Management of ST-Elevation Myocardial Infarction (STEMI)
Immediately administer 162-325 mg of non-enteric coated aspirin upon first medical contact and proceed with urgent reperfusion therapy—either primary PCI within 120 minutes or fibrinolytic therapy within 30 minutes if PCI is not achievable within that timeframe. 1, 2, 3
Initial Assessment and Immediate Actions
Obtain a 12-lead ECG within 10 minutes of emergency department arrival for all patients with chest discomfort or symptoms suggestive of STEMI. 4, 1 If the initial ECG is non-diagnostic but clinical suspicion remains high, perform serial ECGs at 5-10 minute intervals or implement continuous 12-lead ST-segment monitoring. 4, 1
For patients with inferior STEMI, obtain right-sided ECG leads to screen for ST elevation suggestive of right ventricular infarction, as this finding significantly alters management (particularly regarding nitrate and fluid administration). 4, 1
Immediate Medical Therapy
Administer supplemental oxygen only to patients with arterial oxygen desaturation (SaO2 <90%) or overt pulmonary congestion—routine oxygen administration is not indicated. 4, 1, 2
Provide morphine sulfate for patients with ongoing ischemic pain or pulmonary congestion. 4, 1, 2
Initiate oral beta-blocker therapy promptly in patients without contraindications (no frank cardiac failure, pulmonary congestion, or signs of low-output state). 4, 1, 2 Intravenous beta-blockers may be reasonable for patients with tachyarrhythmias or hypertension. 2
Reperfusion Strategy Decision Algorithm
The critical decision point is whether primary PCI can be performed within 120 minutes of first medical contact. 1, 2, 3 For high-risk patients (large anterior infarction, age <75 years) presenting within 2 hours of symptom onset, this PCI-related delay should not exceed 90 minutes. 1, 5
Primary PCI Strategy (Preferred)
If primary PCI can be achieved within 120 minutes of first medical contact:
Transport directly to the cardiac catheterization laboratory, bypassing the emergency room or intensive care unit. 5
Administer dual antiplatelet therapy before PCI: aspirin plus a P2Y12 inhibitor as early as possible. 1, 2, 3
Prasugrel is preferred over clopidogrel for primary PCI due to faster onset and superior effectiveness: 60 mg loading dose (independent of age and weight initially), followed by 10 mg daily (or 5 mg daily if ≥75 years or <60 kg body weight). 6, 5
Use clopidogrel instead of prasugrel if the patient has a history of stroke or TIA (absolute contraindication to prasugrel), or if fibrinolysis was administered. 6, 5
Administer unfractionated heparin for anticoagulation during PCI, with bivalirudin as an alternative, particularly in patients with high bleeding risk. 4, 5
Consider manual thrombus aspiration in patients with high intracoronary thrombus burden. 5, 7
Target door-to-balloon time of ≤90 minutes as a quality measure. 2, 5
Fibrinolytic Strategy
If primary PCI cannot be performed within 120 minutes of first medical contact, administer fibrinolytic therapy within 30 minutes of hospital arrival (or within 30 minutes of EMS arrival if prehospital fibrinolysis capability exists). 4, 1, 5
Fibrinolytic agents in order of preference:
- Tenecteplase (Grade 1A recommendation) 8
- Reteplase (Grade 1B recommendation) 8
- Alteplase (Grade 1C recommendation) 8
- Streptokinase (Grade 2B recommendation) 8
After fibrinolysis, perform cardiac catheterization within 3-24 hours with PCI if applicable—this pharmaco-invasive approach is mandatory even if fibrinolysis appears successful. 5, 8
Adjunctive therapy with fibrinolysis:
- Administer unfractionated heparin with fibrin-specific agents (alteplase, reteplase, tenecteplase): 60 U/kg bolus (maximum 4000 U) followed by 12 U/kg/hour infusion (maximum 1000 U/hour), adjusted to maintain aPTT at 1.5-2.0 times control. 4
- Use clopidogrel 75 mg daily (not prasugrel) as the P2Y12 inhibitor. 5
Management of Specific Complications
Cardiogenic Shock
For patients <75 years with cardiogenic shock developing within 36 hours of MI, immediately transfer to facilities capable of cardiac catheterization and perform emergency revascularization (PCI or CABG) within 18 hours of shock onset. 4, 2, 3 This recommendation applies regardless of time delay from MI onset. 4, 2
For patients ≥75 years with cardiogenic shock, emergency revascularization can be effective, especially in those with good prior functional status, severe triple-vessel or left main disease. 4
Immediate management of cardiogenic shock:
- Perform rapid volume loading with IV infusion in patients without clinical evidence of volume overload. 4
- Administer vasopressor support for hypotension that does not resolve after volume loading. 4
- Insert intra-aortic balloon pump (IABP) for patients who do not stabilize quickly with pharmacological therapy. 4, 2, 3
- Perform urgent echocardiography to estimate LV and RV function and exclude mechanical complications. 4
Pulmonary Congestion/Acute Heart Failure
Immediate goals include adequate oxygenation and preload reduction:
- Administer oxygen supplementation to maintain arterial saturation >90%. 4, 2
- Give morphine sulfate. 4
- Initiate ACE inhibitors with titration of a short-acting agent (e.g., captopril 1-6.25 mg) unless systolic blood pressure is <100 mm Hg or >30 mm Hg below baseline. 4
- Administer nitrates unless systolic blood pressure is <100 mm Hg or >30 mm Hg below baseline. 4
- Give diuretics (low- to intermediate-dose furosemide, torsemide, or bumetanide) if there is associated volume overload; use caution in patients who have not received volume expansion. 4
For patients with pulmonary congestion and marginal or low blood pressure, provide circulatory support with inotropic and vasopressor agents and/or intra-aortic balloon counterpulsation. 4
It may be reasonable to insert an IABP for refractory pulmonary congestion. 4
Mechanical Complications
Ventricular septal rupture, papillary muscle rupture, or free wall rupture require emergency CABG at the time of surgical repair. 4
Post-STEMI Medical Management
ACE Inhibitors
Initiate ACE inhibitors within 24 hours in patients with anterior STEMI, heart failure, or ejection fraction ≤0.40. 4, 1, 2, 3 Begin with low-dose short-acting agents and titrate upward. 4
Beta-Blockers
Continue oral beta-blockers indefinitely in all eligible patients except those at low risk (normal or near-normal ventricular function, successful reperfusion, absence of significant ventricular arrhythmias). 4, 1, 2, 3 For patients with moderate or severe LV failure, initiate low doses with gradual titration. 4
Dual Antiplatelet Therapy
Continue dual antiplatelet therapy (aspirin plus P2Y12 inhibitor) for at least 12 months in all patients receiving stents, regardless of stent type (BMS or DES). 1, 2, 3, 5 This treats the patient, not the stent. 5
Statin Therapy
Initiate or continue high-intensity statin therapy in all STEMI patients without contraindications. 1, 2, 3
Aldosterone Blockade
Prescribe long-term aldosterone blockade for post-STEMI patients without significant renal dysfunction (creatinine ≤2.5 mg/dL in men, ≤2.0 mg/dL in women) or hyperkalemia (potassium ≤5.0 mEq/L) who are already receiving therapeutic doses of an ACE inhibitor, have LVEF ≤0.40, and have either symptomatic heart failure or diabetes. 4
Blood Pressure Management
Treat blood pressure to a target of <140/90 mm Hg (or <130/80 mm Hg for patients with diabetes or chronic kidney disease) using ACE inhibitors, beta-blockers, and if necessary, aldosterone antagonists. 4
Anticoagulation for Specific Indications
Prescribe warfarin (INR 2.0-3.0) for:
- Persistent or paroxysmal atrial fibrillation 4
- LV thrombus noted on imaging (for at least 3 months, indefinitely if no increased bleeding risk) 4
Special Populations and Circumstances
Patients Presenting 12-24 Hours After Symptom Onset
PCI may be beneficial even in asymptomatic patients if signs of ischemia/viability in the infarct artery-related area are demonstrable; if not demonstrable, PCI is not indicated. 5
Prehospital Management
Every community should have a written protocol guiding EMS personnel in determining where to take STEMI patients. 4, 1 Patients with STEMI and shock are high-priority triage cases. 4
Prehospital fibrinolysis is reasonable in settings where physicians are present in the ambulance or in well-organized EMS systems with 12-lead ECG transmission capability, paramedic training in ECG interpretation, online medical command, and continuous quality improvement. 4
Critical Pitfalls to Avoid
Do not delay reperfusion therapy to wait for cardiac biomarker results—initiate treatment based on clinical presentation and ECG findings. 1
Do not administer beta-blockers or calcium channel blockers acutely to STEMI patients with frank cardiac failure evidenced by pulmonary congestion or signs of low-output state. 4, 2
Do not use short-acting dihydropyridine calcium channel blocking agents (such as immediate-release nifedipine) for treatment due to reflex sympathetic activation, tachycardia, and hypotension. 4, 1
Do not discontinue prasugrel or other antiplatelet therapy prematurely—stopping increases the risk of subsequent cardiovascular events including stent thrombosis, MI, and death. 6
When possible, discontinue prasugrel at least 7 days prior to any surgery due to bleeding risk, particularly CABG. 6
Do not routinely administer glycoprotein IIb/IIIa inhibitors upstream—limit to patients with high intracoronary thrombus burden during PCI. 5
Discontinue NSAIDs in patients who routinely took them before STEMI due to increased risks of adverse outcomes. 1