On a standard 12-lead ECG, the QRS complex duration must be less than how many milliseconds to be considered a normal intraventricular conduction?

• A 80 ms
• B 100 ms
• C 120 ms ✓
• D 140 ms

Explanation

Normal QRS duration ranges from 80 to 120 ms. A duration of 120 ms or more indicates an intraventricular conduction delay, such as a bundle branch block. The 100 ms option is a common distractor, but the strict upper limit of normal for the QRS complex is 120 ms.

Reference: Ganong's Review of Medical Physiology, 26th ed.

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