Infective endocarditis Flashcards
define infective endocarditis
Heart has 3 layers: epicardium, myocardium and endocardium.
Endocarditis - infection involving the endocardial surface
Valvular structures- native and prosthetic valves
Chordae tendineae
Sites of septal defects
Mural endocardium- posterior wall of the LA becomes rough and wrinkled
incidence of infective endocarditis
low incidence 3-10/100,000
affects males more than females but when females contract it they have a worse prognosis
risk factors for native valve IE
Mitral valve disease Rheumatic heart disease Congenital heart disease Degenerative heart disease Asymmetrical septal hypertrophy Intravenous Drug abusers Alcoholic cirrhosis Diabetic mellitus Indwelling medical devices
what is mitral valve prolapse
Mitral valve prolapse is a condition in which the two valve flaps of the mitral valve do not close smoothly or evenly, but instead bulge (prolapse) upward into the left atrium
prevalence of mitral valve prolapse
high prevalence 2-4% of general population
20% are young female
52/100,000 who have MVP and a systolic murmur develop IE
Congenital heart disease
10-20% of endocarditis case in young adults
ventricular septal defect, bicuspid aortic valve, patent ductus arteriosus
how does endothelium become infective due to mechanical endothelium disruption?
Mechanical endothelial disruption exposures extracellular matrix protein → production of tissue factors.
Deposition of fibrin and platelets→ Non-bacterial thrombotic endocarditis (NBTE).
NBTE facilitates bacterial adherence and infection.
how can an endothelial valve become damaged?
Turbulent blood flow (Venturi effect-low pressure )
electrodes
catheters
inflammation (rheumatic carditis)
degenerative valve disease (ECHO - 50% of asymptomatic patients >60yrs)
Venturi effect?
there’s a reduction in fluid pressure when a fluid flows through constricted area of pipe. High velocity but low pressure
how does a normal valve become inflamed?
Inflammation of endothelial cell → expression of integrins (β1 family)
integrin acts like a hook that binds circulating fibronectin binding proteins on staph aureus
Adherent organisms trigger active internalisation into valve endothelial cells.
examples of invasive procedures that can cause bacteraemia
Dental procedures requiring manipulation - gingival /periapical region
Dental procedures -perforation of oral mucosa
GU and GI surgery
Intravascular catheters
non-invasive activities that can lead to bacteraemia?
(chewing and tooth brushing)-low grade bacteraemia of short duration but with high incidence.
pathophysiology of infective endocarditis
valvular endothelium - platelet-fibrin deposition - nonbacterial thrombotic endocarditis - adherence - colonisation = vegetation
mucous membranes - trauma - bacteremia - adherence - colonisation - vegetation
causative organisms of IE
Viridans group streptococci Staphylococcus aureus Enterococci Coagulase-negative staphylococci Haemophils parainfluenzae Strep bovis Fungi Brucella species Culture-negative Haemphilus species
acute vs subacute
acute = days/weeks subacute = weeks to months
mode of acquisition of IE
IVDU - IV drug users
healthcare
community
Classification:- localisation of IE
+/- intra-cardiac material
L sided native valve IE
L sided prosthetic valve IE (PVE)
R sided IE
Device related IE (permanent pacemaker/cardioverter -defib)
how can you tell if a patient has active infective endocarditis
IE with persistent fever (>38 °C) and positive blood cultures
active inflammatory morphology found at surgery
patient still under antibiotic therapy
histopathological evidence of active IE
why is IE difficult to diagnose
it’s not a uniform disease
syndrome diagnosis determined by presence of multiple findings ie
Presence or absence of pre-existing cardiac disease
causative microorganisms
presence or absence of complication
underlying patient characteristics
mode of presentation
atypical presentation of IE occurs in which patients?
elderly
immunocompromised
diagnosis of acute IE
fever, embolic signs/symptoms (stroke, splenic infarct) or decompensated HF
diagnosis of subacute IE
fever, non-specific constitutional symptoms or palpitation and immunologic/vascular phenomena.
common symptoms of IE
fever/chills
night sweats, malaise, fatigue, anorexia, weight loss
weakness, arthralgia, headache (may be non-specific or embolic)
SOB
Clinical signs of IE
cardiac murmur (regurgitant murmur) with signs of HF janeway lesions
immune complex depostion:- olser nodes, roth spot
meningeal signs
splinter haemorrhage
cutaneous infarcts
vasculitis rash
