Infective Endocarditis Flashcards
What is IE?
Infection or colonization of endocardium , heart valves , congenital defects by bacteria , rickettsiae , fungi
- Often characterised by a low grade persistent bacteraemia
What causes high mortality?
- Virulence of organism or severe infection
- Presence of underlying disease
- Elderly
- Inadequate treatment
Poor prognostic facrors?
- Candida infection
- Staphylococcus aureus infection
- Gram-negative organisms
- Prosthetic valve (especially ‘early’, acquired during surgery)
- Culture negative endocarditis
- Low complement levels
Mortality according to organism?
Staphylococci - 30%
Bowel organisms - 15%
Streptococci - 5%
Host local factors that increase susceptibility to IE?
- CONGENITAL OR RHEUMATIC HEART DISEASE
- PROSTHETIC HEART VALVES
- HEART SURGERY
General factors increasing susceptibility?
underlying disease
e.g. DM
Drugs that increase susceptibility?
- IATROGENIC:
IMMUNOSUPPRESSIVE TREATMENT
CYTOTOXIC AGENTS - SELF- INFLICTED
ALCOHOLISM
ADDICTION (INJECTED DRUGS )
Protective factors?
antimicrobial chemotherapy
Formation of vegetations?
- Fibrin, platelets (thrombi), bacteria colonies attach to heart valves
- Break off infected emboli and travel to distant organs
e.g. kidney , brain - Immune complex formation causes glomerular damage e.g. haematuria
- Valves infection leads to destruction and subsequent heart failure
- Drug addicts > tricuspid, pulmonary valves of right side of heart causing lung emboli and pneumonia
Pathology?
- Emboli can break off vegetations causing abscesses at distant sites where they lodge leading to sequelae such as septic infarcts or mycotic aneurysms
- Vegetations of subacute endocarditis are associated with less valvular destruction than acute endocarditis
- Gram +ve bacteria are particularly resistant to patient’s innate antibacterial activity (eg complement) which facilitates the adhesion & formation of vegetations
Sources of infection?
- Dental extraction and other dental procedures
- Cardiac surgery ( prosthetic valves)
- Intravenous medication
- Iv. Drug addiction
- Intracardiac or intravenous catheters
- Obstetric or gynaecologic procedures
Portal of entry?
- 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 - oral irrigation device
Pathogenesis of IE?
Which pathogens cause IE?
- staph aureus
- strep viridans
- coag -ve staph
- enterococci
- HACEK group
Staph aureus pathogenesis?
- MSSA is more frequent in community-acquired IE, infects mainly native valves & is associated with bacteraemia of unknown origin
- MRSA is more related to nosocomial infection, wound infection, permanent IV catheters or surgery in previous 6/12
Coag. negative staph causes?
prosthetic valve endocarditis
esp. within first 6-12/12 after valve surgery
N.B: MRSA is more common
HACEK group?
- Haemophilus group
- Actinobacillus group
- Cardiobacterium hominis
- Eikenella corrodens
- Kingella kingae
Fungal causes of IE?
candida and aspergillus
Whos is most likely to have fungal IE?
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
What organisms to suspect if BC is negative?
- Coxiella burnetti
- Legionella spp
- Brucella spp
- Bartonella spp
- Chlamydiae spp
- HACEK
- OR prior antibiotic use
The most common factors predisposing to IE?
are those that cause bacteraemia
1. Dental/surgical procedures
2. Needle sharing amongst IVDU
3. Breaks in skin
Classification of IE based on etiology?
- Native Valve IE
- Prosthetic Valve IE
- Intravenous drug abuse (IVDA) IE
- Nosocomial IE
Classification of IE based on duration?
- acute
- subacute
Acute IE?
- 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
Subacute IE?
- 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