What is arrhythmia? An arrhythmia (also called dysrhythmia) is an abnormal heartbeat. Arrhythmias can start in different parts of your heart and they can be too fast, too slow or just irregular. Normally, your heart beats in an organized, coordinated way.

Normal sinus rhythm and sinus arrhythmia; Obstructive sleep apnea and cardiovascular disease in adults; Second-degree atrioventricular block: Mobitz type I (Wenckebach block) Sinus bradycardia; Sinus node dysfunction: Epidemiology, etiology, and natural history; Sinus node dysfunction: Treatment; Treatment and prevention of hyperkalemia in adults