Infective endocarditis Flashcards
What is infective endocarditis?
Infection of intracardiac endocardial structures (mainly heart valves, particularly tricuspid) –> valvular damage –> platelet & fibrin adherence –> thrombus formation –> bacterial colonisation of thrombus
- Triad - fever, raised ESR and murmur
How can infective endocarditis be classified?
- Native-valve endocarditis
- Prosthetic valve endocarditis
- Right-sided endocarditis (throws of clots into pulmonary circulation)
- Acute-S. Aureus, days to weeks, spiking fever, tachycardia & fatigue
- Subacute-S. Viridans, weeks to months, vague constitutional symptoms
What causes infective endocarditis?
- Staphylococcus aureus → most common cause of acute IE. IV drug use & patients with prosthetic valves
- Staphylococcus epidermidis (coagulase negative) → if <2 months post valve surgery - Streptococcus Viridans → most common cause of subacute IE. Mainly in predamaged native valves. Common cause following dental procedures
- Streptococcus bovis → predisposes to both infective endocarditis and colorectal cancer.
- Coxiella burnetii → It is relatively uncommon, and found in farm animals; those who have contact with animals, such as farm and abattoir workers, Q fever
(Staphylococcus = in clusters. Streptococcus = in chains)
What are the risk factors for infective endocarditis?
- Abnormal valves (e.g. congenital, calcification, rheumatic heart disease)
- Prosthetic heart valves
- Age > 60
- Turbulent blood flow (e.g. patent ductus arteriosus)
- Recent dental work/poor dental hygiene (source of S. viridans)
- Intravenous drug use - commonly affects tricuspid valve
- Miscarriage, chronic cholecystitis, colonic malignancy and pneumonia
What co-morbid conditions can increase the risk of Infective endocarditis?
- Congenital heart disease e.g. bicuspid aortic valve, pulmonary stenosis, ventricular septal defect
- Previous history of infective endocarditis
- Intravascular devices e.g. central catheters, shunts
- Haemodialysis
- HIV infection
What are the presenting symptoms of infective endocarditis?
- Fever with sweats/chills/rigors (might be relapsing and remitting)
- Malaise
- Arthralgia (joint pain due to septic emboli)
- Myalgia (muscle aches and pain)
- Confusion
- Skin lesions
- Night sweats
- Anorexia
- SOB
- Systemic embolization: CNS, lungs, spleen, kidney liver (all highly vascularised)
What signs of infective endocarditis can be found on physical examination?
- Tachycardia
- Splenomegaly
- Vasculitic Lesions
- Fever
- Roth spots on retina
- Osler’s nodes (painful nodes on finger/toe pads due to deposition immune complexes)
- Murmur (new regurgitant murmur or muffled heart sounds) Frequency: mitral > aortic > tricuspid > pulmonary
- Janeway lesions (painless macules on palms which blanch on pressure)
- Anaemia
- Nail - splinter haemorrhages
- Emboli
- Clubbing
What investigations are used to diagnose/ monitor infective endocarditis?
- Blood Cultures → take 3 sets from different sites at 30 min intervals before antibiotic therapy. Will show bacteraemia. Repeat blood culture 48-72 hrs after treatment starting to check effectiveness.
- Echocardiogram (TTE- transthoracic) → most sensitive, diagnostic test. Good for evaluation of complications & prognosis. Will see valvular, mobile vegetations.
- TOE (transoesophageal) if prosthetic heart valve or if TTE comes back negative. - FBC → anaemia, leukocytosis
- Raised CRP
What method used for diagnosing infective endocarditis is based on the findings of the investigations and the symptoms/signs?
● Duke’s Classification :
A useful mnemonic to remember the criteria is ‘BE FIVE PM’:
Major Criteria:
Blood Cultures
Evidence of Endocardial Involvement: Echo
Minor Criteria:
Fever
Immunological phenomena
Vascular phenomena
Echocardiogram minor criteria
Predisposing features
Microbiological evidence that does not meet major criteria.
For a definitive diagnosis of IE two major criteria, or one major and three minor criteria, or all five minor criteria must be present.
How is infective endocarditis managed?
Long Term IV Antibiotics (min 6 weeks)
1. Suspected IE → supportive care (fluids, oxygen etc.) + broad-spectrum (empirical) antibiotics
- Initial Blind Therapy (if native valve) ⇒ amoxicillin
2. Confirmed IE → different combination of antibiotics depending on caustive agent + whether valve is native or prosthetic
- S.Aureus (native valve) ⇒ flucloxacillin
- S.Aureus (prosthetic valve) ⇒ flucloxacillin + rifampicin + low-dose gentamicin
- Staph Epidermidis ⇒ vancomycin (coagulase negative staph are resistant to flucloxacillin)
- Streptococci Viridans ⇒ benzylpenicillin
3. PR prolongation= indication for surgery (valve replacement) as it can be secondary to aortic root abscess.
Describe the pathophysiology of infective endocarditis?
o Vegetations form when organisms deposit on the heart valves during a period of bacteraemia
o The vegetations are made up of platelets, fibrin and infective organisms
o They destroy valve leaflets, invade the myocardium or aortic wall leading to abscess cavities
o Activation of the immune system can lead to the formation of immune complexes 🡪 vasculitis, glomerulonephritis, arthritis
Summarise the epidemiology of infective endocarditis
● UK Incidence: 16-22/1 million per year
What are possible complications of infective endocarditis?
● Valve incompetence
● Intracardiac fistulae or abscesses
● Aneurysm
● Heart failure
● Renal failure
● Glomerulonephritis
● Arterial emboli from the vegetations shooting to the brain, kidneys, lungs and spleen
Summarise the prognosis for patients with infective endocarditis
● FATAL if untreated
● 15-30% mortality even WITH treatment
