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Update onInfective Endocarditis

Larry Baddour, MD

University of Tennessee

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Pathogenesis

• Disruption of the endocardial layer as a complication of abnormal blood flow associated with underlying cardiac defect

• Bacterium-endothelium interaction with bacterial attachment and invasion of endothelial cells

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Epidemiology

• Underlying valvular abnormality predisposing to infective endocarditis– rheumatic fever

a common cause in the past– mitral valve prolapse

currently represents the most common underlying cardiac abnormality

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mitral valve prolapse

• risk for infective ednocarditis is 5x-8x • mitral regurgitation increases the risk• leaflet redundancy with myxomatous

degeneration is a frequent finding• age <20 , female predominate

age >20 , male accounts for 60%age >50 , male accounts for 68%

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Mitral Valve Prolapse and Infective Endocarditis

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Coagulase-negative Staphylococci

• can produce native-valve endocarditis in mitral valve prolapse

• usually subacute, difficult to diagnose, and disregarded as a contaminant

• delay in diagnosis and treatment may account for the severe complications– myocardial abscess formation– valvular insufficiency requiring valve surgery– death

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Prosthetic Heart Valve

• positive blood culture in hospitalized patients with underlying prosthetic valves can be a harbinger of endocarditis

• 43% patients with nosocomial bacteremia or fungemia had prosthetic valve infection

• a serious complication

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IV Drug Use

• Recurrent

• Polymicrobial

• Staph aureus accounts for the majority of cases of endocarditis

• tricuspid valve, either alone or in combination, us most often infected

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Predisposing Factors Polymicrobial Infective Endocarditis

Iv drug use

Central line

Prosthetic valve

Previous IE

Murmur

Dental procedure

Rheumatic disease

Miscellaneous

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Polymicrobial Infective Endocarditisclinical features

• IV drug use is the predominant risk factor• younger age (mean 36.5 years)• 2/3 were male• right-sided cardiac involvement in > 60%• streptococci more frequent than S. aureus• 1/3 of patients died • mortality rate is 4x higher for pure left-

sides vs pure right-sided endocarditis

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Diagnostic (Duke) Criteria

• Definitive infective endocarditis– pathologic criteria

• microorganisms or pathologic lesions: demonstrated by culture or histology in a vegetation, or in a vegetation that has embolized, or in an intracardiac abscess

– clinical criteria (see below) • two major criteria, or one major and three

minor criteria, or five minor criteria

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Diagnostic (Duke) Criteria

• Possible infective endocarditis– findings consistent of IE that fall short of

“definite”, but not “rejected”

• Rejected– firm alternate Dx for manifestation of IE– resolution ofmanifestations of IE, with

antibiotic therapy for 4 days

– no pathologic evidence of IE at surgery or autopsy, after antibiotic therapy for 4 days

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Diagnostic (Duke) Criteria

• Major criteria– positive blood culture for IE– evidence of endocardial involvement

• Minor criteria– predisposition (heart condition or IV drug use)– fever of 100.40F or higher– vascular or immunologic phenomena– microbiologic or echocardiographic evidence

not meeting major criteria

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Duke’s Major Criteria

• positive blood culture for IE– typical microorganism (strep viridans, strep

bovis, HACEK group, staph aureus or enterococci in the absence of a primary locus) for endocarditis from two separate blood cultures

– persistently positive blood culture from:• blood cultures drawn more than 12 hr apart, or• all of 3 or a majority of 4 or more separate blood

cultures, with first and last drqwn at least 1 hr apart

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Duke’s Major Criteria

• Evidence of endocardial involvement– positive echocardiogram for endocarditis

• oscillating intracardiac mass on valve or supporting structure, or in the path of regurgitant jets, or on implanted material, in the absence of an alternate anatomic explanation

• abscess• new partial dehiscence of prosthetic valve

– new valvular regurgitation (increase or change in pre-existing murmur not sufficient)

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Duke’s Minor Criteria

• predisposition (predisposing heart condition or iv drug use)

• fever of 100.40F or higher• vascular phenomena (major arterial

emboli, septic pulmonary infarcts, mycotic aneurysm, intracranial hemorrhage, conjunctive hemorrhages, Janeway lesions)

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Duke’s Minor Criteria

• immunologic phenomena (glomerulonephritis, Osler’s nodes, Roth spots, rheumatoid factor)

• microbiologic evidence (positive blood culture not meeting major criteria or serologic evidence of active infection with organism consistent with IE)

• echocardiogram (consistent with IE but not meeting major criteria)

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Risk for Endocarditis

• High risk– prosthetic cardiac valve– prior episodes of endocarditis– complex congenital cardiac defect– surgically constructed systemic-

pulmonary shunts or conduits

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Risk for Endocarditis

• Moderate risk– patent ductus arteriosus– VSD, primum ASD– coarctation of the aorta– bicuspid aortic valve– hypertrophic cardiomyopathy– acquired valvular dysfunction– MVP with mitral regurgitation

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Risk for Endocarditis

• Low risk– isolated secundum atrial septal defect– ASD, VSD, or PDA >6 months past

repair– “innocent” heart murmur by

auscultation in the pediatric population– “innocent” heart murmur by

echocardiography in adult patients

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Treatment

• Pre-antibiotic era - a death sentence

• Antibiotic era– microbiologic cure in majority of

patients

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New Treatments

• Right-sided infective endocarditis due to methicillin-susceptible S aureus (MSSA) in IV drug users– 2-wk therapy with a penicillinase-resistant

penicillin and an aminoglycoside– 2-wk monotherapy with IV cloxacillin– short-term therapy is inappropriate if

complicated by ostomyelitis, meningitis, myocardial abscess, or concomitant left-sided involvement

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New Treatments

• Highly penicillin-susceptible Streptococcus viridans or bovis– Once-daily ceftriaxone for 4 wks

• cure rate > 98%• easily administered as outpatient, avoid

hospitalization, offers significant cost savings

– Once-daily ceftriaxone 2 g for 2wks followed by oral amoxicillin qid for 2 wks

– Once-daily ceftriazone and netilmicin for 2 wks

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New Treatments

• Prosthetic valve endocarditis due to fluconazole-susceptible Candida species– many are due to bloodstream invasion– chronic oral suppressive therapy with

fluconazole for inoperable disease

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SBE Prophylaxis

Standard general prophylaxis amoxicillin

Unable to take oral meds ampicillin

Allergic to penicilin clindamycin

cephalexin

azithromycin

clarithromycin

Allergic to penicillin and unable clindamycin

to take oral medications cefazolin

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References

• Prevention of bacterial endocarditis. Recommended by the American Heart Association. Dajani AS, Taubert KA, Wilson W, et al. Circulation 1997;96:358-366

• New Criteria for diagnosis of infective endocarditis: Utilization of specific echocardiographic findings. Durack DT, Lukes AS, Bright DK, et al. Am J Med 1994;96:200-209

• Antibiotic treatment of adults with infective endocarditis due to strptococci, enterococci, staphlococci, and HACEK microorganisms. Wilson WR, Karchmer AW, Dajani AS. JAMA 1995;274:1706-1713