Cardiac arrhythmias can be broadly classified into two groups: supraventricular and ventricular arrhythmias. Common supraventricular arrhythmias include atrial fibrillation, atrial flutter, paroxysmal supraventricular tachycardia (PSVT), sinus tachycardia, and bradycardia. Atrial fibrillation is probably the most common sustained cardiac arrhythmia encountered in primary care practice. Atrial fibrillation is the major cause of stroke, especially in the elderly. Ventricular arrhythmias include premature ventricular contractions (PVCs), monomorphic and polymorphic, ventricular tachycardia (VT), and ventricular fibrillation (VF). This chapter discusses the pathophysiology and management of arrhythmias in a primary care setting, with an emphasis on long-term management to prevent complications such as life-threatening ventricular arrhythmias, heart failure, or thromboembolic events. The heart is an organ that is capable of producing an intrinsic electrical rhythm and has automaticity. The electrocardiography (ECG) complexes reflect the cardiac electrical activity. Other morbidity and mortality related to atrial fibrillation include heart failure.