What are the components to rule out Acute Coronary Syndrome (ACS)?

Components of an ACS Rule Out

The essential components to rule out Acute Coronary Syndrome (ACS) include a 12-lead ECG within 10 minutes of first medical contact, high-sensitivity cardiac troponin measurements at 0 and 1-3 hours, and risk stratification using validated clinical scoring systems. 1, 2

Initial Assessment

History and Clinical Evaluation

• Detailed assessment of symptom characteristics (onset, duration, type, location, triggers, relieving factors) 1
• Evaluation of cardiovascular risk factors and medical history 1
• Recognition that atypical symptoms may be more common in elderly, women, and diabetic patients 1
• Consider symptoms like chest pain triggered by emotional stress, dyspnea, pain in arms/jaw/neck/back as potential angina equivalents 1

Immediate Diagnostic Tests

• 12-lead ECG within 10 minutes of first medical contact 1

  • Look for ST-segment elevation/depression, T-wave inversions, or other ischemic changes
  • Additional ECG leads (V3R, V4R, V7-V9) if standard leads are inconclusive 1
  • Additional 12-lead ECG in case of recurrent symptoms or diagnostic uncertainty 1

• High-sensitivity cardiac troponin (hs-cTn) measurements 1, 2

  • Initial measurement immediately upon admission (results within 60 minutes)
  • Follow-up measurement at 1-3 hours (ESC 0h/1h or 0h/2h algorithm)
  • Additional testing after 3 hours if first two measurements inconclusive and clinical suspicion persists

Risk Stratification

Clinical Risk Scores

• TIMI Risk Score 1

  • Age ≥65 years
  • ≥3 coronary risk factors
  • Known CAD (stenosis ≥50%)
  • ASA use in past 7 days
  • Severe angina (≥2 episodes in 24h)
  • ST deviation ≥0.5mm
  • Positive cardiac markers

• HEART Score 1, 2

  • History (suspicious vs. non-suspicious)
  • ECG (normal vs. abnormal)
  • Age
  • Risk factors
  • Troponin level

Imaging and Advanced Testing

• Echocardiography to evaluate regional and global LV function and rule out differential diagnoses 1
• For patients with normal ECG and negative troponins but suspected ACS:
  • Non-invasive stress test (preferably with imaging) for inducible ischemia 1
  • Coronary CT angiography (CCTA) as an alternative to invasive coronary angiography 1

Monitoring

• Continuous cardiac rhythm monitoring until ACS diagnosis is established or ruled out 1
• Admission to a monitored unit for confirmed NSTEMI patients 1
• Extended monitoring (>24h) for patients at increased risk for cardiac arrhythmias 1

Pitfalls and Caveats

• Do not rely solely on cardiac troponins: Using hs-cTnT and cTnI alone measured at 0 and 2 hours is not sufficient to exclude ACS 1
• Do not use ST-segment deviations during supraventricular tachyarrhythmias as reliable evidence of obstructive CAD 1
• Do not routinely measure additional biomarkers such as h-FABP or copeptin in addition to hs-cTn for initial diagnostic purposes 1
• Do not use inpatient-derived risk scoring systems to identify patients who may be safely discharged from the ED 1
• Be aware of atypical presentations: Signs and symptoms alone cannot confirm or exclude ACS (sensitivity ranges from 35% to 92% and specificity from 28% to 91%) 1

Decision Algorithm for ACS Rule Out

1. Initial Assessment:

   • 12-lead ECG within 10 minutes
   • High-sensitivity troponin at presentation
   • Clinical risk assessment

2. If STEMI on ECG: Immediate reperfusion strategy (not a rule-out)

3. If Non-STEMI/Unstable Angina suspected:

   • Second troponin at 1-3 hours
   • Apply ESC 0h/1h or 0h/2h algorithm

4. For low-risk patients (negative troponins, normal ECG, low risk score):

   • Consider discharge with outpatient follow-up
   • Consider non-invasive testing (stress test or CCTA)

5. For intermediate-risk patients:

   • Additional troponin at 3-6 hours
   • Consider non-invasive imaging
   • Consider observation admission

6. For high-risk patients (positive troponins, ischemic ECG changes, high risk score):

   • Admit for further management (not a rule-out)

Remember that the most recent guidelines emphasize rapid assessment protocols using high-sensitivity troponin assays to enable earlier treatment decisions and reduce unnecessary hospitalizations 2.

1, 2