Infective Endocarditis

Question 1

What is infectious endocarditis?

Answer 1

Inflammation of the endocardium, usually to the inner valves, due to infection.

Question 2

What causes infective endocarditis?

Answer 2

Infection of the heart is caused by a variety of organisms
Infective endocarditis is initiated by microbial colonisation of natural or prosthetic heart valves, shunts and the septa
Most often bacteria – bacterial endocarditis

Question 3

How is infective endocarditis classified?

Answer 3

Classified in 2 ways:
Acute – presents with a high fever and high toxicity
- Death if untreated in few days or weeks
Sub-acute – presents with low grade fever, weight loss and night sweats
- Death in weeks to months

Question 4

Who is most at risk for infective endocarditis?

Answer 4

People with heart defects are at risk

Those with previous diseases:
Infective endocarditis, rheumatic heart disease

Question 5

What predisposing factors increase risk of infective endocarditis? (4)

Answer 5

Heart valve replacement
Intravenous drug use
Periodontal disease
Poor oral hygiene

Question 6

What organisms are most commonly associated with infective endocarditis? (6)

Answer 6

Streptococcus viridans (30-40%)
Enterococci (5-18%)
Other streptococci (15-25%)
Staphylococcus aureus (15-40%)
Coagulase-negative staphylococci (4-30%)
Gram negative bacilli (2-13%)

Question 7

What are the symptoms of infective endocarditis? (11)

Answer 7

Symptoms of endocarditis initially resemble influenza
- Febrile - fever never exceeds 39oC
- Chills
- Night sweats
- Anorexia
- Myalgia
- Arthralgia
Some patients experience neurological symptoms
- Strokes
- Intracerebral and subarachnoid haemorrhage
Peripheral symptoms include:
- Petechiae - conjunctiva (Roth spots), bucal mucosa and extremities
- Splinter and subungual haemorrhages
- Osler nodes on digits

Question 8

How does colonisation on the heart valves begin?

Answer 8

• Turbulent flow mechanically damages the endothelium
• Damage induces the deposition of platelets and fibrin
  - Induces further deposition
  - Eddies form that trap circulating bacteria
  - Bacteria bind to cause more damage – inflammation and complement
  - Thrombotic mesh forms - Mature vegetation

Question 9

Why are patients with abnormal valves at higher risk for infective endocarditis?

Answer 9

Abnormal valves are prone to damage

• Turbulent flow mechanically damages the endothelium
• Fibrin and platelets are deposited
• Fibrin deposits colonised by bacteria
• Bacteria are resistant to platelet antimicrobial peptides and persist

Question 10

How does mature vegetation contribute to the survival of bacterial pathogens?

Answer 10

Mature vegetation is a protective mechanism for the bacteria

• It is an example of the biofilm mode of growth
• Bacteria growing in a biological matrix on abiotic or biotic surfaces
• Gives protection from immune system
• Gives protection from antibiotics

Question 11

How do septic emboli form?

Answer 11

Increased turbulence can form septic emboli

• Parts break off due to shear forces
• May block blood vessels leading to stroke or allow abscess formation

Question 12

How does host immunity contribute to damage?

Answer 12

Inflammatory responses

• IL – 1 may have a role in causing increased fibroblast proliferation and profibrotic factors
• Deposition rate increased

Complement

• Responds to immune complexes formed in response to bacterial cells
• Complexes cause glomerulonephritis – physical blockage
• Complement causes arthritis and cutaneous squelae
• Splinter haemorrhages, Osler nodes, Janeway lesions

Question 13

What complications can occur from infective endocarditis?

Answer 13

Heart failure or severe damage
 - Congestive heart failure
 - Ruptured chordae tendineae
 - Perforation of valves
Complications depend on side affected
 - Left - coronary emboli
 - Right - lung complications

Question 14

How is infective endocarditis treated?

Answer 14

Highly aggressive therapy is required due to the protective effects of the mature vegetation

• High concentrations must be given
• Balance toxicity and efficacy
• Treatment is over long periods
• Surgery may be necessary
• Removal and replacement of heart valves is common

Question 15

What treatment would be given for infectious endocarditis due to E. faecium?

Answer 15

IV Ampicillin 2g every 4 hours
IV Gentamicin 80mg twice daily

Both given over a course of 4 weeks, however 6 weeks of combination therapy is recommended in patients who had symptoms that persisted for at least 3 months before beginning therapy

Question 16

How is infective endocarditis diagnosed?

Answer 16

3 sets of blood cultures of 1 hour or longer

Echocardiography if enterococcal endocarditis is suggested.