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Sinus node dysfunction — USMLE Step 3 MCQ

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ModerateInternal Medicine (chronic management)Sinus node dysfunctionUSMLE Step 3

A 78-year-old woman has recurrent presyncope. Ambulatory monitor shows sinus pauses lasting 4 seconds during symptoms and intermittent sinus bradycardia. She takes no AV nodal blocking drugs. Which of the following is the most likely diagnosis?

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Correct answer: C — Sinus node dysfunction

Symptomatic sinus pauses and bradycardia in an older adult without reversible drug causes indicate sinus node dysfunction.

Reference: ACC/AHA/HRS Bradycardia Guideline