A nurse on a telemetry unit is assessing a client who is receiving continuous cardiac monitoring. The client’s heart rate is 69/min and the PR interval is 0.24 seconds. The nurse should interpret this finding as which of the following cardiac rhythms?
A.
Atrial fibrillation
B.
First-degree AV block
C.
Premature ventricular contraction
D.
Sinus bradycardia
The correct answer and Explanation is :
The correct answer is B. First-degree AV block.
Explanation:
In the scenario described, the client’s heart rate is 69 beats per minute, and the PR interval is 0.24 seconds. To interpret these findings correctly, it’s important to understand the significance of the PR interval and how it relates to different cardiac rhythms.
- Heart Rate: A heart rate of 69 beats per minute is considered bradycardic but does not by itself define a specific arrhythmia. It’s a bit slower than the normal range (60-100 beats per minute), but many arrhythmias can present with this heart rate.
- PR Interval: The PR interval represents the time it takes for the electrical impulse to travel from the atria to the ventricles through the AV node. A normal PR interval ranges from 0.12 to 0.20 seconds. A PR interval longer than 0.20 seconds indicates a delay in conduction through the AV node.
- First-degree AV block is characterized by a PR interval that is consistently prolonged beyond the normal range, typically greater than 0.20 seconds. In this case, the PR interval of 0.24 seconds fits this description, indicating a delay in the conduction from the atria to the ventricles.
- Comparison with Other Rhythms:
- Atrial Fibrillation: In atrial fibrillation, the PR interval is not measurable because the atrial activity is erratic and irregular. Instead, you would see an irregularly irregular ventricular rhythm without a discernible PR interval.
- Premature Ventricular Contraction (PVC): PVCs are characterized by early, wide QRS complexes and do not affect the PR interval. They do not cause a prolonged PR interval.
- Sinus Bradycardia: Sinus bradycardia is characterized by a heart rate less than 60 beats per minute but would typically have a normal PR interval. The prolonged PR interval is not a characteristic of sinus bradycardia alone.
Thus, the finding of a PR interval of 0.24 seconds is most consistent with a first-degree AV block, which is defined by a prolonged PR interval.