Certified EkG technician (CET) Practice Exam

What is an expected finding of impaired conduction through the AV node when measuring the intervals on an EKG tracing?

1. Shortened PR interval

2. Normal PR interval

3. Prolonged PR interval

4. Dropped beats in the ECG

The correct answer is: Prolonged PR interval

The prolonged PR interval is an expected finding when there is impaired conduction through the AV node. The PR interval measures the time it takes for electrical impulses to travel from the atria through the AV node to the ventricles. When there is impaired conduction, such as in conditions like first-degree AV block, the conduction time is longer, resulting in an extended PR interval. This reflects the delayed electrical impulse as it moves through the AV node, indicating that the heart’s electrical system is not functioning as efficiently as it should. In contrast, a shortened PR interval would suggest that the electrical impulses are moving too quickly through the AV node, which is not consistent with impaired conduction. A normal PR interval indicates that conduction is occurring at a typical rate, while dropped beats on the ECG would suggest a complete failure of conduction at the AV node, leading to missed impulses, rather than just a delay. Thus, the presence of a prolonged PR interval specifically aligns with the scenario of impaired conduction through the AV node.