Infective Endocarditis
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BACKGROUND
Infective Endocarditis is infection of the innermost lining of the heart - the endothelium. Endothelium of the heart does not have the usual defense mechanisms like rest of the body. When a pathogen seeds in the endothelium of the heart, they grow unopposed. The usual places for these seedings are the heart valves, the rings and the inner linings of the heart chambers.
EPIDEMIOLOGY
Infective Endocarditis is more common in male than females. Elderly population with endocarditis is on the rise. 50% of cases in the US are over 60 years. Two important factors are Rheumatic Heart Disease and proportion of elderly with heart conditions. Among the younger population, drug addiction is an important risk factor.
RISK FACTORS
Major risk factors are Intravenous Drug Use, prosthetic heart valves, structural heart disease and invasive procedures like cystoscopy, dental extractions, etc..
PATHOGENESIS
Onset of infection starts from injury to the endocardium. There is focal adherence of platelets and fibrin, which acts as the nidus for microorganisms. Source of microorganism is usually a distant focal infection, or transient bacteremia from a mucosal or skin source. Once colonization occurs, there is secondary accumulation of more platelets and fibrin, leading to macroscopic excrescence or vegetation.
ORGANISMS
Streptococcus viridans 30-40%, Enterococcus species 5-10 %, Other streptococci 10-25 %, Staphylococcus aureus 10-27 %, Coagulase-ve staphylococci 1-3 %, Gram-negative bacilli 2-13 %, Fungi 2-4 %, Other 5 %, and “Culture negative” 5-24 %.
Inaddition, there are slow-growing Gram negative bacteria called HACEK organisms. They are a normal part of the human flora. They are a frequent cause of endocarditis in children. They are
Haemophilus aphrophilus, Haemophilus parainfluenzae and Haemophilus paraphrophilus, Actinobacillus actinomycetemcomitans, Cardiobacterium hominis, Eikenella corrodens, and Kingella kingae.
CLINICAL PRESENTATION
The usual signs of Infective endocarditis are flu-like" illness, dry cough, body aches / fatigue, low grade fevers, night sweats and weight loss. However these symptoms are not specific for endocarditis and so the clinical suspicion should be very high in patients with multiple risk factors.
DIAGNOSIS
Diagnosis is based on Modified Duke's Criteria.
Duke Criteria for the Diagnosis of Infective Endocarditis(IE)
1)Positive valve culture or histology or
2)Two major criteria:
-typical organism for IE in 2 separate cultures,
-persistent bacteremia blood culture +ve 12 hrs apart
-positive ECHO for vegetations, abscess or valve dehiscence or new
regurgitation
3)Five of six minor criteria:
-valvular heart disease or IVDA,
-fever > 38°C,
-Vascular- arterial emboli, septic infarcts, intracranial or conjunctival
hemorrhage, janeway lesions
-Immunological- glomerulonephritis, Osler’s nodes, Roth spots
-Microbiological- +ve blood cultures not in Major criteria or serological
evidence with consistent organisms or
4)One major and three minor criteria
TREATMENT
Treatment should be started promptly to prevent complications for Endocarditis. Multiple empirical regimens are available based on the risk factors of patients and organisms.
Penicillin-susceptible (MIC 0.1 mcg/mL) S viridans, S bovis, and other streptococci: 1)Penicillin G 12-18 million U/d IV continuous or in 6 divided doses for 4 weeks, or 2)Ceftriaxone 2 g/d IV for 4 weeks Inaddition to either of above, gentamicin 1 mg/kg every 8 hours for 2 weeks If Allergic to penicillin, vancomycin at 30 mg/kg/d IV in 2 divided doses for 4 weeks
Relative Penicillin-susceptible (MIC 0.1-0.5 mcg/mL) S viridans, S bovis, and other streptococci: 1)Penicillin G 24 million U/d IV continuous or in 6 divided doses for 4 weeks, or 2) Ceftriaxone 2 g/d IV for 4 weeks Inaddition to either of above, gentamicin 1 mg/kg every 8 hours for 2 weeks If Allergic to penicillin, vancomycin at 30 mg/kg/d IV in 2 divided doses for 4 weeks
Nonresistant enterococci, resistant S viridans (MICs >0.5 mcg/mL): Penicillin G 18-30 million U/d IV continuous or 6 divided doses, OR ampicillin at 12 g/d by continuous or 6 divided doses OR vancomycin at 30 mg/kg/d 2 divided doses In addition, gentamicin at 1 mg/kg IM or IV every 8 hours for 4-6 weeks
Methicillin-sensitive S aureus should be treated as follows: Nafcillin or Oxacillin at 2 g IV 4 hrly for 4-6 weeks +/- gentamicin for 3-5 days, or cefazolin at 2 g IV 8 hrly for 4-6 weeks +/- gentamicin for 3-5 days Allergic to penicillin or Methicillin-resistant S aureus, vancomycin at 30 mg/kg 4-6 weeks
HACEK microorganisms should be treated for 4 weeks as follows: ceftriaxone 2 g/d IV Ampicillin- sulbactam 12 g/d continuous or 6 hrly divided doses daily Ciprofloxacin
Prosthetic Valve Endocarditis: Methicillin-sensitive S aureus Nafcillin or Oxacillin with Rifampin for 6 weeks Inaddition, gentamicin for 2 weeks.
Methicillin-resistant S aureus Vancomycin with Rifampin for 6 weeks Inaddition, gentamicin for 2 weeks.
For all PVE treatment is for 6 weeks
INTICATIONS FOR SURGERY
Following are the indications for surgery:
1) Congestive heart failure refractory to standard medical therapy, 2) Fungal IE, 3) Persistent sepsis after 72 hours of appropriate antibiotic treatment, 4) Recurrent septic emboli, especially after 2 weeks of antibiotic treatment, 5) Rupture of an aneurysm of the sinus of Valsalva, 6) Conduction disturbances caused by a septal abscess, and 7) "Kissing" infection of the anterior mitral leaflet in patients with IE of the aortic valve.
COMPLICATION
Complications of Endocarditis are as follows:
(1) Valvular dysfunction, usually insufficiency of the mitral or aortic valves (2) Myocardial or septal abscesses, (3) Congestive heart failure, (4) Metastatic infection, (5) Embolic phenomenon, and (6) Organ dysfunction resulting from immunological processes.
Notes & References
[1] Kasper, Dennis L.; Eugene Brunwald, Anthony S. Fauci, Stephen Hauser, Dan L. Longo, J. Larry Jameson (2005). Harrison's Principles of Internal Medicine. McGraw-Hill, pp. 731-740.
[2] Durack D, Lukes A, Bright D (1994). "New criteria for diagnosis of infective endocarditis: utilization of specific echocardiographic findings. Duke Endocarditis Service.". Am J Med 96 (3): 200–9.
Credits & Notices
Authors-contributors to this page (listed alphabetically, last name, first & middle initial only, no institutional affiliations, no scientific titles):
Doraiswamy VA
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