How do you diagnose and manage suspected ST elevation in a patient with right bundle branch block (RBBB)?

ST Elevation in RBBB: Diagnosis and Management

Can ST Elevation Occur in RBBB?

Yes, ST elevation can occur in RBBB, but RBBB itself causes secondary ST-T wave abnormalities in leads V1-V3 that complicate the diagnosis of acute myocardial infarction. 1, 2

Key Diagnostic Principles

Expected ECG Changes in RBBB

• RBBB produces characteristic secondary ST-T abnormalities in leads V1-V3 as part of the normal bundle branch block pattern, making it inherently difficult to assess for acute ischemia in the right precordial leads 2, 3
• The QRS complex is wide (≥0.12 seconds) with a characteristic RSR' pattern in V1-V2 2
• These baseline ST-T changes are expected and do not indicate ischemia by themselves 2

Identifying Acute MI in the Presence of RBBB

Apply concordance and discordance criteria (similar to Sgarbossa criteria developed for LBBB) to identify acute MI in RBBB patients: 3

• ST-segment elevation ≥1 mm concordant with the QRS complex (same direction as the major QRS deflection) in 2 or more contiguous leads is highly specific for acute MI 3
• ST-segment depression ≥1 mm concordant with the QRS in leads V1-V3 suggests acute MI 3
• ST-segment elevation ≥5 mm discordant (opposite direction) from the major QRS deflection may indicate acute MI, though with lower specificity 3

Additional Diagnostic Clues

• Unlike LBBB, anterior Q waves are NOT obscured by RBBB, so new Q wave formation in leads V1-V5 strongly suggests acute MI 3
• Look for "pseudonormalization" of ST segments—when the expected discordant ST changes of RBBB are replaced by concordant elevation 3

Clinical Management Approach

High-Risk Features Requiring Immediate Action

RBBB patients with acute MI have a 64% increased odds of in-hospital death compared to those without bundle branch block, yet they are systematically undertreated—only 32% receive fibrinolytic therapy versus 65.5% without BBB 1, 3

Reperfusion Strategy

For RBBB patients meeting criteria for acute MI (concordant ST elevation ≥1 mm or other high-risk features): 3, 1

1. Primary PCI is the preferred strategy with a first medical contact-to-device time goal ≤90 minutes 4, 1
2. Administer fibrinolytic therapy if PCI cannot be performed within 90 minutes, especially if symptom onset is <3 hours 3, 4
3. Do not delay reperfusion therapy based on difficulty interpreting the ECG—the clinical presentation strongly suggesting AMI combined with any type of BBB (right, left, or atypical—new or old) warrants assessment for fibrinolytic therapy 3

Diagnostic Adjuncts When ECG is Equivocal

• Obtain serial ECGs when clinical suspicion remains high, symptoms persist, or the patient's condition deteriorates 4
• Transthoracic echocardiography can identify focal wall motion abnormalities to confirm ongoing ischemia when ECG interpretation is difficult 4
• High-sensitivity cardiac troponin provides biochemical confirmation, though should not delay reperfusion in unstable patients 4

Critical Clinical Pitfalls

Common Errors to Avoid

• Never dismiss chest pain in RBBB patients because ST-segments are difficult to interpret—these patients have worse outcomes and are systematically undertreated 1, 3
• Do not assume all ST elevation in V1-V3 is "just the RBBB"—look specifically for concordant ST changes that exceed what is expected from the bundle branch block alone 3, 2
• Do not confuse isolated RBBB with bifascicular block (RBBB + hemiblock), which carries higher risk of progression to complete AV block and has even higher mortality (adjusted HR 2.27) 5

Special Considerations

• The likelihood of MI in RBBB patients presenting with chest pain (20.8%) is similar to those without bundle branch block (21.6%), so RBBB alone should not trigger automatic angiography without other high-risk features 5
• RBBB can mask Brugada syndrome type 1 pattern—if RBBB is intermittent, examine beats with normal conduction for characteristic findings 6, 7
• Alternating bundle branch block (RBBB and LBBB on successive ECGs) requires immediate permanent pacing due to high risk of sudden complete heart block 1