What is the recommended treatment for a patient presenting with acute myocardial infarction (AMI) when primary percutaneous coronary intervention (PCI) is not available within 90 minutes of first medical contact?

Thrombolysis for Acute Myocardial Infarction When Primary PCI is Unavailable

If primary PCI cannot be performed within 90 minutes of first medical contact, fibrinolytic therapy should be initiated immediately—ideally within 30 minutes of hospital arrival—in the absence of contraindications. 1

Reperfusion Decision Algorithm

Primary PCI remains the preferred reperfusion strategy when it can be delivered by an experienced team within 90 minutes of first medical contact (or 120 minutes if transfer from a non-PCI capable hospital is required). 1 However, when these time windows cannot be met, fibrinolytic therapy becomes the treatment of choice. 1

Time-Based Decision Points:

• If PCI achievable within 90 minutes: Proceed with primary PCI 1
• If PCI will exceed 90 minutes: Initiate fibrinolytic therapy immediately 1
• Target door-to-needle time: ≤30 minutes for fibrinolytic administration 1
• Symptom onset window: Fibrinolysis is most effective when given within 12 hours of symptom onset 1, 2

Fibrinolytic Agent Selection

For patients presenting more than 4 hours after symptom onset, fibrin-specific agents (tenecteplase or alteplase) are preferred over streptokinase. 1, 3, 4

Recommended Agents:

• Tenecteplase: Single weight-adjusted bolus (30-50 mg based on body weight), preferred for ease of administration 3, 4, 2
• Alteplase: Accelerated dosing regimen, requires weight-adjusted heparin with frequent aPTT monitoring 1, 2
• Reteplase: Double bolus administration, requires weight-adjusted heparin 1, 2
• Streptokinase: Only if fibrin-specific agents unavailable; avoid if prior streptokinase exposure or known allergy 1, 2

For patients presenting within 6 hours of symptom onset, alteplase demonstrates superior outcomes compared to streptokinase. 2

Mandatory Adjunctive Therapy

Antiplatelet Therapy:

• Aspirin 150-325 mg: Administer immediately (chewable, non-enteric coated) 1, 3
• Clopidogrel: Loading dose followed by daily maintenance 3, 4

Anticoagulation:

• With alteplase or reteplase: Weight-adjusted unfractionated heparin with early aPTT adjustments (Class I, Level B) 1
• With tenecteplase: Enoxaparin IV bolus followed by subcutaneous dosing preferred over unfractionated heparin 4
• With streptokinase: Heparin is optional unless high-risk features present (anterior MI, heart failure, atrial fibrillation, LV thrombus) 1, 2

Post-Fibrinolysis Management Strategy

All patients receiving fibrinolytic therapy must be transferred immediately to a PCI-capable center regardless of apparent reperfusion success. 3, 4, 5 This pharmaco-invasive approach has been demonstrated to be non-inferior to primary PCI in patients with long transfer delays. 5

Rescue PCI Indications (Immediate Transfer):

• Failed fibrinolysis: <50% ST-segment resolution at 60-90 minutes 1, 4
• Hemodynamic instability: Cardiogenic shock, severe heart failure 1, 4
• Electrical instability: Sustained ventricular arrhythmias 4
• Recurrent ischemia: Persistent or recurrent chest pain 1

Routine Angiography Timing (Successful Fibrinolysis):

Coronary angiography with PCI should be performed 2-24 hours after successful fibrinolysis (Class I, Level A). 1, 3, 4 This routine early invasive strategy reduces death, reinfarction, and recurrent ischemia by 36-64% compared to conservative management. 6, 5

Absolute Contraindications to Fibrinolysis

When fibrinolysis is contraindicated, primary PCI should be performed despite delays rather than foregoing reperfusion therapy entirely (Class I, Level A). 1

Contraindications:

• Any history of intracranial hemorrhage 2
• Known structural cerebral vascular lesion 4
• Ischemic stroke within 3 months 4, 2
• Suspected aortic dissection 4
• Active bleeding or bleeding diathesis 4
• Significant closed head trauma within 3 months 4, 2

Special Clinical Scenarios

Cardiogenic Shock:

Primary PCI (or CABG) is the preferred reperfusion treatment for patients presenting in cardiogenic shock, even with significant delays. 1 Fibrinolysis should only be considered if there is substantial delay to PCI and after consultation with cardiology. 1 PCI should be performed within 18 hours of shock onset in patients presenting within 36 hours of symptom onset. 1

Anterior Wall MI:

Anterior MI carries higher risk for LV dysfunction, mural thrombus formation, and conduction disturbances, warranting aggressive reperfusion strategy. 3 Echocardiography should be performed to evaluate LV function and detect complications. 3

Pre-Hospital Fibrinolysis:

When appropriate facilities and trained personnel exist, pre-hospital initiation of fibrinolytic therapy is recommended (Class I, Level B). 1 This approach further reduces time to reperfusion and improves outcomes. 1

Critical Pitfalls to Avoid

Delay in Decision-Making:

The most common error is prolonged deliberation about transfer for PCI when the 90-minute window cannot be met. Every 30-minute delay in fibrinolytic administration increases mortality, particularly in patients receiving fibrinolysis compared to those undergoing PCI. 1 Make the decision rapidly based on achievable time windows.

Inadequate Post-Fibrinolysis Planning:

Failure to arrange immediate transfer to a PCI-capable center after fibrinolysis is a critical error. 3, 4, 5 The transfer should be initiated immediately after fibrinolytic administration, not after waiting to assess reperfusion success. 4

Suboptimal Anticoagulation:

Continuing anticoagulation until revascularization or for up to 8 days is essential. 3, 4 Premature discontinuation increases reocclusion risk. With alteplase/reteplase, failure to perform early and frequent aPTT adjustments leads to inadequate anticoagulation. 1

Missing Failed Fibrinolysis:

Assess ST-segment resolution at 60-90 minutes after fibrinolytic administration. 4 Less than 50% resolution indicates failed reperfusion requiring immediate rescue PCI. 1, 4 Delayed recognition of failed fibrinolysis significantly worsens outcomes.