What does a QRS duration of less than 120ms indicate?

What does a QRS duration of less than 120ms indicate?

• A. A normal conduction pathway
• B. A bundle branch block
• C. A ventricular tachycardia
• D. An atrial enlargement

Answer: (A)

A QRS duration of less than 120 milliseconds indicates that the conduction pathway within the ventricles is normal. This means that the electrical impulses are being conducted in a typical manner from the atria to the ventricles, leading to a standard duration for the QRS complex on an electrocardiogram (EKG or ECG). Normal conduction results in the ventricles contracting efficiently in response to the signals from the atria, which is vital for maintaining an effective heart rhythm.

In contrast, a QRS duration greater than 120 milliseconds often points to issues such as a bundle branch block, where there's a delay in the electrical conduction through one of the bundle branches resulting in a wider than normal QRS complex. Ventricular tachycardia typically causes a QRS duration that is also prolonged due to the rapid heart rate and associated abnormal conduction. Atrial enlargement can affect the P wave and might not significantly impact the QRS duration, as it primarily relates to atrial electrical activity rather than that of the ventricles.