What is the management of ST-Elevation Myocardial Infarction (STEMI)?

Management of ST-Elevation Myocardial Infarction (STEMI)

Primary percutaneous coronary intervention (PCI) performed within 90 minutes of first medical contact is the definitive treatment for STEMI, with immediate aspirin administration and dual antiplatelet therapy initiated as early as possible. 1, 2

Immediate Initial Management (First Medical Contact)

Antiplatelet Therapy

• Administer 162-325 mg of non-enteric coated aspirin immediately upon first medical contact, either orally or intravenously if the patient cannot swallow 1, 2
• Initiate a potent P2Y12 inhibitor (prasugrel or ticagrelor preferred over clopidogrel) before or at the time of PCI and continue for 12 months 3, 1
• For patients undergoing primary PCI, prasugrel (60 mg loading dose) is preferred due to faster onset and superior effectiveness compared to clopidogrel (600 mg loading dose) 4

Symptom Management

• Administer morphine sulfate for ongoing ischemic pain or pulmonary congestion, recognizing this addresses patient comfort while reperfusion is being arranged 1, 2
• Provide supplemental oxygen only if arterial saturation is <90% or if pulmonary congestion/hypoxemia is present—routine oxygen in non-hypoxemic patients is not indicated 1, 2

Hemodynamic Support

• Initiate oral beta-blockers promptly in patients without contraindications (heart failure, hypotension, bradycardia, or signs of low-output state), regardless of reperfusion strategy 1, 2
• Intravenous beta-blockers may be considered for patients with tachyarrhythmias or hypertension, but avoid in patients with frank cardiac failure or pulmonary congestion 1
• Start intravenous nitroglycerin (10-20 mcg/min) in the first 48 hours for persistent ischemia, heart failure, or hypertension, provided systolic blood pressure is >100 mm Hg 3, 2

Reperfusion Strategy Decision Algorithm

Primary PCI Pathway (Preferred)

Primary PCI should be performed within 90 minutes of first medical contact (door-to-balloon time) for patients presenting directly to PCI-capable centers 3, 1, 2

For patients presenting to non-PCI capable facilities, transfer for primary PCI is recommended if first medical contact-to-device time can be achieved within 120 minutes 3, 1, 2

• In patients <75 years with large anterior infarction presenting within 2 hours of symptom onset, this time window should not exceed 90 minutes 4
• Patients should bypass the emergency department and be transferred directly to the catheterization laboratory to minimize delays 3
• Regional STEMI networks designed to deliver reperfusion expeditiously are essential, with PCI-capable centers providing 24/7 service 3

Anticoagulation for Primary PCI

• Bivalirudin is indicated as an anticoagulant during PCI with a 0.75 mg/kg intravenous bolus followed by 1.75 mg/kg/h infusion for the duration of the procedure 5
• Assess activated clotting time (ACT) 5 minutes after the bolus; administer an additional 0.3 mg/kg bolus if needed 5
• Consider extending bivalirudin infusion at 1.75 mg/kg/h for up to 4 hours post-procedure in STEMI patients to prevent thrombotic events 5, 4
• In renal impairment (creatinine clearance <30 mL/min), reduce infusion to 1 mg/kg/h; in hemodialysis patients, reduce to 0.25 mg/kg/h 5

Fibrinolytic Therapy Pathway (When PCI Not Timely)

If primary PCI cannot be performed within 120 minutes of first medical contact, administer fibrinolytic therapy within 30 minutes of hospital arrival (preferably in the pre-hospital setting) in patients without contraindications 3, 2

• Use a fibrin-specific agent: tenecteplase, alteplase, or reteplase 3
• Administer clopidogrel in addition to aspirin 3
• Anticoagulation with enoxaparin intravenously followed by subcutaneous (preferred over unfractionated heparin) or weight-adjusted UFH until revascularization or for hospital stay up to 8 days 3

Post-Fibrinolysis Management

• Transfer all patients to a PCI-capable center immediately after fibrinolysis 3
• Perform angiography and PCI of the infarct-related artery between 2-24 hours after successful fibrinolysis 3
• Rescue PCI is indicated immediately if fibrinolysis fails (<50% ST-segment resolution at 60-90 minutes) or with hemodynamic/electrical instability 3
• Emergency angiography and PCI are recommended for patients with heart failure or shock 3

Late Presentation (>12 Hours)

Reperfusion therapy is indicated in all patients with symptoms <12 hours duration and persistent ST-segment elevation 3

In asymptomatic patients, routine PCI of an occluded infarct-related artery >48 hours after STEMI onset is not indicated unless signs of ischemia/viability are demonstrable 3, 4

Management of Complications

Cardiogenic Shock

Emergency revascularization (PCI or CABG) is recommended regardless of time delay from MI onset for patients with cardiogenic shock 1, 2

• Intra-aortic balloon counterpulsation (IABP) is recommended for patients with low-output state or cardiogenic shock not quickly reversed with pharmacological therapy 3, 1, 2
• For patients ≥75 years with cardiogenic shock, emergency revascularization can be effective, especially in those with good prior functional status 1, 2

Hemodynamic Support Algorithm

First-line actions based on blood pressure and shock status: 3

• If SBP >100 mm Hg: Nitroglycerin sublingual, then 10-20 mcg/min IV
• If SBP 70-100 mm Hg with signs/symptoms of shock: Dopamine 5-20 mcg/kg/min IV
• If SBP 70-100 mm Hg without signs/symptoms of shock: Dobutamine 5-20 mcg/kg/min IV

Right Ventricular Infarction

Assess patients with inferior STEMI and hemodynamic compromise with right precordial V4R lead and echocardiogram to screen for RV infarction 3

Management principles for RV infarction: 3

• Early reperfusion should be achieved if possible
• Optimize RV preload with initial volume challenge if jugular venous pressure is normal or low
• Maintain AV synchrony and correct bradycardia
• Optimize RV afterload by treating concomitant LV dysfunction
• Use inotropic support for hemodynamic instability not responsive to volume challenge

Mechanical Complications

Ventricular septal rupture, free-wall rupture, and acute papillary muscle rupture require urgent cardiac surgical repair unless further support is futile 3, 2

• Insert IABP and provide prompt surgical referral for acute VSR 3
• CABG should be performed at the same time as repair of mechanical complications 3
• For patients with acute papillary muscle rupture causing severe mitral regurgitation, urgent surgical repair is indicated 3
• Diagnosis is established with transthoracic or transesophageal echocardiography when a new cardiac murmur is detected 3

Post-STEMI Medical Therapy

Antiplatelet Therapy

Continue dual antiplatelet therapy (DAPT) with aspirin plus a P2Y12 inhibitor for at least 12 months in patients receiving stents 3, 1, 2

• Aspirin 75-162 mg daily indefinitely 2
• Prasugrel 10 mg daily (or 5 mg daily if ≥75 years or <60 kg body weight) or ticagrelor, or clopidogrel 75 mg daily if the others are contraindicated 3, 4

Renin-Angiotensin System Blockade

Initiate ACE inhibitors within 24 hours in all patients, particularly those with anterior MI, previous MI, heart failure, or LVEF <0.40 1, 2

• Consider angiotensin receptor blockers (ARBs) in patients intolerant of ACE inhibitors 2

Beta-Blockers

Start beta-blockers in all eligible patients and continue indefinitely 2

Lipid Management

High-intensity statin therapy should be initiated or continued in all STEMI patients without contraindications 1

Cardiac Rehabilitation and Risk Factor Modification

Participation in a cardiac rehabilitation program is recommended 3

Identify smokers and provide repeated advice on stopping with follow-up support, nicotine replacement therapies, varenicline, and bupropion individually or in combination 3

Monitoring and Assessment

Routine echocardiography during hospital stay is recommended to assess resting LV and RV function, detect early post-MI mechanical complications, and exclude LV thrombus 3

Critical Pitfalls to Avoid

• Never administer beta-blockers or calcium channel blockers acutely to patients with frank cardiac failure, pulmonary congestion, or signs of low-output state 1
• Avoid immediate-release nifedipine in STEMI patients due to reflex sympathetic activation, tachycardia, and hypotension 2
• Do not administer fondaparinux for primary PCI 3
• Bivalirudin should not be administered in the same IV line with alteplase, amiodarone, amphotericin B, chlorpromazine, diazepam, dobutamine, prochlorperazine, reteplase, streptokinase, or vancomycin 5
• Increased risk of thrombus formation, including fatal outcomes, has been associated with bivalirudin use in gamma brachytherapy—avoid this combination 5
• Advanced Killip class (II-IV) at admission, LVEF <35%, age >65 years, and anterior MI location are the most powerful independent predictors of in-hospital mortality in STEMI patients undergoing interventional treatment 6