Diagnosis of endocarditis is usually based on clinical, microbiologic, and echocardiographic findings. Treatment involves antimicrobial therapy targeted to the identified organism. Surgical indications include heart failure, uncontrolled infection, and prevention of embolic events. The latest article in our Clinical Practice series reviews diagnosis and treatment options for infective endocarditis.
Infective endocarditis has an estimated annual incidence of 3 to 9 cases per 100,000 persons in industrialized countries.
• What are the risk factors for infective endocarditis?
The highest rates are observed in patients with prosthetic valves, intracardiac devices, unrepaired cyanotic congenital diseases, and history of infective endocarditis. Other risk factors include chronic rheumatic heart disease (CRHD) (which now accounts for less than 10% of cases in industrialized countries), age-related degenerative valve lesions, and comorbidities such as diabetes, HIV infection, IV drug use, and hemodialysis. Over a third of infective endocarditis cases in the U.S. in recent years were reported to be health care-associated (nosocomial or non-nosocomial). The clustering of several of these predisposing factors with age probably explains the higher infectious endocarditis incidence in persons older than 65 years. The male:female case ratio is more than 2:1.
• What organisms are most often responsible for causing infective endocarditis?
Streptococci and staphylococci account for 80% of infective endocarditis cases, with proportions varying according to valve (native vs. prosthetic), source of infection, patients’ age, and comorbidities. Staphylococci are now the most frequent microorganisms in several situations which results from the increased proportion of health care-associated infective endocarditis. In parallel, the incidence attributable to oral streptococcal has decreased in industrialized countries. Blood culture negative infectious endocarditis (10% of cases) may reflect two situations: infectious endocarditis in patients exposed to antibiotics before the diagnosis of infectious endocarditis and infectious endocarditis due to fastidious microorganisms. In the latter case, serology, valve or blood PCR, and highly specialized microbiological techniques lead to pathogen identification in 60% of cases, the most frequent microorganisms being Bartonella sp., Brucella sp., Coxiella burnetii (Q fever agent), HACEK bacteria, and Tropheryma whipplei.
Morning Report Questions
Q: What is the typical clinical presentation of infective endocarditis?
A: Fever is common (80% of cases). In large contemporary case series, recognition of a new murmur or worsening of a known murmur are reported in 48% and 20% of cases, respectively. Other signs are less common: hematuria 25%, splenomegaly 11%, splinter hemorrhages 8%, Janeway lesions 5%, Roth spots 5%, and conjunctival hemorrhage 5%. Sepsis, meningitis, unexplained heart failure, septic pulmonary emboli, stroke, acute peripheral arterial occlusion, and renal failure may also be presenting manifestations. Elevated inflammatory markers (ESR, C-reactive protein, or both) are observed in two thirds of cases, and leukocytosis and anemia in about half of cases.
Q: What is the appropriate treatment of noncomplicated native valve infective endocarditis?
A: For native valve infectious endocarditis due to usual microorganisms, the duration of antibiotic treatment ranges from 2 weeks (uncomplicated infectious endocarditis due to fully penicillin-susceptible streptococci treated with a beta-lactam + aminoglycoside combination) to 6 weeks (enterococcal infectious endocarditis). In streptococcal infectious endocarditis, clinical trials showed that adding gentamicin permits a shorter 14-day course of treatment in uncomplicated native valve infectious endocarditis and that aminoglycosides can be effectively given once daily instead of twice daily. In enterococcal infectious endocarditis, whenever the strain does not exhibit high-level resistance to gentamicin, gentamicin should be used in combination with a cell-wall active agent. In such cases, gentamicin is generally given for the full 6-week course of antibiotic treatment.