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
Clinical features?
- Onset is insidious ( SBE) – 3 weeks after extraction
- Fever ( mild and prolonged ), chills and sweating
- Malaise , weight loss , weakness
- Changing murmurs
- Anaemia , leucocytosis
- Microscopic haematuria
- Petechiae
- Splenomegaly
- Splinter haemorrhage
- Finger clubbing
Complications?
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
Diagnosis?
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
Lab diagnosis?
- serial blood culture ( 2-3 sets before antibiotic therapy )
- Aerobic
- Anaerobic
- CBC, ESR and CRP, Complement levels (C3, C4, CH50)
- RF
- Urinalysis - serological tests
CFT ( coxiella burniti ) - sensitivity test
Blood for culture contaminated by normal skin flora?
- Staphylococcus epidermidis
- Diphtheriods
- Propioniobacteria (anaerobic diphtheroides)
Avoiding contamination of blood culture by normal flora?
So first clean the site (mainly anticubital fossa) with:
1. alcohol 70% and leave for 1-11/2 minutes)
2. cholorhexidine
3. iodine
Major criteria?
- 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 - Endocardial involvement
- Echocardiogram positive for IE
- New valvular regurgitation
Minor criteria?
- Predisposition, predisposing heart condition or injection drug use
- Fever >38 degrees
- Vascular phenomena
- Immunologic phenomena
- Microbiological evidence
Petechiae?
Nonspecific
Often located on extremities or mucous membranes
Radiology investigatioms?
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
Cardiac complications?
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
Embolic complications?
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)
Metastatic spread of infection?
Metastatic abscess
Kidneys, spleen, brain, soft tissues
Meningitis and/or encephalitis
Vertebral osteomyelitis
Septic arthritis
Criteria for antibiotic treatment?
Bactericidal
Parenteral
High dose
Prolonged
Viridans streptococci?
Benzyl penicillin I.V. 4 MU every 4 hrs for 4 weeks
or If penicillin allergy: vancomycin + low dose gentamicin
Streptococcus faecalis?
ampicillin + gentamicin I.V
Native valve endocarditis caused by staphylococci?
Flucloxacillin
If penicillin allergic or MRSA: vancomycin + rifampicin
Prosthetic valve endocarditis caused by staphylococci?
Flucloxacillin + rifampicin + low-dose gentamicin
If penicillin allergic or MRSA: vancomycin + rifampicin + low-dose gentamicin
Recurrence after cure is common in?
Drug addicts
Immunodeficient patients
Antibiotic prophylaxis is recommended in?
high risk patients
Acquired valvular HD
Previous valve replacement
Structural congenital HD (excluding repaired ASD, VSD or PDA)
Indications for surgery?
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
Complications of surgery?
Persistent septic shock
Coagulopathy
Acute renal failure
Stroke
Refractory heart failure
Conduction abnormalities
