Background Information

Definition

IE is the infection of the endocardial surface of the heart, most commonly involving the heart valves​​​​​​.

Aetiology

Causative Agent

Bacterial causes are most common: ^{[Ref1, Ref2]}

Organism	Description
Staphylococcus aureus	Leading cause overall Esp. in Prosthetic valve and device-related (e.g. central catheter, implantable cardiac devices) endocarditis IVDU
Coagulase-negative staphylococci (e.g. Staphylococcus epidermidis)	2nd most common cause of prosthetic valve and device-related (e.g. central catheter, implantable cardiac devices) endocarditis
Viridans group streptococci (e.g. Streptococcus mitis, Streptococcus sanguinis)	Common in poor dental hygiene, following dental procedures
Streptococcus gallolyticus (formerly known as Streptococcus bovis)	Notable association with colorectal cancer

Other less common causes:

• Culture-negative endocarditis
  • HACEK organisms
  • Coxiella burnetii (Q fever)
  • Bartonella species
  • Brucella species
  • Chlamydia species
  • Fungal (Candida, Aspergillus) (seen mostly in immunocompromised / critical care patients)

 

• Sterile (non-infective causes associated with medical conditions)
  • • Libman-Sacks endocarditis – associated with SLE and antiphospholipid syndrome
    • Non-bacterial thrombotic endocarditis (NBTE) – associated with malignancies and hypercoagulable states

Risk Factors

Cardiac risk factors: ^[Ref]

• Previous IE
• Implanted prosthetic valves
• Acquired valve disease (mitral valve prolapse – most common)
• Hypertrophic cardiomyopathy
• Congenital structural heart disease

Non-cardiac risk factors: ^[Ref]

• IVDU – one of the most important
• Indwelling devices (e.g. intravascular catheters, implantable cardiac devices)
• Poor oral hygiene
• Diabetes mellitus and other causes of immunosuppression (e.g. HIV, steroids)
• Long-term haemodialysis
• Chronic skin infection

Diagnosis

Clinical Features

Clinical features of IE can be grouped as following:

Group	Features
Systemic symptoms	Fever – most common Malaise, chills, night sweats Weight loss
Cardiac manifestations	New or changing regurgitation murmur Heart valve involvement prevalence: mitral > aortic > tricuspid > pulmonary Tricuspid involvement is more common in IVDU patients   Heart failure
Vascular phenomena	Janeway lesions (painless erythematous macules on palms and soles) Splinter haemorrhages Petechiae Conjunctival haemorrhage Septic emboli Ischaemic stroke, brain abscess, mycotic aneurysm Splenic infarct, splenomegaly Renal infarct Pulmonary embolism (mainly in right-sided IE)
Immunologic phenomena (immune-complex mediated)	Osler nodes (painful nodules on fingers and toes) Roth spots (retinal haemorrhages with pale centres) Glomerulonephritis +ve Rheumatoid factor

Investigation and Diagnosis

Perform both in suspected IE:

• Blood cultures (at least 3 sets from separate sites) – first priority
• TTE
  • If TTE is -ve but clinical suspicion is strong → perform TOE

Diagnostic Criteria – Modified Duke Criteria

Interpretation:

• Definitive IE
  • Pathological criteria met, or
  • 2 major criteria, or
  • 1 major criterion + 3 minor criteria, or
  • 5 minor criteria
• Possible IE 
  • 1 major criterion + 1 minor criterion, or
  • 3 minor criteria, or
  • 5 minor criteria

Major Criteria	Blood culture +ve	Typical microorganisms in 2 separate blood cultures, or Persistently +ve blood cultures, or Specific for Coxiella burnetii: 1 +ve blood culture / anti–phase 1 IgG antibody titer ≥1:800
	Evidence of endocardial involvement	Echocardiogram positive for IE Oscillating intracardiac mass on valve / supporting structures, or Abscess, or New valvular regurgitation, or New partial dehiscence of prosthetic valve
Minor Criteria	Presence of predisposition factor: IVDU, or Predisposing heart condition
	Fever (>38°C)
	Vascular phenomena	Major arterial emboli Septic pulmonary infarcts Mycotic aneurysm Intracranial haemorrhage Conjunctival haemorrhages Janeway lesions
	Immunological phenomena	Glomerulonephritis Osler nodes Roth spots Rheumatoid factor
	Microbiological evidence	+ve blood culture/s but not meeting major criterion as noted above, or Serological evidence of active infection with an organism consistent with IE

Management

IE Prevention

General Advice to Prevent IE

• Maintain good oral hygiene
• Maintain strict skin hygiene (including optimised treatment of chronic skin conditions)
• Avoid non-essential invasive procedures (e.g. skin piercing, tattooing, infusion catheters)
• Avoid IVDU
• Patient education

Antibiotic Prophylaxis for IE

Antibiotic prophylaxis is NOT recommended routinely.

NICE specifically states that routine antibiotic prophylaxis against IE is not recommended in the following scenarios:

• Dental procedures
  • This includes chlorhexidine mouthwash (not routinely offered for the purpose of IE prevention)

 

• Non-dental procedures at the following sites:
  • Upper and lower GI tract
  • Upper and lower respiratory tract (including ENT procedures and bronchoscopy)
  • Genitourinary tract (including urological, O&G procedures, childbirth)

NICE recommends that if a person is at risk of IE and is receiving antimicrobial therapy due to a GI / GU procedure for suspected infection → give antibiotics that cover IE organisms.

Acute IE Management

Antibiotic Therapy

Initial Blind Antibiotic Therapy (culture and sensitivities NOT available)

BNF recommends antibiotic therapy depending on native or prosthetic valve IE:

• Native valve
  • 1^st line: amoxicillin / ampicillin ± gentamicin
  • Penicillin allergic / MRSA suspected / severe sepsis: vancomycin + gentamicin
  • Severe sepsis with RF for gram -ve infection: vancomycin + meropenem

 

• Prosthetic valve
  • 1^st line: vancomycin + rifampicin + gentamicin (low-dose)

Targeted Antibiotic Therapy

Duration of antibiotic therapy: generally 4-6 weeks

Recommended antibiotics by BNF:

Organism	1st line antibiotic	2nd line (MRSA / penicillin allergic)
Staphylococci	Native valve → flucloxacillin	Native valve → vancomycin + rifampicin
	Prosthetic valve → flucloxacillin + rifampicin + gentamicin	Prosthetic valve → vancomycin + rifampicin + gentamicin
Streptococci	Benzylpenicillin	Vancomycin / teicoplanin + gentamicin
Enterococci	Amoxicillin / ampicillin + gentamicin / benzylpenicillin	Vancomycin / teicoplanin + gentamicin
HACEK microorganisms	Amoxicillin / ampicillin + gentamicin	Ceftriaxone / cefotaxime + gentamicin

Surgery

Indications

Main indications for surgery:

• Heart failure (secondary to IE-related valvular dysfunction)
• Persistent bacteremia despite appropriate antibiotic therapy (for 5-7 days)
• Presence of complications (any)
  • Heart block
  • Annular / aortic abscess

Choice of Surgical Intervention

• 1st line: surgical valve repair
• 2nd line: surgical valve replacement

References