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

Management of ST-Elevation Myocardial Infarction (STEMI)

Immediately administer 162-325 mg of non-enteric coated aspirin upon first medical contact and proceed urgently with reperfusion therapy—either primary PCI within 120 minutes or fibrinolysis within 30 minutes if PCI cannot be achieved in that timeframe. 1, 2

Initial Assessment and Immediate Actions

Obtain a 12-lead ECG within 10 minutes of emergency department arrival for all patients with chest discomfort or STEMI symptoms. 1, 2 STEMI is defined as ST-segment elevation >0.1 mV in at least two contiguous precordial or adjacent limb leads, new left bundle branch block, or true posterior MI. 1

• If the initial ECG is non-diagnostic but clinical suspicion remains high, perform serial ECGs at 5-10 minute intervals. 1, 2
• For patients with inferior STEMI, obtain right-sided ECG leads to screen for right ventricular infarction. 2
• Administer supplemental oxygen only to patients with arterial oxygen desaturation (SpO2 <90%) or respiratory distress—not routinely to all patients. 2, 3
• Provide morphine sulfate for patients with ongoing ischemic pain or pulmonary congestion. 2, 3

Reperfusion Strategy: The Critical Decision Algorithm

The fundamental decision point is whether primary PCI can be performed within 120 minutes of first medical contact. 1, 2 This is not the same as door-to-balloon time—it includes the entire interval from when EMS is called or the patient presents to any facility.

Choose Primary PCI When:

• First medical contact-to-device time can be achieved within 120 minutes 1, 2
• For high-risk patients (age <75 years with large anterior infarction) presenting within 2 hours of symptom onset, the acceptable delay is only 90 minutes 2, 4
• Patients with cardiogenic shock should be transferred immediately to PCI-capable facilities if revascularization can be performed within 18 hours of shock onset 5, 3
• Patients with contraindications to fibrinolytic therapy should be transferred promptly to PCI-capable facilities (door-to-departure time <30 minutes) 5

Choose Fibrinolytic Therapy When:

• Primary PCI cannot be performed within 120 minutes of first medical contact 1, 2
• Administer fibrinolytic therapy within 30 minutes of hospital arrival 2, 4
• Tenecteplase (TNKase) is administered as a single weight-based IV bolus over 5 seconds 6
• After fibrinolysis, perform cardiac catheterization within 24 hours (but not before 3 hours) with PCI if applicable 4

Critical caveat: In patients with large STEMI, physicians should choose either thrombolysis or PCI as the primary treatment strategy—not both simultaneously. 6 Planned PCI immediately after fibrinolysis shows trends toward worse outcomes including increased mortality (6.7% vs 4.9%), cardiogenic shock (6.3% vs 4.8%), and heart failure (12% vs 9.2%). 6 However, rescue PCI or subsequent elective PCI may be performed if medically appropriate. 5

Antithrombotic and Antiplatelet Therapy

For Primary PCI:

• Dual antiplatelet therapy (DAPT) with aspirin plus a potent P2Y12 inhibitor before PCI, as early as possible 1, 2
• Prasugrel is preferred over clopidogrel (loading dose 60 mg, or 10 mg maintenance; reduce to 5 mg if ≥75 years or <60 kg) 1, 4
• Clopidogrel 600 mg loading dose if prasugrel contraindicated (history of stroke/TIA) 4
• Continue DAPT for at least 12 months in patients receiving stents 1, 2, 3

For Fibrinolysis:

• Use aspirin plus clopidogrel 1
• Administer unfractionated heparin (UFH) with fibrin-specific agents (alteplase, reteplase, tenecteplase): 60 U/kg bolus (maximum 4000 U) followed by 12 U/kg/hour infusion (maximum 1000 U/hr), adjusted to maintain aPTT at 1.5-2.0 times control 5

Glycoprotein IIb/IIIa Inhibitors:

• Reserved only for patients with high intracoronary thrombus burden during PCI 4
• Upstream administration is not recommended 4

Hemodynamic Management and Complications

For Cardiogenic Shock:

Early revascularization (PCI or CABG) is mandatory for patients <75 years who develop shock within 36 hours of MI, if revascularization can be performed within 18 hours of shock onset. 5 This saves 13 lives per 100 patients treated. 5

• Intra-aortic balloon counterpulsation (IABP) is recommended when cardiogenic shock is not quickly reversed with pharmacological therapy as a stabilizing measure for angiography and prompt revascularization 5
• For patients ≥75 years with good prior functional status, emergency revascularization is reasonable 5
• Transfer patients to regional tertiary care centers with revascularization facilities experienced with shock patients 5

Pharmacological Support for Shock:

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

For Pulmonary Edema Without Hypotension:

• Immediate goals: adequate oxygenation and preload reduction 5
• Nitroglycerin 10-20 mcg/min IV if SBP >100 mm Hg 5
• ACE inhibitors (short-acting agent such as captopril 1-6.25 mg) 5
• Avoid beta-blockers or calcium channel blockers in patients with frank cardiac failure evidenced by pulmonary congestion or signs of low-output state 5

Mechanical Complications Requiring Urgent Surgery:

• Ventricular septal rupture: urgent cardiac surgical repair with CABG 5
• Acute papillary muscle rupture: urgent cardiac surgical repair 5
• Free-wall rupture: urgent cardiac surgical repair with CABG 5
• All require IABP insertion and prompt surgical referral 5

Emergency CABG Indications

Emergency or urgent CABG is indicated in the following Class I circumstances: 5

• Failed PCI with persistent pain or hemodynamic instability in patients with suitable coronary anatomy 5
• Persistent or recurrent ischemia refractory to medical therapy with significant myocardium at risk and unsuitable for PCI or fibrinolysis 5
• At the time of surgical repair of ventricular septal rupture or mitral valve insufficiency 5
• Cardiogenic shock in patients <75 years with severe multivessel or left main disease, if revascularization can be performed within 18 hours of shock 5
• Life-threatening ventricular arrhythmias with ≥50% left main stenosis and/or triple-vessel disease 5

Post-STEMI Medical Management

Initiate Within 24 Hours:

• ACE inhibitors in all patients, particularly those with anterior MI, heart failure, or ejection fraction ≤0.40 1, 2, 3
• Oral beta-blockers in all eligible patients (continue indefinitely) 1, 2, 3
• High-intensity statin therapy in all patients without contraindications 2

Continue Long-Term:

• Aspirin 75-162 mg daily indefinitely 3
• DAPT with aspirin plus P2Y12 inhibitor for at least 12 months in patients receiving stents 1, 2, 3
• Beta-blockers indefinitely 1, 2, 3

Additional Considerations:

• Aldosterone antagonists (eplerenone or spironolactone) for patients with LVEF ≤0.40 and either symptomatic heart failure or diabetes, if already receiving therapeutic ACE inhibitor doses and potassium 3.5-5.0 mEq/L 5
• Angiotensin receptor blockers (ARBs) for patients intolerant of ACE inhibitors 3

Critical Pitfalls to Avoid

• Do not delay reperfusion therapy to wait for cardiac biomarker results—initiate treatment based on clinical presentation and ECG findings 2
• Avoid immediate-release nifedipine due to reflex sympathetic activation, tachycardia, and hypotension 2, 3
• Do not administer beta-blockers or calcium channel blockers to patients with frank cardiac failure, pulmonary congestion, or low-output state 5
• Avoid aggressive simultaneous use of hypotensive agents in pulmonary edema, which can precipitate iatrogenic cardiogenic shock 5
• Do not perform routine immediate PCI after successful fibrinolysis—this increases adverse events including bleeding, recurrent ischemia, emergency CABG, and death 5
• Discontinue NSAIDs in patients who routinely took them before STEMI due to increased risks of adverse outcomes 2

Monitoring and Follow-Up

• Perform echocardiography urgently to estimate LV and RV function, detect mechanical complications, and exclude LV thrombus 5, 1
• Pulmonary artery catheter monitoring can be useful for managing cardiogenic shock 5
• Follow-up ECGs at 24 hours and hospital discharge to assess reperfusion success and infarct extent 1