What is the initial workup and management for an acute infarct?

Initial Workup and Management for Acute Infarct

Obtain a 12-lead ECG within 10 minutes of patient arrival and immediately administer aspirin 160-325 mg orally while establishing continuous cardiac monitoring—these are the most critical initial actions that directly impact mortality. 1, 2

Immediate Assessment (First 10 Minutes)

ECG Acquisition and Interpretation:

• Perform 12-lead ECG within 10 minutes to identify ST-segment elevation ≥1 mm in contiguous leads or new left bundle branch block, which indicates need for immediate reperfusion therapy 1, 2
• Do not wait for cardiac biomarkers if ECG shows ST-elevation or new LBBB—ECG findings alone warrant immediate reperfusion 1

Initial Pharmacologic Interventions:

• Administer aspirin 160-325 mg orally immediately without delay—this is the single most important pharmacologic intervention 1, 2
• Give sublingual nitroglycerin (up to 3 doses, 5 minutes apart) unless systolic BP <90 mmHg, heart rate <50 or >100 bpm 3, 1, 2
• Provide supplemental oxygen only if oxygen saturation <90% or PaO₂ <60 mmHg—routine oxygen is not recommended when saturation is adequate 1, 2

Monitoring:

• Establish continuous cardiac monitoring with defibrillator and transcutaneous pacing immediately available 2
• Ensure emergency resuscitation equipment is at bedside 4

Reperfusion Strategy (Within 90-120 Minutes)

Primary PCI (Preferred Method):

• Primary PCI is the preferred reperfusion strategy if door-to-balloon time can be achieved within 90 minutes of first medical contact 1, 2
• Transfer to PCI-capable facility if not immediately available, particularly for high-risk patients with anterior MI, shock, pulmonary congestion, heart rate >100 bpm, or systolic BP <100 mmHg 3, 4

Fibrinolytic Therapy (Alternative):

• Initiate fibrinolytic therapy if PCI cannot be performed within 120 minutes, with door-to-needle time ≤30 minutes 1, 2
• Greatest benefit occurs within first hour (35 lives saved per 1,000 patients), with definite benefit extending to 12 hours 1, 4
• Beyond 12 hours, reperfusion therapy offers little benefit unless ongoing ischemia or mechanical complications present 1

Fibrinolytic Dosing:

• Alteplase (tPA): 100 mg IV over 90 minutes with initial half-life <5 minutes and terminal half-life of 72 minutes 5
• Avoid catheterization within 2-3 hours of fibrinolytic administration due to increased bleeding risk 1

Additional Pharmacologic Management

Antiplatelet Therapy:

• Administer P2Y12 inhibitor (ticagrelor or prasugrel preferred over clopidogrel) immediately 1, 2

Pain Management:

• Administer titrated IV morphine for pain control, though be aware this may delay oral antiplatelet absorption 1, 2

Beta-Blocker Therapy:

• For early treatment during definite or suspected acute MI, administer metoprolol 5 mg IV bolus at 2-minute intervals for 3 doses (total 15 mg) after hemodynamic stabilization 6
• Begin oral metoprolol 50 mg every 6 hours starting 15 minutes after last IV dose, continued for 48 hours, then 100 mg twice daily 6
• Monitor blood pressure, heart rate, and ECG during IV administration 6

Nitroglycerin:

• Begin IV nitroglycerin for 24-48 hours if no hypotension, bradycardia, or excessive tachycardia present 4

Anticoagulation:

• Consider IV heparin, particularly for large anterior MI at high risk for LV mural thrombus and embolic stroke 4

Critical Time Targets

• ECG acquisition: ≤10 minutes 1, 2
• Total initial evaluation: ≤20 minutes 1
• Door-to-balloon (PCI): ≤90 minutes 1, 2
• Door-to-needle (fibrinolysis): ≤30 minutes 1, 2
• Call-to-needle (prehospital): 90 minutes 2

Post-Reperfusion Management

Pharmacoinvasive Strategy:

• For patients receiving fibrinolysis, perform coronary angiography within 24 hours but not within first 2-3 hours due to bleeding risk 1
• Immediate transfer for catheterization (within 24 hours) reduces recurrent MI and ischemia compared to delayed approaches 1

Ongoing Monitoring:

• Continue aspirin 160-325 mg daily indefinitely 4
• Continue beta-blocker therapy for at least 6 weeks 4
• Consider ACE inhibitors, particularly for anterior MI or left ventricular dysfunction 4
• Perform echocardiography to evaluate LV function and detect complications such as mural thrombus 4

Common Pitfalls to Avoid

• Do not delay treatment waiting for cardiac biomarkers in patients with ST-elevation or new LBBB—ECG findings alone warrant immediate reperfusion 1
• Do not perform routine catheterization within 2-3 hours of fibrinolytic administration unless rescue PCI is needed 1
• Do not wait beyond 12 hours to initiate reperfusion unless there is evidence of ongoing ischemia or mechanical complications 1
• Do not withhold treatment for insurance authorization or administrative procedures 3
• Do not send patient to physician's office—transport directly to hospital with 24-hour emergency cardiac care capability 3

Special Considerations for Anterior MI

• Anterior MI carries higher risk for left ventricular dysfunction and heart failure 4
• Consider immediate transfer to PCI-capable facility for anterior MI patients 4
• The TRANSFER-AMI study showed patients with anterior MI benefit from immediate transfer for PCI within 6 hours of fibrinolytic therapy, with lower rates of death, reinfarction, recurrent ischemia, heart failure, and cardiogenic shock (11.0% vs 17.2%) 4