Flashcards in Ebright: Infective Endocarditis Deck (48):
Infection of the endocardial surface of the
Implies the physical presence of
microorganisms in the lesion
Organism location (6)
• Heart valves (most common)
• Septal defects
• Mural endocardium
• Arterio-venous shunts
• Arterio-arterial shunts (patent ductus arteriosus –
persistent communication between left pulmonary
artery and the descending aorta)
• Coarctation of aorta
• Approximately 1 case per 1000 hospital admissions
• More than 50% of cases are older than 50 years
• Males more commonly affected (ratio 1.7:1)
Epidemiology - Valve Involved
• mitral 28-45%
• aortic 5-36%
• mitral/aortic combined 0-35%
• tricuspid 0-6%
• pulmonic <1%
Epidemiology - Association with Underlying
Rheumatic heart disease:
Congential heart disease:
IE essentially does not occur with:
Rheumatic heart disease (25%)
•mitral most common
Congential heart disease
•patent ductus arteriosus, ventricular septal defect,
coarctation of the aorta, tetralogy of Fallot
•congenitally bicuspid aortic valve (20% of cases >age 60 poor prognosis)
*IE essentially does not occur with secundum atrial
defects (low-pressure shunt; little turbulence)
Epidemiology - Association with Underlying Valvular
“Degenerative” cardiac lesions
“Degenerative” cardiac lesions (30-40% cases without underlying valve disease)
• Ex: calcified mitral annulus, post myocardial infarction, thrombus
•syphilitic heart disease
•intracardiac pacemaker wires
•intravenous drug abuse
•mitral valve prolapse with mitral regurgitation
What results in deposition of platelets
Turbulent flow results in deposition of platelets
and fibrin (nonbacterial thrombotic endocarditis).
Non-bacterial thrombotic endocarditis (NBTE)
What is a prerequisite for bacterial colonization?
What are pathogenic mechanisms?
Found most frequently on which side of cardiac valve?
Along what line?
• Alteration of valve surface is prerequisite for bacterial colonization
• Found in many conditions causing acute/chronic illness
• Hypercoagulability and/or endothelial damage are
• Found most frequently on low-pressure side of cardiac valve
• Along the line of closure
Lesions with high degrees of turbulence readily create conditions that lead to bacterial colonization
*low flow states (secundum atrial defects) rarely associated with IE
Where does it occur?
How long does it usually take to clear the bloodstream?
What can the bacteria in the bloodstream then do?
• Occurs when mucosal surface heavily colonized with bacteria is traumatized
• Bloodstream is usually clear 15-30 minutes after the procedure
• Bacteria in bloodstream can then colonize NBTE lesions
Microorganism - NBTE Interaction
How do organisms differ?
What do bacteria do once they bind?
What does vegetation create?
• Organisms differ in their propensity to cause (Infective Endocarditis) IE
• Once bacteria bind they proliferate, causing further platelet –fibrin deposition.
• Vegetation creates an environment of impaired host resistance (bacteria covered by platelets/fibrin)
• Stimulation of humoral and cellular immunity
• Rhematoid factor can be positive
• Antinuclear antibodies can be present
• Circulating immune complexes
Vegetation located along line of closure of valve leaflet
– valve ring abscess
– perforation of valve leaflet
– myocardial abscesses (20%)
– rupture of chordae tendinae, interventricular
septum, papillary muscle
– valvular stenosis (large lesions)
– myocardial infarction (40-60% of autopsied
• glomerulonephritis (focal or diffuse)
secondary to immune complex deposition
Usually develop during:
Tend to occur where?
Mechanism leads to:
direct bacterial invasion:
embolic occlusion of:
immune complex deposition:
Clinically silent until:
• Usually develop during active disease, but can occur
months to years later
• tend to occur at bifurcation points
• mechanism leading to aneurysm
• direct bacterial invasion of arterial wall with
• embolic occlusion of vasovasorum
• immune complex deposition with injury to
• Clinically silent until rupture occurs
Lung (Rt. Sided)
Central nervous system
• cerebral emboli (1/3 of cases)
•also mycotic aneurysms, cerebritis, abscesses
•infarctions common (but usually clinically silent)
Lung (Rt. Sided)
•Osler’s nodes (immune complex)
•Janeway lesions (septic emboli)
Average: Symptom onset to diagnosis
Process contributing to the clinical picture (4)
“Incubation period” 2 weeks but time from symptom onset to diagnosis averages 5 weeks (and depends on causative organism)
Process contributing to the clinical picture
– infectious process on the valve
– bland/septic emboli to any organ system
– constant bacteremia (with metastatic foci)
– circulating immune complexes
• Usually remittent
• absent in: CHF, renal failure, older age,
terminal illness, prior antibiotic therapy
• anorexia, weight loss, fatigue, chills,
weakness, nausea, vomiting, night sweats
• often result in incorrect initial diagnosis
Heart murmur (85%)
(classically a new or changing murmur)
Peripheral manifestations (3):
Peripheral manifestations (50%)
Osler’s nodes: small painful nodular
lesions on the pads of fingers/toes or
thenar eminence 0-25%
(immune complex deposition)
Janeway lesions: hemorrhagic, macular,
painless plaques with predilection for the
Roth spots: oval, pale, retinal lesions
surrounded by hemorrhage, usually near
the optic disk
Major embolic episode
• Splenomegaly 25-60%
• Musculoskeletal complaints
• Major embolic episode to any organ system
Central Nervous System %?
Major cerebral emboli %?
Subarachnoid hemmorhage due to:
• Central Nervous System 20-40%
• Major cerebral emboli 10-31%
• subarachnoid hemorrhage due to
• cranial nerve palsies
• toxic encephalopathy
Renal failure %
• Renal failure 25-35%
Clinical Manifestations in
Injection Drug Users
What is the most common valve affected?
Often present with what?
• tricuspid valve most common
• often present with prominent
pulmonary findings (septic emboli
• often occurs on otherwise normal
• Anemia common 70-90%***
• thrombocytopenia 5-15%
• leukocytosis 20-30%
• sedimentation rate (ESR) nearly
always elevated 90-100%
Red Cell Casts:%
• proteinuria (50-65%)
• microscopic hematuria (30-60%)
• red cell casts (12%)
• gross hematuria
• white cell casts
What is the bacteremia?
What occurs in >90% of the cases?
Less likely to be positive if:
Procedure for collecting blood cultures:
• most important lab test
• bacteremia usually continuous
• In >90% of cases the first 2 sets of blood cultures drawn will yield the organism responsible
• less likely to be positive if patient has received antibiotics in the prior 2 weeks
• procedure for collecting blood cultures – 3 sets within 24 hours (3 separate venipunctures)
What is the most important lab test?
Can visualize vegetations greater than 2 mm in size
Transesophageal echocardiogram (TEE)
What does the negative study not include?
What are rare?
Valuable to assess:
Are patients with vegetation at increased risk of embolization?
•Negative study does not exclude IE
•False-positive results are rare
•Dependent upon experience of technician/reader •Valuable to assess local complications of IE (valve ring abscess)
•Better for visualizing aortic valve than 2D Echo •Patients with vegetations are not at increased risk of embolization.
Combination of clinical and diagnostic criteria used to classify as definite, possible, or not IE.
A common cause of what?
Comprised of what?
Most common cause of endocarditis in pts with:
• typically subacute
• 80% have underlying valve disease
• a common cause of IE (dental procedures)
• many species comprise the viridans group of
• good prognosis
• most common cause of endocarditis in
patients with mitral valve prolapse
Easy to treat?
Commonness of peripheral manifestations:
Seen in what population?
• increasingly common cause of endocarditis
• very difficult to treat
• usually subacute
• peripheral manifestations uncommon
• seen in older men after genitourinary procedures
and young women after obstetrical procedures
Often in what population:
• unusual cause
• usually fulminant (suddenly or quickly)
• predilection for aortic valve (70%)
• often alcoholics
• many have meningitis (70%)
• poor outcome (50% mortality)
(Gram-positive cocci in clusters)
Causes what % of staph endocarditis?
• coagulase-positive staphylococci (S. aureus)
• causes 80-90% of cases of Staphylococcal
• commonly attacks “normal” heart valves (1/3 of
• prognosis poor (40% mortality)
More commonly causes what?
Metastatic infection to where is common?
In what population?
• more commonly causes myocardial abscess,
purulent pericarditis, and valve ring abscesses
than other causes of IE
• metastatic infection to lung, brain, spleen,
• common causes of IE in injection drug users
but in IDU has less fulminant course with
(Gram-positive cocci in clusters)
Common cause of what?
Can cause what in neonates?
• common cause of prosthetic valve endocarditis
• can cause endocarditis in neonates
• medical and/or surgical therapy usually
What is common?
Commonly require what? Where? Why?
• uncommon but increasing
• risks: injection drug users, prosthetic valve
• CHF common
• prognosis poor (70-80% mortality)
• commonly require early valve replacement,
especially left-sided disease due to Pseudomonas spp.
Requires how long to grow?
HACEK stands for:
• Fastidious; require 2-3 weeks to grow
H Haemophilus aphrophilus
A Actinobacilus actinomycetemcomitans
C Cardiobacterium hominis
E Eikenella corrodens
K Kingella kingae (and other species)
• subacute course
• need to alert microbiology lab to supplement media and hold cultures longer
• injection drug users
• patients after reconstructive cardiovascular
• patients after prolonged IV/antibiotic therapy
• cure virtually impossible without surgery
Surgery if (5):
• Prolonged course of antibiotics (4-6 weeks) with bactericidal
agents directed against the specific pathogen
• Surgical intervention indication if:
– congestive heart failure unresponsive to medical therapy
– greater than 1 major systemic embolic complication
– inability to clear organism from blood stream (time varies with organism and antimicrobial used)
– prosthetic valve endocarditis, esp. early (usually)
– certain hard to cure organisms e.g. fungi, Pseudomonas species
Infection of endocardial surface of the heart
Direct infection of “normal” endothelium by
highly virulent organisms (S. aureus)
Secondary infection of damaged endothelium
and platelet-fibrin thrombus during
subsequent bacteremic periods
Most common bacteria:
• Most common are bacteria, such as S. aureus,
viridans streptococcus, and enterococcus
species (high binding potential)
• Less common are other organisms such as
HACEK, gram negative bacilli (pseudomonas),
pneumococcus, chlamydia, and fungi
CLINICAL ILLNESS (3)
2. Systemic (constitutional)
• Persistent, continuous bacteremia
• Blood cultures are “always” positive