A nurse in an emergency department is reviewing a client’s ECG reading.
Which of the following findings should the nurse identify as an indication that the client has first-degree heart block?
A.
Prolonged PR intervals.
B.
Nondiscernible P waves.
C.
More P waves than QRS complexes.
D.
No correlation between P and QRS waves.
The correct answer and Explanation is :
The correct answer is:
A. Prolonged PR intervals.
Explanation:
First-degree heart block, also known as first-degree atrioventricular (AV) block, is characterized by a delay in the conduction through the AV node. This delay results in a prolonged PR interval on the ECG.
PR Interval: The PR interval represents the time it takes for the electrical impulse to travel from the atria through the AV node and into the ventricles. Under normal circumstances, this interval ranges from 0.12 to 0.20 seconds (120 to 200 milliseconds).
In first-degree heart block, the PR interval exceeds 0.20 seconds. This prolongation indicates that the electrical signal is taking longer than usual to pass through the AV node but is still reaching the ventricles effectively.
Analysis of Other Options:
B. Nondiscernible P waves: This finding would suggest issues such as atrial fibrillation or atrial flutter, where the P waves are not clearly visible due to rapid and irregular atrial activity, which is not characteristic of first-degree heart block.
C. More P waves than QRS complexes: This finding is indicative of second-degree heart block (specifically Type II or Mobitz II), where some atrial impulses do not get conducted to the ventricles, leading to more P waves than QRS complexes.
D. No correlation between P and QRS waves: This situation is seen in third-degree heart block (complete heart block), where there is no consistent relationship between P waves and QRS complexes because the atria and ventricles are beating independently of each other.
In summary, a prolonged PR interval is the hallmark of first-degree heart block. The delay in conduction through the AV node causes this elongation, but unlike more advanced degrees of heart block, the conduction to the ventricles is still intact, and the heart maintains a consistent rhythm.