Question

You are monitoring the cardiac rhythm of your 60-year-old female patient with shortness of breath when you note the presence of a possible first-degree atrioventricular block in lead II on the EKG. Which of the following electrocardiogram abnormalities makes you think there is a first-degree AV block present?

A. There are more than one P wave for each QRS complex

B. A P-R interval greater than five small boxes (0.20 seconds) wide on the electrocardiogram tracing

C. The P-R intervals become progressively longer until a QRS complex is dropped altogether

D. The P waves are present but bear no relationship to the QRS complexes

Answer 1

The presence of a P-R interval longer than 0.20 seconds on an EKG indicates a first-degree atrioventricular block, which is a delay in the conduction between the SA and AV nodes.

Step-by-step explanation:

You are correct to suspect a first-degree atrioventricular block if you observe a P-R interval on the EKG that is greater than five small boxes or 0.20 seconds. This is indicative of a delay in the conduction between the SA and AV nodes. A first-degree AV block is characterized by a consistent elongation of the P-R interval, which remains constant across successive beats, unlike in second- or third-degree blocks where the relationship between P waves and QRS complexes becomes more irregular.

First-degree AV block is confirmed by option B in your question: 'A P-R interval greater than five small boxes (0.20 seconds) wide on the electrocardiogram tracing.' Other options, such as more P waves than QRS complexes or P waves with no relation to QRS complexes, refer to more severe AV blockades, specifically second- or third-degree AV blocks.