• After an initial clinical assessment fails to identify a more likely explanation for chest pain other than angina or acute myocardial infarction
• Do not use indiscriminately in all patients presenting with chest pain

Specific features of cardiac chest pain

• Site: central, retrosternal
• Character: pressure, heaviness, squeezing, burning (indigestion like)
• Radiation: arm(s), neck, jaw, gums
• Provoking factors: exercise, stress, cold temperature, lying down
• Relieving factors: rest, GTN
• Associated symptoms: nausea, sweating, breathlessness
• Duration: >15 min 

• Perform 12-lead ECG on arrival. Repeat if further episodes of pain occur

Before troponin I result available

ST-elevation or LBBB

• Inform senior colleague and refer for cardiac assessment immediately - see Acute myocardial infarction

No ST-elevation or LBBB

• Calculate HEART score; assume troponin is negative until result available
  • if HEART score ≤3 (low risk), when troponin result available, recalculate HEART score
  • if HEART score >3 (high risk), discuss with senior colleague and refer for cardiac assessment. See Unstable angina and Acute myocardial infarction
• >2 hr after onset of chest pain, perform single troponin I assay (Siemens analyser only)

When first troponin result available

• Interpret all troponin I results in context with the ECG finding and clinical picture
  • patients with eGFR <40 mL/min/1.73m² may have a chronically raised Troponin I
• Recalculate HEART score

Heart score ≤3 (low risk) and troponin I <5 nanogram/L and ECG non-diagnostic

• Likely non-cardiac diagnosis
• Discuss with senior colleague
• Consider discharge

Troponin I result: male 5-54 nanogram/L: female 5-39 nanogram/L

• Repeat troponin 3 hr after first sample
  • if ≤50% change in troponin value, consider observation/discharge reviewing ECG findings and HEART score
  • if >50% change in troponin value, consistent with acute myocardial necrosis. Consult cardiology

Troponin I result: male >54 nanogram/L: female >39 nanogram/L

• Repeat troponin 3 hr after first sample
  • if ≤20% change in troponin value, indicates chronic troponin elevation
  • if >20% change in troponin value, consistent with acute myocardial necrosis. Consult cardiology

HEART Score

Original Flowchart

• Aspirin 300 mg oral (chew and swallow)
• Glyceryl trinitrate 400 microgram/metered dose spray, 1-2 doses under tongue then close mouth
• Diamorphine - see Acute myocardial infarction guideline

• Ensure patient is pain free
• Repeat ECG before discharge
• Request senior doctor review
• Complete discharge summary - inform GP of ECG and troponin I results
• Give patient an information sheet