Wolff-Parkinson-White Syndrome MCQ — NEET PG Practice Question | NEETPGAI
Wolff-Parkinson-White Syndrome
medium
stethoscope Medicine
A 22-year-old male presents to the emergency department with palpitations and dizziness. His ECG shows a short PR interval (<120 ms), a slurred initial upstroke of the QRS complex (delta wave), and a wide QRS (>120 ms). The structure marked **A** in the diagram represents the electrocardiographic findings of Wolff-Parkinson-White syndrome. Which of the following best explains the mechanism by which the delta wave and short PR interval are produced in this condition?
A. Premature atrial depolarization originating from an ectopic focus in the left atrium, bypassing normal sinus node function
B. Slowed AV nodal conduction with compensatory rapid ventricular depolarization via the right bundle branch
C. An accessory pathway (bundle of Kent) bypasses the AV node, allowing direct atrial-to-ventricular conduction and early ventricular pre-excitation
D. Accelerated conduction through the His-Purkinje system due to enhanced automaticity of the bundle of His
Explanation
Why option 1 is correct
The delta wave and short PR interval in WPW syndrome (marked A) are pathognomonic findings that result from an accessory pathway (bundle of Kent) that bridges the atrium and ventricle, completely bypassing the AV node. This allows the atrial impulse to depolarize the ventricle directly and prematurely, before the normal His-Purkinje conduction system can activate it. The short PR interval (<120 ms) occurs because the impulse avoids the normal AV nodal delay (~100 ms). The delta wave represents the slurred initial portion of the QRS caused by slow muscle-to-muscle conduction in the pre-excited ventricle before the normal His-Purkinje system takes over. This fusion of pre-excited and normal conduction produces the characteristic wide QRS (>120 ms). This mechanism is the defining pathophysiology of WPW syndrome as described in the 2023 AHA/ACC/HRS Guidelines and Harrison's 21e.
Why each distractor is wrong
Option 2: While the His-Purkinje system is involved in normal conduction, it is not accelerated in WPW. The problem in WPW is not enhanced automaticity of the His bundle but rather the presence of an alternative pathway that bypasses the AV node entirely. This would not explain the short PR interval or delta wave.
Option 3: AV nodal slowing would actually prolong the PR interval, not shorten it. WPW is characterized by a SHORT PR interval due to bypass of the AV node, not slowing through it. Right bundle branch conduction does not explain the delta wave morphology, which is a feature of pre-excitation from the accessory pathway.
Option 4: Premature atrial depolarization from an ectopic focus would produce a premature P wave and early QRS, but would not produce the characteristic delta wave or the consistent short PR interval seen in WPW. Additionally, ectopic atrial foci do not bypass the AV node in the way that an accessory pathway does.
High-YieldNEET PG
WPW = accessory pathway (bundle of Kent) → bypasses AV node → short PR + delta wave + wide QRS; DO NOT use AV nodal blockers in pre-excited AF (risk of VF).
2023 AHA/ACC/HRS Guidelines for SVT Management; Harrison's 21e
Practice similar questions
Sign up free to access AI-powered MCQ practice with detailed explanations and adaptive learning.
