🔥 Sample (USMLE Style)

USMLE Practice Exam

Time: 05:00

Q1: A 65-year-old man with long-standing hypertension develops left ventricular hypertrophy. Which change is most likely?

A. Decreased wall thickness B. Increased compliance C. Increased afterload D. Decreased myocardial oxygen demand

Correct Answer: C

Explanation:
Hypertension increases systemic vascular resistance (SVR), which raises afterload — the pressure the heart must overcome to eject blood.

To compensate, the left ventricle undergoes concentric hypertrophy, increasing wall thickness to generate higher pressure.

High-yield:
- ↑ Afterload → LV hypertrophy
- ↓ Compliance occurs later (NOT increased)
- Oxygen demand actually increases, not decreases

Q2: A patient with chronic alcoholism presents with confusion and ataxia. Which deficiency is most likely?

A. Vitamin B12 B. Thiamine (B1) C. Vitamin D D. Vitamin K

Correct Answer: B

Explanation:
Thiamine (Vitamin B1) deficiency causes Wernicke encephalopathy.

Classic triad:
- Confusion
- Ataxia
- Ophthalmoplegia

Chronic alcoholics are at high risk due to poor nutrition and impaired absorption.

Important: Always give thiamine before glucose to prevent worsening symptoms.

Q3: Gram-positive cocci in clusters and catalase-positive organism?

A. Streptococcus B. Staphylococcus C. Enterococcus D. Bacillus

Correct Answer: B

Explanation:
Staphylococcus species are:
- Gram-positive cocci
- Arranged in clusters ("grape-like")
- Catalase-positive

Contrast:
- Streptococcus → catalase-negative, chains
- Enterococcus → similar to Strep but GI origin

Exam trick:
Catalase test differentiates Staph vs Strep.