Update on Infective Endocarditis
Larry Baddour, MD
University of Tennessee
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
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
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%
Mitral Valve Prolapse and Infective Endocarditis
Male
Female
Number of cases
Rev Infect Dis 1986;8:117-137
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
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
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
Predisposing Factors Polymicrobial Infective Endocarditis
Polymicrobial Infective Endocarditis clinical 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
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
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
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
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
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)
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)
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)
Risk for Endocarditis
High risk
prosthetic cardiac valve
prior episodes of endocarditis
complex congenital cardiac defect
surgically constructed systemic-pulmonary shunts or conduits
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
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
Treatment
Pre-antibiotic era - a death sentence
Antibiotic era
microbiologic cure in majority of patients
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
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
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
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
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