What is the management of acute infarct?

Management of Acute Myocardial Infarction

For patients with acute myocardial infarction presenting with ST-segment elevation, primary percutaneous coronary intervention (PCI) is the preferred reperfusion strategy when it can be performed within 120 minutes by experienced operators; if this cannot be achieved, immediate fibrinolytic therapy should be initiated within 12 hours of symptom onset. 1, 2

Immediate Emergency Department Management (First 10-20 Minutes)

Upon arrival to the emergency department, all patients with suspected acute MI should receive the following immediately:

• Aspirin 160-325 mg orally (or IV if unable to swallow) - this is the single most important intervention and should not be delayed while awaiting ECG confirmation 1, 2
• 12-lead electrocardiogram performed within 10 minutes of arrival to identify ST-segment elevation ≥1 mV in contiguous leads or new left bundle branch block 1
• Oxygen via nasal prongs only if oxygen saturation is <90% - routine oxygen in non-hypoxemic patients should be avoided as it may increase myocardial injury 2
• Sublingual nitroglycerin unless systolic blood pressure <90 mmHg or heart rate <50 or >100 bpm 1
• Morphine sulfate or meperidine for adequate analgesia 1

Critical caveat: In patients with inferior MI, obtain a V4R lead early to assess for right ventricular infarction, which occurs in up to 50% of inferior MIs and requires completely avoiding nitroglycerin due to risk of profound hypotension 2

Reperfusion Strategy Decision Algorithm

For STEMI or New LBBB:

If primary PCI can be performed within 120 minutes of diagnosis:

• Primary PCI is the preferred strategy and should be performed by experienced operators with prompt access to emergency CABG 1, 2
• Patients should bypass the emergency department and be transferred directly to the catheterization laboratory 1
• Administer a potent P2Y12 inhibitor (prasugrel or ticagrelor preferred over clopidogrel) before or at the time of PCI 1, 3
• Give high-dose IV unfractionated heparin during the procedure 1, 2

If primary PCI cannot be performed within 120 minutes:

• Initiate fibrinolytic therapy immediately, preferably in the pre-hospital setting 1, 2
• Use fibrin-specific agents: tenecteplase, alteplase, or reteplase 1, 2
• For patients ≥75 years old, reduce tenecteplase dose by 50% to minimize stroke risk 2
• Add clopidogrel 300 mg loading dose (if <75 years) in addition to aspirin 1, 3
• Administer enoxaparin IV followed by subcutaneous (preferred over unfractionated heparin) 1, 2
• Transfer all patients to a PCI-capable center immediately after fibrinolysis 1
• Perform angiography and PCI of the infarct-related artery between 2-24 hours after successful fibrinolysis 1

Critical pitfall to avoid: Do not routinely combine fibrinolysis with planned immediate PCI, as this increases mortality and adverse outcomes 2

For Non-ST-Elevation MI:

• Do not administer thrombolytics - there is no benefit and increased bleeding risk 1, 2
• The benefit of primary PCI in these patients remains uncertain 1
• Proceed with aspirin, P2Y12 inhibitor, and anticoagulation as below 1

Anticoagulation Strategy

For Primary PCI:

• High-dose IV unfractionated heparin is recommended 1, 2
• Fondaparinux is contraindicated for primary PCI 1

For Fibrinolytic Therapy:

• Enoxaparin IV followed by subcutaneous is preferred over unfractionated heparin 1, 2
• Continue anticoagulation until revascularization or for duration of hospital stay up to 8 days 1
• For patients receiving alteplase, continue IV heparin for 48 hours 1

Special Populations:

• For patients with large anterior MI or LV mural thrombus on echocardiography, early IV heparin reduces embolic stroke risk 1
• For patients receiving streptokinase, either IV or subcutaneous unfractionated heparin is suggested 4

First 24 Hours Management

• Continuous cardiac monitoring with defibrillator, atropine, lidocaine, and transcutaneous pacing immediately available 1
• Limit physical activity for at least 12 hours 1
• IV nitroglycerin for 24-48 hours in patients with heart failure, large anterior MI, persistent ischemia, or hypertension - but avoid completely in right ventricular infarction 1, 2
• Serial ECGs and cardiac biomarkers (troponin T/I or CK-MB) to confirm diagnosis 1
• Echocardiography to assess LV and RV function, detect mechanical complications, and exclude LV thrombus 1

Post-24 Hour and Long-Term Management

Antiplatelet Therapy:

• Continue aspirin 75-100 mg daily indefinitely 1, 2
• Dual antiplatelet therapy (aspirin plus ticagrelor or prasugrel) for 12 months after PCI unless excessive bleeding risk 1, 2
• If ticagrelor or prasugrel unavailable or contraindicated, use clopidogrel 1, 3
• Add proton pump inhibitor in patients at high risk of gastrointestinal bleeding 1

Beta-Blockers:

• Initiate oral beta-blockers in patients with heart failure and/or LVEF <40% 1, 2
• Continue for at least 6 weeks, ideally indefinitely 1

ACE Inhibitors:

• Start within first 24 hours in patients with heart failure, LVEF <40%, diabetes, or anterior infarction 1, 2
• Continue indefinitely 2

Statins:

• Initiate high-intensity statin therapy as soon as possible and maintain long-term 2

Special Consideration: Right Ventricular Infarction

• Occurs in up to 50% of inferior MIs 2
• Obtain V4R lead early as ST-elevation may resolve within 10 hours 2
• Maintain RV preload with IV saline boluses for hypotension 2
• Completely avoid nitroglycerin due to risk of profound hypotension 2

Rescue and Emergency Interventions

• Rescue PCI immediately if fibrinolysis fails (<50% ST-segment resolution at 60-90 minutes) or with hemodynamic/electrical instability 1
• Emergency angiography and PCI for patients with heart failure, shock, or recurrent ischemia after fibrinolysis 1

Cardiac Rehabilitation and Risk Factor Modification

• Participation in cardiac rehabilitation program is recommended 1
• Smoking cessation with repeated counseling, nicotine replacement, varenicline, or bupropion 1, 2

Key Mortality Data

The ACC/AHA guidelines demonstrate that thrombolytic therapy produces a 21% proportional reduction in 35-day mortality (21 deaths prevented per 1000 patients treated) when given to patients with ST-elevation MI 1. The benefit is time-dependent: 35 lives saved per 1000 when given within the first hour versus only 16 lives saved per 1000 when given 7-12 hours after symptom onset 1. Primary PTCA has been shown to reduce the combined occurrence of nonfatal reinfarction or death compared to t-PA therapy (8.5% vs 16.8% at 6 months), with lower rates of intracranial hemorrhage 5.