Infective Endocarditis

Endale Tefera, MDDepartment of pediatrics & Child

Health, AAUMF

Definition

• Is a microbial infection of the endocardial (endothelial) surface of the heart.

• Native or prosthetic heart valves are the most commonly involved sites.

• Septal defects, the mural endocardium, or intravascular devices such as intracardiac patches, surgically constructed shunts, intravenous catheters can be involved.

Definition

• Infective endarteritis – involving arteries, including PDA, the great vessels, aneurysms, or arteriovenous shunts.

• Classification as acute or subacute not advised (obsolete).

• Better classification based on etiologic agent.

Etiologies

• Most cases are caused by relatively small number of micro-organisms.

• Gram positive cocci account for 90% of cases (adult studies).

• Streptococcus viridans – are the most common causes at all ages.

• Staphylococcus aureus & CONS – 2nd most common culprit organisms.

Etiologies…

• Gram negative organisms – account for less than10% of cases.

• Anaerobic organisms rarely cause endocarditis in children.

• Fungal endocarditis – one of the most feared forms (complications, like embolization are common).

Etiologies…

• Blood culture negative endocarditis – about 5 – 10% of cases.

N.B. A diagnosis of culture – negative endocarditis is made when a patient has clinical and/or echocardiographic evidence of IE but blood culture is persistently negative.

pathogenesis

Pre-existing congenital or acquired lesion of the heart or great vessels (usual)

Damage to the endothelium & formation of non-bacterial thrombotic endocarditis (NBTE) on the surface of the damaged endothelium

Pathogenesis…

Occurrence of transient bacteremia

Adherence of bacteria to the NBTE

Proliferation of bacteria with in the vegetation

Relative risk of IE for underlying cardiac lesions & conditions

High risk:prosthetic valvesPrevious episode of endocarditisComplex cyanotic congenital heart diseases

(e.g. single ventricle states, TGA, TOF)Surgically corrected systemic artery to

pulmonary artery shuntsInjection drug useIndwelling central venous catheters

Relative risk…

Moderate riskuncorrected PDAUncorrected VSDBicuspid Aortic valveMitral valve prolapse with regurgitationRheumatic mitral or aortic valve diseasesOther acquired valvular diseasesHypertrophic cardiomyopathy

Pathogenesis…

• Virtually all vegetations occur in areas where there is a pressure gradient with resulting turbulence of blood flow.

• Sites of high velocity jets where most vegetations occur are on the atrial side of the atrioventricular valves and ventricular side of the semilunar valves.

Clinical features

Result from:Hemodynamic and structural changes caused

by the local infectionEmbolization from vegetations, orImmunologic reactions by the host

Clinical…

• Bacteremia can cause fever and systemic toxicity.

• Endocarditis involving the left side of the heart frequently results in peripheral embolization, leading to ischemia, infarction or mycotic aneurysms.

Clinical…• Fever (most common)• Nonspecific symptoms (myalgia, arthralgia, headache,

malaise) – in most cases• Heart murmur – new or changing (infrequent)• Heart failure (infrequent)• Petechiae (infrequent)• Embolic phenomena (infrequent)• Splenomegaly (infrequent)• Neurologic findings (infrequent)• Osler nodes, Janeway lesions, Roth spots, splinter

hemorrhages (rare)

Laboratory

• Positive blood culture (off antibiotics) – very common

• Elevated acute phase reactants – very common

• Anemia – in most cases• Hematuria – in most cases• Presence of rheumatoid factor – infrequent• Leukocytosis - infrequent

Blood culture

• Three separate sets of blood cultures, each from a separate venipuncture over a 24hr period.

• 1 to 3mL in infants and young children, 5 to 7mL in older children and 20 to 30mL in adults

Echocardiography

• Two – dimensional echocardiography – principal diagnostic method.

• Sensitivity of more than 80%.• Neither sensitivity nor specificity is 100%.• Transthoracic echo – more helpful in children with

normal cardiac anatomy or with isolated valvular abnormalities and septal defects.

• Transesophageal echo – more sensitive in picking smaller vegetations, paravalvular leaks and complications such as dehiscence of prosthetic valves

Mitral valve vegetationsSystole Diastole

LV

LA

RV

RA

LV

MVTV

RA

LA

RV

Mitral and tricuspid valve vegetations

RV

LV

LA

RA

Aortic valve vegetations

Diastole Systole

LV

LA

AO.V

MV

Perforation in the anterior mitral valve leaflet

2D Color frame

Parasternal short axis view (tricuspid and aortic valve vegetations)

LA

RVOT

TV PV

PA

RA

AO.V

Definition of terms used in the Modified Duke criteria for the diagnosis of IE

Major criteria

1. Blood culture positive for infective endocarditis (IE)A. Typical micro – organisms consistent with IE from 2 separate blood

cultures:i. Viridans streptococci, streptococcus bovis, HACEK group,

staphylococcus aureus; orii. Community acquired enterococci in the absence of a primary focus; orB. Micro – organisms consistent with IE from persistently positive blood

cultures defined as follows:iii. At least 2 positive cultures of blood samples drawn ≥ 12hrs apart; oriv. All of 3 or a majority of ≥ 4 separate cultures of blood (with 1st and last

sample drawn ≥ 1 hour apart)C. Single positive blood culture for Coxiella burnetii or anti – phase 1 IgG

antibody titer > 1: 800.

Definition of terms …2. Evidence of endocardial involvementA. Echocardiogram positive for IE (TEE recommended for

patients with prosthetic valves, rated at least “possible IE” by clinical criteria, or complicated IE [paravalvular abscess]; TTE as first test in other patients) defined as follows:

i. Oscillating intracardiac mass on valve or supporting structures, in the path of regurgitant jets, on implanted material in the absence of alternative anatomic explanation; or

ii. Abscess; oriii. New valvular regurgitation (worsening or changing or pre-

existing murmur not sufficient)

Definition of terms …Minor criteria1. Predisposition, predisposing heart condition, or injection

drug use2. Fever > 38°C3. Vascular phenomena, major arterial emboli, septic

pulmonary infarcts, mycotic aneurysm, intracranial hemorrhages, and Janeway lesions

4. Immunologic phenomena: glomerulonephritis, Osler nodes, Roth spots, and rheumatoid factor

5. Microbiologic evidence: positive blood culture, but does not meet a major criterion, or serologic evidence of active infection with organism consistent with IE

Definition of IE according to the modified Duke criteria

Definite infective endocarditis (IE):1. Pathologic criteria:A. micro – organisms demonstrated by culture

or histologic examination of a vegetation, a vegetation that has embolized, or an intracardiac abscess specimen; or

Definition of IE …

B. Pathologic lesions; vegetation or intracardiac abscess confirmed by histologic examination showing active endocarditis

2. Clinical criteriaC. 2 major criteriaD. 1 major and 3 minor criteriaE. 5 minor criteria

Definition of IE …Possible IE:1. 1 major and 1 minor criteria2. 3 minor criteriaRejected IE:3. Firm alternative diagnosis explaining evidence of IE;

or4. Resolution of IE syndrome with antibiotic

treatment for ≤ 4 days; or5. No pathologic evidence of IE at surgery or autopsy,

with antibiotic treatment for ≤ 4 days; or6. Does not meet the criteria for possible IE as above

Antimicrobial therapy

General principlesWith in vegetations, organisms are embedded in very

high concentrations.Relatively low rates of bacterial metabolism and cell

division decreased susceptibility to beta – lactam and other cell wall active antibiotics.

Bactericidal rather than bacteriostatic antibiotics preferred.

Antimicrobial …Complete eradication of the organisms requires 4 to

6 weeks of antibiotic treatment.Parenteral administration recommended. Combination of antibiotics against the commonest

offending agents. Indications for surgery include: Significant embolic events, Persistent infection, and Progressive cardiac failure

Prophylaxis

Prophylactic regimens for dental, oral, or respiratory tract procedures:

Amoxicillin 50mg/kg p.o. 30 to 60 min before procedure (standard).

Ampicillin or cefazoline or ceftriaxone, IM or IV, if unable to take oral medications.

Clindamycin or cephalexin or azithromycin or clarithromycin for penicillin allergic patients.