A 25-year-old intravenous drug user presents with fever, new systolic murmur, and multiple septic pulmonary emboli on CT. Blood cultures grow Staph aureus. The most likely valve affected and the mechanism is:

• A Aortic valve; rheumatic fever-mediated fusion of commissures
• B Mitral valve; Libman-Sacks endocarditis from antiphospholipid antibodies
• C Pulmonary valve; carcinoid syndrome-mediated fibrosis
• D Tricuspid valve; right-sided endocarditis from venous seeding in IV drug use ✓

Explanation

Right-sided (tricuspid valve) endocarditis is characteristic of intravenous drug users because bacteria from contaminated injections enter the venous system and seed the right heart. Septic pulmonary emboli result from tricuspid vegetations embolizing to the lungs. Libman-Sacks endocarditis (small, sterile vegetations on both surfaces of mitral leaflets) is seen in SLE; carcinoid syndrome causes right-sided fibrosis from serotonin exposure; rheumatic fever primarily affects the mitral valve.

Reference: Robbins & Cotran Pathologic Basis of Disease, 10th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.