L64: Infective Endocarditis, Pericarditis, Myocarditis

Question 1

Pathogenesis of infective endocarditis

Answer 1

1. Damaged valve —> platelet-fibrin deposition —> nonbacterial thrombotic endocarditis
2. Colonised tissue by microorganism —> trauma —> bacteraemia

nonbacterial thrombotic endocarditis + bacteraemia —> adherence to valve —> colonisation —> Mature Vegetation (microorganisms + thrombus + leukocytes)

Question 2

Causes of damaged valves

Answer 2

1. Congenital
   - septal defects
   - valvular defects
2. Acquired
   - degenerative
   - rheumatic heart
   - prosthetic valve

Question 3

Clinical presentation of infective endocarditis

Answer 3

• **Classical signs:
• Splinter haemorrhage
• Osler’s node (painful, red, raised lesions on hands/feets)
• Janeway lesion (haemorrhagic lesion on palms/soles)
• Roth spots

1. Non-specific
   - fever
   - weight loss
2. Damaged valve
   - murmur
   - heart failure
3. Emboli
   - stroke
   - MI
4. Immunological
   - glomerulonephritis

Question 4

Causative microorganisms in infective endocarditis (ALMOST ALWAYS BACTERIAL)

Answer 4

Characteristics: 1. Serum resistance 2. Ability to adhere (MSCRAMM) 3. Resist host defence in vegetation

Native valve:

• S. aureus (skin —> IV drug addict)
• Viridans S. (oral)
• S. bovis
• Enterococci (gut, UT)
• HACEK (oral gram -ve bacilli: H. Influenzae, Actinobacillus, Cardiobacterium, Eikenella, Kingella)

Prosthetic valve

• Early: Coagulase -ve Staph
• Late: same as native valve

Animal contact

• Coxiella burnetii (Q fever from sheep)
• Bartonella henselae (cat scratch)

Question 5

Diagnosis of infective endocarditis

Answer 5

Definitive diagnosis:
Pathological criteria:
- evidence of lesion / abscess / vegetation on histology
- microorganisms on histology / culture of vegetation / abscess

Clinical criteria (Duke’s criteria): (2 major / 1 major + 3 minor / 5 minor)
Major:
- positive blood culture:
—> 2 separate / persistently positive blood cultures (12 hours apart)
- evidence of endocardial involvement:
—> NEW valvular regurgitation
—> positive echocardiogram (pendulum-like intracardiac mass on valve)

Minor:

• predisposition: heart condition
• fever: >38oC
• vascular symptoms: Janeway lesion, arterial emboli
• immunological symptoms: GN, Osler’s nodes, Roth’s spots
• microbiological evidence not enough for major: serology

Question 6

Why need multiple blood cultures

Answer 6

Infective endocarditis: CONTINUOUS bacteraemia

Question 7

Taking blood culture

Answer 7

1. Skin disinfection (iodophors, 70% alcohol)
2. Drawn before antibiotic
3. 3 sets from different site (1st and last 1 hour apart)
4. 10ml each set
5. Incubate: 5-7 days, may extend to 14 days

DO NOT: change needle prior to inoculating, draw blood from intravascular catheter

Culture negative reasons:

• Prior antibiotics
• Inadequate blood sample
• Diffuiclt to grow (HACEK, Bartonella, Coxiella)
• Non-infective cause

Question 8

Treatment for infective endocarditis

Answer 8

1. Bactericidal antibiotics
   —> Viridans S.: Penicillin G
   —> Methicillin-sensitive SA: Cloxacillin (anti-staphylococcal, narrow spectrum, beta-lactamase resistant antibiotics)
   —> MRSA: Vancomycin
   —> Enterococcus: Ampicillin + Gentamicin
   —> Staph prosthetic valve: Add Rifampicin
2. High dose IV —> penetrate into vegetation
3. Long duration —> kill dormant bacteria

Difficulty:

• Biofilm
• Reduced cell division
• High bacterial load

Question 9

Prevention of IE

Answer 9

Antibiotic prophylaxis —> reduce bacterial load during procedures

Considerations: Risk of procedure, Underlying heart abnormalities
Choice: Cover most probable organism
Dose: > MIC
Time: Immediately before procedure
Duration: for duration of transient bacteraemia

Current guidelines:
- NICE: No prophylaxis
- American / European:
—> High dental procedures (Manipulation of gingival / periapical region of teeth / Perforation of oral mucosa)
—> Patients at highest risk for IE (Previous episode of IE / Prosthetic valve / Cyanotic congenital heart disease)

Question 10

Myocarditis

Answer 10

Inflammation of myocardium

Symptoms:

• chest pain
• arrhythmia
• heart failure

Source:

• adjacent organs
• haematogenous
• direct invasion, toxin, immune-mediated

Question 11

Causative microorganisms in myocarditis (ALWAYS ALMOST VIRAL)

Answer 11

1. Virus (MOST common)
   - enterovirus
   - respiratory virus: adeno, influenza
   - dengue
   - MMR
2. Bacteria
   - Corynebacterium diphtheriae
3. Parasite
   - Trypanosoma cruzi
4. Dimorphic fungi

Question 12

Diagnosis of myocarditis

Answer 12

1. Cardiac enzyme (Troponin, CKMB)
2. ECG
3. Echocardiogram
4. Biopsy
5. Blood culture
6. Nasopharyngeal aspirate
7. Swab
8. Serology
9. ASO titre

Question 13

Treatment of myocarditis

Answer 13

1. Treat microorganism
2. Manage heart failure
3. Rest

Question 14

Pericarditis

Answer 14

Inflammation of pericardium

Symptoms:

• chest pain
• pericardial effusion (cardiac tamponade)
• pericardial rub

Source:

• adjacent
• haematogenous

Question 15

Causative microorganisms in myocarditis (SIMILAR TO MYOCARDITIS)

Answer 15

1. Virus
   - enterovirus
   - respiratory virus: adeno, influenza
   - dengue
   - MMR
2. Bacteria
   - gram +ve: S. aureus, Streptococcus
   - gram -ve: Enterobacteriaceae, H. Influenzae
   - Anaerobes
   - M. Tb
3. Parasite
4. Dimorphic fungi

Question 16

Diagnosis of pericarditis

Answer 16

1. Diffuse ST elevation (concave up)
2. Echocardiogram (pericardial effusion)
3. Biopsy (pericardial fluid bioscopy)
4. Blood culture
5. Serology

Question 17

Treatment of pericarditis

Answer 17

1. Treat microorganism
2. Drainage of pericardial fluid
3. Rest
4. NSAID (symptom relief: NOT in myocarditis)