Arrhythmias or dysrhythmias describe an absent or abnormal heart rhythm with a concomitant abnormal or irregular heartbeat. They result from abnormalities of impulse generation, impulse conduction, or both. Main causes are delayed after-depolarization, re-entry, ectopic pacemaker activity, or heart block such as AV block.

Arrhythmias can be classified according to their site of origin into supraventricular (with origin in the atria or AV node) or ventricular; and according to heart rate into tachycardia (increased HR) or bradycardia(decreased HR). Supraventricular arrhythmias include AV block, atrial tachycardia, and atrial flutter or fibrillation. Ventricular arrhythmias include ventricular tachycardia, torsades de pointes, and ventricular fibrillation. There are diverse underlying causes: arteriosclerosis, coronary artery spasm, myocardial ischemia, reperfusion, and heart block mostly starting in the AV-node.

Arrhythmias are defined according to their ECG. Characteristics of the most common arrhythmias are:


In which arrhythmia is the cardiac output insufficient to support life?