Is echocardiography (echo) indicated for all patients with Methicillin-Sensitive Staphylococcus aureus (MSSA) bacteremia?

From the Guidelines

Echocardiography is recommended for all patients with Methicillin-Sensitive Staphylococcus aureus (MSSA) bacteremia, with transthoracic echocardiography (TTE) as the initial modality, and transesophageal echocardiography (TEE) if TTE is negative or technically inadequate, due to the significant risk of infective endocarditis and potential for serious complications if left undetected 1.

Key Considerations

• The risk of infective endocarditis in MSSA bacteremia is significant, approximately 10-15% of cases, which can lead to serious complications if not detected early 1.
• Echocardiography helps identify cardiac vegetations, valvular damage, or abscess formation that may require surgical intervention or prolonged antibiotic therapy 1.
• The timing of echocardiography should be as soon as MSSA bacteremia is identified, ideally within 24-48 hours of diagnosis.
• Even in patients without obvious clinical signs of endocarditis, echocardiography is warranted as endocarditis can present subtly, and findings will impact treatment decisions, including antibiotic duration (typically 2 weeks for uncomplicated bacteremia versus 4-6 weeks for endocarditis) 1.

Diagnostic Approach

• TTE is recommended as the first-line imaging modality in suspected infective endocarditis, with TEE recommended in patients with a negative or non-diagnostic TTE, or when clinical suspicion for endocarditis remains high 1.
• TEE has better sensitivity and accuracy than TTE for identifying paravalvular abscesses and is indicated for suspected infective endocarditis of prosthetic valves 1.

Management Implications

• Early detection of endocarditis through routine echocardiography in MSSA bacteremia improves patient outcomes by ensuring appropriate treatment length and interventions 1.
• The size and other characteristics of vegetations on echocardiography have been shown to be useful in predicting complications such as peripheral embolization, and can guide management decisions 1.

From the Research

MSSA Bacteremia and Echocardiography

• The use of echocardiography in patients with Methicillin-Susceptible Staphylococcus aureus (MSSA) bacteremia is a topic of interest, particularly in determining the risk of infective endocarditis (IE) 2, 3, 4.
• Studies have shown that transthoracic echocardiography (TTE) may not be sufficient to rule out IE in all patients, especially those with high-risk factors such as intracardiac prosthetics or persistent fever despite appropriate antibiotic therapy 5, 3.
• Transesophageal echocardiography (TEE) is recommended for patients at high risk for endocarditis, as it has a higher sensitivity for detecting IE compared to TTE 2, 3, 4.

Risk Factors for IE

• Certain clinical risk factors have been identified as increasing the risk of IE in patients with MSSA bacteremia, including:
  • Implanted permanent pacemaker 3
  • Persistent fever despite appropriate antibiotic therapy 3
  • Intracardiac prosthetics 4
  • Recent surgical procedures 4
  • Injection drug use 4
  • Diabetes 4
  • Previous S aureus infection 4

Diagnostic Utility of TEE

• TEE has been shown to be essential in establishing the diagnosis of IE and detecting associated complications 2, 3.
• The sensitivity of TEE for detecting IE is higher than that of TTE, ranging from 88% to 100% 2, 3.
• TEE should be considered after a negative TTE in patients with high-risk factors for IE 3, 4.