Accelerated IVR has a QRS duration of

• A. Less than 0.12 seconds
• B. 0.10 seconds
• C. 0.15 seconds
• D. 0.12 seconds or greater

Answer: (D)

A widened QRS complex signals that the heartbeat is being conducted through the ventricles rather than the normal His-Purkinje pathway. Normal QRS duration is up to 0.12 seconds. When an accelerated idioventricular rhythm occurs, the rhythm originates in the ventricles, so the impulse spreads through ventricular muscle and the QRS becomes broader. Because of this, the duration is 0.12 seconds or greater. Among the options, the statement that captures this threshold is the best, since it includes all values at or above 0.12 seconds (for example 0.12, 0.13, 0.15). A duration less than 0.12 would be normal conduction and not ventricular in origin.