Early identification

• Electrocardiogram (ECG) should be performed within 10 minutes upon arrival to the emergency department if not obtained by Emergency Medical System (EMS) prearrival.
• If initial ECG is not diagnostic and patient remains symptomatic, repeat ECG every 15-30 minutes to detect ischemic changes.

• Assess responsiveness, airway, breathing, and circulation.
• Look for evidence of systemic hypoperfusion (hypotension; tachycardia; impaired cognition; cool, clammy, pale skin); cardiogenic shock requires aggressive management.
• Left heart failure with hypoxia (dyspnea, hypoxia, pulmonary edema, and/or impending respiratory compromise) requires aggressive oxygenation, airway stabilization, diuretic therapy and afterload reduction.
• Treat ventricular arrhythmias immediately due to effect on cardiac output and exacerbation of myocardial ischemia.

• Continuous cardiac monitoring with emergency resuscitation equipment nearby.
• Administer oxygen to patients with arterial saturation less than 90%, patients in respiratory distress including those with heart failure, or those with other high-risk factors for hypoxia. Note: Supplemental oxygen shows no benefit to patients with oxygen saturation greater than or equal to 90%.
• Establish intravenous (IV) access.
• Obtain serial cardiac troponin I or T levels at presentation and 2-3 hours after symptom onset.
• Obtain basic electrolyte panel, kidney function tests, complete blood count with platelets, and coagulation panel if patient is on warfarin therapy or has liver disease.

• Administer sublingual NTG every 5 minutes up to 3 times for continuing ischemic pain; administer IV NTG for persistent ischemia, heart failure, or hypertension. Contraindicated  in patients with one or more of the following: hypotension (SBP less than 90 mm Hg), suspicion/confirmed right ventricular failure, marked bradycardia (HR less than 50 bpm) or tachycardia (HR greater than 100 bpm), known hypertrophic cardiomyopathy, severe aortic stenosis or if phosphodiesterase inhibitor (e.g., Viagra) has been taken within the previous 24 hours.
• IV morphine should be avoided unless patient has an unacceptable level of pain. Initial dose is 2-4 mg, with increments of 2-8 mg at 5- to 15-minute intervals.
• Discontinue nonsteroidal anti-inflammatory drugs (NSAIDs), except aspirin, because of increased risk of adverse cardiac events.

Stabilize hemodynamics/prevent and manage arrhythmias

• Atrial fibrillation and flutter can cause symptomatic hypoperfusion; ventricular tachycardia and fibrillation are life-threatening.
• Treat with prophylactic IV β-blocker and maintain serum potassium between 3.5 and less than 4.5 mEq/L and serum magnesium above 2.0 mEq/L.
• Avoid prophylactic lidocaine.
• Treat symptomatic bradycardia and heart block with atropine or temporary pacing.

Estimation of Risk

• High risk patients require aggressive management. This includes those of advanced age, or those with low blood pressure, tachycardia, heart failure, and an anterior MI. (See TIMI score below).

• Used to prevent recurrent ischemia and life-threatening ventricular arrhythmias.
• Start β-blocker (metoprolol or atenolol) in all patients without contraindications within 24 hours; defer in patients that are hemodynamically unstable.
• Contraindications are heart failure, low output state, risk for cardiogenic shock, bradycardia, PR interval greater than 0.24 seconds, second- or third- degree heart block without permanent pacemaker, reactive airway disease/active bronchospasm.

Dual antiplatelet therapy (O’Gara et al., 2013; Cutlip & Lincroft, 2022)

• Aspirin: loading dose 325 mg uncoated aspirin, to be chewed or crushed to allow for rapid absorption; maintenance dose 81mg/day is preferred as there is no benefit to higher doses but there is a higher risk of bleeding with higher daily dosages, especially gastrointestinal bleeding events. Also note, 81 mg/day is the only dose option when used concomitantly with ticagrelor.
• P2Y12 inhibitors for 12 months, regardless if treated with primary- PCI or ischemia-guided strategy. Loading and maintenance doses are the same for both indications, however prasugrel is an option only in primary PCI, not in ischemia-guided strategy.
• Clopidogrel: Loading dose 300-600 mg; maintenance dose 75 mg/day
• Ticagrelor: Loading dose 180 mg; maintenance 90 mg every 12 hours (must only be given with aspirin 81 mg/day)
• Prasugrel (primary PCI only): Loading dose 60 mg; maintenance dose 10 mg/day (contraindicated with history of stroke or TIA, age 75 years or older, and weight less than 60 kg)

Cholesterol therapy 
(Rosenson, 2020)

• High-intensity statin therapy should be initiated as early as possible; obtain fasting lipid panel within 24 hours.
• Atorvastatin 80 mg daily or rosuvastatin 20 or 40 mg daily
• LDL goal is 50 mg/dL or less
• Add ezetimibe 10 mg daily to high dose statin therapy if LDL not a goal.
• Add PCSK9 inhibitor for patients with statin allergy or intolerance or if LDL not a goal with high dose statin therapy and ezetimibe alone.

Long-term management

• Antiplatelet therapy to reduce the risk of recurrent coronary artery thrombosis or, with PCI, coronary artery stent thrombosis
• Statin therapy indefinitely
• Oral anticoagulation in the presence of left ventricular thrombus or chronic atrial fibrillation to prevent embolization
• Angiotensin converting enzyme (ACE) inhibitors, especially in STEMI patient with or without reduced left ventricular function and/or patients with diabetes, hypertension, and chronic kidney disease
• β-blockers, if no contraindications

• Urgent/immediate diagnostic angiography with intent to re- vascularize (within 2 hours) in NSTE-ACS patients with:
  • Hemodynamic instability or cardiogenic shock
  • Severe left ventricular dysfunction or heart failure
  • Recurrent or persistent rest angina despite intensive medical therapy
  • New or worsening mitral regurgitation or new ventricular septal defect
  • Sustained ventricular arrhythmias
• Within 24 hours of admission for initially stabilized high-risk patients.
• Not recommended in those with extensive co-morbidities, for whom the risks are likely to outweigh the benefits of revascularization OR in those with acute chest pain and low likelihood of ACS who are troponin negative (especially women).

• Reperfusion therapy should be administered to all eligible patients with STEMI with symptom onset within the prior 12 hours:
  • PCI-capable hospitals – door-to-balloon time within 90 minutes upon arrival.
  • Non-PCI-capable hospitals transfer to PCI hospital for door-to-balloon time of 120 minutes. If arrive within 2 hours of onset of symptoms, administer lytic therapy then transfer.
• Fibrinolysis is recommended for patients with symptom onset within 12 hours who cannot receive primary PCI within 120 minutes of first medical contact. Time from hospital arrival to initiation of fibrinolytic drug infusion (door-to-needle time) should be less than 30 minutes. High risk of bleeding with fibrinolysis.

• Choice of agent (enoxaparin, bivalirudin, fondaparinux or unfractionated heparin [UFH]) depends on the intervention strategy planned.

• UFH to maintain therapeutic activated clotting time (ACT). If given with GP IIb/IIIa receptor antagonist planned: 50-70 U/kg IV bolus; if no GP IIb/IIIa receptor antagonist planned: 70-100 U/kg bolus
• Bivalirudin 0.75 mg/kg IV bolus, then 1.75 mg/kg/h infusion with or without prior treatment with UFH. (Preferred if high risk of bleeding).
• Fondaparinux: not recommended as sole anticoagulant for primary PCI.