Infective endocarditis

The European Society of Cardiology state the following should cause infective endocarditis to be suspected: 
  • New regurgitant heart murmur 
  • Embolic events of unknown origin 
  • Sepsis of unknown origin 
  • Fever in certain cases 

The most frequent sign of IE is fever (up to 90% of cases) 
There are often systemic symptoms 
Heart murmurs are present in 85% of cases 

The classic (but not necessarily common) signs associated with IE are:
  • Roth spots
  • Janeway lesions
  • Osler nodes
  • Splinter haemorrhages

Diagnosis is by the Modified Duke Criteria:
  • Diagnosis is definite in the presence of:
    • 2 major criteria or 
    • 1 major and 3 minor criteria or 
    • 5 minor criteria
  • Major criteria 
    • Blood cultures positive for IE 
    • Evidence of endocardial involvement
      • Echocardiography positive for IE or 
      • New valvular regurgitation 
  • Minor criteria 
    • Predisposition (predisposing heart condition, IVDU) 
    • Fever (>38C) 
    • Vascular phenomena (major arterial emboli, septic pulmonary infarcts, mycotic aneurysm, intracranial haemorrhages, conjunctival haemorrhages, Janeway lesions)
    • Immunologic phenomena (glomerulonephritis, Osler’s nodes, Roth’s spots, rheumatoid factor) 
    • Microbiological evidence that does not meet major criteria

Key investigations are therefore
  • Blood cultures – 3 sets an hour apart 
  • Echocardiography – TTE has a sensitivity of around 46% while TOE’s sensitivity is 93%

Most cases of IE are left sided. 
5-10% are right-sided and most of these are associated with IVDUs 

In terms of microbiology, IE can be divided into:

1) Infective endocarditis with positive blood cultures = 85% of cases 
  • Commonest causative organism = streptococcus viridans
  • Commonest causative staphylococcal organism on native valve = s. aureus 
  • Commonest causative staphylococcal organism on prosthetic valve = coagulase-negative straphylococci 
  • Commonest causative organism in right sided IE = s. aureus 
  • Third most common causative organism after strep and staph = enterococci 

2) Infective endocarditis with negative blood cultures due to prior antibiotic treatment 

3) Infective endocarditis frequently associated with negative blood cultures 
  • HACEK group = Haemophilus parainfluenzae, H. aphrophilus, H. paraphrophilus, H. influenzae, Actinobacillus actinomycetemcomi- tans, Cardiobacterium hominis, Eikenella corrodens, Kingella kingae, and K. denitrificans Brucella 
  • Fungi 
4) Infective endocarditis associated with constantly negative blood cultures = 5% of cases 
  • Intracellular bacteria – coxiella burnetii, bartonella, chlamydia, tropheryma whipplei 

  • Antibiotics 
    • Initial empirical treatments:
      • Native-valve IE and prosthetic valves >12months post surgery
        • Co-amoxiclav and gentamicin, or 
        • vancomycin, gentamicin and ciprofloxacin if beta-lactam allergy 
      • Prosthetic valves, <12 months post surgery: 
        • vancomicin with gentamicin and rifampin 
    • Treatments once bacteria is identified:
      • Strep infections 
        • Strains susceptible to penicillin: 4 weeks of either penicillin G or amoxicillin or cefriazone 
        • Strains relatively resistant to penicillin: 4 weeks of penicillin or amoxicillin plus gentamicin for the first 2 weeks 
      • Staph infections 
        • On native valve: 4 to 6 weeks of flucloxacillin or oxacillin with 3 to 5 days of gentamicin 
        • On prosthetic valve: at least 6 weeks of flucloxacillin or oxacillin plus oral rifampin plus 2 days of gentamicin 
      • In case of beta lactam allergy, use vancomycin wherever a beta lactam has been listed. 
  • Surgery – indications include heart failure due to valve destruction and uncontrolled infection 

Prognosis: In-hospital mortality rate: 10 to 26% 

  • Heart failure 
    • Most frequent complication of IE – 50-60% of cases 
    • More common when IE affects the aortic valve
  • Embolisms 
    • Occurs 20-50% of patients before antibiotics are started 
    • risk highest during first 2 weeks of antibiotics 
    • risk related to size of vegetation 
    • left-sided IE is most associated with embolisms to brain (=risk of stroke) and spleen 
    • right sided IE is most associated with PE 
  • Acute renal failure – around 30% of patients
  • Abscess 

NICE defines the following as being at increased risk of developing endocarditis: 
  • Acquired valvular heart disease with stenosis or regurgitation 
  • Valve replacement 
  • Structural congenital heart disease (but excluding isolated atrial septal defects, fully repaired ventricular septal defects, fully repaired patent ductus arteriosus and closure devices that are endothelialised Hypertrophic cardiomyopathy 
  • Previous infective endocarditis 

Antibiotic prophylaxis???
  • NICE doesn’t recommend antibiotic prophylaxis in any scenario. 
  • The European Society of Cardiology recommends prophylaxis only in:
    • ‘highest risk’ patients (such as previous IE, valve replacement and some forms of congenital heart disease) and only for:
      • dental procedures that perforate the oral mucosa or manipulate the gingival region (use amoxicillin, ampicillin or clindamycin)
      • skin procedures involving infected skin (use cephalosporin) 

  • Small print gems:
  • strep bovis can cause IE and is strongly associated with bowel cancer 
  • Libman-Sacks endocarditis is a form of endocarditis characterized by sterile fibrofibrinous vegetations, usually on the left side. It is associated with SLE
  • Marantic endocarditis, also known as non-bacterial thrombotic endocarditis, is a form of sterile endocarditis associated with a variety of inflammatory states including malignancy. 

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Secret collector of interesting anonymised ECGs. Fan of the Bath Photomarathon. Lover of cream teas. [Sarah Hudson] (Your Picture)