INFECTIVE ENDOCARDITIS

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INFECTIVE ENDOCARDITIS

• Michael Sales
• 20/02/13

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Infective Endocarditis

• Colonisation or invasion of heart valves or mural
  endocardium by microbes
• Formation of vegetations composed of thrombotic
  debris organisms
• Often associated with destruction of underlying
  cardiac tissue
• Aorta, aneurysmal sacs, other blood vessels
  prosthetic devices can be involved
• Most cases bacterial

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Acute IE

• Infection of previously normal heart valve by a
  highly virulent organism that produces
  necrotising, ulcerative, destructive lesions
• Difficult to cure with Abx usually require Sx
• Death can occur within days to weeks despite Rx

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Subcute IE

• Organisms are usually of lower virulence
• Cause insidious infections of deformed (native)
  valves that are less destructive
• Can take prolonged course weeks to months
• More amenable to treatment with antibiotics

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Aetiology Pathogenesis

• Incidence 1.7-7.2 cases per 100 000
• Female to male 12
• Median age has increased from 30-40 to 47-69 yrs
• Rheumatic HD is no longer the major risk factor
  in Western countries

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Aetiology Pathogenesis

• More common causes now
• Mitral valve prolapse
• Degenerative calcific valvular stenosis
• Bicuspid aortic valve
• Prosthetic valves
• Congenital defects

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Aetiology Pathogenesis

• Majority of cases of IE are caused by gram ve
  bacteria
• Staphylococcus aureus is now more common (31-54)
  than oral Streptococci
• MSSA is more frequent in community-acquired IE,
  infects mainly native valves is associated with
  bacteraemia of unknown origin
• MRSA is more related to nosocomial infection,
  wound infection, permanent IV catheters or
  surgery in previous 6/12

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Aetiology Pathogenesis

• Strep viridans is now less common (12-26) but
  difficult to isolate confers partial resistance
  to ABx
• Coag -ve Staph were main cause of prosthetic
  valve endocarditits in the past, esp within first
  6-12/12 after valve surgery, MRSA is now more
  common

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Aetiology Pathogenesis

• Enterococci
• HACEK group
• Haemophilus group
• Actinobacillus group
• Cardiobacterium hominis
• Eikenella corrodens
• Kingella kingae
• All commensals in the oral cavity

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Other Causes

• Candida Aspergillus species cause the majority
  of fungal IE (1-3 of IE)
• Patients with IVDU, prosthetic valve long-term
  CVC are more likely to have fungal IE needs to
  be considered in presence of bulky vegetations,
  metastatic infection, perivalvular invasion, or
  embolisation to large blood vessels despite -ve
  BC
• In 10-15 of all cases of endocarditis no
  organism can be isolated from BC
  (culture-negative endocarditis)

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Other Causes

• Whenever BC -ve IE is suspected other organisms
  such as Coxiella burnetti, Legionella spp,
  Brucella spp, Bartonella spp , Chlamydiae spp,
  must be considered

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Aetiology Pathogenesis

• The most common factors predisposing to IE are
  those that cause bacteraemia
• Dental/surgical procedures
• Needle sharing amongst IVDU
• Breaks in skin
• The risk in those with predisposing factors (eg
  valve abnormalities) can be lowered by using
  prophylactic Abx however the use of prophylactic
  Abx is no longer recommended (discussed further
  later)

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Morphology

• Presence of friable, bulky, potentially
  destructive vegetations containing fibrin,
  inflammatory cells infective organism (ie
  bacteria, fungi) on heart valves
• Aortic mitral most common sites
• Right heart more common in IVDU
• Vegetations can be single or multiple may
  involve more than one valve
• Vegetations can erode into underlying myocardium
  producing abscesses (ring abscess)

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Morphology

• Emboli can break off vegetations causing
  abscesses at distant sites where they lodge
  leading to sequelae such as septic infarcts or
  mycotic aneurysms
• Vegetations of subacute endocarditis are
  associated with less valvular destruction than
  acute endocarditis
• Gram ve bacteria are particularly resistant to
  pts innate antibacterial activity (eg complement)
  which facilitates the adhesion formation of
  vegetations

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Morphology

• When the left heart is involved vegetations most
  often develop on the ventricular aspect of the
  aortic valve atrial surface of mitral valve,
  usually along the valve leaflets
• Septic embolism has usually occurred before
  diagnosis
• Up to 30 of patients have renal or splenic
  infarcts at the time of diagnosis
• Septic emboli can also occur in the heart, brain,
  intestine other large organs

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Diagnosis

• The modified Duke criteria based on clinical,
  microbiological echo findings providing high
  sensitivity specificity (80) for diagnosis of
  IE when applied to patients with native valve IE
  with ve BC

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Modified Duke Criteria

• Major Criteria
• Posititive blood cultures
• Positive echocardiogram for IE defined as
• Oscillating intracardiac mass
• Intracardiac abscess
• New partial dehiscence of prosthetic valve
• Minor Criteria
• Predisposition such as a heart condition or IV
  drug use
• Fever
• Vascular phenomena or immunological phenomena
  such as major arterial emboli, septic pulmonary
  infarcts, mycotic aneurysm, intracranial
  haemorrhage, conjunctival haemorrhage, Janeway
  lesions
• Other microbial evidence such as PCR,
  serological tests, or a positive blood cuture but
  does not meet a major criterion

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Diagnosis

• The dx is confirmed in presence of 2 major
  criteria, 1 major 2 minor or 5 minor criteria
• IE considered in presence of 1 major 1 minor or
  3 minor

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Clinical Features Diagnosis

• The modified Duke criteria have low sensitivity
  when BC -ve, infection affecting prosthetic
  valve/pacing system when IE effects right heart
• Its not always useful for rapid diagnosis one
  of its major criteria includes ve blood cultures

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Clinical Features

• Fever, chills, weakness, lethargy, weight loss,
  flu-like illness (not always present)
• Longstanding IE (rarely seen now with earlier
  diagnosis) splinter haemorrhages, Janeway
  lesions, Osler nodes, Roth spots
• Murmurs are present in 90 of patients with left
  sided IE

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Splinter Haemorrhages
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Janeway Lesions
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Osler Nodes
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Roth Spots
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Clinical Features

• In IVDU right sided IE usually affect the
  tricuspid valve occasionally the pulmonary
  valve, instead of systemic issues pulmonary
  embolism is the most important complication which
  can evolve into
• Pulmonary infarction
• Pulmonary abscess
• Bilateral pneumothoraces
• Pleural effusion
• Empyema

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Clinical Features

• The severity of valvular destruction depends on
  virulence of infecting organism infection
  duration
• Heart failure can be the initial presentation

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Micro

• ve BC still the best method for identifying the
  causative agent considered a major diagnostic
  criteria
• BC are ve in 80 of cases
• BC -ve in cases of intracellular or fastidious
  pathogens or after prior Abx treatment
• BC are important in suspected IE (eg T gt 38, new
  regurgative murmur, hx of valvular disease,
  IVDU) in cases where Abx have been commenced
  prior to BC the recovery rate is only 35-40

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Micro

• It is recommended to draw 3 sets of cultures
• Culture -ve IE delays diagnosis initiation of
  treatment/correct treatment
• Using PCR has been proposed in these cases
• PCR of excised valve tissue or embolic material
  should be performed in culture -ve IE (in cases
  of valve surgery or embolectomy)

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Echo

• Important non-invasive technique for diagnosis
  management
• Sensitivity of TTE ranges from 45-60
• TOE offers better quality sensitivity ranges
  from 90-100, it is necessary whenever
  perivalvular complications or mitral valve
  involvement is suspected

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Echo

• Findings
• Vegetation (hallmark lesion of IE) mobile
  echodense mass attached to valvular leaflets or
  mural endocardium. Sensitivity TTE 75 TOE 90
• Periannular abscess
• New dehiscence of valvular prosthesis

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Echo Findings

• 10 of IE involves right side of heart most
  commonly the triscupid valve alone (98),
  although the pulmonary valve Eustachian valve
  (junction of IVC RA) can be involved
• Isolated right sided involvement is well detected
  by TTE in those cases a TOE isnt necessary
• However 15 IVDU associated IE affects
  left-sided valves a TOE should be considered

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Echo Findings

• An abscess usually affects the aortic root
  presents as a perivalvular zone of reduced echo
  density without blood flow. TTE (45-50) TOE
  (gt90)
• Important because the diagnosis of an abscess is
  an indication for early surgery
• Aortic/mitral regurg is secondary to valvular
  necrosis, perforation or prolapse
• 50-60 of pts with IE develop HF secondary to
  valvular destruction require early surgery
  (mortality without surgery 80)

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Echo Findings

• Vegetation size mobility is important
• Stroke complicates 20-40 of left-sided IE is
  the second most common cause of death
• Vegetation gt 10mm /or high vegetation mobility
  are associated with increased embolic risk,
  early surgery (within 1/52 of dx) is associated
  with improved long-term outcomes through
  reduction in systemic embolic events
• If vegetations are small or have already
  embolised, echo can provide false -ve results in
  15. When suspicion is high a TOE can be
  repeated in 7-10 days

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Echo

• In the emergency department bedside USS is
  starting to be used in patients suspected of IE
  to help speed up diagnosis it has its
  limitations (should be used to rule in IE not
  rule out) must be followed up with a formal USS

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Prophylaxis

• 2008 National Institute of Clinical Excellence
  (NICE) produced guidelines re antimicrobial
  prophylaxis for IE in pts undergoing
  interventional procedures
• The guidelines suggest there is weak evidence to
  support routine preop Abx for pts at risk of IE
• They state risk of allergic reaction, cost
  resistance implications from Abx overuse
• Therefore the routine use of Abx prophylaxis is
  no longer recommended

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Prophylaxis

• However in the case of infection at the operative
  site, Abx prophylaxis is still recommended in
  high-risk patients eg
• Acquired valvular HD
• Previous valve replacement
• Structural congenital HD (excluding repaired ASD,
  VSD or PDA)

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Antibiotics

• Empirical treatment flucloxacillin gentamicin
  are the usual first line
• Adjusted according to MCS
• Vancomycin is used in pts with intracardiac
  prosthetic material or suspected MRSA
• Benzylpenicillin is the first choice for
  Streptococcus or Enterococcus penicillin-susceptib
  le strains
• For vanc-resistant MRSA teicoplanin, lipopeptide
  daptomycin or oxazilidones (linezolid) is
  recommended

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Fungal IE

• Usually requires surgery
• Amphotericin B doesnt penetrate well into
  vegetations however is used successfully against
  Candida endocarditis
• Fluconazole is a fungistatic only active
  against Candida spp
• Caspofungin is usually fungicidal for Candida spp
  but its penetration into vegetations is unknown

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Treatment Course

• IV Abx is normally continued for 4-6 weeks, with
  the aim of sterilising the vegetations
• ID should be involved in BC -ve IE

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Surgery

• Antimicrobial therapy can only offer curative
  treatment in 50
• The other 50 require surgery
• The surgical goal is valve repair but most
  require valve replacement
• Pts with IE large vegetations, intracardiac
  abscess (9-14) or persisting infection (9-11)
  almost always require surgery

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Surgery

• Anaesthetic can be complicated secondary to
  haemodynamic instability
• Mitral or aortic regurg particularly challenging
• Induction often complicated by hypotension
  despite hyerdynamic left ventricle hypoxaemia
  secondary to severe pulmonary oedema
• Some pts may develop acute RV dysfunction
  severe tricuspid regurg
• These pts require arterial pressure CVP
  monitoring may require inotropes/vasopressors

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Surgery

• Pts with peri-annular abscess have higher risk of
  para-valvular regurgitation valve dehiscence
  after OT
• Current IE perioperative mortality is 5-15
• If sepsis is under control the mortality is
  similar to non-infected valve replacement

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Surgery

• Most common complications
• Persistent septic shock
• Coagulopathy
• Acute renal failure
• Stroke
• Refractory heart failure
• Conduction abnormalities

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Summary

• Challenging diagnosis therefore diagnosis often
  delayed
• Need to have a high index of suspicion esp high
  risk pts
• Clinical examination is still very important
• Cultures are extremely important for
  diagnosis/treatment
• The use of TTE/TOE is vital for Dx Tx planning
• Bedside USS is now being used for rapid
  assessment in ED
• Treatment needs to be started early to reduce
  morbidity/mortality
• Many pts require surgical intervention
• Pts can be haemodynamically unstable
  peri-operatively
• ID involvement is useful esp in BC -ve IE

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References

• Martinez, G., Valchanov, K., Infective
  Endocarditis, Continuing Education in
  Anaesthesia, Critical Care Pain, 2012 123
• Kumar., Abbas., Fausto., Aster., Robbins and
  Cotran Pathological Basis of Disease, 8th
  Edition, 2010
• Deng, H., Ma, Y., Zhia, H., Miao, Q., Surgical
  valve repair of isolated pulmonary valve
  endocarditis, Interactive Cardiovascular and
  Thoracic Surgery, 2013 16 384-386
• Seif, D., Meeks, A., Mailhot, T., Perera, P.,
  Emergency department diagnosis of infective
  endocarditis using bedside emergency ultrasound,
  Clinical Ultrasound Journal, 2013 51
• Kang, D., Kim, s., Yun, S., Choo, S., Song, J.,
  Sohn, D., Early Surgery versus conventional
  treatment for infective endocarditis, The New
  England Journal of Medicine, 2012 366 2466-73

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References

• Wikipedia (images)
• Dermnet.nz (images)
• Beaulieu, A., Rehman, H., Janeway Lesions,
  Canadian Medical Association Journal, 2010
  18210 (images)