Accelerated Idioventricular Rhythm

AIVR is a rhythm that occurs under conditions of enhanced automaticity. An enhanced ectopic ventricular pacemaker outpaces more superior pacemakers (e.g. sinus node) and, thus, becomes the dominant pacemaker by usurping control. It occurs at a rate faster than ventricular escape, but slower than ventricular tachycardia (i.e. between 50 and 110 beats/min). AIVR can occur for many reasons including electrolyte abnormalities and drug toxicity (e.g. digoxin), however, it occurs most commonly in the setting of reperfusion – that is, after myocardial infarction or cardiac arrest. The prognosis is not adversely affected because the ventricular rate is in the normal range.