Review Question - QID 217232

This patient with constitutional symptoms, fever, tachycardia, holosystolic murmur over the left lower sternal border (indicative of tricuspid regurgitation), and splinter hemorrhage of the nail beds with intravenous drug use is most likely suffering from infectious endocarditis due to Staphylococcus aureus. The most appropriate next step is urgently obtaining blood cultures.

Infectious endocarditis is the result of bacterial seeding and growth upon the heart endometrium and valves. Patients with HIV are at increased risk of endocarditis. The tricuspid valve is most commonly affected in patients who use intravenous drugs, due to it being the first valve in contact with the systemic venous return system in patients who typically use veins of the arms and legs to inject. Constitutional symptoms are characteristic of infectious endocarditis, including vital sign derangements such as tachycardia and fever. The Duke criteria is used for diagnosis. Staphylococcus aureus is the most commonly implicated bacterial pathogen in intravenous drug use. Other notable pathogens with characteristic associations include Streptococcus bovis (gallolyticus) in the setting of colorectal cancer, Enterococcus species in the setting of gastrointestinal/genitourinary procedures, Streptococcus viridans in the setting of dental procedures, Streptococcus progenies in the case of seeding from pharyngeal infections, and Staphylococcus epidermidis in the setting of prosthetic valves.

Holland et al. review the diagnosis and management of infectious endocarditis. They discuss how clinical, microbiological, and echocardiographic data must be combined in order to make an accurate diagnosis of infectious endocarditis. They recommend that a multidisciplinary team with expertise in infectious diseases, cardiology and cardiac surgery be involved in treating this condition.

Figure A/Illustration A shows splinter hemorrhages (red arrow) that are embolic phenomena and are a characteristic finding in patients with infectious endocarditis.

Incorrect Answers:
Answer 2: Chest radiograph is an important part of the workup and diagnosis in patients with infectious endocarditis that has seeded the lungs via with septic emboli and/or have concomitant pulmonary signs and symptoms consistent with pneumonia. In such patients, a chest radiograph is an important part of the workup and diagnosis, but is not the most appropriate first step in the workup.

Answer 3: Echocardiogram is a vital diagnostic tool for visualization of seeding of valve leaflets in patients with infectious endocarditis and may be diagnostic in the workup. However, it should be obtained after clinical stabilization and after other more urgent diagnostic imaging.

Answer 4: Intravenous antibiotics should not be administered prior to obtaining blood cultures as they dramatically reduce the yield of blood cultures. Infectious endocarditis is a condition that is often treated with weeks of intravenous antibiotic therapy. Therefore, it is important to generally deliver antibiotic therapy only after blood cultures are drawn.

Answer 5: Recheck of CD4+ cell counts is appropriate in patients being treated for HIV. Counts should be checked by their infectious diseases physician to assess response to therapy and for screening purposes. This patient had a recent CD4+ count that was checked and above 400 cells/mm^3. While this is not in the normal range, it makes it less likely that the patient may be suffering from an atypical opportunistic infection, which more often presents with counts under 250 cells/mm^3.

Bullet Summary:
The most important first step in a hemodynamically stable patient with a presentation concerning for infectious endocarditis is obtaining urgent blood cultures.