Infective Endocarditis

Question 1

Nonbacterial thrombotic endocarditis(NBTE) or marantic endocarditis

Answer 1

uninfected platelet-fibrin thrombus often a nidus for microbial adhesion during bacteremia

Question 2

Prototypic native valve endocarditis (NVE) lesion

Answer 2

mass of platelets, fibrin, microbial microcolonies with scant inflammatory cells

Question 3

Cardiac Locations of Infective Endocarditis

Answer 3

Native (especially aberrant, e.g. rheumatic) or prosthetic valves
Low-pressure side of a ventricular septal defect
Mural endocardium damaged by aberrant jets of blood or foreign bodies
Intracardiac devices
Infective endarteritis - analogous process in arteriovenous shunts, arterioarterial shunts (PDA), or aortic coarctation

Question 4

Cardiac Valve Blood Supply

Answer 4

no dedicated blood supply
Host immune response blunted
Limits access of antibiotics to valve

Question 5

Subacute bacterial endocarditis (SBE)

Archaic Classification

Answer 5

Streptococci of low virulence (strep viridans)
Mild to moderate illness progressing slowly over weeks to months
Low propensity to hematogenously seed extracardiac sites

Question 6

Acute bacterial endocarditis (ABE)

Archaic Classification

Answer 6

More typically due to Staph aureus, higher virulence
Fulminant illness over days to weeks
Frequently causes metastatic infection

Question 7

Current Etiology of Infective Endocarditis

Answer 7

Congenital heart disease
Illicit IV drug use
Degenerative valve disease
Intracardiac devices
Incidence notably increased in elderly (e.g. degenerative & intracardiac devices)
30–35% of cases of NVE related to health care
16–30% of endocarditis involve prosthetic valves (PVE), greatest risk within 6–12 months of valve replacement

Question 8

Oral cavity, skin, and upper respiratory tract

Microbiology of Infective Endocarditis

Answer 8

Viridans streptococci
Staphylococci
HACEK organisms from oral cavity (Haemophilus, Actinobacillus, Cardiobacterium, Eikenella, and Kingella; Haemophilus aphrophilus & Actinobacillus actinomycetemcomitans–now genus Aggregatibacter)

Question 9

Gastrointestinal

Microbiology of Infective Endocarditis

Answer 9

Streptococcus gallolyticus (formerly S. bovis) - polyps and colonic tumors

Question 10

Health care–associated NVE

Microbiology of Infective Endocarditis

Answer 10

(55% nosocomial & 45% community onset: HC exposure within 90 days)
Staphylococcus aureus
Coagulase-negative staphylococci (CoNS)
Enterococci

Question 11

Procedure Induced Bacteremia, risks, rates, and organisms

Answer 11

Endoscopy - 0-20%; coagulase-negative staphylococci (CoNS), streptococci, diphtheroids
Colonoscopy - 0-20%; Escherichia coli, Bacteroides species
Barium enema - 0-20%; enterococci, aerobic and anaerobic gram-negative rods
Dental extractions - 40-100%; S viridans
Transurethral resection of the prostate - 20-40%; coliforms, enterococci, S aureus
Transesophageal echocardiography (TEE) - 0-20%; S viridans, anaerobic organisms, streptococci

Question 12

Prosthetic valve endocarditis

Answer 12

Prosthetic valve endocarditis (PVE)
Nosocomial usually < 2 months of valve surgery
Intraoperative contamination of the prosthesis
Bacteremic postoperative complication
Typically S aureus, CoNS (coag neg staph), facultative gram-negative bacilli, diphtheroids & fungi
PVE >12 months after surgery infective organisms similar to community-acquired NVE
CoNS presenting 2–12 months after surgery often represents delayed-onset nosocomial infection
68–85% of CoNS strains methicillin resistant

Question 13

Infective Endocarditis– illicit drug users

Answer 13

Tricuspid valve most common
Usually S. aureus; often methicillin resistant
Left-sided valve infections
Typical IE organisms plus
Pseudomonas aeruginosa
Candida species
Sporadic Bacillus, Lactobacillus & Corynebacterium species
Polymicrobial endocarditis
HIV infection in drug users does not significantly change types of microbes

Question 14

Infective Endocarditis– Transvenous pacemaker & implanted defibrillator

Answer 14

Usually nosocomial, occur within weeks of implantation or generator change
S. aureus or CoNS - commonly methicillin resistant

Question 15

Blood Cultures in Infective Endocarditis

Answer 15

5 - 15% have negative blood cultures
33 – 50% due to prior antibiotic exposure
Fastidious organisms
Nutritionally variant organisms (now designated Granulicatella and Abiotrophia species)
HACEK organisms, Coxiella burnetii, and Bartonella species
Tropheryma whipplei - indolent, culture-negative, afebrile form of IE

Question 16

Infective Endocarditis - Pathogenesis

Answer 16

Adhesin molecules - microbial surface components recognizing adhesin matrix molecules (MSCRAMMs)
Fibronectin-binding proteins - gram-positive bacteria
Required for S aureus to attach to intact endothelium
Clumping factor (a fibrinogen- & fibrin-binding surface protein) on S. aureus
Glucans or FimA (oral mucosal adhesins) on streptococci
Platelet-fibrin vegetations form dense microcolonies of microbes
Organisms deep in vegetations are metabolically inactive (non-growing) & resistant to antimicrobial agents (especially static agents)
Surface organisms continuously shed into bloodstream

Question 17

Pathophysiologic consequences and clinical manifestations for Infective Endocarditis

Answer 17

Constitutional symptoms - probably result from cytokine production
Damage to intracardiac structures
Embolization of vegetation fragments, leading to infection or infarction of remote tissues
Hematogenous infection of sites during bacteremia
Tissue injury from deposition of circulating immune complexes or immune responses to deposited bacterial antigens

Question 18

Presentation of Infective Endocarditis

Answer 18

Murmurs
CHF
MI
Fever
Roth Spots
Janeway Lesions
Osler Nodes
Subungual hemorrhages
Petechiae

Question 19

Roth Spot

Answer 19

a white-centered hemorrhage (cotton wool spot surrounded by hemorrhage)
Cotton wool is ischemic bursting of axons
Hemorrhage is ischemic bursting of a pre-capillary arteriole.
Not specific to bacterial endocarditis!

Question 20

Janeway Lesions

Answer 20

nontender, erythematous, hemorrhagic, or pustular lesions, often on the palms or soles.

Question 21

Oslers nodes

Answer 21

tender, subcutaneous nodules, often in the pulp of the digits or thenar eminence

Question 22

Other Signs of Infective Endocarditis (12)

Answer 22

Splenomegaly
Stiff neck
Delirium
Paralysis, hemiparesis, aphasia
Conjunctival hemorrhage
Pallor
Gallops
Rales
Cardiac arrhythmia
Pericardial rub
Pleural friction rub
Subacute native valve endocarditis

Question 23

Subacute native valve endocarditis presentation

Answer 23

Low-grade fever –absent in 3-15% of patients
Anorexia
Weight loss
Influenza-like syndromes
Polymyalgia-like syndromes
Pleuritic pain
Syndromes similar to rheumatic fever, e.g. fever, dulled sensorium (as in typhoid), headaches
Abdominal symptoms, e.g. RUQ pain, vomiting, postprandial distress, appendicitis-like symptoms

Question 24

Transthoracic echocardiography (TTE) for Infective Endocarditis

Answer 24

Noninvasive and exceptionally specific
Cannot image vegetations <2 mm in diameter
20% of patients inadequate due to emphysema or body habitus
Sensitivity ~65% of patients with definite clinical endocarditis
Not adequate for prosthetic valves or detecting intracardiac complications

Question 25

Transesophageal echocardiography (TEE) for Infective Endocarditis

Answer 25

Sensitivity >90% of patients with definite endocarditis
Initial studies false-negative in 6–18% (does not exclude diagnosis; repeat 7-10 days)
More sensitive & accurate for PVE ; myocardial abscess; valve perforation; intracardiac fistulae; R heart pathology

Question 26

Dukes Criteria for rejecting endocarditis

Answer 26

Alternative diagnosis is established
Symptoms resolve and do not recur with ≤4 days of antibiotic therapy
Surgery or autopsy after ≤4 days of antimicrobial therapy yields no histologic evidence of endocarditis

Question 27

Dukes Criteria for definite endocarditis

Answer 27

2 major criteria
1 major criterion & 3 minor criteria
5 minor criteria
Possible infective endocarditis
1 major & 1 minor criteria
3 minor criteria

Question 28

Initial Management for Infective Endocarditis

Answer 28

3-5 sets(2 bottles) of blood cultures within > 60 minutes apart over 24 hrs from different venipuncture sites
Negative BCs at 48-72 hrs require 2-3 repeat culture sets (fastidious versus prior antibiotic Rx in previous 2 wks)
Empiric antibiotic regimen based on most likely microbe
NVE - penicillin G and gentamicin for synergistic coverage of streptococci
IV drug users – nafcillin and gentamicin covering methicillin-sensitive staphylococci and gram negative bacilli
Emergent methicillin-resistant Staphylococcus aureus(MRSA) & penicillin-resistant streptococci - now liberal substitution of vancomycin (versus penicillin based antibiotic)
Prosthetic valve Rx typically a couple weeks longer in duration
Choice of antibiotic for PVE similar for NVE (except S aureus)
PVE associated with MRSA or coagulase-negative staph (CoNS) vancomycin and gentamicin recommended
Withhold empirical antimicrobial Rx if hemodynamically stable with presumed SBE

Question 29

Increased Risk of Mortality for Infective Endocarditis

Answer 29

Increased age
Involvement of aortic value
CHF
CNS complications, all types increase morbidity & mortality
Underlying/chronic medical conditions, e.g. DM
Mortality rates vary with infecting microbe
S aureus 30-40%, except related to IV drug use
Streptococci ~ 10%

Question 30

Prognosis for Infective Endocarditis

Answer 30

Left untreated, generally fatal; overall mortality 14.5%
Cure rates NVE w/ appropriate medical & surgical Rx
S viridans & S bovis infection 98%
Enterococci & S aureus infection in IV drug abusers 90%
Community-acquired S aureus (no IV abuse) 60-70%
Aerobic gram-negative organisms 40-60%
Fungal organisms < 50%
Cure rates PVE w/ appropriate medical & surgical Rx
Rates 10-15% lower for each categories (both early/late PVE)
Surgery more frequently required
~ 60% early CoNS PVE; 70% of late CoNS PVE are curable
Anecdotal reports of resolution of right-sided valvular S aureus infection in IV drug abusers just a few days of oral antibiotics