Arrhythmia is the most common perioperative cardiac complication during noncardiac surgery. Most perioperative arrhythmia is benign, but fatal arrhythmia can occur, requiring emergency care. Arrhythmia is divided into tachycardia and bradycardia. Both arrhythmias often result in cardiac failure. Ischemic heart disease often causes premature ventricular contraction or ventricular tachycardia. Hypertensive heart disease or valvular heart disease can lead to atrial fibrillation or supraventricular tachycardia. Although patients may not have cardiac disease, hypoxia, hypovolemia, electrolyte disturbance, acidosis, and hypothermia can also cause arrhythmia. Patients with pacemakers or implantable cardiodefibrillators (ICDs) are affected by electric cauterization, which interferes with the sensing and inhibits the pacing of pacemakers as well as ICDs If this occurs, the mode of pacemakers and ICDs must be reset during surgery.