A shortened PR interval, slurring (called a delta wave) of the initial QRS deflection, and prolonged QRS dura… - AIIMS Jodhpur SNO-2023

AIIMS Jodhpur SNO-2023

Medical Surgical Nursing

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Appeared in: AIIMS Jodhpur SNO-2023

Explanation

Wolff-Parkinson-White (WPW) syndrome is defined by the presence of an accessory electrical pathway (bundle of Kent) that bypasses the AV node.
This bypass leads to pre-excitation of the ventricles, causing a shortened PR interval (less than 0.12 seconds) because the normal AV nodal delay is skipped.
The early, slow ventricular activation through the accessory pathway creates a slurred upstroke on the QRS complex, known as a delta wave.
The QRS complex is widened (prolonged) because it represents a fusion beat—the combination of the early pre-excitation and the normal ventricular conduction.

Option A: Atrial tachycardia is a supraventricular tachycardia characterized by a rapid heart rate originating from the atria. It typically presents with a narrow QRS complex and does not feature a delta wave or a short PR interval, unless WPW is also present.
Option C: Myocardial ischemia is characterized by changes in the ST segment (depression or elevation) and T wave (inversion) due to reduced blood flow to the heart muscle. It does not cause the triad of a short PR, delta wave, and wide QRS.
Option D: Left bundle branch block (LBBB) involves a conduction delay in the left ventricle, which causes a prolonged QRS duration. However, unlike WPW, the PR interval is typically normal, and there is no delta wave.

Visual 1: ECG Strip - An ECG showing the classic features of WPW syndrome: a short PR interval, a clear delta wave slurring the start of the QRS, and a widened QRS complex. This helps learners visualize the key diagnostic criteria.
Visual 2: Diagram - A diagram of the heart's conduction system comparing the normal pathway (SA node -> AV node -> His-Purkinje) with the accessory pathway (Bundle of Kent) in WPW syndrome. This clarifies the underlying anatomical cause.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain ECG interpretation of ventricular pre-excitation syndromes as background academic context rather than a clinical decision trigger.
Patients with WPW syndrome are at risk for developing rapid tachyarrhythmias, such as atrioventricular re-entrant tachycardia (AVRT) or pre-excited atrial fibrillation, which can be life-threatening.
Nursing assessment includes monitoring for palpitations, dizziness, syncope, and signs of hemodynamic instability. It is crucial to obtain a 12-lead ECG if a patient reports these symptoms.
Certain AV nodal blocking agents (like adenosine, verapamil, diltiazem) are contraindicated in patients with pre-excited atrial fibrillation as they can paradoxically increase the ventricular rate and lead to ventricular fibrillation.

How to Approach the Question

First, identify the key features described in the question stem: short PR interval, delta wave, and prolonged QRS.
Recognize this specific triad as the classic ECG signature of a ventricular pre-excitation syndrome.
Systematically evaluate each option against this triad.
Eliminate 'myocardial ischemia' and 'atrial tachycardia' as their primary ECG findings (ST/T wave changes and narrow-complex tachycardia, respectively) do not match.
Differentiate between WPW and LBBB. Both can have a wide QRS, but only WPW has the characteristic short PR interval and delta wave. LBBB has a normal PR interval and no delta wave.
Conclude that the only condition matching all three criteria is Wolff-Parkinson-White (WPW) syndrome.

Concept Tested & Keywords

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