What is the management of myocardial infarction (MI)?

Management of Myocardial Infarction

The management of myocardial infarction requires immediate reperfusion therapy for patients with ST-segment elevation or new left bundle-branch block, along with comprehensive pharmacological therapy including aspirin, P2Y12 inhibitors, beta-blockers, and ACE inhibitors to reduce mortality and improve outcomes. 1

Initial Management and Recognition

• Rapid identification and treatment of MI is critical, as most patients delay seeking medical care for 2 hours or more after symptom onset, with reperfusion therapy offering little benefit beyond 12 hours 1
• Initial management includes pain relief with intravenous opioids (4-8 mg morphine with additional 2 mg doses at 5-minute intervals) and oxygen (2-4 L/min) for patients with breathlessness or heart failure 1
• Aspirin should be administered immediately (160-325 mg) to all patients without contraindications 1
• Patients with suspected MI and ST-segment elevation or bundle-branch block should undergo immediate reperfusion therapy 1

Reperfusion Strategies

Primary PCI

• Primary percutaneous coronary intervention (PCI) is the preferred reperfusion strategy when it can be performed in a timely manner by skilled operators 1
• Patients should be transferred directly to the catheterization laboratory, bypassing the emergency department 1
• For patients undergoing primary PCI, a potent P2Y12 inhibitor (prasugrel or ticagrelor) should be administered before or at the time of PCI and maintained for 12 months 1, 2

Fibrinolytic Therapy

• If primary PCI cannot be performed in a timely manner, fibrinolytic therapy is recommended within 12 hours of symptom onset 1
• A fibrin-specific agent (tenecteplase, alteplase, or reteplase) is preferred 1
• Clopidogrel should be given in addition to aspirin 1
• Transfer to a PCI-capable center following fibrinolysis is indicated in all patients 1

Pharmacological Therapy

Antiplatelet and Anticoagulant Therapy

• Aspirin (75-100 mg daily) should be continued indefinitely 1
• Dual antiplatelet therapy (DAPT) with aspirin plus a P2Y12 inhibitor is recommended for 12 months after PCI 1
• A proton pump inhibitor should be used in combination with DAPT in patients at high risk of gastrointestinal bleeding 1

Beta-Blockers

• Early intravenous beta-blocker therapy followed by oral therapy should be initiated in patients with evolving acute MI, provided there are no contraindications 1
• For metoprolol, administer three bolus injections of 5 mg intravenously at 2-minute intervals, followed by 50 mg orally every 6 hours for 48 hours, then 100 mg orally twice daily 3
• Beta-blockers should be avoided in patients with hypotension, acute heart failure, AV block, or severe bradycardia 1

Nitrates

• Intravenous nitroglycerin can be titrated with frequent monitoring of heart rate and blood pressure 1
• Nitroglycerin should not be used as a substitute for narcotic analgesics 1

ACE Inhibitors

• ACE inhibitors should be started within the first 24 hours of STEMI in patients with evidence of heart failure, LV systolic dysfunction, diabetes, or anterior infarction 1
• An angiotensin receptor blocker (ARB), preferably valsartan, is an alternative for patients intolerant of ACE inhibitors 1

Statins

• High-intensity statin therapy should be started as early as possible and maintained long-term 1
• Target LDL-C should be <1.8 mmol/L (70 mg/dL) or a reduction of at least 50% if baseline LDL-C is between 1.8-3.5 mmol/L 1

Management of Complications

Heart Failure

• Patients with heart failure should receive a diuretic (usually intravenous furosemide) and an afterload-reducing agent 1
• For patients with cardiogenic shock, consider intra-aortic balloon counterpulsation and emergency coronary angiography followed by PCI or CABG 1

Right Ventricular Infarction

• Treat with vigorous intravascular volume expansion using normal saline and inotropic agents if hypotension persists 1

Recurrent Chest Pain

• For recurrent chest pain due to pericarditis, administer high-dose aspirin (650 mg every 4-6 hours) 1
• For recurrent chest pain due to ischemia, treat with intravenous nitroglycerin, analgesics, and antithrombotic medications (aspirin, heparin) 1

Pre-Discharge Evaluation

• Routine echocardiography should be performed during hospital stay to assess LV and RV function, detect mechanical complications, and exclude LV thrombus 1
• Before discharge or shortly thereafter, patients should undergo exercise testing (submaximal at 4-7 days or symptom-limited at 10-14 days) 1

Long-Term Management

• Continue aspirin, beta-blockers, and ACE inhibitors indefinitely 1
• Encourage smoking cessation with support, nicotine replacement therapies, varenicline, and bupropion 1
• Recommend participation in a cardiac rehabilitation program 1
• Advise patients to achieve ideal weight and follow a diet low in saturated fat and cholesterol 1
• Encourage regular exercise (at least 20 minutes of brisk walking three times weekly) 1

Common Pitfalls and Caveats

• Calcium channel blockers have not shown mortality benefits in acute MI and may be harmful in certain patients with cardiovascular disease 1
• Avoid oral nitrate preparations in acute MI due to inability to titrate the dose in evolving hemodynamic situations 1
• Do not administer intravenous beta-blockers to patients with hypotension, acute heart failure, or AV block 1
• Prasugrel should not be used in patients with a history of stroke or TIA, and should be used with caution in patients ≥75 years or <60 kg 2