Low Risk Acute Coronary Syndrome Management


Low Risk Acute Coronary Syndrome Management, Non-diagnostic Electrocardiogram Protocol, Non-diagnostic EKG Protocol, Atypical Chest Pain, Low Risk Chest Pain

  • Precautions
  • Atypical Chest Pain
  1. Atypical Chest Pain is avoided as a diagnosis due to misinterpretation by patients as a benign findings
  2. Define Low Risk Chest Pain into one of three categories
    1. Cardiac Chest Pain
    2. Possible Cardiac Chest Pain
    3. Noncardiac Chest Pain
  1. Normal or unchanged Electrocardiogram
  2. ST Depression 0.5 to 1.0 mm
  3. T Wave Inversion (<0.2 mV) or flattening
    1. Leads with dominant R Wave
  • Contraindications
  • Moderate or Intermediate Risk patient (or other concerning findings)
  1. See Moderate Risk Acute Coronary Syndrome Management
  2. Concerning history findings
    1. Unstable Angina (low threshold or increased frequency of provoked Angina)
    2. New onset Angina
  3. Significant comorbidity
    1. Coronary Artery Disease
    2. Peripheral Vascular Disease
    3. Prior PCI (stenting) or Coronary Artery bypass (especially if in last 6 months)
    4. Heart Failure
    5. Structural heart disease (e.g. Aortic Stenosis)
    6. Pulmonary Hypertension
  4. Concerning examination findings
    1. Hemodynamic abnormalities (e.g. Hypotension)
    2. Syncope
    3. Pulmonary Edema
    4. Ill appearing
  5. Concerning diagnostic findings
    1. Troponin Increased
    2. Significant EKG changes (e.g. ST Segment Elevation or T Wave Inversion)
    3. Arrhythmia
  6. Factors that may require additional vigilence but may not absolutely contraindicate following the low risk protocol
    1. Diabetes Mellitus (especially if longstanding >10 years or uncontrolled)
    2. Typical Chest Pain (central, heavy, crushing, pressure or squeezing pain)
      1. Especially if associated with Dyspnea, diaphoresis, Nausea or Vomiting
      2. Higher risk presentation than Atypical Chest Pain (sharp, localized or lateral Chest Pain)
  1. Highly sensitive Troponin Is sufficiently sensitive to replace all other biomarkers (e.g. CK-MB, Myoglobin, CRP)
  2. Decision rules are used by accelerated protocols to shorten time between Troponins
    1. HEART Score 0-3 (and normal first Troponin)
      1. Three hours between standard Troponins (Used by University of Maryland)
      2. One normal Troponin and a HEART Score 0-3 has a risk of major adverse cardiac event rate of 1.7% at 30 days
        1. Backus (2013) Int J Cardiol 168(3):2153-8 [PubMed]
      3. Two Troponins at 3 hours apart lowers the major adverse cardiac event rate risk to <1% at 30 days
        1. Mahler (2015) Circ Cardiovasc Qual Outcomes 8(2): 195-203 [PubMed]
    2. TIMI Score 0
      1. Two hours between Troponins (Used by some centers)
      2. However TIMI Score was not intended for risk stratification in undifferentiated Chest Pain
      3. TIMI Score is not for risk stratification in 2018 ACEP guidelines
      4. Berg and Orman in Herbert (2014) EM:Rap 14(9): 3-4
  3. Presentation >6 hours from Chest Pain onset (IF Chest Pain stopped more than 6 hours prior to presentation)
    1. Single Troponin Typically rules-out acute Myocardial Infarction
    2. However, if Chest Pain present in last 6 hours, or waxing and waning during this time, repeat Troponin at 3 hours
  4. Presentation <6 hours from Chest Pain onset
    1. Precaution
      1. Pathway assumes decision rules (see above) to shorten the duration between Troponins to 2-3 hours
      2. HEART Score of 0-3: May follow accelerated pathway
        1. Lowers the major adverse cardiac event rate risk at 30 days to less than 1%
      3. HEART Score >3: Observation stay with standard serial Troponins is typically pursued
    2. Highly sensitive Troponin
      1. See protocols below
      2. Obtain two High Sensitivity Troponins 2 hours apart
    3. Standard Troponin
      1. Obtain two standard Troponins 3 hours apart (or second Troponin at 6 hours from symptom onset)
      2. Alternative: Patient declines a second Troponin
        1. Assumes a 1.7% major adverse cardiac event rate risk at 30 days
        2. See Disposition below
  5. References
    1. Diercks (2012) Am Heart J 163(1):74-80 [PubMed]
  1. hs-Troponin on arrival
    1. Normal if first hs-Troponin undetectable or <6 to 22 ng/L (upper normal range varies by gender, assay)
      1. Sufficient to exclude ACS if >3 hours of symptoms, low HEART Score, EKG negative for significant findings
    2. Intermediate range hs-Troponin If <52 ng/L (indication for repeat testing)
    3. Positive hs-Troponin If >52 ng/L
  2. Indications for a second hs-Troponin at least 1 hour from first hs-Troponin
    1. Abnormal first hs-Troponin
    2. First hs-Troponin performed <3 hours from onset of symptoms
      1. A single negative hs-Troponin Is sufficient if >3 hours from onset
  3. References
    1. Swaminathan and Mattu (2020) EM:Rap 20(6): 4-5
    2. Januzzi (2019) J Am Coll Cardiol 73(9):1059-77 [PubMed]
    3. Baugh (2019) Crit Pathw Cardiol 18(1):1-4 [PubMed]
  • Diagnostics
  1. Cardiac Monitoring (Telemetry)
    1. Vital Signs including Heart Rate and Blood Pressure
    2. Continuous ST Segment monitoring
    3. Cardiac Monitoring discontinuation
      1. Indications to discontinue monitoring (Ottawa Chest Pain Cardiac Monitoring Rule)
        1. No current Chest Pain AND
        2. Normal or non-sepcific EKG (no prolonged interval, no LVH, no LBBB) AND
        3. No Arrhythmia in first 8 hours of emergency department presentation
        4. Syed (2017) CMAJ 189(4): E139-45 +PMID:28246315 [PubMed]
      2. Low risk patients do not require telemetry (however often performed in standard practice)
        1. Goldman Risk Score <8% and
        2. Troponin I <0.3 ng/ml and
        3. CK-MB <5 ng/ml
        4. Hollander (2004) Ann Emerg Med 43:71-6 [PubMed]
  2. Serial Electrocardiogram (EKG)
    1. EKG Test Sensitivity is only 90% for Myocardial Infarction (normal EKG despite true MI in 10% of cases)
    2. ACS should not be excluded based on a single EKG
      1. Perform EKG at time of serial Troponins AND
      2. Perform EKG with changes in patient symptoms (e.g. increased Chest Pain)
      3. Positive examples are not uncommon with multiple (e.g. 3-5 q5-10 min) serial EKGs
        1. Ongoing Chest Pain with ischemia seen only on the last EKG is not a rare phenomenon
      4. However ACC/AHA protocols do not require more than one Electrocardiogram (EKG)
    3. EKG normal, unchanged, or nominally changed (T Wave Flattening, <1 mm ST depression)
      1. Continue with the low risk protocol (see below)
    4. EKG with significant change (symmetric ST Segment change >1mm, T Wave Inversion >0.2 mV)
      1. Switch to Moderate Risk Acute Coronary Syndrome Management
  • Imaging
  1. Approach
    1. Age <65 years or lower suspicion for obstructive Coronary Artery Disease
      1. Start with Coronary CT Angiogram (CTCA)
      2. Consider Stress Testing if CCTA equivocal
    2. Age >65 years or higher suspicion for obstructive Coronary Artery Disease
      1. Start with stress testing
      2. Consider Coronary CT Angiogram (CTCA) if stress testing equivocal
  2. Stress Testing
    1. Precautions
      1. Test Sensitivity for Ischemic Heart Disease: 85-90% (esp if evaluation delayed from time of symptoms)
        1. Best Test Sensitivity for coronary lesions >70% (but MI may occur with 30-50% stenosis)
        2. Normal stress test may offer 1 year reassurance for similar symptom presentations
      2. Poor Test Specificity in low risk populations
        1. Exercise caution in stress testing low risk patients (high False Positive Rate)
    2. Tests
      1. Exercise Treadmill Test (Test Sensitivity 50-80%)
      2. Stress Echocardiogram
      3. Perfusion Radionuclide scan (SPECT, Stress Cardiolite, Test Sensitivity >90%)
      4. Pharmacologic Stress Test (e.g. Lexiscan)
  3. Resting Echocardiogram (for wall motion abnormality)
    1. Efficacy is typically not sufficient to rule-in or rule out ACS
    2. Does not distinguish between old and new Myocardial Infarction
    3. Decreased Test Sensitivity if patients present after symptom resolution
  4. Resting Sestamibi (e.g. Cardiolite, SPECT)
    1. Negative test confers a good prognosis for the next 12 months
    2. Positive test is highly predictive of major adverse cadiac events
    3. Test Sensitivity 71%, Test Specificity 92%
    4. Amsterdam (2010) Circulation 122:1756-76 [PubMed]
    5. Kosnik (1999) Acad Emerg Med 6(10):998-1004 [PubMed]
  5. Coronary CT Angiogram (CTCA)
    1. Indications
      1. Single elevated or equivocal serum Troponin without other findings of ischemia
      2. Alternative to stress test per 2007 AHA guidelines in low to intermediate risk patients
      3. Consider in patients under age 65 years old without known coronary disease
    2. Advantages
      1. May decrease Chest Pain admission rates
      2. Lower radiation dose than angiography (3 to 5 mSv compared with 4 to 10 mSv)
    3. Disadvantages
      1. Increased radiation exposure and intravenous radiographic contrast load
      2. Test efficacy for coronary ischemia decreases with Triple Screen (ACS, PE, Aortic Dissection)
      3. Associated with greater intervention rate for PCI and CABG (due to False Positives) without decreased MI
        1. Morris (2016) Acad Emerg Med 23(9): 1022-30 +PMID:27155236 [PubMed]
  6. Angiography
    1. Indicated for high suspicion cases such as unequivocally positive ekg or cardiac biomarker for ischemia
  7. References
    1. Orman, Mattu and Swaminathan in Herbert (2016) EM:Rap 16(10): 8-9
    2. (2016) J Am Coll Radiol 13(2): e1-29 +PMID:26810814 [PubMed]
  • Evaluation
  1. Initial evaluation for high risk, intermediate risk and Low Risk Chest Pain begins the same
    1. See Acute Coronary Syndrome Immediate Management (includes giving Aspirin 325 mg)
    2. Low Risk Chest Pain protocol is only per indications listed above
  2. Approach
    1. Assess Angina Diagnosis likelihood
    2. Consider Chest Pain differential diagnosis
  3. Decision Rules
    1. See Chest Pain Decision Rules
    2. Preferred, validated tests in Low Risk Chest Pain risk stratification (accelerated diagnostic protocols)
      1. HEART Score (more subjective than EDACS or T-Macs)
      2. Emergency Department Assessment of Chest Pain Score (EDACS)
      3. Troponin-Only Manchester Acute Coronary Syndrome Decision Aid (T-Macs)
      4. Body (2020) Emerg Med J 37(1):8-13 [PubMed]
      5. Greenslade (2018) Ann Emerg Med 71(4): 439-51 [PubMed]
    3. Other tests that have been used in Low Risk Chest Pain risk stratification
      1. TIMI Risk Score
      2. GRACE Score
      3. Goldman Risk Score
  4. Precautions
    1. Cardiac Risk Factors are not useful in the exclusion of acute coronary disease in the emergency department
      1. Despite the evidence, Cardiac Risk Factors are included in most decision rule calculators
      2. Body (2008) Resuscitation 79(1): 41-5 [PubMed]
      3. Patel (2000) West J Med 173(6): 423-4 [PubMed]
    2. As of 2017, HEART Score is the most used for risk stratification but does not appear to alter management
      1. Compared to usual care, HEART Score did not result in worse outcomes, but did not decrease resource use
      2. HEART Score assigns an objective score to clinical gestalt and is useful for documenting decision making
      3. Poldervaart (2017) Ann Intern Med 166(10): 689-97 +PMID: 28437795 [PubMed]
  • Management
  • Patient Triage Based on Findings
  1. Findings suggestive of Myocardial Ischemia or NSTEMI (e.g. EKG change or Troponin Increase)
    1. See Moderate Risk Acute Coronary Syndrome Management
    2. See Myocardial Ischemia Protocol
    3. Consider MI Adjunctive Therapy
  2. Findings without signs of ACS or Myocardial Ischemia
    1. High risk for adverse event in near future (based on decision rules listed above)
      1. See Myocardial Ischemia Protocol
      2. Treat same as signs of Myocardial Ischemia above
    2. Intermediate risk for adverse event in near future
      1. Consider early discharge with expedited stress testing (see protocol below)
      2. Consider Stress Imaging prior to discharge (See imaging above)
        1. Recent stress testing does not exclude a subsequent Acute Coronary Syndrome presentation
        2. Avoid repeat stess test (same modalilty, e.g. cardiolite) if negative or nondiagnostic within prior 12 months
          1. Unlikely to be diagnostic if done for similar symptoms
          2. Consider alternative testing (e.g. CT angiogram)
      3. Consider admission to Chest Pain unit
      4. Consider Coronary CT Angiogram (CCTA)
        1. May be preferred in stable Chest Pain with intermediate risk
      5. Reassuring history that may allow for early discharge
        1. Negative prior myocardial perfusion scan does not alter disposition
        2. Prior negative coronary angiogram in last 5 years
          1. Stenosis <50% should have expedited follow-up and testing as indicated (but no admission)
        3. Prior negative Coronary CT Angiogram (CCTA) in the last 2 years
          1. Should have expedited follow-up and testing as indicated (but no admission)
        4. Orman and Mattu in Herbert (2017) EM:Rap 17(6): 5
    3. Low risk for adverse event in near future (TIMI Score 0 or HEART Score <3)
      1. Discharge from Emergency Department
      2. Close follow-up with primary physician
      3. Discuss warning signs
      4. Discuss Chest Pain differential diagnosis
      5. Consider outpatient Exercise Stress Testing
        1. Stress testing is not required in very low risk patients (e.g. TIMI Score 0)
        2. Low risk patients (<1% risk of major cardiac event at 30 days) do not require urgent follow-up
  • Management
  • Early Disposition of Low Risk Chest Pain in an Intermediate Risk Patient
  1. Indications
    1. Intermediate risk for adverse event in near future (see above)
      1. See Moderate Risk Factors listed above
      2. Patient has Cardiac Risk Factors, but is risk stratified to low risk protocol
    2. Risk based on patients stratified to low risk
      1. TIMI score of 0
      2. HEART Score of 0-3
      3. EDACS <16, nonischemic EKG and 0 and 2 hour Troponin negative
      4. T-Macs <1%
  2. Exclusion criteria
    1. See contraindications listed above
    2. Follow Moderate Risk Acute Coronary Syndrome Management instead if any are true
    3. Unreliable patient
    4. Hypotension with systolic Blood Pressure <110
    5. Congestive Heart Failure
    6. Pulmonary rales
    7. Known previous Myocardial Infarction
    8. Worsening Angina
    9. Positive Troponin
    10. Significantly abnormal Electrocardiogram (symmetric ST Segment change >1mm, T Wave Inversion >0.2 mV)
    11. Other criteria met for Moderate Risk Acute Coronary Syndrome Management
  3. Evaluation
    1. See diagnostics above including monitoring and cardiac biomarker (Troponin) timing
  4. Disposition (based on protocol listed above under labs)
    1. Contraindications
      1. Exclusion criteria met
    2. Protocol
      1. Confirm patient hemodynamically stable with negative Troponins and no exclusion criteria present
      2. Discharge to home with precautions, Nitroglycerin and close interval follow-up
      3. Outpatient expedited stress testing
        1. Stress test timing had been recommended within 72 hours and was controversial
        2. Some argue removing the time stipulation (as has been done in Europe)
        3. Study with no outcome difference between early (<3 days), late (<30 days) and no stress testing
          1. Natsui (2019) Ann Emerg Med 74(2): 216-23 +PMID: 30955986 [PubMed]
    3. Education
      1. Alert the patient that you are still concerned about their heart
        1. Cannot fully exclude Angina in the Emergency Department
      2. Warn the patient
        1. Return to the Emergency Department for changes or worsening ("listen to your body")
      3. Discuss with patient the overall risk of cardiovascular event before work-up complete
        1. Between early emergency department discharge and stress testing on follow-up
      4. For every 100 people with lower risk Chest Pain
        1. Adverse Event: 2 had a heart or pre-heart attack within 45 days
        2. No Adverse Event: 98
      5. Patient is given choice
        1. Choices from the University of Maryland protocol (see links below)
          1. Based on a TIMI score or 0, or a HEART Score of 0-3
        2. I would like a repeat Troponin blood test (e.g. in 3 hours)
          1. If the Troponin blood test is negative I will be discharged for follow-up
          2. I understand my risk of heart attack or heart complications is <1% in the next 30 days
          3. I will see either my primary care doctor or cardiologist for follow-up
        3. I would like to be placed in observation for further testing
          1. This testing may include urgent cardiac stress testing
          2. I understand this may increase the cost of my evaluation
          3. I understand this may increase the duration of my emergency stay
        4. I will decline a repeat Troponin blood test (e.g. in 3 hours)
          1. I will see either my primary care doctor or cardiologist for follow-up
          2. I understand my risk for a heart attack or heart complications is ~2% in the next 30 days
      6. Consider demonstrating this in the form of a graphical card
      7. References
        1. Hess (2012) Circ Cardiovasc Qual Outcomes 5(3): 251-9 [PubMed]
        2. Mahler (2015) Circ Cardiovasc Qual Outcomes 8(2): 195-203 [PubMed]
    4. Rationale
      1. Risk of short-term Myocardial Infarction or death in this cohort is less than 1%
        1. Hamm (1997) N Engl J Med 337(23): 1648-53 [PubMed]
        2. Weinstock (2015) EM:Rap 175(7): 1207-12 [PubMed]
      2. Stress testing does not effectively risk stratify this low risk cohort further
        1. Kosowsky (2011) Emerg Med Clin North Am 29(4): 721-7 [PubMed]
      3. Hospital observation is not without risk
        1. Overall risk of in-hospital death due to iatrogenic complication is as high as 1 in 160
          1. James (2013) J Patient Saf 9(3): 122-8 [PubMed]
      4. Positive stress testing in low risk patients does not improve outcomes
        1. No intervention was done in 90% of low risk patients with a positive stress test
          1. Penumetsa (2012) Arch Intern Med 172(11):873-7 [PubMed]
        2. Low risk patients who undergo PCI have worse outcomes
          1. Hoenig (2010) Cochrane Database Syst Rev (3): CD004815 [PubMed]
          2. Swahn (2012) European Heart Journal 33(1):51-60 [PubMed]
        3. For every stress test in low risk patients, 90 more angiograms, 11 more stents, no prevented MIs
          1. Sandhu (2017) JAMA Intern Med 177(8): 1175-82 PMID:28654959 [PubMed]
      5. Missed acute cardiac ischemia, NSTEMI or Unstable Angina in low risk patients
        1. Does not significantly impact outcomes
        2. Pope (2000) N Engl J Med 342(16): 113-70 [PubMed]
        3. Montelescot (2009) JAMA 302(9):947-54 [PubMed]
      6. Chest Pain units are often used because of availability, but may not be indicated
        1. Up to 50% of patients admitted to Chest Pain unit would have been discharged if not available
        2. Blecker (2016) Ann Emerg Med 67(6): 706-13 +PMID: 26619756 [PubMed]
  5. References
    1. Newman, Shreves and Weingart in Majoewsky (2012) EM:Rap 12(11): 5-7
    2. Berg and Orman in Herbert (2014) EM:Rap 14(9): 3-4
  • Management
  • Empiric Management of Diagnoses of Exclusion
  1. Chest Wall Pain
  2. Gastroesophageal Reflux
    1. Gastrointestinal causes may be responsible for up to 20% of Chest Pain presentations
  3. Anxiety Disorder or Panic Attacks
    1. Consider in Low Risk Chest Pain (e.g. low HEART Score) when other serious conditions have been excluded
    2. Many low-risk Chest Pain patients will present with a self-diagnosis of stress and anxiety
    3. Consider asking Low Risk Chest Pain patients about stress and anxiety
    4. Consider recommending Mindfulness strategies (e.g. breathing Exercises)
    5. Consider outpatient mental health referral (or at the very least primary care follow-up)
    6. Musey (2017) J Emerg Med 52(3): 273-9 +PMID:27998631 [PubMed]