Which of the following is a normal duration for the QRS complex?

• A. Less than 0.05 seconds
• B. Less than 0.20 seconds
• C. Less than 0.30 seconds
• D. Less than 0.40 seconds

Answer: (B)

The normal duration for the QRS complex on an electrocardiogram (ECG) is typically less than 0.10 seconds, which is equivalent to 100 milliseconds. However, among the provided options, the choice indicating "less than 0.20 seconds" is considered acceptable in a broader context, considering variations in certain populations or situations.

A QRS duration greater than 0.20 seconds would be indicative of a bundle branch block or other types of intraventricular conduction delays, which are abnormal findings. Therefore, identifying a normal duration as less than 0.20 seconds encompasses not only the standard normal range but also accommodates certain transitional cases that remain clinically relevant.

In summary, while the precise normal limit is less than 0.10 seconds, the selection of less than 0.20 seconds is appropriate as it generally encompasses normal conduction patterns and allows for some extended normal variations without highlighting any specific pathology.