Should we consider septic emboli as a cause of cavitary pneumonia and look for vegetations on echocardiogram (ECHO)?

Septic Emboli and Cavitary Pneumonia: When to Consider Endocarditis

Yes, cavitary lesions in the lungs should prompt consideration of septic emboli from infective endocarditis, and echocardiography should be performed to look for vegetations, especially when risk factors are present.

Relationship Between Cavitary Pneumonia and Septic Emboli

Cavitary lesions in the lungs can be a manifestation of septic emboli, which are a common complication of infective endocarditis (IE):

• Systemic embolization occurs in 22-50% of IE cases 1
• While most emboli affect the central nervous system (65%), pulmonary emboli are frequent in right-sided and pacemaker lead IE 1
• Septic pulmonary emboli typically present as peripheral, multiple nodular lesions that may progress to cavitation 2

When to Consider Endocarditis as a Source

Consider endocarditis as a source of septic emboli causing cavitary pneumonia in the following scenarios:

1. Specific pathogens:

   • Staphylococcus aureus bacteremia (particularly high risk) 1, 3
   • Candida species
   • HACEK organisms

2. Clinical features:

   • Multiple, peripheral nodular lesions on chest imaging
   • Cavitary lesions that develop over time
   • Concurrent bacteremia
   • Persistent fever despite appropriate antibiotics

3. Risk factors for endocarditis:

   • Intravenous drug use
   • Prosthetic valves or cardiac devices
   • Congenital heart disease
   • Previous history of endocarditis
   • Indwelling catheters

Diagnostic Approach

When cavitary pneumonia is identified:

1. Blood cultures: Obtain multiple sets before starting antibiotics 1

2. Echocardiography:

   • Transthoracic echocardiography (TTE) should be performed urgently in patients with suspected endocarditis 1
   • Transesophageal echocardiography (TEE) is indicated if:
     • TTE is negative but clinical suspicion remains high
     • Staphylococcus aureus bacteremia is present 1
     • Prosthetic valves or cardiac devices are present
     • Image quality on TTE is suboptimal

3. Advanced imaging:

   • CT angiography may help reduce equivocal cases 1
   • [18F]FDG PET/CT can be useful to detect septic emboli and identify the source of infection in suspected or confirmed IE 1

Clinical Significance

The identification of septic emboli and endocarditis has important implications:

• Requires prolonged antimicrobial therapy (typically 4-6 weeks)
• May necessitate surgical intervention if large vegetations (>10mm) are present
• Affects prognosis and risk of further embolic events
• Requires monitoring for additional complications (e.g., mycotic aneurysms)

Important Caveats

• Not all cavitary lung lesions are septic emboli; differential diagnosis includes primary lung abscess, tuberculosis, fungal infections, and malignancy
• Septic pulmonary emboli can occur without evidence of right-sided IE 4
• Right-to-left cardiac shunts can lead to systemic septic emboli even with isolated right-sided endocarditis 5
• The risk of embolization decreases significantly after 2-3 weeks of appropriate antibiotic therapy 1, 3
• Negative initial echocardiography does not exclude endocarditis; repeat imaging may be necessary if clinical suspicion remains high 1

In summary, the presence of cavitary lesions in the lungs should trigger consideration of septic emboli from endocarditis, particularly in the setting of bacteremia or risk factors for IE. Prompt echocardiography is essential for diagnosis and management planning.