Endocarditis Flashcards
What is Infective Endocarditis
A destructive process that affects mostly valves, leads to CHF, embolization and death if untreated
How to diagnose Endocarditis
Blood Tests 95% of cases
What are the causes of Endocarditis
Bacterial - Staphylococcus aureus and Streptococcus viridans cause > 80%, Yeast or Fungal infections
Where does Endocarditis occur?
Mostly valves, also paps or endocardial surface of ventricles, catheters, pacemaker wires, prosthetic materials
What is the classic presentation of Endocarditis?
Vegetations usually on the low pressure side of the valve(flow side) which is the atrial side for MV/TV and ventricle for PV/AOV
What does Endocarditis look like?
Shaggy smudgy, pedunculated, usually highly mobile and can seed other areas. Vegetations vary widely in appearance
what are the consequences of bacteria forming a plaque in heart valve?
Heart failure
Septicaemia with possible septic shock
Blood vessel blockage – tissue death
how does this happen?
Cant open properly
Can cause blockage
results in tissue death
what can predispose you to endocarditis?
Damaged heart valves
Replacement heart valves
Intravenous drug abuse
Long term venous access
Eg cancer patients, ICU patients
Subacute Endocarditis
Subtle presentation- Usually by streptococcus viridans carrying a low grade fever, fatigue, weight loss, cough, weakness, patient may not recognize seriousness of it
Acute Endocarditis
Usually staphylococcus aureus, carrying a high fever, rapid onset of symptoms like heart murmurs and can lead to CHF symptoms
Acute Endocarditis continued
Embolization signs with left heart involvement- petechiae and purpuric skin lesions and Janeway lesions, TIA, CVA
Purpuric skin lesions and petechiae
clumps on legs
Janeway lesions
on palms and soles of the feet
How to diagnose Endocarditis?
FUO, + new murmurs+ blood cultures
Blood cultures not always accurate for endocarditis
multiple samples needed, antibiotics for 2+ days affects results and fungal etiologies often have negative cultures
What size veg can echo detect?
> 3mm
What size veg can TEE detect?
> 1mm
If no veg does that mean no endocarditis?
No, must follow DUKE criteria
what are the major indicators of endocarditis
on criteria of DUKE?
Multiple positive blood cultures
- Typically 3 sets over 24 hours
Positive for typical endocarditis
- associated organism
Positive echocardiogram
- Visualisation of obstructing mass
what are the minor indicators of endocarditis?
Temperature above 38C
Predisposing heart condition
Immunologic phenomena
glomerulonephritis
Vascular phenomena
emboli
Positive blood culture – not fitting with major
Positive echo – not fitting with major
diagnosis based on DUKE criteria
2 major criteria
1 major and 3 minor criteria
5 minor criteria
Complications of endocarditis
Valvular regurgitation that worsens as lesion enlarges, valvular destruction, CHF from severe or acute regurg
Perivalvular abscesses (MV/AOV ring)
extensions of active infective disease, echolucent or echodense areas adjacent to valve apparatus, fistula formation, evaluate with color and doppler carefully, TEE
Perivalvular abscesses - what can happen
Emobization -TIA, CVA, LV wma- pulmonary embolus, pericarditis and pericardial effusion can result, mycotic aneurysm can occur- echolucent but hard to tell from abscess
Can Mechanical and tissue valves be affected by Infective endocarditis?
Yes - shadows and artifacts may impair visualization and perivalvular leaks or dehiscence may cause a rocking motion of the sewing ring
which organism causes 40% of endocarditis?
Viridans streptococci
where is it normally found?
a oral flora
how can infection start?
from brushing teeth with cut up mouth
which organism causes another 15% of infections?
Enterococci
where is it normally found?
gut
which organism causes 30% of infections?
Staphylococcus aureus
which group of people if Staphylococcus aureus infections much higher?
iv drug users
which group of organisms cause 10% of infections?
HACEK group -
Haemophilus aphrophilus
Actinobacillus actinomycetemcomitans
Cardiobacterium hominis
Eikenella corrodens
Kingella kingeae
where are HACEK group found?
oral flora
pathogenesis of endocarditis?
Damaged or inflammed valve
Organism binds to exposed antigens
Eg fibronectin
Immune response with fibrin deposition
Binding of organism to fibrin antigens
how does the infection progress?
the cycle repeats
Formation of growth - “vegetation”
Disrupts valve function
May shed infective fragments
in diagnosis, how is blood drawn for culture?
Clean skin site with alcohol - based wipe (make sure alcohol evaporates)
Draw 5 – 10mls venous blood
how is the blood then processed?
Change needle on syringe
Inject blood into culture vial
Contains liquid culture media
what does culture vial base include to aid diagnosis?
fluorescent dye
how does the dye help?
Dye reacts with products of bacterial metabolism
Fluorescent spectrum of dye changes with such reactions
how is this processed?
Automated system detects spectrum shift
Automated system sounds alarm to indicate possible positive culture
what is done if a culture vial is flagged as positive?
~ 1ml removed
Gram stain
what happens once Gram stain report completed?
Clinical team notified
- Presumptive diagnosis discussed
- presumptive antibiotics discussed
what is done to confirm diagnosis more?
Subculture to solid media
- Purity plate for subsequent identification
what is done to aid antibiotic prescribing?
Disc sensitivity testing
what media is used for the subculture when gram negative bacillus suspected?
GNB’s
MacConkey and chocolate at 37C in 5% CO2
Blood agar at 37C anaerobic
Neomycin Blood agar 37C anarobic
gram negative cocci?
GNC’s
chocolate at 37C in 5% CO2
Blood agar at 37C anaerobic
clumped cells?
GPC’s
Chocolate at 37C in 5% CO2
Blood agar at 37C anaerobic
DNA’ase plate
Plasma solution
chains?
GPC and GPB
Blood and MacConkey at 37C in 5% CO2
Blood agar at 37C anaerobic
what must be passed onto clinical team?
With final identification
With actual sensitivity profile
Allows modification of initial therapy if needed
how long is Normal blood culture incubation?
5 days
why is it increased length of time in endocarditis?
increased to 10 days
Fastidious and slow growing HACEK organisms
what is the standard therapy for Gram positive endocarditis?
a penicillin + gentamicin
what are the roles of each antibiotic?
Penicillin – breaks cell wall
Gentamicin – attacks ribosome and prevent recovering from cell wall damage
what special requirements do Streptococci need in sensitivity testing?
Use “High dose” gentamicin disc
Sensitive streptococci show synergy with penicillin and low dose gentamicin.
Resistant streptococci: no synergy so gentamicin not used
why is Penicillin MIC testing a good idea?
Need an indication of degree of sensitivity
Influences treatment duration
how long is treatment normally?
prolonged; months
how do you check on progress?
But testing blood regularly to insure enough antibiotic are in the blood to kill the specific organism infecting
