Management of Infective Endocarditis

Infective endocarditis (IE) is infection of the endocardium of the heart. Diagnosis can be difficult and the condition can be overlooked.The article on infective endocarditis covers epidemiology, presentation, diagnosis and investigation. Management of endocarditis covers the main aims of:

• Eradication of the infectious agent from the thrombus
• Treating the complications of valvular infection which may be both intracardiac and extracardiac

Successful treatment requires:

• Prompt diagnosis of IE
• Accurate and early identification of the infecting organism
• Careful monitoring of patients for complications of disease and treatments
• Surgical management of mechanical complications when necessary

• Most native valve IE is caused by viridans streptococci (50-70%).
• Most late prosthetic valve endocarditis (PVE) is caused by viridans streptococci (50-70%).
• Other organisms include:
  • Staphylococcus aureus (25%)
  • Enterococci (10%)
• In early PVE the most common organisms are:
  • S. epidermis
  • S. aureus
• Less common but serious causes of IE include:
  • Gram-positive and Gram-negative bacilli
  • HACEK group of organisms (Haemophilus, Acinobacillus, Cardiobacterium, Eikenella and Kingella species)
  • Fungi

With suspected IE it is necessary to follow the correct procedures to identify the presence or absence of the Duke criteria. The following outline is recommended by the Royal College of Physicians:

• Admit the patient to hospital for full investigation:
  • Blood cultures
  • Temperature records
  • Basic haematology and biochemistry investigations
  • ECG and CXR
  • Comprehensive transthoracic echocardiography (TTE)
• Blood cultures:
  • With a sick patient (acute IE) take 3 sets of cultures at >1 hour intervals.
  • Less obvious IE (sub-acute presentation) requires 6 sets of cultures over 24-48 hours.
  • Cultures negative for the commoner organisms should be checked for unusual slow growing organisms and fungi.
• Referral:
  • When blood cultures are positive to a cardiologist.
  • At the outset to a microbiologist.
• Transoesophageal echocardiography:
  • If TTE difficult or suboptimal.
  • In order to further assess vegetations, abscesses or valvular perforations.
  • In all patients with prosthetic valve endocarditis (PVE).
• Serological testing:
  • If the diagnosis is still suspected but cultures negative after 7 days.
  • Tests for Coxiella burnetii, Bartonella species and Chlamydial organisms are available and should be performed.
• Testing of biopsied tissue with special techniques to identify bacteria and fungi are being developed.

The detail of management will depend on the specific diagnosis. The following elements of medical care are likely to be important:

• Treatment of cardiac failure. Congestive cardiac failure can result from valvular insufficiency or myocarditis.
• Antibiotic therapy. These are the most important part of medical therapy. The following general points are worthy of mention:
  • In acute IE antibiotic therapy should be started as soon as possible, but not until between 3 and 5 blood cultures have been taken. The initial antibiotic selection will depend on an assessment of the most likely organism but should cover both Gram-positive and Gram-negative organisms.
  • In subacute IE waiting for the results of blood cultures is permissable as this does not increase complications. It also allows antibiotics to be started in the knowledge of sensitivities.
  • Bactericidal antibiotics are necessary for the cure of valvular infection.
  • To achieve the required therapeutic drug levels the intravenous route is necessary for the administration of antibiotics. This should be for 4-6 weeks and through a large central vein. Only penicillin-sensitive streptococci should be considered for shorter courses of penicillin.
  • Unusual organisms will need special regimens and advice from a microbiologist.
  • Patients who are penicillin allergic will require alternative antibiotics (vancomycin, teicoplanin, gentamicin) and advice should be sought from the microbiologist.
  • Antibiotic treatment requires hospitalisation and suitably skilled monitoring of patients. It is particularly important to monitor patients for complications, relapses or recurrence.
• Anticoagulation. This is controversial. Despite thrombosis being an important element in the pathogenesis of IE, outcomes in patients receiving anticoagulation appear worse. Intracerebral bleeds occur in the anticoagulated patients. Only patients with other indications for anticoagulation should receive it.

Guidelines have been produced for treating IE.^1,2

As many as 25% of patients with IE will eventually need surgery which may range from valve replacement to neurosurgery for cerebral abscess. Even in stable patients an early consultation with a cardiac surgeon is recommended in case emergency surgery is required.

Indications for surgical intervention

• Native valve endocarditis:
  • Congestive cardiac failure from valvular incompetence is the main indication for surgery. This is required when there has been a second relapse of congestive cardiac failure during or after treatment. This may need to be done as an emergency when there is life-threatening CCF, pulmonary oedema or cardiogenic shock and the prospects of recovery and reasonable quality of life are favourable.¹
  • Sepsis continuing 72 hours after start of antibiotics (that is infections resistant to antibiotics)
  • Annular or aortic abscesses
  • Large mobile vegetations
  • Recurrence of septic emboli (after 2 weeks of antibiotics)
  • Septal abscess causing conduction defects
  • Kissing anterior leaflet mitral valve infection when there is coexistent aortic valve infection
  • Fungal valvular infections (other than Histoplasma capsulatum)
  • Rupture of aneurysms of sinus of Valsalva
• Prosthetic valve endocarditis

• This should be regular and by a suitably skilled team to identify complications, relapse or recurrence.^1,2 Relapse of IE usually occurs within 2 months of finishing therapy and may occur when still an inpatient or after discharge.
• Examinations should incorporate:
  • Cardiac assessment including identification of new or changing murmurs and CCF
  • Monitoring for embolic or immunological complications
  • Repeat echocardiography

Patients should continue to be monitored with particular attention to delayed development of CCF. Relapse of IE usually occurs within 2 months of finishing therapy and this may occur after hospital discharge.

An important part of management is early identification and treatment of complications. Patients should be monitored for:

• Valvular insufficiency
• Myocardial abscess formation (including septal abscess)
• Metastatic infection
• Embolic complications
• Immunological complications

This is covered in the article prevention of endocarditis.