Infective endocarditis

• A fever plus new murmur is endocarditis unless proved otherwise

Classification

• 50% of all endocarditis occurs on normal valves, this follows an acute course and presents with acute heart failure
• Endocarditis on abnormal valves tends to run a more subacute course

Causes

• Bacteria
  • Any cause of bacteraemia can expose the valves to risk of colonisation
  • Strep viridans in the most common cause
  • Other – enterococci, Staph aureus or epidermidis
  • Rarely HACEK group of Gram negs, Haemophilus, Actinobacillus, Cardiobacterium, Eikenella, Kingella and Coxiella burnetti and Chlamydia
• Fungi
  • Candida, aspergillus and histoplasma
• Other causes;
  • SLE (Libman-Sacks endocarditis), malignancy

Clinical features

• Septic signs
  • Fever, rigors, night sweats, weight loss, anaemia, splenomegaly, clubbing
• Cardiac lesions
  • Any new murmur or change in pre-existing murmur
  • Vegetations may cause valve destruction, severe regurgitation or valve obstruction
  • An aortic root abscess may prolong the P-R interval or lead to complete heart block
• Immune complex deposition
  • Vasculitis may affect any vessel
  • Glomerulonephritis and acute renal failure
  • Splinter haemorrhages
  • Roth spots (boat shaped retinal haemorrhages with pale centre)
  • Osler’s nodes (painful pulp infacts in fingers and toes)
  • Janeway lesions (painless palmar or plantar macules)
• Embolic phenomenon
  • Emboli may cause abscesses in the relevant organ (brain, heart, kidney, spleen, GI tract)
  • In right sided IE pulmonary abscesses are common

Tests

• Blood cultures – 3 sets at different times and from different places at peak fever
  • 10% are negative
• Bloods – normocytic normochromic anaemia, neutrophilic leukocytosis, high ESR/CRP, also check U&E’s, Mg+ and LFTs
• Urinalysis – haematuria
• ECG – prolonged P-R interval
• ECHO – may show vegetations if >2mm

Diagnosis

• Duke criteria
  • Need to have 2 major or 1 major and 3 minor or all 5 minor criteria for diagnosis
• Major criteria
  • Positive blood culture
  • Endocardium involved – positive ECHO (vegetation, abscess, dishiscence of prosthetic valve) or new murmur
• Minor criteria
  • Predisposition – cardiac lesion or IV drug abuse
  • Fever >38ºC
  • Vascular/immunological signs
  • Positive blood cultures that don’t meet diagnostic criteria
  • Positive ECHO that doesn’t meet major criteria

Management

• Antibiotics – empirical – benzylpenicillin, gentamycin +/- flucloxacillin if acute
• Consider surgery if – heart failure, valvular obstruction, repeated emboli, fungal endocarditis, persistent bacteraemia, myocardial abscess, unstable infected prosthetic valve

Prognosis

• 30% mortality with staphylococci
• 15% with bowel organisms
• 6% with sensitive streptococci