What is Idioventricular Tachycardia
Idioventricular tachycardia, more accurately termed "accelerated idioventricular rhythm" (AIVR), is an ectopic ventricular rhythm with 3 or more consecutive ventricular beats at a rate of 40-100 beats per minute—faster than the normal ventricular escape rate but slower than true ventricular tachycardia (>100 bpm). 1
Key Distinguishing Features
AIVR differs fundamentally from ventricular tachycardia in several critical ways:
- Rate: AIVR runs at 40-100 bpm, while ventricular tachycardia is defined as ≥100 bpm 2, 1
- Onset pattern: AIVR begins with a long coupling interval, whereas VT typically has shorter coupling 1
- Termination: AIVR ends gradually through either a decrease in ventricular rate or increase in sinus rate, not abruptly 1
- Prognosis: AIVR carries a benign prognosis and requires no specific treatment, unlike VT which can be life-threatening 3, 1
Clinical Context and Causes
The most common setting for AIVR is acute myocardial infarction:
- AIVR is a common arrhythmia in patients with acute MI, particularly those undergoing primary PCI for ST-elevation MI 3
- Its occurrence after thrombolysis is actually a marker of successful reperfusion, though the arrhythmia relates more to infarct extent than reperfusion itself 3, 1
Contributing electrophysiologic factors include:
- Increased sympathetic tone, hypokalemia, hypomagnesemia, intracellular calcium overload, hypercalcemia, acidosis, and free fatty acid production from lipolysis 3
- Free radical production from reperfusion of ischemic myocardium 3
Benign Presentations
- AIVR can occur in otherwise healthy newborns and infants as a coincidental finding, representing a benign arrhythmia that typically disappears without treatment in the first year of life 3
- It may also occur in adults without structural heart disease 1
Critical Management Principle
Treatment of AIVR is contraindicated (Class III recommendation)—this includes isolated ventricular premature beats, couplets, AIVR episodes, and nonsustained VT in this context. 3
The appropriate management approach:
- Prophylactic antiarrhythmic drugs for AIVR are contraindicated 3
- Correction of electrolyte and acid-base abnormalities is important to prevent recurrent episodes 3
- AIVR is usually hemodynamically well-tolerated and not associated with malignant ventricular arrhythmias 1
- No specific treatment beyond managing the underlying heart disease is necessary 1
Common Pitfall to Avoid
The main clinical error is mistaking AIVR for ventricular tachycardia and inappropriately treating it with antiarrhythmic drugs. The rate distinction (<100 bpm vs ≥100 bpm), gradual onset/termination pattern, and benign clinical course should prevent this error 1.