Infective Endocarditis Flashcards
What is infective endocarditis and how can it be described?
Infective endocarditis is an infection of the endocardium of the heart usually involving the heart valves.
It can be described as low and high virulence depending on the causative organism.
Which patients are prone to IE?
Low virulence
Patients with previous heart valve damage (usually following rheumatic fever).
Patients with heart valve replacements and those with CHD.
Poor dental hygiene (cause of bacteraemia particularly strep viridens).
High Virulence
IV drug use (staph. aureus), note will also often have pulmonary infective emboli.
What are the clinical features of IE?
History:
Systemic symptoms of infection (malaise, night sweats, rigors) with a transient high temperature.
Embolisms (infarct of distal organ or spread of infection)
O/E:
New onset or changed heart murmur.
Immune complex depositions:
Oslers nodes. (Tender red nodes in the finger pulps)
Janeway Lesions. (Painless palmar nodes)
Roth spots. (A pale area surrounded by haemorrhage seen on the retina)
Splinter haemorrhages.
Splenomegaly.
What are the common causative organisms?
Bacteria:
Strep Viridans (most common) Lower virulence associated with poor dental hygiene
Staph Aureus High Virulence (IV drug use)
Other streptococci.
Gram -ve IE is rare.
Fungi:
Candida
Aspergillus
Histoplasma
What are the morphological changes seen on a heart valve?
Normally made of endothelium, elastic tissue and collagen (contains no vascualture)
When damaged it becomes vascularised more collagenous tissue is laid down and it is then calcified and distorted.
What are the pathological complications of IE?
Valvular Incompetency which may lead to heart failure.
Vegetations on the heart valves (infective plaques) can embolise and cause a distal infarct and spread the disease.
Common embolism sites:
Left side: Brain, Spleen, Kidneys.
Rt Side: Pulmonary abscesses.
Glomerulonephritis: Immune complexes against the causative organisms antigens form and can occur in the kidney causing a form of glomerulonephritis.
What important investigations should be done in IE?
Blood cultures:
2 separate blood samples at different times within an hour in symptomatic IE.
In sub acute/chronic 3 samples should be taken 6 hours apart.
In IE bacteraemia is continuous therefore samples should all be positive.
Echocardiograph: To assess heart valves
ESR/CRP: General markers of infection therefore should be raised.
FBC: Can cause normocytic anaemia, neutrophil leucocytosis and thrombocytopenia
Renal Function Test: To assess whether there has been any renal complications (glomerulonephritis)
What are the general principles of managing IE?
Must be 2 positive blood culture tests, sensitivities assessed.
Empirical treatment before sensitivities are back is:
benzylpenicillin + gentamicin (+ flucloxacillin if acute) IV for 4 weeks.
What are the indications for surgery?
A surgical opinion should be sought for any of the following indications:
IE in patients with prosthetic heart valves and heart failure
Aortic or mitral IE with:
Severe acute regurgitation or valve obstruction causing refractory pulmonary oedema/shock (emergency).
Fistula into a cardiac chamber or pericardium causing refractory pulmonary oedema/shock (emergency).
Severe acute regurgitation or valve obstruction and persisting heart failure or echocardiographic signs of poor haemodynamic tolerance (urgent).
Severe regurgitation and no heart failure (elective).
