A condition characterized by a prolonged PR interval more than 0.2 seconds in ECG is called?

KPSC Staff Nurse - 2016

Medical & Surgical Nursing

Easy

Appeared in: KPSC Staff Nurse - 2016

Explanation

First-degree AV block is defined by a delay in atrioventricular conduction, not a complete block of any impulse.
The key diagnostic criterion on an ECG is a fixed and prolonged PR interval of more than 0.20 seconds (200 ms).
In this condition, every atrial impulse (P wave) is followed by a ventricular contraction (QRS complex), meaning there are no 'dropped' beats.

Option A: Second-degree AV block involves the intermittent failure of atrial impulses to conduct to the ventricles, resulting in 'dropped' QRS complexes. This is different from first-degree block, where all impulses are conducted, just delayed.
Option B: Mobitz type II is a specific form of second-degree AV block characterized by a constant PR interval followed by an unexpected, non-conducted P wave (a dropped QRS complex). This is a more serious condition than a simple prolonged PR interval.
Option D: Complete block, or third-degree AV block, is characterized by the complete absence of conduction between the atria and ventricles. On the ECG, P waves and QRS complexes are completely dissociated and have no relationship with each other.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain ECG Interpretation of Atrioventricular (AV) Blocks as background academic context rather than a clinical decision trigger.
While often benign, a new finding of first-degree AV block requires a review of the patient's medications (e.g., beta-blockers, digoxin, calcium channel blockers) as these can cause or worsen the block.
Nurses should monitor patients with first-degree AV block for any signs of hemodynamic instability, such as dizziness, syncope, or hypotension, which could indicate progression to a higher-degree block.
What if? If the patient with a first-degree AV block suddenly develops periods of dizziness and the ECG now shows intermittently dropped QRS complexes with a stable PR interval, the condition has likely progressed to a Mobitz II second-degree block, which is more dangerous and requires urgent medical evaluation for potential pacemaker insertion.

How to Approach the Question

First, identify the key clinical finding in the question stem: 'prolonged PR interval more than 0.2 seconds'.
Recall the definitions of the different types of atrioventricular (AV) blocks based on their ECG characteristics.
Match the specific finding (PR > 0.20s with no other details like dropped beats) to its corresponding definition.
First-degree AV block is defined as a PR interval greater than 0.20 seconds where every P wave is followed by a QRS.
Evaluate the other options: Second-degree and complete blocks involve dropped beats or AV dissociation, which were not mentioned in the stem.

Concept Tested & Keywords

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E6 Medicine Harrison 22e Part 1 pp. 1966-1968, 1967-1969

E6 Nelson Textbook of Pediatrics(2024) — Volume 2 p. 647-649