Infective Endocarditis

Question 1

What is the etiology of infective endocarditis

Answer 1

Endocarditis is usually the consequence of two factors: the presence of organisms in the bloodstream and abnormal cardiac endothelium facilitating their adherence and growth. Although bacteraemia may occur there is no good evidence that it leads to infective endocarditis. Damaged endocardium promotes platelet and fibrin deposition which allows organisms to adhere and grow, leading to an infected vegetation.

Question 2

What are the clinical presentations for infective endocarditis

Answer 2

The clinical presentation of infective endocarditis is dependent on the organism and the presence of predisposing cardiac conditions. Infective endocarditis may occur as an acute, fulminating infection but also occurs as a chronic or subacute illness with low-grade fever and nonspecific symptoms. A high index of clinical suspicion is required to identify patients with infective endocarditis and certain criteria should alert the physician.
High clinical suspicion:
New valve lesion/(regurgitant) murmur
Embolic event(s) of unknown origin
Sepsis of unknown origin
Haematuria, glomerulonephritis and suspected renal infarction
‘Fever’ plus:
– Prosthetic material inside the heart
– Other high predisposition for infective endocarditis, e.g. i.v. drug use
– Newly developed ventricular arrhythmias or conduction disturbances
– First manifestation of congestive cardiac failure
– Positive blood cultures (with typical organism)
– Cutaneous (Osler, Janeway) or ophthalmic (Roth) manifestations
– Peripheral abscesses (renal, splenic, spine) of unknown origin
Low clinical suspicion
Fever plus none of the above.

Question 3

What are some investigations to be made when infective endocarditis is suspected

Answer 3

Investigations are required to confirm the diagnosis of infective endocarditis; to identify the organism to ensure appropriate therapy; and to monitor the patient’s response to therapy. Echocardiography is an extremely useful tool if used appropriately. A negative echocardiogram does not exclude a diagnosis of endocarditis. It is not an appropriate screening test for patients with just a fever or an isolated positive blood culture, where there is a low pre-test probability of endocarditis.
Blood cultures
3 sets from different venepuncture sites
FBC - Reduced haemoglobin, increased white cells, increased or reduced platelets
Urea and electrolytes - Increased urea and creatinine
LFTs - Increased serum alkaline phosphatase