Infective Endocarditis

Introduction

Infective endocarditis is a bacterial infection of the endocardial surface of the heart, most commonly the valves. A high index of suspicion is needed  as it is a very serious but commonly missed diagnosis.

 

Staphylococci (vast majority) and streptococci spp are the most common pathogens.

Risk Factors

  • Structural Defects – Prosthetic Valves, Rheumatic heart disease, Septal defects, Mitral valve prolapse, Congenital heart disease

    • Especially if dental or high risk surgery

  • IVDU – most commonly have right heart valve lesions

  • Foreign Bodies – PPM, Central venous catheter.

Clinical Features

Endocarditis is a multi-system disease. Symptoms and signs are usually non specific.

 

Symptoms

  • Systemic symptoms

    • Fever, malaise, headache, myalgia, arthralgia, anorexia, weight loss

  • Symptoms of complications

    • e.g. chest pain, SOB, Abdo Pain

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Signs

  • Signs of Sepsis

    • Fever of unknown origin, tachycardia, hypotension, Tachypnoea, Hypoxia, altered conscious state

  • Cardiac

    • New or changed murmur, signs of CCF,

  • Neurology

    • From embolic events. Sign of meningitis, focal neuro deficits, stroke

  • Abdominal signs

    • Splenomegaly (30%), Hepatomegaly

  • Peripheral Stigmata (extremely rare)

    • Splinter haemorrhage, conjunctival petechial, Oslers Nodes, Janeway’s Lesion, Roth’s Spots on fundoscopy

 

Complications

  • Valve destruction leading to heart failure

  • Septic emboli to the lungs, brain, liver or spleen leading to abscesses

  • Stroke

  • Renal Failure

  • Anaemia

Differential Diagnosis

Fever of Unknown Origin

  • Infective – Pneumonia, abdo/pelvic abscess, TB (pulm + extrapulm), HIV, CMV, EBV

  • Inflammatory – SLE, Rheumatoid

  • Malignancy - lymphoma

Clinical Investigations

 
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Bedside

  • VBG

    • ?evidence of sepsis, high lactate, low pH, low Hb, low Na

  • Urinalysis

    • often proteinuria + microscopic haematuria

  • ECG

    • Prolonged PR interval, TWI, Dysrhythmia, conduction disturbance

 
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Laboratory

  • Blood Cultures

    • Very important. Multiple sets from multiple sites taken over at least a few hours. Ideally taken before antibiotic therapy

  • FBC

    • ? leucocytosis, ? anaemia

  • U&E

    • Renal Impairment is recognised complication

  • Elevated CRP

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Echocardiography

  • Trans-thoracic echo

    • 60% sensitive for vegetations

  • Trans-oesophageal echo

    • 90-99% sensitive, 90% specific.

 
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Radiology

  • CXR

    • may show cardiomegaly or signs of cardiac failure, cavitations in the lungs.

  • CT TAP/CT Brain

    • if concerned about septic emboli to brain, liver, spleen etc

Diagnostic Criteria

 

Modified Dukes Criteria is used to make diagnosis

  • 2 major criteria, or

  • 1 major and 3 minor criteria, or

  • Five minor criteria

Major Criteria

  • Positive blood cultures for Infective endocarditis pathogen

  • Evidence of endocardial involvement on echo i.e. vegetation or abscess

  • New valvular regurgitation on echo.

Minor Criteria

  • Risk Factor

  • Fever > 38

  • Vascular Phenomena

    • septic emboli, Janeway lesion, Conjunctival petechia

  • Immunological phenomena

    • Glomerulonephritis, Roth Spots, Osler Nodes

  • Microbiological Evidence

    • positive blood culture but don’t fulfil major criteria

  • Echo findings

    • consistent with IE but don’t fulfil major criteria

Management & Disposition

 

Initial Resuscitation

  • ABC Approach

  • IV Fluid resus as required

 

Specific Management

  • 3 sets of blood cultures must be taken 30 minutes apart prior to commencing antibiotics.

    • Can be a shorter period if patient critically unwell

  • Broad spectrum antibiotics to cover likely pathogens, as per local guidelines pending culture results.

    • E.g. Ceftriaxone 2g IV + Vancomycin 25mg/kg IV + Gentamicin 3mg/kg IV

  • Cardio-thoracic surgical intervention may be necessary in some cases

Symptomatic Management

  • Anti pyretics are best avoided so not to mask fevers

 

Disposition

  • All patients with ? IE should be admitted to hospital to have the diagnosis confirmed and the appropriate treatment initiated

  • Infectious Diseases, Microbiology, Cardiology +/- Cardio-thoracics should all be involved in the patients care

 

References

1.    Case courtesy of Dr Yair Glick, Radiopaedia.org, rID: 53674

2.    Hung K, Cameron P et al. Chapter 5.7 Heart valve emergencies. Adult Textbook of Emergency Medicine 4th edition.

3.    Mylonakis E, Calderwood S. Infective Endocarditis in Adults. N Engl J Med, Vol 345, No. 18. 2001

4.    https://litfl.com/infective-endocarditis/

5.    SJH Prescribers Capsule. Empiric Antimicrobial Guidelines. Bacterial Endocarditis

This blog was written by Dr Deirdre Glynn and was last updated in November 2020

 Before you go have another look at the clinical case and see have your answers to any of the questions changed and if so how?