This document discusses arrhythmias in the emergency department. It defines arrhythmia as an irregular, too fast, or too slow heartbeat. A normal rhythm originates from the sinoatrial node with a P wave before every QRS complex going in the same direction. Tachy-arrhythmias can be regular like sinus tachycardia or supraventricular tachycardia, or irregular like ventricular tachycardia or atrial fibrillation. Brady-arrhythmias include sick sinus syndrome. The document provides an overview of different types of arrhythmias that may present in the emergency department.