Infective endocarditis - intrinsic Flashcards
What is infectious endocarditis?
An infection involving:
- endothelial surface of the heartt
- valvular structures
- chordae tendineae
- sites of septal defects
- mural endocardium.
What is the cause of infective endocarditis?
bacteria
- Viridans group streptococci (alpha-haemolytic streptococci)
- Staph aureus
- Enterococci
- Coagulase-negative staphylococci
- Haemophilus parainfluenzae
- Actinobacillus
- Strep bovis
- Coxiella burnetii
- oBrucella species
- Culture negative Haemophilus species, Actinobacillus actinomycetemocomitans
fungi
What is the pathophysiology of infectious endocarditis?
- typically develops on the valvular surfaces of the heart, which has sustained endothelial damage secondary to turbulent flow.
- –> platelets and fibrin adhere to the underlying collagen surface
- –> create a prothrombotic milieu
- Bacteraemia –> to colonisation of the thrombus and perpetuates further fibrin deposition and platelet aggregation,
- –> develops in a mature infected vegetation.
What are the risk factors for infectious carditis?
strong
- prior Hx of IE
- artificial prosthetic heart valves
- congenital heart disease (some types)
- post-heart transplant (patients who develop a cardiac valvulopathy)
weak
- cardiac implanted electronic device
- intravascular catheters (e.g. for haemodialysis)
- acquired degenerative valve disease
- mitral valve prolapse with valvular regurgitation
- Hypertrophic cardiac myopathy
- intrvenous drug users (patients at greater risk of developing acute Staph aureus endocarditis)
Summarise the epidemiology of infective endocarditis
- About 10,000-15,000 cases in the US each year
- About half of patients are over 60 years old
- Men are affected 2.5 times more often than women
What are the presenting symptoms of infective endocarditis?
- Fever/chills
- Night sweats, malaise, fatigue, anorexia, weight loss, myalgias
- Weakness
- Arthralgias
- Headache
- SOB
- ~ chest pain or back pain
What are the signs of infective endocarditis O/E?
- Cardiac murmur (the classic new or worsening cardiac murmur is rare)
- Meningeal signs (secondary to septic emboli)
- Janeway lesions
- Osler’s nodes
- Roth spots
- Splinter haemorrhages
- Cutaneous infarcts
- Palatal petechiae
What are roth spots?
flame-shaped haemmorhages seen on the retina
What is palatal petechiae?
A petechia is a small red or purple spot on the skin or conjunctiva, caused by a minor bleed from broken capillary blood vessels
What are the primary investigations for ?infective endocarditis?
-
FBC
- most patients have a normocytic, normochromic anaemia. Leukocytosis is seen in about one third of cases often with neutrophilia
-
Serum chemistry panel with glucose (provides baseline assessment)
- normal or elevated urea
-
Urinalysis
- (septic emboli are common complications of IE, and urinalysis may demonstrate active sediment assisting in the clinical diagnosis)
- may see RBC casts, WBC casts, proteinuria, pyuria.
-
Blood cultures
- (it is generally recommended that 3 sets of blood cultures be obtained 1 hour apart prior to initiating Abx therapy to ensure greatest yield
- should see bacteraemia or fungaemia.
-
ECG
- (progression of the infection may lead to conduction system disease)
- may see prolonged PR interval, non-specific ST/T wave abnormalities, AV block
-
Echocardiogram
- should be performed in all cases of suspected IE, as early as possible to confirm or rule out the diagnosis)
- will see valvular, mobile vegetations
What are some possible secondary investigations for infective endocarditis?
- Rheumatoid factor
- ~ positive
- ESR
- non-specific
- should be high
- complement levels
- should be low
- CT heart
- should see valvular abnormalities and vegetations
- MRI brain
- useful in identifying cerebral lesions as a complication of IE
What is the name of the criteria used to diagnose infective endocarditis?
Duke’s criteria
What number of criteria must be met for a diagnosis of infective endocarditis?
Must meet
- 2 major criteria OR
- 1 major and 3 minor criteria OR
- 5 minor criteria
What are the major criteria for diagnosis of infective carditis?
Positive blood culture for IE:
- Typical micro-organism for IE from 2 separate blood cultures
- Persistently positive blood cultures
Evidence of endocardial involvement:
- Oscillating intracardiac mass on valve/supporting structures, or in the path of regurgitant jet in the absence of an alternative anatomical explanation
- Abscess
- New partial dehiscence of prosthetic valve or new valvular regurgitation
What are the minor criteria for a diagnosis of infective carditis?
Predisposing heart condition or IVDU
Fever over 38C
Vascular phenomenon such as major arterial emboli, septic pulmonary infarcts, mycotic aneurysm, intracranial haemorrhage, conjunctival haemorrhage, Janeway lesions
Immunological phenomenon:
- o Glomerulonephritis
- o Osler nodes
- o Roth spots
- o Rheumatoid factor
Microbiological evidence:
- o Positive blood cultures not meeting major criteria
Echocardiogram
- o Consistent with IE but not meeting major criterion
