Accelerated idioventricular rhythm
Accelerated idioventricular rhythm is a ventricular rhythm with a rate of between 40 and 120 beats per minute. Idioventricular means “relating to or affecting the cardiac ventricle alone” and refers to any ectopic ventricular arrhythmia. Accelerated idioventricular arrhythmias are distinguished from ventricular rhythms with rates less than 40 and those faster than 120. Though some other references limit to between 60 and 100 beats per minute. It is also referred to as AIVR and "slow ventricular tachycardia."
It can be present at birth, however, it is more commonly associated with reperfusion after myocardial injury. AIVR is generally considered to be a benign abnormal heart rhythm. It is typically temporary and does not require treatment.
Pathophysiology
The accelerated idioventricular rhythm occurs when depolarization rate of a normally suppressed focus increases to above that of the "higher order" focuses. This most commonly occurs in the setting of a sinus bradycardia.Accelerated idioventricular rhythm is the most common reperfusion arrhythmia in humans. However, ventricular tachycardia and ventricular fibrillation remain the most important causes of sudden death following spontaneous restoration of antegrade flow. Prior to the modern practice of percutaneous coronary intervention for acute coronary syndrome, pharmacologic thrombolysis was more common and accelerated idioventricular rhythms were used as a sign of successful reperfusion. It is considered a benign arrhythmia especially in the setting of STEMI that does not require intervention, though atrioventricular dyssynchrony can cause hemodynamic instability, which can be treated through overdrive pacing or atropine.