In IV drug users with endocarditis, which valve is most commonly affected?

• A. Aortic valve vegetation
• B. Tricuspid valve vegetation
• C. Mitral valve vegetation
• D. Left ventricular hypertrophy

Answer: (B)

IV drug use introduces bacteria directly into the venous circulation, so the valve most often encountered by those organisms is the tricuspid valve. This makes tricuspid valve vegetations the classic finding in infectious endocarditis among people who inject drugs. The infection is typically caused by Staphylococcus aureus, which can seed the tricuspid valve and lead to septic emboli that travel to the lungs, causing pulmonary symptoms.

Left-sided valves like the aortic or mitral are more commonly involved in endocarditis overall, but in this specific population they are less likely than the tricuspid valve. The left ventricle refers to a chamber, not a valve, so left ventricular hypertrophy isn’t a valve issue and isn’t relevant to endocarditis.