What is the immediate management for a patient with myocardial infarction (MI)?

Immediate Management of Myocardial Infarction

Upon arrival to the emergency department, immediately administer aspirin 160-325 mg orally, obtain a 12-lead ECG within 10 minutes, provide oxygen only if saturation is <90%, give sublingual nitroglycerin (unless contraindicated), and administer morphine for pain control, followed by urgent reperfusion therapy with primary PCI preferred over fibrinolysis when available within 120 minutes. 1

Initial Assessment and Stabilization (First 10 Minutes)

Immediate Actions Upon Arrival

• Obtain 12-lead ECG within 10 minutes (maximum 20 minutes) to identify ST-segment elevation ≥1 mm in contiguous leads or new left bundle branch block 2, 1, 3
• Administer aspirin 160-325 mg orally immediately upon arrival—do not wait for ECG confirmation, as this reduces 35-day mortality by 21% when combined with reperfusion therapy 2, 1, 3
• Establish continuous cardiac monitoring with defibrillation capacity to detect life-threatening arrhythmias 2, 3
• Provide oxygen via nasal prongs only if oxygen saturation <90%—avoid routine oxygen in non-hypoxemic patients as hyperoxia may increase myocardial injury 1, 3

Pain Management and Hemodynamic Support

• Give sublingual nitroglycerin (up to 3 doses, 5 minutes apart) unless systolic blood pressure <90 mmHg or heart rate <50 or >100 bpm 2, 1
• Administer morphine sulfate or meperidine for adequate analgesia, though be aware this may delay oral antiplatelet absorption 2, 1, 3
• Completely avoid nitroglycerin in right ventricular infarction due to risk of profound hypotension 1

Reperfusion Strategy Decision

Primary PCI (Preferred Method)

Primary percutaneous coronary intervention is the preferred reperfusion strategy when it can be performed within 120 minutes of STEMI diagnosis by experienced operators with prompt access to emergency CABG 1, 3

• Door-to-balloon time should be ≤90 minutes 4
• Transfer patients directly to catheterization laboratory, bypassing the emergency department when possible 3
• Administer potent P2Y12 inhibitor (ticagrelor or prasugrel preferred over clopidogrel) before or at time of PCI 1, 3

Fibrinolytic Therapy (When PCI Unavailable)

If primary PCI cannot be performed within 120 minutes, initiate fibrinolytic therapy immediately if presenting within 12 hours of symptom onset and no contraindications exist 1

• Door-to-needle time should be ≤30 minutes 4
• Fibrin-specific agents (tenecteplase, alteplase, or reteplase) are preferred 1
• Reduce tenecteplase dose by 50% in patients ≥75 years to minimize stroke risk 1
• Greatest benefit occurs within 6 hours of symptom onset, with 35 lives saved per 1,000 patients treated within first hour versus 16 lives saved per 1,000 patients treated between 7-12 hours 2, 4

Beta-Blocker Therapy

Early Intravenous Administration

Initiate early intravenous beta-blocker therapy followed by oral therapy in hemodynamically stable patients, as beta-blockers diminish morbidity and mortality regardless of whether reperfusion therapy was given 2

• Begin with three bolus injections of 5 mg metoprolol tartrate IV at approximately 2-minute intervals 5
• Monitor blood pressure, heart rate, and ECG during IV administration 5
• In patients tolerating full IV dose (15 mg), start metoprolol 50 mg orally every 6 hours, 15 minutes after last IV dose, continued for 48 hours 5
• Maintenance dosage is 100 mg orally twice daily thereafter 5
• Continue beta-blockers for at least 6 weeks 3

Additional Pharmacotherapy

Antiplatelet and Anticoagulation

• Administer dual antiplatelet therapy (DAPT) with aspirin plus P2Y12 inhibitor (ticagrelor or prasugrel preferred) 6
• Initiate parenteral anticoagulation with unfractionated heparin, low-molecular-weight heparin, bivalirudin, or fondaparinux 6
• Consider proton pump inhibitors in combination with DAPT for patients at high risk of gastrointestinal bleeding 3, 6

Nitrates and ACE Inhibitors

• Use intravenous nitroglycerin for 24-48 hours in patients with heart failure, large anterior MI, persistent ischemia, or hypertension—but avoid in right ventricular infarction 1
• Initiate ACE inhibitors within first 24 hours in patients with heart failure, LVEF <40%, diabetes, or anterior infarction 1, 3

Statin Therapy

• Start high-intensity statin therapy as soon as possible and maintain long-term 1, 3

Management of Complications

Heart Failure

• Administer diuretics (usually IV furosemide) and afterload-reducing agents for patients developing heart failure 2, 3

Cardiogenic Shock

• Consider hemodynamic support devices (intra-aortic balloon pump) and perform emergency coronary angiography followed by PTCA or CABG 2, 3

Right Ventricular Infarction

• Up to 50% of inferior MIs involve right ventricular infarction—obtain V4R lead early 1
• Maintain right ventricular preload with IV saline boluses and use inotropic agents if hypotension persists 2, 1
• Completely avoid nitroglycerin due to risk of profound hypotension 1

Recurrent Ischemia

• Treat recurrent chest discomfort with IV nitroglycerin, analgesics, and antithrombotic medications (aspirin, heparin) 2
• Consider coronary angiography with subsequent revascularization 2

Pericarditis

• Administer high-dose aspirin (650 mg every 4-6 hours) for recurrent chest pain believed due to pericarditis 2

Critical Pitfalls to Avoid

• Do not give thrombolytics to patients with non-ST-elevation MI—there is no benefit and increased bleeding risk 1
• Do not routinely combine fibrinolysis with planned immediate PCI—this increases mortality and adverse outcomes 1
• Do not delay aspirin administration—give immediately, not after ECG confirmation 1
• Do not use routine oxygen—only administer if saturation <90% 1
• Do not perform catheterization within 2-3 hours of fibrinolytic administration unless rescue PCI is needed due to increased bleeding risk 4
• Do not use calcium channel blockers—they have not been shown to reduce mortality and may be harmful 2
• Do not send patient to physician's office—transport directly to hospital with 24-hour emergency cardiac care capability 4

Long-Term Management

Discharge Medications

For indefinite period after acute MI, continue aspirin, beta-blocker, and ACE inhibitor 2

Risk Factor Modification

• Achieve ideal weight and low saturated fat/cholesterol diet 2
• Initiate drug therapy if LDL cholesterol >130 mg/dL despite diet, with goal of reducing LDL to <100 mg/dL 2
• Smoking cessation is essential 2
• Participate in formal rehabilitation program with goal of 20 minutes of exercise at brisk walking level at least three times weekly 2

Pre-Discharge Testing

Perform standard exercise testing before discharge or shortly thereafter (submaximal at 4-7 days or symptom-limited at 10-14 days) to assess functional capacity, evaluate medical regimen efficacy, and stratify risk for subsequent cardiac events 2, 3

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