, adult congenital heart disease, and Brugada syndrome. Identifying what causes different types of long QT syndrome, catecholaminergic polymorphic ven- tricular tachycardia, Brugada syndrome, HCM, and arrhythmogenic right ventricular cardiomyopathy and advancing the genotype-phenotype relation- ships, genotype-dependent risk, and genotype- based tailoring of therapies for patients with inherited cardiomyopathies and inherited channelopathies. Defining the most appropriate and beneficial use of wearable cardioverter-defibrillators. 