Cardio - Infective Endocarditis Flashcards
describe the pathophysiology of IE
i) Transient bacteraemia (e.g. due to dental procedures, surgery, distant primary infections and non-sterile injections)…
ii) adhesion and invasion of a non-bacterial thrombotic endocarditis (sterile fibrin-platelet vegetation)…
iii) infection of endocardial surface of heart, which may involve 1 or more heart valves, mural endocardium or a septal defect.
which valves are most most commonly affected by IE?
aortic valve > mitral valve > combined aortic and mitral valves > tricuspid valve > pulmonary valve (rare)
name possible causative organisms for IE
- Staph. aureus - most common cause of IE overall (acute and subacute), esp. with prosthetic valves, acute IE and IV drug-abuse related IE. High mortality.
- Streptococci:
- S. viridans - 50-60% of subacute IE cases
- Group D streptococci - usually subacute, 3rd most common IE cause
- others, inc. S. intermedius and Group A, B, C and G - Pseudomonas aeruginosa - usually acute IE, requires surgery for cure
describe the 2 types of IE. which organisms are usually responsible?
- Acute IE: fulminant disease over days-weeks (<2wks). More likely due to S. aureus which has greater virulence and frequently causes metastatic infection.
- Subacute IE: mild to moderate disease which progresses slowly over weeks-months (>2wks) and has low propensity to haematogenously seed extracardiac sites. Often due to streptococci of low virulence, e.g. S. viridans.
suggest risk factors for dev. of IE
60% have a predisposing heart condition
- valvular heart disease with stenosis or regurgitation (e.g. bicuspid aortic valve)
- valve replacement
- structural congenital heart disease
- prev. IE
- hypertrophic cardiomyopathy
- IV drug use (non-sterile injection into venous system)
- invasive vascular procedures
which symptoms would a pt with IE present with?
Clinical presentation very variable, according to causative MO, presence of pre-existing cardiac disease, prosthetic valves and type of disease.
Emboli to brain, lung or spleen is presenting complain in 30%.
Symptoms:
- fever (90%)
- systemic symptoms: chills, poor appetite, weight loss (esp. in subacute)
- loin pain and haematuria - due to renal infarction
describe what signs you might find in a pt with IE
- heart murmurs (85%)
- peripheral stigmata:
- splinter haemorrhages)
- Janeway’s lesions
- Osler’s nodes
- petechiae (conjunctiva, dorsum hands and feet, chest and abdo. wall, oral mucosae and soft palate)
- clubbing (in chronic disease - fundoscopy: Roth spots
- splenomegaly - if splenic infarction
which investigations would you request for a pt with suspected IE?
- Blood
- FBC: increased WCC, anaemia
- CRP and ESR: increased as inflammation markers
- lactate: increased in severe sepsis
- bilirubin: increased in severe sepsis
- blood cultures (+/- blood PCR): cornerstone of Dx and provide live bacteria for ID and susceptibility testing. At least 3 sets taken at 30min intervals at different sites of body. - Bedside tests:
- urine dipstick: microscopic haematuria
- ECG: detect 20% who develop conduction defects - Imaging:
- CXR: as part of initial assessment
- echocardiograph: vegetation, abscess or pseudoaneurysm and new dehiscence of prosthetic valve are diagnostic for IE
- multislice CT: alternative for Dx in some pts (e.g. risk of vegetation embolisation)
- cerebral MRI: for detection of cerebral consequences of IE in pts with neurological Sx - Histology
- pathological examination of resected valvular tissue or embolic fragments: gold standard for IE diagnosis
describe the modified Duke criteria for diagnosis of IE
Dx requires 2 major criteria, 1 major + 3 minor criteria or 5 minor criteria.
MAJOR CRITERIA
- +ve blood culture for IE (typical microorganism consistent with IE from 2 separate blood cultures)
- +ve echo for IE (oscillating intracardiac mass on valve or supporting structures, abscess, new partial dehiscence of prosthetic valve, new valvular regurgitation)
MINOR CRITERIA
- predisposing heart condition or IV drug use
- fever >38 degrees
- vascular phenomena: major arterial thrombi, septic pulmonary infarcts, mycoctic aneurysms, intracranial or conjunctival haemorrhage and Janeway’s lesions
- immunological phenomena: glomerulonephritis, Osler’s nodes, Roth’s spots and rheumatoid factor
- microbiological phenomena: +ve blood cultures but does not meet a major criterion, or serological evidence of active infection with organism consistent with IE
- PCR: broad-range PCR of 16S
- echocardiographic findings consistent with IE but does not meet major criterion
how would you treat a pt with IE?
ANTIMICROBIAL THERAPY
- initial empirical therapy whilst awaiting culture results
- native valve endocarditis (NVE): amoxicillin +/- gentamicin
- prosthetic valve endocarditis: vancomycin + gentamicin + rifampicin - when culture results available, start targeted antimicrobial therapy according to sensitivities and local guidelines.
Drug Tx for PVE should last longer (>6 wks) than for NVE (2-6 wks) but is otherwise similar, exc. for staphylococcal PVE where regimen should include rifampicin whenever strain is susceptible.
in which cases of IE is surgical Tx required?
Required in about 50% due to severe complications. 3 main indications for early surgery in IE are:
- HF
- uncontrolled infection
- prevention of embolic events
suggest possible complications of IE
- congestive HF (most frequent complication, 42-60% NVE cases) - mainly caused by new or worsening aortic/mitral regurgitation
- uncontrolled infection - perivalvular extension of IE is most frequent cause, e.g. abscess formation, pseudoaneurysms and fistulae.
- embolic events (20-50%) - brain and spleen emboli most frequent in L-sided IE whilst PE most frequent in R-sided IE
- AKI (6-30%) - causes often multi-factorial: i. immune complex and vasculitic glomerulonephritis, ii. renal infarction due to septic emboli, iii. antibiotic toxicity. etc.
- Arrhythmias - due to spread of infection beyond endocardium to conduction pathways. mainly 1st, 2nd and 3rd degree atrio-ventricular blocks.
- Septic shock
what is the overall 1yr mortality rate
30%
