What is the management approach for a patient presenting with chest pain and a new right bundle branch block (RBBB)?

Management of Chest Pain with New Right Bundle Branch Block (RBBB)

Patients presenting with chest pain and new RBBB should be evaluated urgently for acute myocardial infarction (AMI), with immediate cardiac biomarker testing and consideration for reperfusion therapy, as they have a 64% increased risk of in-hospital mortality compared to patients without bundle branch block. 1

Initial Assessment and Diagnosis

ECG Interpretation

• In patients with RBBB, ST-elevation is indicative of STEMI, while ST-segment depression in leads I, aVL, and V5-6 is indicative of NSTE-ACS 1
• New or presumably new RBBB is not an uncommon presentation of transmural AMI, occurring in approximately 5-10% of AMI patients 1
• RBBB can obscure ST-segment analysis, making diagnosis more challenging 1
• Pay special attention to leads V1-V3, as baseline ST-segment depression in these leads can mask anterior ST-elevation 2

Biomarker Testing

• Measurement of high-sensitivity cardiac troponin (hs-cTn) is mandatory in all patients with suspected ACS, including those with RBBB 1
• Serial troponin measurements should be performed at presentation and 1-3 hours later 1
• Interpret troponin as a quantitative marker: higher initial levels or greater absolute changes during serial sampling indicate higher likelihood of MI 1

Risk Stratification

High-Risk Features in RBBB Patients with Chest Pain:

• ST-segment elevation in any lead (especially V1-V3) 2, 3
• Hemodynamic instability 1
• Positive cardiac biomarkers 4
• History of coronary artery disease 1
• Alternating bundle branch block 5
• Associated left anterior fascicular block (bifascicular block) 5

Management Algorithm

Immediate Management:

1. For hemodynamically unstable patients with RBBB and chest pain:

   • Immediate coronary angiography regardless of ECG findings 1
   • Provide oxygen if SaO₂ < 90% or PaO₂ < 60 mmHg 1
   • Consider titrated IV opioids for pain relief (noting potential interaction with antiplatelet medications) 1

2. For hemodynamically stable patients with RBBB and chest pain:

   • Obtain hs-cTn measurement at presentation 1
   • If ST-elevation is present in any lead (especially V1-V3), consider for immediate reperfusion therapy 2
   • If initial hs-cTn is elevated or clinical suspicion is high, proceed with urgent coronary angiography 1
   • If initial hs-cTn is normal, perform serial measurements and await results before deciding on invasive strategy 1

Reperfusion Considerations:

• Multiple studies have demonstrated that patients with RBBB have similar outcomes (if not worse) to patients with LBBB in the setting of AMI 1
• After adjusting for patient characteristics, patients with RBBB had a 64% increased odds ratio of in-hospital death compared to patients without BBB 1
• Patients with RBBB historically received lower rates of treatment with aspirin, heparin, nitrates, and beta-blockers during the first 24 hours of ED presentation 1

Important Clinical Considerations

Diagnostic Challenges

• More than 50% of patients presenting with acute chest pain and RBBB will ultimately be found to have a diagnosis other than MI 1
• However, the presence of new RBBB in the setting of chest pain should not delay evaluation for AMI 4
• Consider additional posterior leads (V7-V9) in patients with suspected posterior MI, as standard ECG may only show ST depression in V1-V3 1

Common Pitfalls

1. Missing STEMI in RBBB patients:

   • Current voltage criteria for identification of anterior STEMI in patients with RBBB may be insufficient 3
   • Any ST-elevation in a patient with RBBB and chest pain should prompt consideration for emergent coronary angiography 2

2. Undertreatment:

   • Historically, patients with RBBB received less aggressive treatment than those with LBBB or ST-elevation 1
   • Do not delay reperfusion therapy in patients with strong clinical suspicion of AMI, even if ECG changes are subtle 1

3. Over-reliance on ECG alone:

   • Integrate clinical presentation, ECG findings, and biomarker results for optimal decision-making 1
   • Remember that RBBB alone is not a criterion for emergent catheterization, but RBBB with ST-elevation or positive biomarkers warrants urgent intervention 4, 2

By following this algorithm and being aware of the potential pitfalls, clinicians can optimize outcomes for patients presenting with chest pain and new RBBB.