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endocarditis

Etiology: 1) common microbiologic causes (see common organisms by study) - native valve - Streptococci - Streptococcus viridans with bicuspid aortic valve, mitral valve prolapse [22] - Staphylococci (S aureus most common cause) - Gram-negative rods - prosthetic valve & IV drug abuse - Staphylococci - Streptococci & Enterococci - Gram-negative rods - fungi 3) specific mediators of bacterial adherence influence likelihood of bacteremic organism's attachment to cardiac valve [4] 2) uncommon microbiologic causes - HACEK bacterial group (Haemophilus, Actinobacillus, Cardiobacterium, Eikenella, Kingella) - anaerobes - Chlamydia - Rickettsia - Brucella - Legionella - Coxiella - viruses - echovirus - coxsackie virus - adenovirus 3) culture negative infectious endocarditis (3-5%) - prior antibiotics - fastidious organisms - viral or fungal etiology - indolent tricuspid valve disease 4) non infectious thrombotic endocarditis - systemic lupus erythematosus (Libman-Sacks endocarditis) 5) risk factors for endocarditis - prosthetic heart valve* - congenital heart disease: Tetralogy of Fallot - rheumatic heart disease - mitral valve prolapse with regurgitation - bicuspid aortic valve - prior endocarditis* - Marfan's syndrome - valvular stenosis - valvular insufficiency - hypertrophic cardiomyopathy - intravenous drug abuse (IVDA) [25] - central venous catheters - hemodialysis catheters & shunts - wires from pacemakers & implantable defibrillators - recent dental work or surgery - older age [4] 6) endocarditis is much more likely to result from regular bacteremia from daily activities than from bacteremiaduring dental procedures, gastrointestinal or urogenital procedures [4] * high-risk of endocarditis Epidemiology: - mean age of patients is > 50 years - more restrictive antibiotic prophylaxis recommendations & practices have not led to an increase in endocarditis [19] Pathology: 1) cardiac complications - valve-ring abscess - valvular perforation - valvular rupture - myocardial abscess - valvular stenosis secondary to large vegetations - systemic embolization - mycotic aneurysms 2) kidney complications (common) - renal abscess - renal embolization & infarction - glomerulonephritis 3) CNS involvement - ischemic stroke secondary to cardiac emboli - cerebral vasculitis - meningitis - cerebral abscess - subarachnoid hemorrhage due to ruptured mycotic aneurysm 4) affected valves: - single valve involvement - mitral > aortic > tricuspid > pulmonic - involvement of right & left heart valves (3-5%) - involvement of both aortic & mitral valves (30-35%) - heroin associated with right-sided endocarditis [6] 5) mitral valve endocarditis is generally associated with mitral regurgitation Clinical manifestations: 1) protean manifestations due to: - cardiac complications of valvular dysfunction - bacteremia - bland or septic emboli - circulating immune complexes 2) common manifestations - fever/chills (90-95%) - bacteremia - malaise - heart murmur (> 80%) - embolic phenomena - focal neurologic signs - congestive heart failure - cough, pleuritic chest pain & pneumonia more common in right-sided endocarditis (IV drug abuse) 3) uncommon manifestations - splenomegaly - retinal lesions (Roth spots) - meningitis - cutaneous manifestations - splinter hemorrhages - Osler's nodes - Janeway lesions - petechiae - hematuria 4) mitral valve endocarditis generally results in a holosystolic murmur best heard at the cardiac apex due to mitral regurgitation Diagnostic criteria: - Duke criteria for diagnosis of infectious endocarditis Laboratory: 1) complete blood count (CBC) a) normocytic anemia b) leukocytosis c) monocytosis (< 25%) 2) urinalysis (abnormal < 65%) a) proteinuria b) pyuria c) hematuria 3) blood cultures (positive in > 93%) - if blood cultures negative, consider culture-negative endocarditis 4) antibiotic sensitivities a) determination of the minimum inhibitory (MIC) & minimum bactericidal concentration (MBC) b) assess aminoglycoside synergy for penicillin-resistant streptococci & enterococci c) Schlicter test 5) erythrocyte sedimentation rate (ESR) increased in > 90% 6) see ARUP consult [12] Special laboratory: 1) electrocardiogram (ECG) - may show conduction abnormalities - conduction abnormalities suggest extension of infection into perivalvular tissue [4] 2) echocardiogram a) transthoracic echocardiogram (TTE) 1] initial imaging test in most clinical situations 2] all septic or bacteremic patients 3] TTE with lower sensitivity than TEE, but better specificity b) transesophageal echocardiogram (TEE) 1] initial test of choice in patients with moderate to high probability of endocarditis [4]; maybe not [4] 2] septic or bacteremic patients with negative transthoracic echocardiogram 3] better sensitivity than transthoracic echo, but higher incidence of false positives 4] patients with prosthetic valves 5] perivalvular abscess - new onset cardiac conduction defect may be clue [4] 6] intracardiac device leads present 7] if transthoracic echocardiogram negative & blood cultures negative, consider transthoracic echocardiogram for culture-negative endocarditis [29] c) role of echocardiography in assessing prognosis or need for surgery is controversial 3) colonoscopy to assess colon cancer in patients with blood cultures positive for: a) Streptococcus gallolyticus (Streptococcus bovis) b) Clostridium septicum [4] Radiology: 1) chest X-ray may show multiple bilateral small nodules 2) multislice computed tomography (CT) may be alternative to TEE [7] Complications: 1) embolic strokes are common with left-sided endocarditis, but often clinically silent - vegetation size > 10 mm associated with increased risk of embolism & mortality [20] 2) severe aortic regurgitation with acute heart failure & pulmonary edema - urgent aortic valve replacement 3) in-hospital or 14.7% & 1-year mortality of 23.2% when associated with cardiac device (pacemaker, mechanical valve) [11] Management: 1) antibiotic therapy a) empiric therapy (after obtaining blood cultures) if clinical suspicion for endocarditis is intermediate or high [4] - community-acquired endocarditis - vancomycin plus gentamicin, or - ampicillin sulbactam (Unasyn) plus gentamicin - nosocomial endocarditis - vancomycin, gentamicin + rifampin (S epidermidis) + carbapenem or cefepime (gram-negative baccilli) [4] - prosthetic valve endocarditis - vancomycin, gentamicin + rifampin [4] b) general considerations - 4-6 weeks duration of intravenous therapy* - oral antibiotics after 10 days of IV therapy may be an option [23,26,28] - oral linezolid or TMP-SMX non-inferior to IV vancomycin [26] - PICC line vs internal jugular catheter [4] - use of synergistic combinations of antibiotics - selection of antibiotic(s) on the basis of an isolated organism (see laboratory) - recognition of indications for surgical management - switching to oral antibiotics after at least 10 days of IV antibiotics in stable patients not associated with delayed treatment failure [27] c) specific organisms - Streptococcus - penicillin-sensitive (MIC < 0.2 ug/mL) - penicillin G 10-20 million units IV QD for 4 weeks +/- 2 weeks of gentamicin 1 mg/kg IV every 8 hours - vancomycin 15 mg/kg IV every 12 hours for 4 weeks - penicillin-resistant (MIC > 0.5 ug/mL) - penicillin G 20 million units IV QD plus gentamicin 1 mg/kg every 8 hours for 6 weeks - ampicillin 2 g IV every 6 hours plus gentamicin 1 mg/kg every 8 hours for 6 weeks - vancomycin 15 mg/kg IV every 12 hours plus gentamicin 1 mg/kg every 8 hours for 6 weeks - Enterococcus - ampicillin + high-dose ceftriaxone [18] - linezolid + high-dose daptomycin +/- beta-lactam for Enterococcus resistant to penicillin, aminoglycosides & vancomycin [18] - Staphylococcus - add rifampin for prosthetic valve endocarditis - gentamicin for 2 weeks for prosthetic valve endocarditis - gentamicin no longer considered for native valve S aureus endocarditis [18] - MSSA: nafcillin 1.5-2.0 g IV every 4 hours for 4-6 weeks [18] - uncomplicated right-sided native value MSSA endocarditis can be treated with 2 weeks of IV nafcillin [4] - MRSA: vancomycin 15 mg/kg IV every 12 hours plus rifampin 300 mg PO every 12 hours for 4-6 weeks [18] - area under the curve (AUC) to minimum inhibitory concentration (MIC) AUC/MIC should be used to guide therapy [4] - AUC/MIC target is 400-600 mg*hour/L assuming MIC <= 1 ug/mL [4] - cephalothin 2 gm IV every 6 hours for 4-6 weeks [18] - daptomycin is an alternative agent for treating MSSA or MRSA [18] - Enteric gram-negative bacilli (E coli, Klebsiella, Proteus, Pseudomonas, Serratia) - cephalosporin or broad-spectrum penicillin plus an aminoglycoside determined by antibiotic sensitivityfor 6 weeks - left-sided endocarditis due to Pseudomonas or Serratia may require combined medical & surgical intervention - fungal - prognosis poor - antifungal agents with poor activity - prosthetic valve - Staphylococcus aureus & epidermidis, diphtheroids - vancomycin + gentamicin + cefepime - vancomycin + gentamicin + rifampin - nafcillin + gentamicin - Candida or aspergillus - amphotericin B + 5-FC + surgery consult 2) indications for surgery [4,9] a) hemodynamic instability - surgery should not be delayed while active infection is treated b) acute heart failure or progressive congestive heart failure [10] c) recurrent embolization d) antibiotic-refractory disease - persistent bacteremia or fever > 5-7 days on appropriate antibiotics [4] - aortic regurgitation resulting from structural damage to the aortic valve requires aortic valve replacement vs removal of vegetation e) extension of infection into perivalvular tissue [4] - extravalvular intracardiac abscess (ring abscess or aortic abscess) - heart block not present prior to endocarditis - destructive or penetrating lesion [4] - urgent surgery, do not wait 6 weeks [4] f) mycotic aneurysm g) any treatment failure with prosthetic valve endocarditis h) prosthetic valve endocarditis caused by fungi, Pseudomonas aeruginosa or Staphylococcus aureus i) left-sided endocarditis due to Staphylococcus aureus, fungus, or other resistant organism [4] j) severe cardiac valvular dysfunction identified by echocardiography 3) surgical management - valve replacement if structural damage to valve - heart failure due to endocarditis indicates structural damage to valve - aortic regurgitation [29] 4) see prophylaxis for bacterial endocarditis * special case of right-sided endocarditis caused by methicillin-sensitive S. aureus may be treated by 2 weeks of IV nafcillin + an aminoglycoside [4] Comparative biology: - combination of aspirin & ticlopidine reduces incidence of both streptococcal & staphylococcal endocarditis in rats - abciximab (ReoPro) is also effective in rats [16]

Interactions

disease interactions

Related

antibiotic prophylaxis for bacterial endocarditis Duke criteria for diagnosis of infectious endocarditis empiric antibiotic therapy etiology of bacterial endocarditis, common organism Janeway spot or lesion (smoke ring) Osler's node Slichter test

Specific

culture-negative endocarditis Libman-Sacks endocarditis marantic endocarditis; non-bacterial thrombotic endocarditis

General

carditis valvular heart disease

References

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