What are the steps in managing myocardial infarction (MI)?

Management of Myocardial Infarction

The immediate priority in MI management is rapid ECG diagnosis within 10 minutes of first medical contact, followed by urgent reperfusion therapy—primary PCI if achievable within 120 minutes, otherwise immediate fibrinolysis—combined with dual antiplatelet therapy (aspirin plus prasugrel/ticagrelor) and anticoagulation to reduce mortality. 1

Initial Recognition and Diagnosis

First Medical Contact (Target: Within 10 Minutes)

• Obtain and interpret 12-lead ECG within 10 minutes of first medical contact to classify as STEMI versus NSTEMI 1, 2
• Initiate continuous ECG monitoring with defibrillator capacity immediately 1
• Assess for ST-segment elevation ≥1mm in two contiguous leads or new left bundle branch block to identify STEMI 1

Immediate Symptom Management

• Administer aspirin loading dose (chewed for rapid absorption) at symptom onset 1, 2
• Give sublingual nitroglycerin (up to 3 doses, 5 minutes apart) for chest pain unless contraindicated 1
• Avoid routine oxygen unless SaO₂ <90% 1
• Provide analgesia (morphine) if chest pain persists despite nitroglycerin 3

Reperfusion Strategy for STEMI

Decision Algorithm (Time Zero = STEMI Diagnosis)

• If primary PCI achievable within 120 minutes of STEMI diagnosis: Proceed directly to catheterization laboratory 1, 2
• If PCI will exceed 120 minutes: Initiate fibrinolysis immediately (within 10 minutes of STEMI diagnosis) 1
• Emergency Medical Services should bypass emergency departments and transfer directly to 24/7 PCI-capable centers 1

Primary PCI Technical Approach

• Use radial artery access as standard approach 1
• Implant drug-eluting stents routinely 1
• Do NOT perform routine thrombus aspiration or deferred stenting (contraindicated) 1
• Treat severe non-infarct-related artery stenoses before hospital discharge (either during index procedure or staged) 1
• In cardiogenic shock, consider immediate PCI of non-infarct arteries during index procedure 1

Antithrombotic Therapy

For Primary PCI

• Anticoagulation: Unfractionated heparin (enoxaparin or bivalirudin as alternatives) 1
• Dual antiplatelet therapy (DAPT): Loading dose of aspirin PLUS prasugrel or ticagrelor (preferred over clopidogrel) 1, 2
• Continue DAPT for one year in majority of patients 1

For Fibrinolysis

• Anticoagulation: Enoxaparin preferred (unfractionated heparin as alternative) 1
• DAPT: Loading dose of aspirin PLUS clopidogrel 1

Early Intravenous Metoprolol (STEMI)

• Administer three 5mg IV boluses at 2-minute intervals after hemodynamic stabilization 4
• Monitor blood pressure, heart rate, and ECG continuously during administration 4
• Begin oral metoprolol 50mg every 6 hours starting 15 minutes after last IV dose, continue for 48 hours 4
• Reduce to 25mg every 6 hours if patient shows intolerance 4
• Maintenance dose: 100mg orally twice daily thereafter 4

Management of NSTEMI

Risk Stratification

• Calculate TIMI or GRACE score immediately to determine invasiveness of strategy 2

High-Risk Patients

• Perform coronary angiography within 24 hours 2
• Initiate aspirin plus P2Y12 inhibitor (prasugrel or clopidogrel) 2
• Use anticoagulation (unfractionated heparin or enoxaparin) 1

Low-Risk Patients

• Conservative strategy with selective invasive approach based on recurrent symptoms or positive stress testing 2

Management of Complications

Right Ventricular Infarction (Occurs in 50% of Inferior MIs)

• Diagnose with ST-elevation ≥1mm in lead V4R (88% sensitive, 78% specific) 5
• Clinical triad: hypotension, clear lung fields, elevated jugular venous pressure 5
• Aggressive IV normal saline boluses to maintain RV preload 5
• AVOID nitrates and diuretics (can cause profound hypotension by reducing preload) 5
• Dobutamine if cardiac output fails to increase after volume loading 5
• Consider intra-aortic balloon pump for persistent shock 5
• AV sequential pacing for symptomatic high-degree heart block unresponsive to atropine 5

Cardiogenic Shock

• Insert hemodynamic support device (intra-aortic balloon pump) 1, 5
• Emergency coronary angiography followed by PCI or CABG 1, 5
• For RV shock: volume expansion with normal saline, then inotropic agents if hypotension persists 1, 5

Heart Failure

• IV furosemide for volume overload 1
• Afterload-reducing agents (ACE inhibitors) 1
• Avoid nitrates in RV infarction 5

Conduction Disturbances

• IV atropine 0.3-0.5mg (repeat up to 1.5-2.0mg total) for symptomatic sinus bradycardia with hypotension 5
• Temporary pacing for symptomatic high-degree AV block unresponsive to atropine 5

Recurrent Chest Pain

• Pericarditis: High-dose aspirin 650mg every 4-6 hours 1, 5
• Recurrent ischemia: IV nitroglycerin, analgesics, antithrombotic medications (aspirin, heparin), consider urgent angiography with revascularization 1, 5

In-Hospital Monitoring and Early Care

• Monitor continuously for minimum 24 hours post-reperfusion 1
• Observe closely for mechanical complications (free wall rupture, ventricular septal rupture, acute mitral regurgitation) 6
• Early ambulation and early discharge for uncomplicated patients 1

Pre-Discharge Risk Stratification

• Perform exercise stress testing before discharge: submaximal at 4-7 days OR symptom-limited at 10-14 days 1, 2
• Assess functional capacity for home/work activities 1
• Evaluate efficacy of current medical regimen 1
• Stratify risk for subsequent cardiac events 1

Long-Term Secondary Prevention (Indefinite Duration)

Pharmacotherapy

• Aspirin (indefinitely) 1, 2, 7
• Beta-blocker (indefinitely) 1, 2, 7
• ACE inhibitor (indefinitely, especially if ejection fraction reduced or heart failure present) 1, 2, 7
• High-intensity statin with goal LDL <100 mg/dL (initiate if LDL >130 mg/dL despite diet) 1

Lifestyle Modifications

• Mandatory smoking cessation 1, 7
• Diet low in saturated fat and cholesterol 1, 7
• Achieve ideal body weight 1
• Exercise minimum 20 minutes at brisk walking intensity at least 3 times weekly 1, 7
• Formal cardiac rehabilitation program participation 1
• Regular blood pressure monitoring 7

Critical Pitfalls to Avoid

• Never administer nitrates in suspected RV infarction before confirming adequate preload—can cause catastrophic hypotension 5
• Do NOT use routine thrombus aspiration during primary PCI (contraindicated by current evidence) 1
• Avoid calcium channel blockers—not shown to reduce mortality and may be harmful 1
• Record lead V4R early in inferior MI (ST elevation resolves within 10 hours) 5
• Do not delay reperfusion for extensive risk stratification—time is myocardium 1