What two characteristics define Accelerated Idioventricular Rhythm (AIVR)?

• A. QRS duration 0.12 seconds or greater and rate 50-100 bpm
• B. Narrow QRS and rate 60-100 bpm
• C. Narrow QRS and rate 140-180 bpm
• D. Wide QRS and rate 40-60 bpm

Answer: (A)

AIVR is defined by two key features: a ventricular-origin rhythm with wide QRS complexes and a rate that sits in the accelerated range. The QRS complexes are wide (≥0.12 seconds) because the impulse originates in the ventricles rather than being conducted through the normal His-Purkinje system, so the ventricle takes a slower, more circuitous path to depolarize. The rate is in the 50–100 beats per minute range, which is faster than a typical idioventricular escape rhythm but slower than ventricular tachycardia. This combination—wide QRS from a ventricular focus and an intermediate, “accelerated” rate—distinguishes AIVR from other rhythms. If the QRS were narrow, it would suggest a supraventricular source; if the rate were higher than about 100 bpm, it would lean toward ventricular tachycardia; if the rate were lower than about 50 bpm, it would be a slower idioventricular rhythm.