Infective Endocarditis Flashcards
What is the definition of infective endocarditis?
Inflammation of the endocardial surfaces of the heart, including heart valves, which is caused by certain microorganisms
What are the types of endocarditis?
Infective endocarditis - Microbes colonise the heart valves and form friable vegetations. Can be acute or subacute
Non bacterial thrombotic endocarditis - characteristically occurs in the setting of malignancy (adenocarcinoma)
Libman sacks endocarditis - typically occurs in the setting of cancers
Why are patients with rheumatic heart disease and replacement heart valves more susceptible to IE?
Blood usually flow smoothly over the valves, when these valves are damaged or replaced, there is an increased chance of bacterial colonisation on the damaged tissue
What is the pathophysiology of Rheumatic Heart Disease
- Acute rheumatic fever results from host immune response to group A streptococcal antigens that cross react with host proteins
- antibodies and CD4+ T cells directed against streptococcal M proteins can in some cases recognise cardiac self antigens
- Antibody binding can activate complement, as well as recruit Fc- receptor bearing cells (neutrophils and macrophages)
- Cytokine production by the stumlated T cells leads to macrophage activation
- Damage to heart tissue may by caused by combination of antibody and T cell mediated reactions
- Recurrent inflammation, progressive fibrosis, narrowing and stiffening of the valve leaflets with commissural fusion, retraction of the leaflet edges, valve thickening, calcification leading to stenosis
What are the gross findings in infective endocarditis?
Acute phase: valvular vegetations (verrucae) along the lines of closure, having little effect on cardiac function
Chronic phase: commissural fibrosis, valve thickening, and calcification and shortened and fused chordae tendinae
What are the microscopic findings in infective endocarditis?
Aschoff bodies, a form of granulomatous inflammation which consists of a central zone of degenerating ECM infiltrated by lymphocytes, plasma cells and Anitschkow cells (activated macrophages also termed as caterpillar cells due to wavy nuclear outlines), found in all 3 layers of the heart - pericardium, myocardium and endocardium
What can be seen macroscopically in infective endocarditis?
Ashcoff nodules
Fibrinoid necrosis
What investigation is used to diagnose vegetations in infective endocarditis?
2D Echo
What are the features of infective endocarditis on 2D echo?
- valvular regurgitations
- leaflet - prolapse, coaptation failure, thickening, reduced mobility, nodules
- annular dilatation
- chordal elongation/rupture
- increased echogenicity of subvalvular apparatus
- pericardial effusion
- ventricular dilatation and dysfunction (almost always with significant regurgitation)
What are the common organisms which cause infective endocarditis?
Viridans strep or staph
Coagulase negative staph
enterococci
Hacek group of microorganisms (oropharyngeal commensals)
How is infective endocarditis diagnosed?
Using the Duke’s criteria
- 2 Major and 0 minor
- 1 major and 3 minor
- 0 major and 5 minor
What are the major criteria for diagnosis of infective endocarditis?
- typical microorganisms consistent with IE in 2 separate blood cultures
- microorganisms consistent with IE from persistently positive blood cultures
- single positive blood culture for coxiella burnetti or antiphase IgG antibody titre >1:800 - Echocardiogram positive for IE, abscess, new partial dehiscence of prosthetic valve, new valvular regurgitation
What are the minor criteria for the diagnosis of endocarditis?
- Predisposing heart condition or IVDU
- vascular phenomena (major arterial emboli, septic pulmonary infarcts, mycotic aneurysms, intracranial haemorrhage, conjunctival haemorrhages, Janeway lesion’s
- Microbiological evidence
- positive blood culture but does not meet the major criteria or serological evidence of active infection with organisms consistent with IE - Fever
- great or equal to 38 - Immunological phenomena
- Glomerulonephritis, Osler’s nodes, Roth’s spots, rheumatoid factor - Echocardiographic findings
- consistent with endocarditis but do not meet the major criteria
Name some causes or risk factors for Infective Endocarditis
- Acquire valvular heart disease with stenosis of regurgitation
- valve replacement
- structural congenital heart disease, including surgically corrected (excluding isolated ASD, fully repaired VSD or PDA)
- Previous IE
- HOCM
- Devices
- Cyanotic congenital heart defects
- Colorectal cancer (streptococcus bovis)
- UTI
- IVDU
- Rheumatic heart disease
- HIV
- Malignancy
- DM
- Alcohol
What are the complications of Infective endocarditis?
Cardiac
- Acute MI
- Pericarditis
- Arrhythmias
- Valvular insufficiency
- CCF
- Sinus valsalva
- Aneurysms
- Intra-cardiac abscess
- arterial emboli
Non Cardiac
- GN
- AKI
- Stroke
- Mesenteric/splenic abscess or infarct
