What to give to a patient complaining of chest pain with Right Bundle Branch Block (RBBB)?

Management of Chest Pain with Right Bundle Branch Block

For a patient presenting with chest pain and right bundle branch block (RBBB), immediate administration of aspirin, oxygen if hypoxemic, sublingual nitroglycerin (if not contraindicated), and IV morphine for pain relief should be initiated while preparing for urgent cardiac evaluation.

Initial Assessment and Management

Immediate Interventions

• Aspirin: Administer 160-325 mg orally immediately 1
• Oxygen:
  • Give only if oxygen saturation <90% or PaO₂ <60 mmHg 1
  • Routine oxygen is not recommended if SaO₂ ≥90% 1
• Nitroglycerin:
  • Sublingual nitroglycerin 0.4 mg every 5 minutes for a total of 3 doses 1
  • Follow with IV nitroglycerin if chest pain persists 1
  • Contraindications: Systolic BP <90 mmHg or ≥30 mmHg below baseline, severe bradycardia (<50 bpm), tachycardia (>100 bpm), RV infarction, or recent use of phosphodiesterase inhibitors 1, 2
• Morphine: IV morphine titrated for pain relief if discomfort not relieved by nitroglycerin 1
  • Note: Morphine may slow the uptake and delay the onset of oral antiplatelet agents 1
• Benzodiazepines: Consider for significant anxiety 1

Immediate Diagnostic Steps

• Obtain 12-lead ECG within 10 minutes of arrival 1
• Establish IV access 1
• Obtain initial cardiac markers, electrolytes, and coagulation studies 1
• Portable chest X-ray (within 30 minutes) 1

Special Considerations for RBBB

RBBB alone is not considered a diagnostic criterion for acute myocardial infarction according to current guidelines 3, 4. However, it requires careful assessment because:

1. RBBB does not typically interfere with ST-segment interpretation 3
2. Look specifically for ST-segment elevation in leads V1-V3, which may indicate anterior MI even with RBBB 4
3. Patients with RBBB may have more left ventricular contraction abnormalities, especially in the anteroapical area, compared to patients with normal ECGs 5

Decision Algorithm for Reperfusion Therapy

If RBBB with ST-segment elevation:

• Notify receiving hospital with ECG transmission/interpretation 1
• Note time of symptom onset and first medical contact 1
• Consider for immediate reperfusion therapy (PCI preferred) 1
• Door-to-balloon inflation goal: 90 minutes 1
• Door-to-needle (fibrinolysis) goal: 30 minutes 1

If RBBB without ST-segment elevation:

• Continue medical therapy as above
• Consider admission to ED chest pain unit 1
• Perform serial cardiac markers (including troponin) 1
• Repeat ECG/continuous ST-segment monitoring 1
• Consider noninvasive diagnostic testing 1

Important Caveats

1. Masked ST-elevation: In some patients with RBBB, baseline ST-segment depression in leads V1-3 may mask anterior ST-elevation 4. Consider this possibility in patients with concerning symptoms.

2. Rate-related bundle branch block: Some patients may have intermittent, rate-related bundle branch block that can cause chest pain even in the absence of obstructive coronary disease 6.

3. Posterior MI: In patients with suspected posterior MI, ST-segment depression in leads V1-V3 may represent the dominant finding. These should be managed as STEMI 1.

4. Bifascicular block: The presence of RBBB with left anterior or left posterior fascicular block does not appear to offer additional clinical utility when evaluating patients with suspected AMI 4.

By following this algorithm, you can ensure appropriate and timely management of patients presenting with chest pain and RBBB, focusing on early recognition of myocardial infarction and prompt initiation of reperfusion therapy when indicated.