What imaging can be ordered for a patient with a bifascicular block and normal cardiac (cardiac enzyme) markers?

Imaging for Bifascicular Block with Normal Cardiac Markers

Transthoracic echocardiography is the primary imaging modality recommended for patients with bifascicular block to evaluate for structural heart disease. 1, 2

Initial Imaging Approach

Echocardiography (First-Line)

• Transthoracic echocardiography is reasonable for patients with bifascicular block when structural heart disease is suspected, even though the strongest Class I recommendation is specifically for newly detected left bundle branch block (LBBB). 1, 2
• The echocardiogram should assess for:
  • Left ventricular systolic dysfunction 1
  • Cardiomyopathy 1
  • Valvular heart disease 1
  • Congenital anomalies 1
  • Infiltrative processes 1

Advanced Imaging (Second-Line)

• If the echocardiogram is unrevealing but structural heart disease remains suspected, advanced imaging with cardiac MRI, CT, or nuclear studies is reasonable. 1, 2
• Cardiac MRI is particularly useful for detecting:
  • Subclinical cardiomyopathy (detected in one-third of patients with asymptomatic LBBB and normal echocardiogram) 1
  • Sarcoidosis 1
  • Myocarditis 1
  • Connective tissue disease 1

Stress Testing with Imaging

• In asymptomatic patients with bifascicular block where ischemic heart disease is suspected, stress testing with imaging may be considered. 1, 2
• This is particularly relevant since bifascicular block can interfere with standard ECG interpretation during stress testing. 2

Important Clinical Context

When Imaging is Most Critical

The threshold for obtaining imaging is higher when patients have:

• Symptoms suggestive of heart failure 1
• Family history of cardiomyopathy 1
• Syncope or presyncope 1, 2
• Known conditions predisposing to structural heart disease 1

Monitoring vs. Imaging

• Ambulatory electrocardiographic monitoring is complementary to imaging, not a replacement, and should be considered in symptomatic patients to document intermittent bradycardia or higher-degree atrioventricular block. 1, 2
• In selected asymptomatic patients with extensive conduction system disease (bifascicular or trifascicular block), ambulatory monitoring may be considered to document suspected higher-degree atrioventricular block. 1, 2

Common Pitfalls

• Do not assume bifascicular block is benign without imaging evaluation, as it may be the first manifestation of progressive cardiac conduction disease or cardiomyopathy. 2
• Right bundle branch block (RBBB) with left anterior fascicular block carries lower risk than LBBB, but still warrants echocardiographic evaluation if structural heart disease is suspected. 1, 2
• Normal cardiac markers do not exclude structural heart disease that may be driving the conduction abnormality. 1
• Patients with bifascicular block have increased risk of left ventricular systolic dysfunction compared to those with normal ECGs, though the yield is lower than with LBBB. 1