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MBBS 3: Internal Medicine > Infective Endocarditis > Flashcards

Infective Endocarditis Flashcards

1
Q

What is IE?

A

Infection or colonization of endocardium , heart valves , congenital defects by bacteria , rickettsiae , fungi
- Often characterised by a low grade persistent bacteraemia

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2
Q

What causes high mortality?

A
  1. Virulence of organism or severe infection
  2. Presence of underlying disease
  3. Elderly
  4. Inadequate treatment
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3
Q

Poor prognostic facrors?

A
  1. Candida infection
  2. Staphylococcus aureus infection
  3. Gram-negative organisms
  4. Prosthetic valve (especially ‘early’, acquired during surgery)
  5. Culture negative endocarditis
  6. Low complement levels
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4
Q

Mortality according to organism?

A

Staphylococci - 30%
Bowel organisms - 15%
Streptococci - 5%

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5
Q

Host local factors that increase susceptibility to IE?

A
  1. CONGENITAL OR RHEUMATIC HEART DISEASE
  2. PROSTHETIC HEART VALVES
  3. HEART SURGERY
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6
Q

General factors increasing susceptibility?

A

underlying disease
e.g. DM

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7
Q

Drugs that increase susceptibility?

A
  1. IATROGENIC:
    IMMUNOSUPPRESSIVE TREATMENT
    CYTOTOXIC AGENTS
  2. SELF- INFLICTED
    ALCOHOLISM
    ADDICTION (INJECTED DRUGS )
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8
Q

Protective factors?

A

antimicrobial chemotherapy

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9
Q

Formation of vegetations?

A
  1. Fibrin, platelets (thrombi), bacteria colonies attach to heart valves
  2. Break off infected emboli and travel to distant organs
    e.g. kidney , brain
  3. Immune complex formation causes glomerular damage e.g. haematuria
  4. Valves infection leads to destruction and subsequent heart failure
  5. Drug addicts > tricuspid, pulmonary valves of right side of heart causing lung emboli and pneumonia
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10
Q

Pathology?

A
  1. Emboli can break off vegetations causing abscesses at distant sites where they lodge leading to sequelae such as septic infarcts or mycotic aneurysms
  2. Vegetations of subacute endocarditis are associated with less valvular destruction than acute endocarditis
  3. Gram +ve bacteria are particularly resistant to patient’s innate antibacterial activity (eg complement) which facilitates the adhesion & formation of vegetations
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11
Q

Sources of infection?

A
  1. Dental extraction and other dental procedures
  2. Cardiac surgery ( prosthetic valves)
  3. Intravenous medication
  4. Iv. Drug addiction
  5. Intracardiac or intravenous catheters
  6. Obstetric or gynaecologic procedures
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12
Q

Portal of entry?

A
  1. Dental, extraction bleeding bacteremia
    - Rocking the tooth in the socket pumping effect on the vessels of periodontal ligament, forces bacteria from gingival pockets into blood stream
  2. oral irrigation device
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13
Q

Pathogenesis of IE?

Which pathogens cause IE?

A
  1. staph aureus
  2. strep viridans
  3. coag -ve staph
  4. enterococci
  5. HACEK group
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14
Q

Staph aureus pathogenesis?

A
  1. MSSA is more frequent in community-acquired IE, infects mainly native valves & is associated with bacteraemia of unknown origin
  2. MRSA is more related to nosocomial infection, wound infection, permanent IV catheters or surgery in previous 6/12
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15
Q

Coag. negative staph causes?

A

prosthetic valve endocarditis
esp. within first 6-12/12 after valve surgery
N.B: MRSA is more common

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16
Q

HACEK group?

A
  1. Haemophilus group
  2. Actinobacillus group
  3. Cardiobacterium hominis
  4. Eikenella corrodens
  5. Kingella kingae
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17
Q

Fungal causes of IE?

A

candida and aspergillus

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18
Q

Whos is most likely to have fungal IE?

A

Patients with:
1. IVDU
2. prosthetic valve
3. long-term CVC
- needs to be considered in presence of bulky vegetations, metastatic infection, perivalvular invasion, or embolisation to large blood vessels despite -ve BC

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19
Q

What organisms to suspect if BC is negative?

A
  1. Coxiella burnetti
  2. Legionella spp
  3. Brucella spp
  4. Bartonella spp
  5. Chlamydiae spp
  6. HACEK
  7. OR prior antibiotic use
20
Q

The most common factors predisposing to IE?

A

are those that cause bacteraemia
1. Dental/surgical procedures
2. Needle sharing amongst IVDU
3. Breaks in skin

21
Q

Classification of IE based on etiology?

A
  1. Native Valve IE
  2. Prosthetic Valve IE
  3. Intravenous drug abuse (IVDA) IE
  4. Nosocomial IE
22
Q

Classification of IE based on duration?

A
  1. acute
  2. subacute
23
Q

Acute IE?

A
  • Infection of previously normal heart valve by a highly virulent organism that produces necrotising, ulcerative, destructive lesions
  • Difficult to cure with Abx & usually require Sx
  • Death can occur within days to weeks despite Rx
24
Q

Subacute IE?

A
  • Organisms are usually of lower virulence
  • Cause insidious infections of deformed (native) valves that are less destructive
  • Can take prolonged course: weeks to months
  • More amenable to treatment with antibiotics
25
Q

Clinical features?

A
  1. Onset is insidious ( SBE) – 3 weeks after extraction
  2. Fever ( mild and prolonged ), chills and sweating
  3. Malaise , weight loss , weakness
  4. Changing murmurs
  5. Anaemia , leucocytosis
  6. Microscopic haematuria
  7. Petechiae
  8. Splenomegaly
  9. Splinter haemorrhage
  10. Finger clubbing
26
Q

Complications?

A

In IVDU right sided IE usually affect the tricuspid valve & occasionally the pulmonary valve, instead of systemic issues pulmonary embolism is the most important complication which can evolve into
Pulmonary infarction

Pulmonary abscess

Bilateral pneumothoraces

Pleural effusion

Empyema

27
Q

Diagnosis?

A

The dx is confirmed in presence of 2 major criteria, 1 major + 2 minor or 5 minor criteria

IE considered in presence of 1 major + 1 minor or 3 minor

28
Q

Lab diagnosis?

A
  1. serial blood culture ( 2-3 sets before antibiotic therapy )
    - Aerobic
    - Anaerobic
    - CBC, ESR and CRP, Complement levels (C3, C4, CH50)
    - RF
    - Urinalysis
  2. serological tests
    CFT ( coxiella burniti )
  3. sensitivity test
29
Q

Blood for culture contaminated by normal skin flora?

A
  1. Staphylococcus epidermidis
  2. Diphtheriods
  3. Propioniobacteria (anaerobic diphtheroides)
30
Q

Avoiding contamination of blood culture by normal flora?

A

So first clean the site (mainly anticubital fossa) with:
1. alcohol 70% and leave for 1-11/2 minutes)
2. cholorhexidine
3. iodine

31
Q

Major criteria?

A
  1. Blood culture positive for IE
    - typical microorganisms consistent with IE from 2 separate blood cultures
    e.g. viridans streptococci, HACEK, staphylococcus aureus
    - at least 2 positive cultures of blood samples >12h apart
    - 4 cultures with at least first and last sample drawn at least 1 hr apart
  2. Endocardial involvement
  3. Echocardiogram positive for IE
  4. New valvular regurgitation
32
Q

Minor criteria?

A
  1. Predisposition, predisposing heart condition or injection drug use
  2. Fever >38 degrees
  3. Vascular phenomena
  4. Immunologic phenomena
  5. Microbiological evidence
33
Q

Petechiae?

A

Nonspecific
Often located on extremities or mucous membranes

34
Q

Radiology investigatioms?

A

Chest x-ray
Look for multiple focal infiltrates and calcification of heart valves

ECG
Rarely diagnostic
Look for evidence of ischemia, conduction delay, and arrhythmias

Echocardiography

35
Q

Cardiac complications?

A

Heart failure
Extensive valvular damage

Paravalvular abscess (30-40%)
Most common in aortic valve, IVDA, and S. aureus
May extend into adjacent conduction tissue causing arrythmias
Higher rates of embolization and mortality

Pericarditis

Fistulous intracardiac connections

36
Q

Embolic complications?

A

Stroke

Myocardial Infarction
Fragments of valvular vegetation or vegetation-induced stenosis of coronary ostia

Ischemic limbs

Hypoxia from pulmonary emboli

Abdominal pain (splenic or renal infarction)

37
Q

Metastatic spread of infection?

A

Metastatic abscess
Kidneys, spleen, brain, soft tissues

Meningitis and/or encephalitis

Vertebral osteomyelitis

Septic arthritis

38
Q

Criteria for antibiotic treatment?

A

Bactericidal

Parenteral

High dose

Prolonged

39
Q

Viridans streptococci?

A

Benzyl penicillin I.V. 4 MU every 4 hrs for 4 weeks
or If penicillin allergy: vancomycin + low dose gentamicin

40
Q

Streptococcus faecalis?

A

ampicillin + gentamicin I.V

41
Q

Native valve endocarditis caused by staphylococci?

A

Flucloxacillin
If penicillin allergic or MRSA: vancomycin + rifampicin

42
Q

Prosthetic valve endocarditis caused by staphylococci?

A

Flucloxacillin + rifampicin + low-dose gentamicin
If penicillin allergic or MRSA: vancomycin + rifampicin + low-dose gentamicin

43
Q

Recurrence after cure is common in?

A

Drug addicts
Immunodeficient patients

44
Q

Antibiotic prophylaxis is recommended in?

A

high risk patients
Acquired valvular HD

Previous valve replacement

Structural congenital HD (excluding repaired ASD, VSD or PDA)

45
Q

Indications for surgery?

A

Severe valvular incompetence/large vegetations
Aortic abscess (often indicated by a lengthening PR interval) (9-14%)
Infections resistant to antibiotics/fungal infections (9-11%)
Cardiac failure refractory to standard medical treatment
Recurrent emboli after antibiotic therapy

46
Q

Complications of surgery?

A

Persistent septic shock

Coagulopathy

Acute renal failure

Stroke

Refractory heart failure

Conduction abnormalities

MBBS 3: Internal Medicine (72 decks)

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