Describe the most commonly used classification scheme.
- Clinical course (most commonly used)
Acute Bacterial Endocarditis (ABE):
• Fulminant infection caused by virulent and
invasive organisms
• Ex: Staphylococcus aureus
• Can occur on previously healthy native valves
Subacute Bacterial Endocarditis (SBE):
• Infection with less virulent organisms
• Ex: viridans group streptococci
• Usually occurs on previously damaged valves
Describe the “host substrate” classification scheme.
- Host substrate
Native valve:
• 60-80% of cases of IE
Prosthetic valve
• Coagulase-negative staphylocci are common cause
IV drug abuse:
• right-sided heart valve endocarditis
• 30X risk
Describe the infecting organism classification scheme.
- Infecting Microorganism:
• Gram-positive organisms cause the vast majority
of cases of IE
Name 6 steps in the pathogenesis of IE?
Endothelial Damage, Sterile Thrombus, Adherence of bacteria, microcolony formation of bacteria, vegetation, complications
What are some examples of endothelial damage that may lead to IE?
75% have underlying
abnormality:
- Rheumatic valvular disease
- Mitral valve prolapse
- Cardiomyopathy
- Congenital heart disease
- Hardware
What kinds of things lead to a sterile thrombus?
Thrombus formation:
- Platelet adherence
- Fibrin deposition
- Forms sterile vegetation
What kinds of things can lead to the adherence of bacteria to the sterile thrombus? What enables the microbes to form a microcolony then vegetation?
- Tooth brushing/dental procedures
- IV catheters
- IV drug abuse
- Spread from other infected systems
- Bacteria adept at escaping the innate immune response will have an advantage
- Organisms that adhere to endothelial and platelet surfaces have an advantage
- Reproduce protected within thrombus
What are some complications of IE?
- Valvular damage/abscess formation
- Thrombotic/septic emboli
- Immune injury
How can SLE lead to IE? What is this called?
Endocarditis of Systemic Lupus Erythematosus (Libman-Sacks Disease):
- Small sterile vegetations on the mitral and tricuspid valves seen SLE patients
- Can cause fibrosis and serious valvular deformity.
What is the clinical picture of ABE? SBE?
ABE:
- High fever
- Shaking chills
- Rapid progression
SBE:
- Low-grade fever
- Non-specific symptoms (fatigue, anorexia, weakness, myalgia, night sweats)
What are some categories of physical findings in IE?
Cardiac, emboli related, peripheral stigmata, mycotic aneurysm
What are some cardiac related physical findings in IE
- Murmur: underlying or IE-induced damage
- Tricuspid regurgitation: common in IVDA IE
- Signs of heart failure due to valvular damage
What are some emboli related physical findings in IE
- CNS: neurologic findings in 40% of IE cases
- Kidney: flank pain, hematuria, renal failure (may
also me immune mediated)
• Lungs: septic pulmonary emboli or pneumonia
Mycotic aneurysm in IE
• Aneurysm caused by bacterial infection of
arterial wall
• May form in aorta, viscera, CNS, other organs
What are some Peripheral stigmata associated with IE? What are they?
• Skin findings resulting from septic embolism or immune complex vasculitis.
Petechiae on skin or mucosal surfaces Splinter hemorrhages beneath nails Janeway lesions: discolorations on palms and soles Osler nodes: nodules on fingers and toes Roth spots: emboli to the retina
What lab findings are there in IE?
• Positive blood cultures
- Elevated WBC with left shift
- Elevated erythrocyte sedimentation rate
- Elevated C-reactive protein
What diagnostic tests can be performed to verify IE?
Transthoracic echocardiography (TTE): Useful for detecting large vegetations, non-invasive, but insensitive (90% sensitivity).
What is used to diagnose IE? What does it require?
- 2 major criteria
- 1 major and 3 minor criteria
- 5 minor criteria.
What are the major criteria in the duke criteria?
Positive blood culture
Evidence of endocardial involvement
What are the two ways to get a positive blood culture?
A. Typical microorganism for IE from 2 separate blood cultures
- Viridans streptococci, Streptococcus bovis, HACEK group; or
- Staphylococcus aureus or enterococci, in the absence of a primary focus
B. Microorganisms consistent with IE from persistently positive blood cultures
• Blood cultures drawn >12 hours apart, or
• All of 3, or most of 4 separate cultures drawn at least 1 hour apart
• Single positive blood culture for Coxiella burnetii or antiphase I IgG antibody titer >1:800
What are the two ways to evidence endocardiac involvement?
A. Echocardiogram positive for endocarditis:
- Oscillating intracardiac mass, or
- Myocardial abscess, or
- New partial detachment of prosthetic valve
B. New valvular regurgitation
What are the minor criteria in the duke criteria?
- Predisposing cardiac condition or IV drug use
- Fever (≥38.0°C)
- Vascular phenomena (septic arterial or pulmonary emboli, mycotic aneurysm, intracranial hemorrhage, conjunctival hemorrhage, Janeway lesions)
- Immunologic phenomena (glomerulonephritis, Osler nodes, Roth spots, rheumatoid factor)
- Positive blood cultures not meeting major criteria, or serologic infection of organism consistent with IE
What are the HACEK group of organisms? Why are they significant?
HACEK group organisms:
~3% of endocarditis
Often difficult to culture
- Haemophilus spp.
- Aggregatibacter actinomycetemcomitans
- Cardiobacterium hominis
- Eikenella corrodens
- Kingella spp.
What are the most common gram negative bacteria that cause IE? Fungi? What is the most common organism found in IV drug users with IE? What is seen almost exclusively in IV drug users?
• The most common Gram-negative organisms isolated are
E. coli and Pseudomonas aeruginosa
- Candida spp. is the most common fungal isolate
- The most common organism found in IV drug users is
S. aureus (particularly MRSA), followed by β-hemolytic
streptococci, fungi, and Gram-negative bacilli
• Candida parapsilosis is seen almost exclusively in IV drug
users.
