High Risk Acute Coronary Syndrome Management

Aka: High Risk Acute Coronary Syndrome Management, STEMI, ST Elevation MI, ST Elevation Myocardial Infarction, Q-Wave MI, Myocardial Infarction Protocol, STEMI Equivalent, New Left Bundle Branch Block, Occlusion Myocardial Infarction

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II. Indications: Occlusion Myocardial Infarction

  1. ST Elevation 0.1 mV (1 mm) or more in 2 or more contiguous leads (limb or precordial) OR
  2. STEMI Equivalent (e.g. Wellens Syndrome, De Winter T Wave) OR
  3. True posterior Myocardial Infarction (only reason to use reperfusion therapy for ST depression)
    1. See Posterior Myocardial Infarction EKG Changes

III. Precautions

  1. Aggressively decreasing door to balloon time is associated with significant adverse effects
    1. Higher False Positive Rate on angiography (with higher mortality risk)
    2. Missed alternative diagnoses (e.g. Pulmonary Embolism, Aortic Dissection, Sepsis, Subarachnoid Hemorrhage)
    3. Control Heart Rate in secondary strain patterns (SVT, Atrial Fibrillation with Rapid Ventricular Response)
    4. Consider Pericarditis, Hyperkalemia, Bundle Branch Block
    5. False cardiac catheterization lab activations (high resource utilization)
    6. Obtain an adequate initial history and examine the EKG carefully
    7. Fanari (2015) Mayo Clin Proc 90(12): 1614-22 +PMID: 26549506 [PubMed]
    8. Lange (2018) Circ Cardiovasc Qual Outcomes 11(8): e004464 +PMID:30354373 [PubMed]
  2. ST Elevation causes are seen in more than just acute Myocardial Infarction
    1. See ST Elevation
    2. False PositiveST Elevation without acute coronary Occlusion: 15 to 20% of cases
    3. Consider Aortic Dissection when Chest Pain is associated with neurologic changes (See Chest Pain Plus)
      1. Avoid delaying PCI in STEMI, but consider CTA when strong dissection indicators are present
      2. STEMI due to Aortic Dissection accounts for only one in 1500 STEMI cases (0.07% of STEMI cases)
  3. Rarely, embolic events cause both ST Elevation Myocardial Infarction AND Cerebrovascular Accident (without Aortic Dissection)
    1. Consult stroke neurology and intervention cardiology
    2. AHA/ASA preferred approach (2022): CVA Thrombolysis followed by Percutaneous Coronary Intervention (PCI)
  4. Occlusion Myocardial Infarction is a newly coined phrase to replace the term STEMI
    1. Up to 25 to 30% of cases of acute coronary Occlusion do not have ST Elevation
    2. Be vigilant in acute Chest Pain presentations (history, exam, serial EKG, serial Troponin)
    3. Evaluate for STEMI Equivalents (e.g. Wellens Syndrome, De Winter T Wave, Posterior MI)
    4. DeMeester and Swaminathan in Swadron (2023) EM:Rap 23(5): 2-3

IV. Indications: New Left Bundle Branch Block (LBBB)

  1. Background
    1. Accounts for ~2% of Acute Coronary Syndrome cases but is the least clear of 2010 ACC Guidelines
      1. Reperfusion therapy for new LBBB as STEMI Equivalent is in question (but still in 2010 ACC guidelines)
      2. See Myocardial Infarction Protocol for details
    2. Left Bundle Branch Block has multiple chronic causes and is likely a marker of coronary disease
    3. However most Chest Pain presentations in patients with LBBB are unlikely to be STEMI Equivalent
      1. Acute LBBB requires a large, diffuse cardiac insult and is associated with a very ill appearing patient
      2. Chest Pain in a hemodynamically stable patient with LBBB is unlikely to be a STEMI Equivalent
  2. Reperfusion Indications in LBBB (Neeland article, not an official guideline in 2012)
    1. Suspected Acute Coronary Syndrome in a patient with LBBB on ekg AND
    2. One of the following
      1. Hemodynamic instability OR
      2. Acute Heart Failure OR
      3. Sgarbossa Criteria OR
      4. Bedside Echocardiogram with signs of ACS (e.g. acute wall motion abnormality) OR
      5. Serial cardiac enzyme elevation
  3. Precautions
    1. Consult with local cardiology for unclear cases
  4. References
    1. Mattu and Herbert in Majoewsky (2012) EM:Rap 12(11): 4-5
    2. Chang (2009) Am J Emerg Med 27(8): 916-21 [PubMed]
    3. Jain (2011) Am J Cardiol 107(8): 1111-6 [PubMed]
    4. Neeland (2012) J Am Coll Cardiol 60(2): 96-105 [PubMed]

V. Management: Reperfusion

  1. Indications: Immediate Reperfusion Strategy
    1. Time from Chest Pain onset <12 hours
    2. Manage as Myocardial Ischemia Protocol if time from Chest Pain onset >12 hours
  2. Start MI Adjunctive Therapy (do not delay reperfusion)
  3. Angioplasty with cardiothoracic back-up
    1. Protocol assumes PCI-capable facility
      1. Best outcomes at facilities performing more than 36 PCI procedures per year
    2. Primary PCI/Angioplasty
      1. Door to balloon goal within 90 minutes of ED arrival
      2. PCI preferred over Thrombolytics if door to ballon time <120 minutes (new extension from 90 minutes as of 2013)
        1. Allows hospitals without PCI capability additional 30 minutes to transfer to PCI facility
        2. Fibrinolytics are preferred if transport time to PCI facility >30 minutes
      3. Other indications for PCI
        1. STEMI and symptoms less than 12 hours
        2. STEMI with CHF or Cardiogenic Shock (Thrombolytics are unlikely to improve CHF)
        3. Post-arrest patient with STEMI or Ventricular Tachycardia
          1. Initiate Hypothermia protocol immediately on ROSC (cool and cath protocol)
    3. Rescue PCI/Angioplasty after failed Thrombolysis
      1. Moderate infarction area and <50% reduction in ST Elevation at 30 minutes
      2. Hemodynamically unstable from ventricular Arrhythmia
      3. Cardiogenic Shock or severe Congestive Heart Failure
    4. Facilitated PCI/Angioplasty
      1. Avoid overall as planned strategy
      2. Reasonable to follow Thrombolytics with PCI in patients without significant improvement
    5. Example medication protocol for inter-hospital transport to catheter lab (consult local experts)
      1. Heparin bolus 70 units/kg up to 5000 units
        1. Consider bolus without maintenance start on arrival at receiving facility if short transport (unless no delays)
        2. Do not use Low Molecular Weight Heparin (LMWH) or Fondaparinux (Risk of catheter thrombosis)
        3. Consider Bivalirudin as alternative to Unfractionated Heparin if high risk of bleeding (rarely used now)
      2. Antiplatelet agent
        1. Give Aspirin 325 mg chewed on presentation and
        2. P2Y Receptor Inhibitor
          1. May be delayed until arrival at the catheterization lab (discuss with receiving interventionist)
          2. Clopidogrel (Plavix) 600 mg orally (then continued at 75 mg daily) or
          3. Ticagrelor (Brilinta) 180 mg orally (then continued at 90 mg twice daily)
          4. Avoid administering Prasugrel (Effient) in ED due to bleeding risk
            1. Delay Presugrel until at catheter lab
      3. References
        1. (2012) Circulation 126(7): 875-910 [PubMed]
  4. Thrombolytic therapy (Fibrinolysis)
    1. See Thrombolysis in ST Elevation Myocardial Infarction
    2. Goal within 30 minutes of ED arrival
      1. Primary indications AND
      2. Not contraindicated AND
      3. Angioplasty (PCI) not available within 90-120 minutes (door to balloon time)
    3. Additional associated immediate measures
      1. P2Y Receptor Inhibitor (Clopidogrel or Ticagrelor) at loading doses above AND
      2. Anticoagulation with Unfractionated Heparin at doses above for at last 48 hours
        1. Enoxaparin and Fondaparinux are alternatives, but not if angiogram planned
    4. Urgent angiography after Fibrinolysis is typically performed as soon as possible (<24 hours)
      1. Typically recommended in all post-Fibrinolytic patients
      2. Cohorts with increased benefit
        1. Acute severe CHF or Cardiogenic Shock
        2. Failed reperfusion with Fibrinolytic (persistent ST Elevation, persistent or recurrent Chest Pain)
  5. Efficacy: Comparing Angioplasty with Fibrinolysis
    1. Similar outcomes and complication rates
      1. Mehta (2002) J Am Coll Cardiol 40:1034-40 [PubMed]
    2. Angioplasty preferred if transport delay <1 hour
      1. Andersen (2003) N Engl J Med 349:733-42 [PubMed]
    3. Specific cohorts with better outcomes with Angioplasty (PCI)
      1. Women
      2. Pulmonary Edema
      3. Systolic Blood Pressure <100 mmHg and Heart Rate >100 bpm
      4. Associated shock-related findings (e.g. Cool and clammy skin)

VI. Management: STEMI with Hypotension (Cardiogenic Shock)

  1. Background
    1. Cardiogenic Shock complicates 6% of acute Myocardial Infarctions
  2. Causes
    1. Right ventricular infarction
    2. Acute Left Ventricular Failure (Left main, left anterior descending or circumflex artery Occlusion)
    3. Aortic Dissection
    4. Massive Pulmonary Embolism
    5. Tension Pneumothorax
    6. Cardiac Tamponade
    7. Ventricular Rupture
    8. Esophageal Rupture
  3. Evaluation
    1. Right sided EKG
    2. Bedside Ultrasound
  4. Management
    1. Emergent reperfusion therapy is critical to stabilization if Myocardial Infarction
      1. However, exclude non-cardiogenic causes above
    2. Medications
      1. Aspirin
      2. Oxygen (if Hypoxia)
      3. Avoid Beta Blockers or Calcium Channel Blockers
      4. Small crystalloid fluid boluses (250 ml) if not in Pulmonary Edema
      5. Norepinephrine (although risk of increased ischemia, Arrhythmia)
  5. References
    1. Adaka in Herbert (2018) EM:Rap 18(2):2-3

VII. Management: Acute Medications

  1. See Post Myocardial Infarction Medications (includes Beta Blockers, ACE Inhibitors, Statins)
  2. Beta Blockers are used selectively only
    1. Consider in hypertensive patients or with tachydysrhythmia such as Atrial Fibrillation with Rapid Ventricular Response
    2. Avoid in Sinus Tachycardia which may indicate large Myocardial Infarction with risk of Cardiogenic Shock
    3. Exercise caution with Beta Blockers following the acute phase post-STEMI
    4. See Post Myocardial Infarction Medications for contraindications and indications

VIII. Management: Long-term Medications

  1. See Post Myocardial Infarction Medications
  2. Oral antiplatelet medications are used routinely following ST Elevation MI (especially after stenting)
    1. See Antiplatelet Therapy for Vascular Disease
    2. Clopidogrel (Plavix)
    3. Ticagrelor (Brilinta)
    4. Prasugrel (Effient)

IX. Management: Contraindicated Medications

  1. NSAIDS are absolutely contraindicated in acute post-STEMI period
    1. See Post Myocardial Infarction Medications
  2. Morphine (and presumed other Opioids) - possible relative contraindication (based on initial study)
    1. Morphine decreased (35%) and delayed (2 hours) Ticagrelor absorption
    2. Presumed to apply to other Opioids
    3. Kubica (2016) Int J Cardiol 215:201-8 [PubMed]

X. References

  1. Mattu and Orman in Herbert (2013) EM:Rap 13(4): 7-8
  2. Swaminathan and Mattu in Swadron (2022) EM:Rap 22(10): 4-5
  3. (2000) Circulation 102(suppl I):I172-203 [PubMed]
  4. Antman (2008) Circulation 117(2): 296-329 [PubMed]
  5. O'Gara (2013) Circulation 127(4): e362-425 [PubMed]
  6. Switaj (2017) Am Fam Physician 95(4): 232-40 [PubMed]

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