Kaplan USMLE Step 1: Cardiac valves reveal what underlying condition?

If you’re preparing for the United States Medical Licensing Examination® (USMLE®) Step 1 exam, you might want to know which questions are most often missed by test-prep takers. Check out this example from Kaplan Medical, and read an expert explanation of the answer. Also check out all posts in this series.

A 30-year-old woman is admitted to the hospital because of malaise and chills for 3 days. Her past medical history is significant for chronic hepatitis B. She has a history of IV drug use. Her temperature is 39.4°C (103°F). Physical examination shows a systolic murmur. She develops worsening respiratory distress and dies. A photograph of the cardiac valves at autopsy is shown.

Which of the following is the patient's most likely underlying condition?

A. Acute infective endocarditis

B. Carcinoid heart disease

C. Libman-Sacks endocarditis

D. Nonbacterial thrombotic endocarditis

E. Q fever endocarditis

The correct answer is A.

Acute infective endocarditis is most commonly caused by bacteria introduced into the blood from the skin by intravenous drug use. Bacteremia leads to infection of the endocardial lining and cardiac valves, resulting in the formation of vegetations (as seen in the image) that cause turbulent blood flow and new systolic murmurs.

Choice B: Carcinoid heart disease, which is caused by 5-HT oversecretion from neuroendocrine tumors, results in right-sided endocardial fibrosis, pulmonary stenosis and tricuspid regurgitation (not vegetations).