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USMLE (United States Medical Licensing Examination) Practice Exam 01

Practice exam for USMLE (United States Medical Licensing Examination).

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Question 1 of 160%
Time remaining180:00
Attempts allowedUnlimited
Difficulty mixE • M • H
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Question 1

MEDIUM

A 19-year-old man is brought to the emergency department after collapsing during basketball practice. He is awake but anxious. He has had several episodes of palpitations and near-syncope during intense exercise over the past year. Family history is notable for a paternal uncle who died suddenly at age 28. Physical examination shows a harsh systolic murmur at the left sternal border that increases with standing and decreases with squatting. Which of the following cellular changes most directly contributes to this patient's condition?

This presentation is consistent with hypertrophic cardiomyopathy (HCM): exertional syncope/palpitations, family history of sudden death, and a murmur that increases with decreased preload (standing) and decreases with increased preload (squatting). HCM is characterized histologically by myocyte hypertrophy and myofiber disarray, which predisposes to ventricular arrhythmias and dynamic LV outflow obstruction.

Key distractors: Fibrofatty replacement of the right ventricle suggests arrhythmogenic right ventricular cardiomyopathy. Fragmentation of elastic fibers in the tunica media is seen in cystic medial degeneration (eg, Marfan-associated aortic aneurysm/dissection).

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