QRS width criterion for ventricular rhythms such as idioventricular?

• A. 0.10 seconds or less
• B. 0.15 seconds
• C. Wide QRS >0.12
• D. QRS duration cannot be measured

Answer: (C)

The key point is how QRS width reflects ventricular activation. Normal conduction uses the specialized His-Purkinje system, giving a narrow QRS, usually up to about 0.10 seconds. When the rhythm originates in the ventricles (as with idioventricular escape rhythms) or when ventricular conduction is disrupted, depolarization spreads through ventricular muscle more slowly, producing a wider QRS complex. The standard criterion for a ventricular rhythm is a QRS duration greater than 0.12 seconds. That’s why the best answer is a QRS width exceeding 0.12 seconds.

So, a QRS of 0.10 seconds or less would be not ventricular in origin; a single fixed value like 0.15 seconds is wide but doesn’t capture the universal threshold as precisely as “greater than 0.12 seconds”; and QRS duration can indeed be measured.