Infection of the endocardium. Most commonly affects the heart valves, especially the mitral valve. Risk factors include rheumatic, congenital, or valvular heart disease; prosthetic heart valves; IV drug use; and immunosuppression.
Etiologies are as follows (see Table 1):
- S aureus: The causative agent in > 80% of cases of acute bacterial endocarditis in patients with a history of IV drug use.
- Viridans streptococci: The most common pathogens for left-sided subacute bacterial endocarditis and following dental procedures in native valves.
- Coagulase ⊝ Staphylococcus: The most common infecting organism in prosthetic valve endocarditis.
- Streptococcus bovis: S bovis endocarditis is associated with coexisting GI malignancy. Perform colonoscopy if S bovis diagnosed.
- Candida and Aspergillus species: Account for most cases of fungal endocarditis. Predisposing factors include long-term indwelling IV catheters, malignancy, AIDS, organ transplantation, and IV drug use.
Presentation of endocarditis—
- Constitutional symptoms are common (fever/FUO, weight loss, fatigue).
- Exam reveals a heart murmur. The mitral valve (mitral regurgitation) is more commonly affected than the aortic valve in non–IV drug users; more right-sided involvement is found in IV drug users (tricuspid valve > mitral valve > aortic valve).
- Osler nodes (small, tender nodules on the finger and toe pads), Janeway lesions (small peripheral hemorrhages; see Figure 1), splinter hemorrhages (subungual petechiae; see Figure 1), and Roth spots (retinal hemorrhages).
- Guided by risk factors, clinical symptoms, and the Duke criteria (see Table 2). The presence of two major, one major + three minor, or five minor criteria all merit the diagnosis of endocarditis. Obtain serial blood cultures from different sites before starting antibiotic therapy.
- CBC with leukocytosis and left shift; ↑ ESR and CRP.
- Early empiric IV antibiotic treatment for acutely ill patients. Vancomycin + gentamicin is an appropriate choice for most patients. Tailor antibiotics once the causative agent is known. Acute valve replacement is sometimes necessary if rupture occurs. The prognosis for prosthetic valve endocarditis is poor.
- Pre-procedure prophylaxis: Endocarditis prophylaxis is only indicated in patients with the following:
- Significant cardiac defects (prosthetic valves, unrepaired cyanotic congenital heart disease, prior history of endocarditis, transplanted heart with valvular disease).
- Undergoing high-risk procedures (dental work involving gingival tissue or perforation of mucosa, respiratory tract surgery involving perforation of mucosa, GI or GU surgeries in patients with ongoing GI or GU infections).
- Amoxicillin is the preferred antibiotic prophylaxis. For patients who are penicillin allergic, use cephalexin, clindamycin, azithromycin, or clarithromycin.
Focal neurologic deficits from embolic strokes, metastatic infection (most common cause of splenic abscess), heart failure caused by valvular insufficiency, and glomerulonephritis.