What does a prolonged QRS complex indicate?

A prolonged QRS complex on an electrocardiogram (ECG) indicates a delay in ventricular conduction. The QRS complex represents the electrical activity that leads to the contraction of the ventricles. When the duration of the QRS complex is longer than normal (typically greater than 0.12 seconds), it suggests that there is a disruption in the normal conduction pathway within the ventricles. This can occur due to various conditions, such as bundle branch blocks, ventricular hypertrophy, or other types of intraventricular conduction delays.

In contrast, the other options do not directly relate to the length of the QRS complex. An increase in heart rate is more often indicated by changes in the frequency of heartbeats rather than the duration of QRS complexes. A decrease in blood pressure may be secondary to various conditions but is not indicated directly by the QRS duration. Atrial enlargement is typically assessed through changes in the P wave rather than the QRS complex. Thus, the correct interpretation of a prolonged QRS complex is that it signifies a delay in how the electrical impulses are transmitted through the ventricles.