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Infective endocarditis
Infective endocarditis

Infective endocarditis

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Infective endocarditis is an infection of the endocardial surface of the heart. This includes the valves, chordae tendinae, septa, and the mural endocardium.s

It is more commonly the left-sided valves (mitral and aortic valves) that are implicated in infective endocarditis. The mitral valve is most commonly implicated (unless IV drug user, which is tricuspid valve).

⚠️ Risk factors

⭐️ The biggest risk factor for developing infective endocarditis is previous episode of endocarditis.

  • Prosthetic heart valves
  • Congenital heart diseases such as structural heart defects, including those that have been surgically corrected.
  • Rheumatic heart disease - 1/3rd of IE patients have rheumatic heart disease.
  • Age >60 years old
  • Male gender
  • IV drug use
  • Poor dentition and dental infections
  • Recent piercings
  • Valvulopathy - post heart transplantation
  • Haemodialysis
  • Intravascular devices such as shunts and catheters.

🦠 Causative agents

There are 4 main causative agents that are cultured:

  1. Staph. aureus - most common cause. Especially acutely in IVDUs.
  2. Viridans streptococci - most common cause in developing countries. Linked with poor dental hygiene and dental procedures.
  3. Coagulase-negative staphylococci such as staph. epidermidis - commonly following prosthetic valve surgery (within 2 months, after which it is most commonly s. aureus still).
  4. Streptococcus bovis - associated with colorectal cancer.
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There is also what we refer to as blood culture negative endocarditis (BCNE), in which blood cultures remain sterile when using traditional lab methods. Some of the reasons for this could include:

  1. Prior antibiotic therapy
  2. Coxiella burnetii
  3. Bartonella
  4. Brucella
  5. HACEK:
    1. Haemophilus
    2. Actinobacillus
    3. Cardiobacterium
    4. Eikenella
    5. Kingella
🫀
Non-infective causes of endocarditis:

For example:

  1. SLE - known as Libman-Sacks endocarditis.
  2. Marantic endocarditis - associated with hypercoagulability states (cancer, autoimmune diseases, HIV). It is non-infective thrombotic endocarditis.

😷 Presentation

Its presentation varies greatly.

In patients with normal heart valves → present acutely and can rapidly progress.

In patients with prosthetic heart valves → presents subacutely/chronically with non-specific, constitutional signs and symptoms (such as night sweats, malaise, fatigue, anorexia, weight loss and myalgia).

  • ⭐️ Fever/chills - this is the most common symptom.
  • New cardiac murmur - any patient with a fever and new murmur should raise high suspicion for endocarditis.
  • Arthralgia
  • Headache
  • Abdominal pain
  • Cough
  • Dyspnoea
  • Pleuritic chest pain
👀
Signs on examination:
  1. Janeway lesions
  2. Osler nodes
  3. Splinter haemorrhages
  4. Roth spots

The most significant difference between Janeway lesions and Osler nodes is that Osler nodes are tender while Janeway lesions are not

Janeway lesions
Janeway lesions
Osler nodes
Osler nodes
Splinter haemorrhages
Splinter haemorrhages
Roth spots
Roth spots

🔍 Investigations

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Imaging:
  1. Transthoracic echocardiogram is the first-line imaging modality.
  2. Transoesophageal echocardiogram is the most sensitive imaging modality for IE.
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Blood tests:
  • FBC - may show normocytic anaemia and neutrophilia.
  • U&Es
  • LFTs
  • CRP - will be significantly raised.
  • ⭐️ Blood cultures - 3 sets of cultures from 3 different sites at 30 minute intervals are required prior to antibiotic therapy. Blood cultures are needed for major Duke criteria in the Duke criteria classification.

🔢 Classification

The Duke criteria classifies the diagnosis into 3 categories: definite, possible and rejected. It considers major criteria, minor criteria and pathological criteria.

Major Duke criteria:

  1. Blood cultures
    1. 2 separate positive blood cultures showing typical IE organisms.
    2. 2 positive cultures from samples drawn >12 hours apart (indicating persistent bacteraemia).
    3. 3 or 4 separate positive blood cultures, all in total drawn within 1 hour, but for a less specific IE pathogen.
    4. Single positive culture for coxiella or anti-phase 1 IgG antibody titrated >1:800.
  2. Endocardial involvement
    1. Echocardiogram positive (due to abscess formation, prosthetic valve dehiscence.
    2. New valvular regurgitation

Minor Duke criteria:

  1. Predisposition
  2. Fever >38ºC
  3. Vascular phenomena such as arterial emboli, intracranial/conjunctival haemorrhages, Janeway lesion, splenomegaly, purpura , clubbing.
  4. Immunological phenomena - such as glomerulonephritis, Osler’s nodes, Roth spots, Rheumatoid factor positive.
  5. Microbiological evidence - positive blood cultures not meeting Duke’s major criteria, or serological evidence of an active infection by an organism consistent with IE.

Pathological criteria:

  1. Microorganisms on a vegetation (growth), embolus or intracardiac abscess.
Photo thanks to www.openmed.co.in

🧰 Management

Our initial management is broad spectrum antibiotics and once the causative agent is identified with cultures, we give targeted antibiotic therapy.

💊
Empirical antibiotics:

This is dependant on whether the valve is native or prosthetic (prosthetic valves have worse prognosis).

  • Native valve:
    • Amoxicillin and consider low-dose gentamicin.
    • Vancomycin + low-dose gentamicin may be given if there is penicillin allergy/MRSA/severe sepsis.
  • Prosthetic valve:
    • Vancomycin + rifampicin + low-dose gentamicin
🧫
Targeted antibiotic therapy:
  • Staphylococci
    • Flucloxacillin if it is a native valve.
    • Vancomycin + rifampicin if there is a penicillin allergy with a native valve.
    • Flucloxacillin + rifampicin + low-dose gentamicin if there is a prosthetic valve.
    • Vancomycin + rifampicin + low-dose gentamicin if there is a prosthetic valve and pencillin allergy.
  • Streptococcus
    • Benzylpenicillin (Penicillin G) we may opt to add low-dose gentamicin if it is less sensitive.
    • Vancomycin + low-dose gentamicin if there is penicillin allergy.
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Surgical indications:

We can remember the indications for surgery through the mnemonic HARPS:

  • H - Heart failure that is resistant to standard medical therapy.
  • A - Antibiotic resistant infection
  • R - Recurrent emboli post-treatment
  • P - PR elongation due to aortic abscess
  • S - Severe valvular incompetence (most commonly mitral valve)

🔮 Prophylaxis

NICE changed their guidelines in 2008. A lot of people are now excluded from prophylactic antibiotics (such as dental patients, upper and lower GI procedures, GU procedures, and respiratory tract procedures.

According to NICE, prophylactic antibiotics are solely given to high-risk patients if:

  • They have an episode of infection
  • They have GI or GU procedures and are given antibiotics due to suspected infection at the site of the procedure. The antibiotics given should cover common IE causative agents.

🚨 Complications

As IE is often asymptomatic, a lot of the time the presenting complaint is the sign/symptom of the complication.

These complications may include:

  1. Acute valvular insufficiency → heart failure.
  2. Neurological complications such as stroke, abscess, mycotic aneurysm.
  3. Embolic complications causing infarctions at the kidney, spleen or lungs.
  4. Infections such as osteomyelitis and septic arthritis.