Infective endocarditis Flashcards
What is infective endocarditis?
Infection involving the endocardial surface of the heart, including the valvular structures, the chordae tendinae, sites of septal defects, or the mural endocardium
What are risk factors for infective endocarditis?
- Previous episode of endocarditis (strongest)
- Prev normal valves (50% typically acute presentation)
- Rheumatic valve disease (30%)
- Prosthetic valves
- Congenital heart defects
- Intravenous drug users (IVDUs, eg. typically causing tricuspid lesion)
What are other differential diagnoses for infective endocarditis?
- Rheumatic fever → pts w/ rheumatic heart disease may present very similarly with predominantly constitutional symptoms
- Atrial myxoma → pts may present w/ constitutional symptoms 2o to cytokine release or have systemic disease 2o to embolic phenomenon. Often pts will describe waxing and waning symptoms as opposed to the subacute progressive nature of IE
- Non-bacterial thrombotic endocarditis (NBTE) → endocarditis in which sterile vegetations are deposited on cardiac valves. Most common tumours producing NBTE are pancreatic, lung + colon, so pts may report signs and symptoms consistent with those underlying conditions
What are the most likely organisms to cause infective endocarditis?
- Staph aureus (mortality: 30%)
- Strep viridans (mortality: 5%)
HACEK
Rarely gram -ve bacteria can cause infective endocarditis.
Which are the gram -ve bacteria?
- Haemophilus species
- Actionbacillus actinomycetemocomitans
- Cardiobacterium hominis
- Eikenella corrodens
- Kingella species
What are clinical features of infective endocarditis?
SEPTIC SIGNS
- Fever, rigors, night sweats
- Malaise
- Weight loss
- Anaemia
- Splenomegaly
- Clubbing
Which cardiac lesions may be present in someone with infective endocarditis?
- New murmur or change in pre-existing murmur should raise suspicion to IE
- Vegetations may cause valve destruction + severe regurgitation, or valve obstruction
- An aortic root abscess causes prolongation of the PR interval, and may lead to complete AV block
- LVF is a common cause of death
What are the clinical features resulting from immune complex deposition?
- Vasculitis may affect any vessel
- Microscopic haematuria is common; glomerulonephritis + AKI may occur
- Roth spots on fundoscopy (oval, pale, retinal lesions surrounded by haemorrhage)
- Splinter haemorrhages
- Osler’s nodes (small, painful, nodular lesions usually found on pads of fingers/toes)
Which embolic phenomena may occur with IE?
Emboli may cause abscesses in relevant organ eg. brain, heart, kidney, spleen, gut, skin (termed Janeway lesions)
The time-frame can be classified as acute or subacute.
Describe features of the acute presentation
- Typically over period of days to weeks
- Characterised by spiking fevers, tachycardia, fatigue + progressive damage to cardiac structures
- Classical immunological features (Oslers nodes) are uncommon due to rapid onset of disease process
Describe features of the subacute presentation
- Typically develops over course of weeks to months
- Patients present w/ fever + chills, non-specific constitutional symptoms (night sweats, malaise, fatigue, anorexia, weight loss, myalgias) or palpitations
- Physical examination reveals more classic immunological features
What is the modified Duke criteria?
Diagnosed if any one of the below:
- pathological criteria positive
- 2 major
- 1 major and 3 minor
- 5 minor
What is the pathophysiology of IE?
- IE typically develops on valvular surfaces of heart
- Turbulent blood flow → sustained endothelial damage
- Platelets + fibrin adhere to underlying collagen surface → prothrombotic mileu
- Bacteraemia leads to colonisation of thrombus
- Perpetuates further fibrin deposition and platelet aggregation
- Develops into mature infected vegetation
Which bedside investigations should be done for IE?
- Urine dip → microscopic haematuria
- ECG → ?heart block
Which bloods should be done for IE?
- FBC → normocytic, normochromic anaemia / neutrophilia
- ESR → raised
- RF → +ve (immunologic phenomenon in minor criteria)
- U+Es → baseline
- Blood cultures → 3 sets obtained in 1hr apart prior to initiating ABx
