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

Management of Myocardial Infarction

For patients presenting with acute myocardial infarction, immediate reperfusion therapy via primary PCI (if available within 90-120 minutes) or fibrinolytic therapy (if PCI unavailable) combined with aspirin, potent P2Y12 inhibitors, and anticoagulation represents the cornerstone of treatment to reduce mortality and preserve myocardial function. 1

Immediate Management (First 24 Hours)

Initial Interventions in Emergency Department

• Administer aspirin 160-325 mg orally (chewed) or IV immediately upon arrival unless contraindicated 1, 2
• Provide supplemental oxygen by nasal cannula 1
• Give sublingual nitroglycerin unless systolic BP <90 mmHg, heart rate <50 or >100 bpm 1
• Administer morphine sulfate or meperidine for adequate analgesia to minimize pain and anxiety 1, 2
• Obtain 12-lead ECG within 10 minutes of arrival 1

Reperfusion Strategy Selection

Primary PCI is the preferred reperfusion strategy and should be performed within 90-120 minutes of first medical contact if available at a center with 24/7 capability 1

• Patients should bypass the emergency department and go directly to the catheterization laboratory 1
• Reperfusion therapy is indicated for all patients with symptoms ≤12 hours duration and persistent ST-segment elevation 1

If primary PCI cannot be performed within the appropriate timeframe, initiate fibrinolytic therapy within 12 hours of symptom onset (preferably pre-hospital) 1

• Use fibrin-specific agents: tenecteplase, alteplase, or reteplase 1
• Transfer all patients to PCI-capable center immediately after fibrinolysis 1
• Perform angiography and PCI of infarct-related artery 2-24 hours after successful fibrinolysis 1
• Rescue PCI is indicated immediately if fibrinolysis fails (<50% ST-segment resolution at 60-90 minutes) 1

Antithrombotic Therapy for Primary PCI

Administer a potent P2Y12 inhibitor (prasugrel or ticagrelor preferred over clopidogrel) before or at the time of PCI and continue for 12 months unless excessive bleeding risk exists 1

• High-dose IV heparin is recommended during primary PCI 1
• Fondaparinux is not recommended for primary PCI 1

Antithrombotic Therapy for Fibrinolysis

• Clopidogrel 75 mg daily is indicated in addition to aspirin 1, 2
• Anticoagulation is required until revascularization or for hospital stay up to 8 days 1:
  • Enoxaparin IV followed by subcutaneous (preferred over UFH) 1
  • UFH as weight-adjusted IV bolus followed by infusion 1

Beta-Blocker Therapy

Initiate early IV beta-blocker therapy (e.g., metoprolol 5 mg IV every 2 minutes for 3 doses) followed by oral therapy if no contraindications exist 1, 2

• Begin metoprolol 50 mg orally every 6 hours starting 15 minutes after last IV dose, continue for 48 hours, then transition to 100 mg twice daily 3
• Avoid IV beta-blockers in patients with hypotension, acute heart failure, AV block, or severe bradycardia 1
• Beta-blockers reduce morbidity and mortality regardless of whether reperfusion therapy was given 1

Nitroglycerin Administration

• Infuse IV nitroglycerin for 24-48 hours in patients without hypotension, bradycardia, or excessive tachycardia 1, 2
• IV nitroglycerin allows titration with frequent BP and heart rate monitoring 1
• Do not use nitroglycerin as substitute for narcotic analgesics 1

Medications to Avoid

• Calcium channel blockers have not reduced mortality and may be harmful 1
• Discontinue NSAIDs (except aspirin) due to increased mortality and reinfarction risk 2

Special Considerations for Inferior MI

Assessment for Right Ventricular Involvement

Right ventricular infarction occurs in up to 50% of inferior MIs and significantly increases mortality risk 2

• Look for clinical triad: hypotension, clear lung fields, elevated jugular venous pressure 2
• Obtain right-sided ECG leads, particularly V4R (ST elevation ≥1mm highly predictive) 2
• Record lead V4R early as ST elevation can resolve within 10 hours 2

Management of Right Ventricular Infarction

Maintain RV preload through aggressive volume loading with IV normal saline for hypotension 1, 2

• Avoid nitrates and diuretics as they cause profound hypotension by reducing preload 2
• Provide inotropic support with dobutamine if cardiac output fails to increase after volume loading 2
• Consider intra-aortic balloon pump for persistent shock 1, 2

Management of Conduction Disturbances

• Treat symptomatic sinus bradycardia with IV atropine 0.5 mg, repeated up to 2.0 mg total 2
• Consider temporary pacing for symptomatic high-degree AV block unresponsive to atropine 2
• Maintain AV synchrony through AV sequential pacing for symptomatic high-degree heart block 2
• Have emergency equipment readily available: atropine, lidocaine, transcutaneous pacing patches, transvenous pacemaker, defibrillator, epinephrine 2

Management of Complications

Heart Failure

• Administer IV furosemide and afterload-reducing agents 1
• Emergency angiography and PCI are recommended in patients with heart failure/shock 1

Cardiogenic Shock

• Consider intra-aortic balloon pump and emergency coronary angiography followed by PCI or CABG 1
• Consider pulmonary artery catheter monitoring for progressive hypotension unresponsive to fluids 2
• Use intra-arterial pressure monitoring 2

Recurrent Ischemia

• Treat with IV nitroglycerin, analgesics, and antithrombotic medications (aspirin, heparin) 1
• Consider coronary angiography with subsequent revascularization 1

Pericarditis

• Administer high-dose aspirin 650 mg every 4-6 hours 1

Long-Term Management (Post-Discharge)

Antiplatelet Therapy

Continue dual antiplatelet therapy (DAPT) with low-dose aspirin 75-100 mg plus ticagrelor or prasugrel (or clopidogrel if unavailable/contraindicated) for 12 months unless excessive bleeding risk 1

• After 12 months, continue aspirin indefinitely 1
• Add PPI in patients at high risk of gastrointestinal bleeding 1

Beta-Blockers

Oral beta-blockers are indicated in patients with heart failure and/or LVEF <40% unless contraindicated 1

ACE Inhibitors

Initiate ACE inhibitors within first 24 hours in patients with heart failure, LV systolic dysfunction, diabetes, or anterior infarct 1

• Start lisinopril 5 mg within 24 hours, then 5 mg after 24 hours, then 10 mg daily 4
• Use 2.5 mg if systolic BP <120 mmHg at baseline 4
• ARB (preferably valsartan) is alternative if ACE inhibitor not tolerated 1

Statin Therapy

Start high-intensity statin therapy as early as possible and maintain long-term 1

• Target LDL-C <1.8 mmol/L (70 mg/dL) or ≥50% reduction if baseline LDL-C 1.8-3.5 mmol/L 1
• For LDL >130 mg/dL despite diet, use drug therapy to reduce LDL to <100 mg/dL 1

Cardiac Rehabilitation and Risk Factor Modification

• Participation in cardiac rehabilitation program is recommended 1
• Identify smokers and provide repeated cessation advice with nicotine replacement, varenicline, or bupropion 1
• Educate about diet low in saturated fat and cholesterol, achieve ideal weight 1
• Plan 20 minutes of exercise at brisk walking level at least three times weekly 1

Pre-Discharge Assessment

Perform routine echocardiography to assess LV and RV function, detect mechanical complications, and exclude LV thrombus 1

• Conduct submaximal exercise testing at 4-7 days or symptom-limited at 10-14 days to assess functional capacity, evaluate medical regimen efficacy, and stratify risk 1

Critical Pitfalls to Avoid

• Never administer nitrates in right ventricular infarction due to risk of profound hypotension 2
• Volume depletion may mask signs of RV involvement 2
• Do not administer beta-blockers or calcium channel antagonists to patients in low-output state from pump failure 2
• Routine PCI of occluded infarct-related artery >48 hours after STEMI onset is not indicated in asymptomatic patients 1