Non-Infective Endocarditis

Overview – Non-Infective Endocarditis

Non-infective endocarditis (also known as Non-Bacterial Thrombotic Endocarditis or NBTE) is a condition characterised by sterile thrombus formation on cardiac valve leaflets, commonly in the setting of a hypercoagulable state. While it does not involve an active infection, NBTE can result in significant embolic complications and may become secondarily infected, leading to classical infective endocarditis. Prompt recognition is crucial, especially in patients with systemic illness, malignancy, or autoimmune disease.

Definition

Non-infective endocarditis refers to the deposition of sterile thrombi on cardiac valve leaflets, often occurring in hypercoagulable states. Despite the “-itis” suffix, the condition does not involve inflammation or infection unless secondarily complicated.

Aetiology

NBTE is most commonly associated with systemic conditions that promote a hypercoagulable state, including:

• Disseminated intravascular coagulation (DIC)
• Malignancy (especially mucinous adenocarcinomas)
• Sepsis
• Systemic lupus erythematosus (SLE)
• Pregnancy

Morphology / Pathophysiology

• Sterile thrombi form along the valve leaflets, particularly the mitral valve, followed by aortic, tricuspid, and pulmonary valves.
• The vegetations are non-destructive and friable, increasing the risk of embolisation.
• They may become a nidus for secondary infection, converting into infective endocarditis.

Clinical Features

Signs of Underlying Hypercoagulable State

• DIC: acutely unwell, bleeding (mouth, nose, bruises), shock, renal dysfunction
• Sepsis: fever, rigors, infective focus, hypotension
• SLE: fatigue, malar rash, arthritis, lymphadenopathy
• Pregnancy: signs of venous thromboembolism (e.g. DVT)

Signs of NBTE

• Heart murmurs (due to valvular vegetations)
• Systemic embolisation:
  • Stroke (if emboli reach cerebral circulation)
  • Myocardial infarction (coronary embolism)

If Secondary Infective Endocarditis Develops

• Fever + new murmur
• Septic embolic signs:
  • Splinter haemorrhages
  • Osler’s nodes
  • Janeway lesions
  • Roth spots
  • Haematuria, renal infarcts

Investigations

• Clinical diagnosis based on embolic signs, murmur, and systemic illness
• Blood cultures ×3 – taken at different times/sites to exclude infection
• Coagulation studies – to identify DIC or thrombophilia
• Echocardiogram – may reveal sterile vegetations
• ECG – to assess for ischaemia, arrhythmias

Management

• Treat the underlying cause (e.g. malignancy, autoimmune disease, DIC, sepsis)
• Anticoagulation to prevent thromboembolism
  • Start with heparin, then switch to warfarin
• If secondary bacterial endocarditis is diagnosed:
  • IV vancomycin for 2–6 weeks
  • Cardiothoracic referral for valve surgery if:
    • Antibiotics fail
    • Structural valve destruction causes heart failure

Summary – Non-Infective Endocarditis

Non-infective endocarditis (NBTE) is the sterile deposition of thrombi on cardiac valves, commonly seen in hypercoagulable conditions such as malignancy, SLE, and sepsis. It may present with systemic embolic events like stroke or myocardial infarction and can evolve into infective endocarditis. Management includes treating the underlying cause and initiating anticoagulation. For a broader context, see our Cardiovascular Overview page.