Week Four - Case Two Flashcards
what is infective endocarditis
condition caused by infection of the endocardium by bacteria, or rarely fungus. it most commonly affects the heart valves but can occur anywhere along the lining of the heart or blood vessels
where will staph. aureus commonly infect in IV drug users
most commonly infect the tricuspid valve
what is the epidemiology of infective endocarditis
50% of all cases of infective endocarditis will occur on normal valves. This type of infection tends to follow and acute course.
50% of infections occur on abnormal tissue, and these infections will tend to follow a sub-acute course.
what is the mortality rate without treatment
close to 100%
what are the valvular damage risk factors for infective endocarditis
previous rheumatic heart disease
age related valvular degeneration
prosthetic valve
what is the risk factor with IV drug use
more chance of multiple organisms with IV drug users. IV drug users are usually affected at the tricuspid valve, and the right side of the heart
often the endocarditis is less clinically severe in IV drug users
what does endocardial damage lead to
the formation of thrombi at the damaged site
what is the thrombus mainly made up of
platelets and fibrin
where does the endocardial damage tend to occur
The endocardial damage tends to occur around damaged valves, as aberrant jets of blood around these valves cause increased shearing forces in the endocardium, leading to endocardial damage. Also, the valve cusps themselves are avascular, and thus normal immune responses in this region are impaired.
where do these thrombi and IE tend to occur
at sites of high haemodynamic pressure, due to the increased shearing force in these areas.
what are the two factors that are essentially required for infective endocarditis
- the presence of organisms in the blood - many things cause this. common mechanisms include poor dental hygiene, IV drug use, soft tissue infection and iatrogenic causes
- abnormal/unusual endocardial tissue
what do we call it when a thrombi has been colonised by bacteria
vegetation
why is infective endocarditis particularly hard to treat with antibiotics
because the platelets and fibrin in the vegetation prevent antibiotic agent, and white blood cells from being in direct contact with the bacteria
what valves are most commonly affected and why
the aortic and mitral valves are most commonly affected because these exist in a higher pressure system than the tricuspid and pulmonary valves
what infection is more common in drug users
right sided infection - although the mechanism for this is poorly understood
what two symptoms mean it is endocarditis until proven otherwise
if the patient has a new murmur and a fever
what is SBE
IE most commonly presents sub-acute with an insidious course. in this instance it is sometimes refer to as sub-acute bacterial endocarditis
what is the acute presentation of IE
Fever + new heart murmur (90%)
Petechiae (50%)
what are petechiae
these are red/purple spots of 1-2mm in diameter.
they often form at sites of trauma, and in this instance they will usually disappear within a couple days.
extreme bouts of vomiting, coughing or crying can also produce them around the eyes.
they mat also be a sign of low platelet count
what are petechiae caused by
bleeding under the skin - they are non-blanching
what type of failure can develop rapidly
Cardiac / renal failure can develop rapidly (50-70%)
Haematuria secondary to renal failure present in about 70% of patients
what are splinter haemorrhages
red lines that run vertically along the nails.
a non-specific sign often associated with rheumatologic conditions as well as infective endocarditis
