Infective Endocarditis and Bacteraemia

Question 1

Infective Endocarditis - Definition

Answer 1

• Bacterial (or fungal) infection of a heart valve or area of endocardium
• Clinical presentation traditionally classified as:
  
  • Acute
  • Sub-acute
• Particular constellations of clinical signs + investigation results necessary to meet diagnostic criteria

Question 2

Infective Endocarditis - Epidemiology

Answer 2

• Uncommon: 2-6 per 100,000 population per year, M=F
• Invariably lethal pre-antibiotics, it has still not gone away and may be on the increase in some categories of patients
• Still significant mortality (20%) and morbidity
• Risk factors and infecting organisms have changed over time. e.g. rheumatic fever was prime risk factor in up to 75% of cases in the pre-antibiotic era, but rare now.
• Different organisms associated with different risk factors

Question 3

Infective Endocarditis - Native Valve Endocarditis

Answer 3

• Native Valve Endocarditis:
  
  • Associated with
    
    • Congenital heart disease (high to lower pressure gradients greatest risk)
    • Rheumatic heart disease
    • Mitral valve prolapse
    • Degenerative valve lesion
  • Organisms typically responsible = viridans streptococci (oral flora)

Question 4

Infective Endocarditis - Prosthetic Valve Endocarditis

Answer 4

• 1-5% of cases
• Early (within first 2 months after surgery) or late
• Coagulase negative staphylococci predominate

Question 5

Infective Endocarditis - IVDU-associated Endocarditis

Answer 5

• Median age 30 (M>F)
• Right sided infection more common
• Sites:
  
  • Tricuspid 50%
  • Aortic 25%
  • Mitral 20%
• Staphylococcus aureus predominates, but other organisms, including fungi, sometimes responsible

Question 6

Infective Endocarditis - Nosocomial Infective Endocarditis

Answer 6

• Increasing incidence (>10% in recent survey)
• Age >60 years
• Often underlying cardiac disease
• Intravenous lines, invasive procedures
• Increasing right sided IE due to CVP lines and pulmonary artery catheters

Question 7

Infective Endocarditis - Pathogenesis

Answer 7

• Heart defect ==> pressure gradient across valve
  
  • ==> Fibrin-platelet deposition
    
    • • Bacteraemia ==> colonised fibrin-platelet deposit
        
        • ==> Further deposition of thrombus
          
          • ==> Vegetation
• Once on endocardium difficult for immune system to eradicate

Question 8

Infective Endocarditis - Causes of Bacteraemia

Answer 8

• Secondary to infection elsewhere e.g. pyelonephriris
• Line associated
• Transient bacteraemia:
  
  • Chewing, toothbrushing, dental proceedures
    
    • Worse in the prescence of gingivitis
• Medical and surgical proceedtures in non sterile sites e.g. urethral catheterisation, endoscopy

Question 9

Infective Endocarditis - Predisposing Host Factors

Answer 9

• Pre-existing lesions of the layer of endothelial cells covering the valve or endovascular surface
• Congenital cardiac abnormalities causing turbulent blood flows
• Rheumatic fever resulting in valvular damage
• Prosthetic valves
• Sclerotic valves in elderly patients
• Invasive procedures/intravascular lines

Question 10

Infective Endocarditis - Causative Organisms

Answer 10

• Typical
  
  • Staphylococcus aureus, Streptococcus sp., Enterococci together responsible for >80% of cases
  • Ability to adhere to and colonise damaged valves
• HACEK group
• “Culture negative” - serum sample on admission and 4 weeks later
  
  • Q fever - Coxiella burnetti
  • Chlamydiae
  • Brucella **spp.

Question 11

Infective Endocarditis - Clinical Features

Answer 11

• Acute vs. subacute
• Symptoms:
  
  • Malaise
  • Pyrexia
  • Arthralgia
  • Cardiac murmurs
  • Cardiac failure
  • Osler’s nodes
  • Janeway lesions
  • Splinter haemmorrrhages
  • Roth spots
  • Splenomegaly
  • Cerebral emboli
  • Haematuria
  • Petechiae

Question 12

Infective Endocarditis - Clinical Criteria For Diagnosis - Major Criteria

Answer 12

• Major Criteria
  
  • Positive blood cultures:
    
    • Typical organisms for IE from 2 seperate blood cultures
    • Persistently positive blood cultures
  • Evidence of endocardial involvement
    
    • Positive echocardiogram:
      
      • Vegetations
      • Abscess
      • New partial dehiscence of prosthetic valve
      • New valvular regurgitation

Question 13

Infective Endocarditis - Clinical Criteria For Diagnosis - Minor Criteria

Answer 13

• Minor Criteria:
  
  • Predisposition:
    
    • Heart condition
    • IVDU
  • Fever >/= 38ºC
  • Vascular phenomena:
    
    • Major arterial emboli
    • Septic pulmonary infarcts
    • Intracranial haemmorhage
    • Janeway lesions
  • Immunological phenomena:
    
    • Glomerulonephritis
    • Osler’s nodes
    • Roth spots
    • Rheumatoid factor
  • Microbiological evidence:
    
    • Positive blood cultures but not meeting major diagnostic criteria
  • Echocardiogram:
    
    • Consistent with IE but not meeting major criteria

Question 14

Infective Endocarditis - Investigations

Answer 14

• Multiple sets of blood cultures from different sites
• FBC:
  
  • Normocytic, normochromic anaemia
  • Increased WCC (neutrophilia)
• CRP - raised
• ESR - raised
• Urine - proteinuria and microscopic haematuria
• Echocardiography - transthoracic and transoesophageal
• Serology

Question 15

Infective Endocarditis - Complications

Answer 15

• Valvular destruction leading to cardiac failure
• Surgery indicated if:
  
  • Extensive damage to valve
  • Infection of prosthetic valve
  • Worsening renal failure
  • Persistent infection but failure to culture organism
  • Embolisation
  • Large vegetations
• Embolisation – cerebral, pulmonary
• Acute renal failure
  
  • Secondary to IE or to treatment – aminoglycosides/glycopeptides
• Mycotic aneurysms
• Death

Question 16

Infective Endocarditis - Treatment (Typical)

Answer 16

• Acute fulminant infection - empirical *vancomycin *and *ceftriaxone *IV
• Ideally try to get microbiological diagnosis first
  
  • Targeted antibiotic therapy
• Low dose gentamycin for synergy where possible
• In most cases at least 4 weeks of paraenteral therapy will be required

Question 17

Infective Endocarditis - Q Fever and Chlamydiae Treatment

Answer 17

• Seek microbiology assistance
• Q-fever tetracyclines, co-trimoxazole
  
  • >1 year therapy
  • Valve replacement
• Chlamydiae
  
  • Tetracyclines

Question 18

Infective Endocarditis - Prevention - Cardiac Conditions Specifically Associated With Risk

Answer 18

• NICE guidance review concluded that:
  
  • Cardiac conditions that were associated with IE included:
    
    • Acquried valvular heart disease with stenosis or regurgitation
    • Valve replacement
    • Structural congenital heart diease
      
      • BUT not!
        
        • Isolated atrial septal defect
        • Fully repaired ventricular septal defect
        • Fully repaired patent ductus arteriousus
        • Closure devices that are endothelialised
    • Previous infective endocarditis
    • Hypertrophic cardiomyopathy

Question 19

Infective Endocarditis - Antibiotic Prophylaxis

Answer 19

• Historically antibiotic therapy to prevent IE was given to at-risk people undergoing dental, GI, and GU proceedures due to their association with bacteraemia
• Side effects of antibiotic use include allergy (as severe as anaphylaxis and death), Clostridium difficile associated diarrhoea and increasing antibiotic resistance
• The 2008 NICE review guidance concluded that:
  
  • ​There is an inconsistent association between recent interventional proceedures and the development of IE
  • Antibiotic prophlaxis does not eleiminated bacteraemia following dental proceedures but some studies show it reduces its duration
  • There is insufficient evidence to determine whether antibiotic prophylaxis in those at risk of IE reduces the incidence of IE after an interventional proceedure
  • Therefore antibiotic prophylaxis is not reccomended to prevent IE for people at risk of IE undergoing dental and non-dental proceedures (GI/GU/RT)

Question 20

Infective Endocarditis - Reccomended Prevention Strategies

Answer 20

• For those at risk of infective endocarditis give advice on:
  
  • Maintaining good oral health
  • Symptoms that may indicate IE and when to seek help
  • Risks of undergoing invasive proceedures - discourage non-medical proceedures such as body piercing and tattooing
• Any episodes of infection in people at risk of IE should be investigated and treated promptly to reduce the risk of IE developing
• If a patient at risk of IE is recieving antimicrobial therapy because they are to undergo a GU/GI proceedure at a site where there is suspected infection - they should recieve and antibiotic that covers organisms that cause IE