What is the normal duration of a QRS complex in milliseconds?

The normal duration of a QRS complex is typically less than 120 milliseconds (msec), which aligns with the answer indicating less than 12.0 msec in this context. A QRS complex representing ventricular depolarization should not exceed this duration to indicate normal conduction through the ventricles.

A duration of less than 12.0 msec reflects normal electrical activity and suggests that electrical impulses are being conducted efficiently without delay. Prolongation of the QRS complex beyond this range may indicate a conduction abnormality, such as a bundle branch block or other disturbances in the heart's electrical conduction system.

To provide context for the other options, durations such as less than 10.0 msec, less than 15.0 msec, and less than 20.0 msec are all outside the accepted normal range, as they either represent unrealistically short intervals or extend beyond the physiological norm for QRS duration. These lengths do not accurately reflect the typical values seen in a healthy adult, reinforcing that the correct answer closely aligns with established clinical standards.