Lecture 22: Fever and a New Murmur (Endocarditis) Flashcards
What are the symptoms/signs of endocarditis?
Endocarditis include:
- Symptoms and signs of infection
- Embolic phenomena (blockage of blood vessels causing splinter hemorrhage)
- Abnormal heart valve (source of splinter hemorrhage)
A 39 year old Samoan/Niuean man presents with a fever and lethargy for the past 2 weeks (gradually worse, problems may be before symptomatic). On examination he has a fever, splinter haemorrhages and an early diastolic murmur.
What does the end diastolic murmur suggest?
Aotic valve leaking (sound of blood going back into the Left Ventricle from the aorta)
Infective endocarditis can present with Embolic features
4 embolitic features include…
- Splinter haemorrhage (tiny blood clots that tend to run vertically under the nails),
- Conjunctival petechiae (haemorrhage),
- Osler’s node (painful, red, raised lesions found on the hands and feet),
- Janeway’s lesion (non-tender, small erythematous or haemorrhagic macular or nodular lesions on the palms or soles)
= these lesions can just be called embolic phenomena
They all involve blocked, thrombosed then haemorrhagic lesions
Describe the Pathogenesis of Endocarditis
- _Turbulent flow t_hrough abnormal valve, due to congenital abnormality, nodules from rheumatic heart disease, trauma to heart valve, etc
- Platelets and fibrin attach to damaged valvular epithelium forming sterile vegetations
- Transient bacteraemia arising from mouth, skin, gut, urinary tract, etc, seeds bacteria onto s_terile vegetations_ (small possibility of sticking onto platelets and fibrin clot)
-
Infected vegetation enlarges and sheds i_nfected emboli_ and leads to valvular destruction
- Viridans streptococci has slower rate of infection, so vegetation has time to grow and shed;
- Staphylococcus aureus has faster rate of infection, so valves ruptures (dies in 1-2 hours) before vegetation breaks
What are the 3 groups/bacteria that can cause endocarditis?
1) Viridans streptococci **
2) Staph Aureus
3) Enterococcus faecalis
Why do we need antibiotics to cure endocarditis? Why is our immune system insufficient?
Heart valves d_o not have capillaries_, thus no infiltration of neutrophil (need blood leakage to leak neutrophils).
Generally, blood comes from lungs delivered by pulmonary veins into left ventricle (speed does not allow neutrophil to stick to valves).
Endocarditis cannot be cured without antibiotics due to minimal neutrophil infiltration! Bacterial infection with ~100% mortality rate.
How do you diagnose endocarditis?
Document (Continuous Bacteraemia)
1) Is there vegetation on his heart valve?
2) Can we find organisms in his blood stream?
- High concentration of bacteria in and on vegetation, with bacteria (little amount) continually shed from vegetation into blood.
- Therefore the organisms will be seen in the blood
- Unlike infection in other areas e.g. teeth
- Constant bacteraemia, therefore expect all blood cultures to be positive (with an organism likely to cause endocarditis)
- Culture blood on 3-4 occasions at least 20 mins apart (90-100% +ve)
- (Culture excised valve)
- Organism is usually identified in about 95% cases.
Define Bacteraemia
Bacteria cultured from blood sample/the presence of bacteria in the blood.
What are the 3 types of Bacteraemia?
True Bacteraemia (Continuous or Intermittent)
- Pathogen cultured (S. Aureus, E. Coli, S. Pneumoniae, etc)
- Sometimes m_ore than one_ set of blood cultures positive
- Clinically compatible infective source identified
Contaminant Bacteraemia
- Skin commensal cultured (Staphylococcus epidermidis, etc)
- Only one set of blood cultures positive
- No apparent infective source
Transient Bacteraemia
- Gut or mouth organism cultured
- Blood cultures only positive briefly
- No apparent infective source
Diagnose
A 39 year old Samoan/Niuean man presents with a fever and lethargy for the past 2 weeks. On examination he has a fever, splinter haemorrhages and an early diastolic murmur.
Investigation shows infection on heart valves results in continuous bacteraemia.
Therefore, collect three sets of blood cultures over next few hours, expect that all will grow the same microbe
What other investigations could you do?
Endocarditis
Investigation shows infection on heart valves results in development of vegetations, that impair valve function
- Listen for a murmur (usually regurgitant)
- Perform an echocardiogram
- Look for evidence of emboli (fragments of vegetation that have blocked distal arterioles)
Describe the Treatment of Endocarditis
- Antibiotic is dependent on organism
- Therefore it is very important that we get this right.
- Method of administration is always IV
- Dose is always high dose
- Duration is usually at least 2 weeks, often 4 weeks
- Cure rate is usually 70-90%
1) Antimicrobial Agent
- Activity against organism:
- Sensitive or resistant
- Exquisitely sensitive or just sensitive (how much antibiotics is needed)
- Bactericidal or bacteristatic (kills bacteria or just stop them from growing)
- In this case we must kill it
2) Dose and Method of Administration
- Concentration of agent at site of infection (oral or IV, dose)
3) Duration of Treatment for Cure and Prevention of Relapse
- Speed of bacterial killing and contribution of host defences to eradication of infection (few or many weeks)
Viridans streptococci is _______ haemolytic streptococci
Alpha haemolytic (green)
(not a type of streptococci)
Viridans means producing alpha haemolysis (green). Viridans streptococci generally reside in mouth.
Describe the susceptibility Of Viridans Streptococci To Penicillin (MIC Distribution)/Serum Levels After Penicillin 3g (5mu) IV
How much dose and for how long must we treat people with endocarditis?
Both duration and dose are important! Current treatment is penicillin 3mU 6rly for 28 days
Treatment of endocarditis caused by a viridans streptococcus
1) Drug
2) Dose
3) Fequency
4) Method of administration
5) Duration
1) Penicillin
2) High dose (higher than MIC?)
3) 4-6 hours
4) Intravenously
5) Some weeks
Serum Concentrations Of Penicillin During A 24hr Period In Relation To Penicillin Mics For Viridans Streptococci
In an adult treated with 3_g (5Mu) of benzyl penicilli_n IV every 6 hours, level of penicillin in blood will be greater than minimum inhibitory concentrations (MIC) of penicillin for a viridans streptococcus for ~3.5-4.0 hours after each dose, i.e. for ~14-16 hours in a 24 hour period.
Describe the usefulness of synergy of antibiotics when treating endocarditis
Antimicrobial Killing
Use a bactericidal drug or drug combination, becausse neutrophils have difficulty entering vegetation.
Sometimes, synergy between two antibiotics is useful.
- Synergy when penicillin is combined with gentamicin in treatment of Viridans streptococci.
- Synergy when amoxycillin is combined with gentamicin in treatment of Enterococcus faecalis
Describe the differences between Rheumatic fever and Endocarditis
Rheumatic Fever and Endocarditis: A Common Area Of Confusion!
Comparison of Rheumatic Fever and Endocarditis
Rheumatic Fever
- Streptococcus pyogenes only pharyngitis (from throat)
- Immunologic damage to valves nodules on valves (no infection)
- Treatment with oral penicillin for 10 days
- Prophylaxis with IM penicillin for many years
Endocarditis
- Viridans streptococci and others mouth commensals (from mouth)
- Infection and vegetation on valves
- Treatment with IV penicillin for one month
- Prophylaxis with oral penicillin when dental work
