Part I: Background -- Development and Structure of the Cardiac Conduction System -- Physiology of the Cardiac Conduction System -- Clinical Electrophysiology of the Cardiac Conduction System -- Part II: Clinical Electrophysiology in Infants and Children -- Atrioventricular Reentry Tachycardia -- Atrioventricular Nodal Reentry Tachycardia -- Persistent Junctional Reciprocating Tachycardia -- Sinoatrial Reentrant Tachycardia: Inappropriate Sinus Tachycardia -- Atrial Flutter Intra-atrial Reentrant Tachycardia -- Atrial Fibrillation -- Atrial Ectopic Tachycardias -- Junctional Tachycardia- Congenital, Acquired, Post-Operative -- Multifocal Atrial Tachycardia -- Ventricular Tachycardia -- Sick Sinus Syndrome -- First- and Second-Degree Atrioventricular Block -- Complete Atrioventricular Block Third-Degree Heart Block -- Syncope -- Cardiac Pacemakers and Implantable Cardioverter-Defibrillators -- Genetic Disorders of the Cardiac Impulse -- Fetal Arrhythmias -- Sudden Cardiac Death in the Young -- Pharmacology ofAntiarrhythmic Agents -- Transcatheter Ablation of Cardiac Arrhythmias in the Young -- Allied Professional Roles in the Management of Arrhythmias in the Young.