Infective endocarditis Flashcards
List some DDx for a presentation of:
- fever
- new onset murmur at L sternal edge
- pleuritic chest pain
- haemoptysis
- risk factor: IVDU or dental procedure
PDx. Infective endocarditis DDx. Respiratory o Embolism- thrombotic, septic o Pneumothorax o Infection- pneumonia, TB, abscess o Neoplastic- lung ca, mets Cardiac o Pericarditis o Endocarditis (50% tricuspid, 20% aortic, 20% mitral) - Infective- streptococci or staphylococci - Non-infective- hypercoagulable state, Libman-Sacks (SLE, immune comlpex deposition) o MI, angina o Rheumatic fever
What investigations would you order for endocarditis?
Diagnostic: - TOE - Blood cultures Bedside - ECG - ABG - Sputum MCS Bloods - FBC - CRP/ESR - Troponins - Coag panel - EUC (renal septic emboli) - LFT - Rheumatoid factor - Iron studies Imaging: - CXR - Venous Doppler US - CT pulmonary angiogram - VQ scan - CT
What abnormalities do you expect to see on CXR and why?
• Cardiomegaly- valvular dysfunction -> increased work of heart muscle -> hypertropy
• Calcified valves
• Infectious spread to lung- consolidation
• PE signs- valvular vegetation embolised (tricuspid valve in IVDU) -> lung infarction
- Fleisher’s signs (20%)- enlarged pulmonary a proximal to thrombus (HTN from distal emboli)
- Hampton’s hump (20%)- peripheral wedge of airspace opacity distal to thrombus
- Westermark’s signs (10%)- regional hypovolaemia (due to segmental artery occlussion)
- Pleural effusion (35%)- visible pleural edge
- Knuckle sign- abrupt tapering pulmonary a (due to distal embolus)
- Atelectasis
Describe the process of taking blood cultures?
- Blood is collected from 3 different sites at differing times (>10 mins apart, infective endocarditis samples taken over 24hrs)
- Collection ideally prior to abx
- Aseptic venepuncture technique
- Aerobic (first) and anaerobic bottles filled 10mL each
- Incubated at body temperature for 5 days
- If bacteria present -> metabolise nutrients -> CO2 released will cause pH change -> flourescent disc colour change
What is the likely causative organism of infective endocarditis?
- Strep viridans (most common, low virulence requires damaged valve)
- Strep sanguinis
- Strep oralis
- Staph aureus- IVDU, acute/severe illness, MRSA potential, metastatic infection risk
Prosthetic valve- staph aureus, staph epidermis, haemophilus
What are some causes of non-infective endocarditis?
- hypercoagulable state
- Libman-Sacks (SLE, immune comlpex deposition)
Which valve is it most likely to be affected in an IVDU?
- Tricuspid valve (50% all IE)
- IVUD: pathogens enter venous system and encounter tricuspid valve first
- Likely causative organism: staph aureus
What is the pathophysiology of infective endocarditis?
⇒ Risk factor (IVUD, dental surgery)
⇒ Virulent organism (e.g. staph aureus) directly injures endocardium -> endothelial erosion
⇒ Platelet and fibrin adhere to injured site
⇒ Bacteria protected from host defences by overlying fibrin and avascularity of valve leaflet -> vegetations form
⇒ Bacterial proliferates -> colonies
⇒ Leukocytosis -> vegetation growth
⇒ Neutrophils release protelolytic enzymes -> friable vegetation (prone to embolisation)
What are the virulence factors of Staph aureus?
Enzymes:
o Coagulase -> clots plasma, coats bacterial cell (avoid phagocytosis)
o Hyaluronidase -> breaks down hyaluronic acid (in plasma membrane)-> allow bacterial spread
o Deoxyribonuclease -> breaks down DNA
o Staphylokinase -> dissolves fibrin -> aids spread
o B-lactamase -> drug resistance
Toxins:
o Super antigens (e.g. Toxic Shock Syndrome Toxin 1 (TSST 1) -> toxic shock syndrome
o Exfoliative toxins -> skin peeling
Other:
o Protein A -> binds to Fc regions of Ab -> impairs phagocytosis -> cripples antibody-mediated response
o Staphyloxanthin (gold pigment) -> antioxidant allowing avoidance of ROS
Compare community vs hospital acquired MRSA?
Community acquired MRSA
o Risk: IVDU, young people, indigenous, aged care residents
o Resistance: B-lactam resistance only -> usually susceptible to Flouroquinolone (Ciprafloxacin) and Sulfonamide (sulfamethoxazole)
o Clincial: skin infection
Hospital acquired MRSA:
o Risk: elderly, DM, dialysis, prolonged hopsitalisation, ICU, IV lins
o Resistance: multi-drug resistance common -> usually susceptible to Sulfonamide (sulfamethoxazole), NOT Flouroquinolone (Ciprafloxacin)
o Clinical: pneumonia, UTI, blood stream
What is the diagnostic criteria for infective endocarditis?
Clinically modified Dukes Criteria:
(needs 2 major criteria OR 1 major and 3 minor OR 5 minor)
Major criteria:
o Blood culture- positive typical organisms on 2 cultures, single culture Coxiella Burnetti
o Endocardial involvement on Echo (e.g. mass, abscess, new valve regurg)
Minor criteria:
o Fever >38
o Immunological phenomena (e.g. peripheral stigmata, Rheumatoid factor, glomerulonephritis)
o Vascular findings (e.g. Janeway lesions, major embolic infarct, intracranial haemorrhage)
o Microbio evidence not fulfilling major criteria
o Risk factors (e.g. IVDU, RHD, congenital heart disease)
List some risk factors for infective endocarditis?
- IVDU
- Dental surgery
- Immunocompromised- HIV, malignancy/chemo
- Prosthetic valve
- Rheumatic heart disease
How would you treat infective endocarditis?
Empirical Rx:
1) Benzylpenicillin (1.8g IV QD) –cover strep
2) Flucloxacilin (2g IV QD)- cover staph
3) Gentamicin (4-6mg/kg, based on renal function)- cover gram neg bacilli
- If MRSA risk (IVDU, prosthetic valve, pacemaker): Vancomycin and Gentamicin
- If penicillin allergy: Cephazolin (cephalosporin class)
List some possible complications of infective endocarditis?
Cardiac: - valve dysfunction - conduction defects (damage AV node fibers or Bundle of HIS) - myocotic aneurysm - suppurative pericarditis - HF Septic emboli: - neuro (embolic stroke, intracerebral haemorrhage, metastatic abscess) - lung (septic PE) - kidney (infarction, metastatic abscess) - spleen (infarction, metastatic abscess) Immune response: - glomerulonephritis (Ig GMB deposition) - AKI - CKD (immune-complex mediated GN) Metastatic infection - vertebral osteomyelitis - septic arthritis - psoas abscess Sepsis
