Lecture 15: Endocarditis and Meningitis Flashcards
What is infective endocarditis
An infection of the encardial surface of the heart
What part of the heart is infective endocarditis most involved in
mostly involved in the heart valves, but the wall of the heart may be involved or infected ion may occur at the site of structural defects
It I’d also very common for patients with prosthetic valves and other foreign materials in their valves
Explain how the heart works
The blood comes up the great veins and gets into the right side of the heart and then down into the right ventricle and is pumped out into the pulmonary truck and goes out to the lungs, comes back through the left atrium into the left ventricle and shut out through the aorta
What are considered acute infections in infective endocarditis
Presenting within 6 weeks, often caused by more virulent organisms that cause more damage more quickly
Ex. S. Aureus, S. pneumoniae
What are considered Subacute infections in infective endocarditis
Presenting from 6 weeks to 3 months
Often caused by organisms of low virulence with gradual destruction of valves
Ex. Viridans (alpha haemolytic) Streptococci
What are considered chronic infections in infective endocarditis
Presenting after more then 3 months
Often caused by organisms of low virulence wirh gradual destruction of the valves
Ex. Viridans (alpha hemolytic) Streptococci
How do Viridans work in infective endocarditis
They are found in the mouth, they produce these sticky substances that enable them to stick onto the side of the teeth, they can also use this sticky substance to hang on in the heart valves
What is the epidemiology of endocarditis
Infective endocarditis is very rare; approximately 20 cases per year might be seen at the QEII
What type of hearts does endocarditis take place on
Normal and abnormal heart valves and on congenital abnormal hearts
What bacteria typically infects normal hearts with endocarditis
S. Aureus (a highly virulent bacterial)
What is most likely to cause endocarditis on abnormal valves and where are these organisms most common
Low virulence, oral and skin microorganisms are more likely to cause infection on abnormal valves (e.g. alpha hemolytic streptococci, enterococci, and coagulase negative staphylococci).
Most common in the oral and gastric flora and produce capsular materials to aid in sticking to teeth (and heart valves)
What is the most common organism to cause native valve IE
Alpha haemolytic (“Viridans”) Streptococci
What are the risks of infection in prosthetic valves
They are most susceptible and may be infected by all of the above in addition to bacteria contaminating the valve at the time of its insertion
Ex. Coagulate negative staphylococci are commonest in PV IE
What is bacteremia
Bacteria circulating in the blood
Describe the steps in the pathogenesis of Endocarditis
- Mucous membranes and skin are colonized
- Trauma results in bacteremia
- Organisms adhere to roughed endocardial surfaces
- Adherence is promoted by fibrin, platelet aggregation, and endothelial damage
- Further platelet fibrin depositions takes place
- Bacteria divided begins and vegetations (looks like warts) develop
- Vegetations develop with dormant organisms at the centre
- As vegetation fragment, parts break off into the blood stream and embolism other organs (ex., brain or kidney)
What are the consequences of infection of the heart valves
Cauliflower vegetations may develop on the valves, and impair normal valve function or mat break off into the systemic circulation
Ongoing inflammation may destroy the valve and produce valvular insufficiency
Small emboli may enter the coronary arteries and cause myocardial infarction
Abscesses may develop in the heart muscle which impair electrical conduction
What are the consequences in the brain of endocarditis
The cortex may be showered with multiple micro-emboli (block vessels in the brain from blood clots) regulating in the development of confusion or coma
Large emboli may produce a stroke
Large emboli may occasionally result in one or more brain abscesses
Meningitis may occur from ongoing bacteraemia or emboli
What are the consequences in the kidney of endocarditis
Large emboli may break off and obstruct renal arteries
Immune complexes (bacterial antigens, complement and immunoglobulin) may cause renal kidney inflammation and damage
Can endocarditis affect the spleen
yes, emboli from large vegetations may go to the spleen, extremities, eye, or other organs
In endocarditis occasionally involved blood vessels will ____ and result in ___
weaken
stretching and bursting
What are janeway lesions
They are peripheral emboli that look like black dots on the skin or under nails
What increases the risk of developing endocarditis
previously recognized valvular heart disease
Preceding dental or other surgical procedures
Intravenous drug use (Encouraging bacteria to get into the blood)
Recent heart surgery
Long standing indwelling lines
How is endocarditis diagnosed
Blood cultures: they are positive in approximately 90% of cases
Negative cultures may occur with prior treatment or with organisms that do not grow in blood cultures
Echocardiogrpahy (looking at the action of heart in real time) it recognizes vegetations, if valves are moving abnormally
What is the treatment for endocarditis
The treatment is customized for every patient and depends on;
- They type of organism and its susceptibility pattern
- The presence or absence of foreign material (harder to treat)
- The feasibility of surgery
- Allergies, toleration of the therapy and convince
