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Treatment of Myocardial Infarction (MI)

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1. Immediate General Measures (All MI Types)

• Washington Manual of Medical Therapeutics, p. 148-156; Harrison's Principles of Internal Medicine 22E, p. 2160

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2. Reperfusion Therapy (STEMI)

Primary PCI (Preferred)

• Gold standard when available within 90 min of first medical contact (FMC-to-device ≤90 min at PCI-capable center; ≤120 min if transfer required).
• Superior to fibrinolysis: better vessel patency (TIMI 3 flow), less reinfarction, lower intracranial hemorrhage risk, improved survival regardless of age or infarct location.
• Best for symptom onset <12 hours; still offered at 12-24 hours if ongoing symptoms.
• Transradial access is preferred - reduces bleeding and may have a mortality benefit over transfemoral.
• Complete revascularization of non-culprit lesions (either at index procedure or staged) reduces cardiovascular death and future MI.
• CULPRIT-SHOCK exception: In cardiogenic shock, culprit-lesion-only PCI (not multivessel) reduces all-cause mortality and need for renal replacement therapy.
• Coronary stenting (DES preferred) is superior to balloon angioplasty alone.

Fibrinolytic Therapy

• Used when PCI cannot be achieved within 120 min (non-PCI-capable center with anticipated FMC-to-device >120 min).
• Administer within 30 min of hospital arrival ("door-to-needle" ≤30 min).
• Agents: tPA (alteplase), reteplase, tenecteplase (fibrin-specific preferred over streptokinase).
• After successful fibrinolysis: transfer for angiography and revascularization within 3-24 hours.
• Failed reperfusion (persistent ST elevation or hemodynamic instability): urgent transfer for rescue PCI.

• Washington Manual of Medical Therapeutics, p. 156; Harrison's 22E, p. 2160-2162

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3. Antiplatelet and Anticoagulant Therapy

Dual Antiplatelet Therapy (DAPT)

• Aspirin (see above) +
• P2Y12 inhibitor:
  • Ticagrelor 180 mg load then 90 mg BID (preferred in ACS if no contraindication)
  • Prasugrel 60 mg load then 10 mg/day (avoid if prior TIA/stroke, age >75, weight <60 kg)
  • Clopidogrel 300-600 mg load then 75 mg/day (used when ticagrelor/prasugrel contraindicated, or with fibrinolysis)
• DAPT duration: typically 12 months after ACS/PCI; may be shortened/extended based on bleeding vs. ischemic risk.
• Cessation of P2Y12 inhibitor within 30 days of stent placement carries a 30- to 100-fold increase in stent thrombosis risk.

Anticoagulation (Acute Phase)

• Unfractionated heparin (UFH): IV bolus + infusion; or
• Enoxaparin (LMWH): subcutaneous, often preferred in NSTEMI/UA
• Bivalirudin: direct thrombin inhibitor; alternative in PCI
• Fondaparinux: NSTEMI/medical management; do not use alone for primary PCI
• Anticoagulation is continued until revascularization is complete or through the hospital stay in medically managed patients.

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4. Adjunctive Medical Therapy

Beta-Blockers

• Start within 24 hours if no contraindications (HF, low output state, heart block, active bronchospasm).
• Reduce myocardial O2 demand, limit infarct size, reduce ventricular arrhythmias.
• Oral agents preferred (metoprolol, carvedilol); IV beta-blocker if hypertensive or tachycardic without HF.
• Continued indefinitely post-MI for LV dysfunction.

ACE Inhibitors / ARBs

• Start within 24 hours in STEMI, especially anterior MI or EF <40%.
• Prevent ventricular remodeling, reduce mortality.
• ACE inhibitors are "ideal" for long-term management of ventricular dysfunction after STEMI.
• Use ARB if ACE inhibitor intolerant.
• Aldosterone antagonist (eplerenone/spironolactone): add if EF ≤40% with symptomatic HF or diabetes; monitor K+ and renal function.

Statins (High-Intensity)

• Start in-hospital regardless of baseline LDL.
• Atorvastatin 40-80 mg or rosuvastatin 20-40 mg.
• Fasting lipid panel recommended as baseline (note: lipids may fall in first 24-48 hours post-MI).

Nitrates

• Long-term oral nitrates for ongoing angina or HF symptoms.
• Not for routine use post-MI without ongoing ischemia or HF.

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5. Management of Specific Complications

Cardiogenic Shock (Killip Class IV)

• Defined by hypotension + evidence of end-organ hypoperfusion.
• Occurs when ≥40% of LV myocardium is infarcted.
• Primary PCI is always preferred even with time delays.
• Inotropes: dobutamine (improves contractility, reduces peripheral resistance).
• Mechanical circulatory support: IABP, Impella, ECMO.
• Swan-Ganz catheter for hemodynamic monitoring in refractory cases.
• In cardiogenic shock with multivessel disease: culprit-only PCI first (CULPRIT-SHOCK trial).

Right Ventricular (RV) Infarction

• Occurs with proximal RCA occlusion causing inferior STEMI.
• Classic triad: hypotension + elevated JVP + clear lung fields.
• ECG: ST elevation ≥1 mm in V1 or V4R lead.
• Management: IV fluids (RV is preload-dependent); avoid nitrates and diuretics.
• If unresponsive: dobutamine + IABP; right-sided mechanical support if needed.
• Temporary pacing if AV block present.

Heart Failure Post-MI

• Loop diuretics (furosemide IV) for pulmonary congestion.
• Nitrates to reduce preload without reducing plasma volume.
• ACE inhibitors for long-term LV dysfunction.
• Digitalis is not useful in post-MI HF.

Arrhythmias

• VF/VT: immediate defibrillation; IV amiodarone or lidocaine for recurrent VT.
• Complete heart block (especially inferior MI - RCA): temporary pacing; resolves in most.
• AF: rate control with beta-blockers; anticoagulation per CHA2DS2-VASc.

LV Thrombus

• Risk in anterior MI with apical akinesis.
• Anticoagulate if thrombus detected.
• Warfarin not routinely prescribed for apical hypokinesis without confirmed thrombus (increased bleeding and death without clear benefit).

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6. NSTEMI / Unstable Angina Management

• Same antiplatelet + anticoagulant therapy as STEMI.
• No role for immediate fibrinolysis in NSTEMI.

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7. Secondary Prevention (Discharge Medications - "ABCDE")

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8. CABG

• Anatomy is unsuitable for PCI (left main disease, multivessel disease with complex anatomy, especially in diabetics).
• Failed PCI with ongoing ischemia.
• Mechanical complications requiring surgical repair (VSR, papillary muscle rupture).

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Key Time Targets Summary

• Harrison's Principles of Internal Medicine 22E (2025), p. 2160-2170
• Goldman-Cecil Medicine, p. 3557-3560
• Washington Manual of Medical Therapeutics, p. 148-162