Accelerated idioventricular rhythm (AIVR) was first described by Thomas Lewis in 1910.
AIVR is currently defined as an enhanced ectopic ventricular rhythm with at least 3 consecutive ventricular beats, which is faster than normal intrinsic ventricular escape rhythm (≤40 bpm), but slower than ventricular tachycardia (at least 100-120 bpm). Importantly, there is potential rate overlap between AIVR and some slow ventricular tachycardia. AIVR should not be diagnosed solely based on ventricular rate; context is important. Other characteristics of AIVR are helpful for its correct diagnosis (see Differentials).
AIVR is generally a transient rhythm, rarely causing hemodynamic instability and rarely requiring treatment. However, misdiagnosis of AIVR as slow ventricular tachycardia or complete heart block can lead to inappropriate therapies with potential complications.
AIVR is often a clue to certain underlying conditions, like myocardial ischemia-reperfusion, digoxin toxicity, and cardiomyopathies.
There are multiple causes of AIVR including: Reperfusion phase of an acute myocardial infarction (= most common cause) Beta-sympathomimetics such as isoprenaline or adrenaline. Drug toxicity, especially digoxin, cocaine and volatile anaesthetics such as desflurane.
Under these situations, atropine can be used to increase the underlying sinus rate to inhibit AIVR. Other treatments for AIVR, which include isoproterenol, verapamil, antiarrhythmic drugs such as lidocaine and amiodarone, and atrial overdriving pacing are only occasionally used today.