INFECTIVE ENDOCARDITIS IN ADULTS
[Mylonakis E and Calderwood SB NEJM 2001;345:1318]:
The authors, from MGH, provide a review of endocarditis. This is the subject of multiple reviews, but few that are recent, scholarly, practical and comprehensive. This is a superb review with multiple important observations:
- Incidence: The incidence of endocarditis in various populations is defined by frequency/100,000 person-years as summarized in Table 2.
- The frequency with native valves in the general population is 1.7–6.2/100,000 person-years with a male: female ratio of 1.7:1 and a median age that is increasing and now reported at 47–69 years. Nosocomial infections account for 7–29% and intravascular devices account for at least half of these (CID 1995;20:16).
- Microbiology: The results for native-valves vs. prosthetic valve endocarditis according to more recent reports are summarized in Table 3.
- Culture-negative endocarditis: These cases account for 5–7% when there are strict criteria used for endocarditis and blood cultures have been obtained prior to antibiotic treatment. The laboratory should be alerted to this probability when cultures are negative at 48–72 hours to permit more prolonged incubation for 7–10 days and intensification of efforts to recover organisms such as use of the lysis centrifugation system with specialized media for fastidious microbes. Specific recommendations are included in Table 4.
- Diagnosis: The Duke criteria have become generally accepted (Am J Med 1994;96:200) and multiple reviews show a specificity of 99% and a negative predictive value of 92% (Am Heart J 1994;128:1200;CID 1998;26:1302).
- Echocardiography: Transthoracic echo is inadequate in up to 20% of adults due to obesity, chronic lung disease, and chest wall deformities. The sensitivity for vegetations is 60–70% (J Am Coll Cardiol 1991;18:391;Am J Med 1996;100:90). Transesophageal echo increases sensitivity for detecting vegetations to 75–95% and shows specificity of 85–98% (Am J Med 1999;107:198). Guidelines for use (J Am Coll Cardiol 1997;29:862) suggest the preference for transthoracic echo to evaluate native valves in patients who are good candidates for imaging, especially if the probably of endocarditis is less than 4%. For patients with a probability of 4–60%, initial use of transesophageal echo is more costeffective. TEE is more sensitive for evaluating periovascular extension in myocardial abscesses.
- S. aureus bacteremia: Endocarditis is found in 13–25% (CID 2000;30:633). TEE is useful in determining the duration of therapy in patients with uncomplicated, intravascular-catheter-associated S. aureus bacteremia (Am J Med 1999;107:198;Ann Intern Med 1999;130:810;CID 1999;28:106).
- Treatment: Recommendations for antibiotic treatment are provided in Table 5.
For prosthetic valve endocarditis, the recommendations are generally for a 6-week course using combinations of penicillin, nafcillin/oxacillin, or vancomycin with gentamicin for staph or strep endocarditis. With regard to anticoagulants, these agents may be continued unless there are CNS emboli or endocarditis involving S. aureus (Arch Intern Med 1999;159:473).
Surgery: The major indications are congestive failure, perivalvular disease, or uncontrolled infection despite antibiotic treatment. Organisms that bode an ominous prognosis for success with medical management are:P. aeruginosa, Brucella, Coxiella burnetii, fungi, and enterococci with no synergistic bactericidal regimen. Prosthetic valve endocarditis is another common indication for surgery, but medical management in these cases is most likely if these are late in onset and/or involves Viridans strep, HACEK organisms, or enterococci. Most authorities recommend surgery when there have been two episodes of embolization or one episode with residual large vegetation, but there are no controlled trials to support this. The author points out that the size of the vegetation alone is rarely a surgical indication. Recent neurologic complication is considered a relative contraindication to cardiac surgery due to the potential for postop neurologic deterioration.
Mortality: This varies by organism as follows: Viridans strep and Strep bovis-4 to 16%, enterococci-15 to 25%; S. aureus-25 to 47%; Q fever-5 to 37% and P. aeruginosa-50%. The overall mortality for native valve and prosthetic valve endocarditis is 20 to 25%; for right-sided endocarditis in injection drug users it is about 10%. The relapse rate with prosthetic valve endocarditis is 10–15% and represents an indication for surgery. Most native valve endocarditis cases that relapse do so within 2 months of discontinuing antibiotic treatment; the rate is generally less than 2% with penicillin sensitive Viridans strep and 8–20% for enterococcal endocarditis.