Alteplase Administration in Myocardial Infarction
Alteplase is NOT the preferred reperfusion strategy for acute myocardial infarction—primary percutaneous coronary intervention (PCI) should be performed whenever possible within 120 minutes of first medical contact. 1 However, when primary PCI cannot be achieved within this timeframe, alteplase remains a critical fibrinolytic option that must be administered within 12 hours of symptom onset. 1
When to Use Alteplase vs. Primary PCI
Primary PCI is the definitive reperfusion strategy and should be performed by an experienced team within 90-120 minutes of first medical contact for all STEMI patients with symptoms <12 hours duration. 1 Fibrinolytic therapy with alteplase is only recommended when primary PCI cannot be performed within this critical time window. 1
For patients presenting very early (<2 hours after symptom onset) with large infarcts and low bleeding risk, consider fibrinolysis if the anticipated time from first medical contact to balloon inflation exceeds 90 minutes. 1
Alteplase Dosing Protocol for MI
The dosing for myocardial infarction differs critically from stroke dosing—using the stroke protocol (0.9 mg/kg) for MI is incorrect and potentially harmful. 2
For acute MI, alteplase is administered as 100 mg total dose over 90 minutes using an accelerated "front-loaded" regimen: 1, 3, 4
- 15 mg IV bolus over 1-2 minutes
- 50 mg IV infusion over the next 30 minutes
- 35 mg IV infusion over the following 60 minutes
This accelerated regimen has demonstrated superior 30-day survival compared to streptokinase and maintains this advantage for at least one year. 4
Essential Adjunctive Antithrombotic Therapy
Aspirin (oral or IV if unable to swallow) must be administered immediately to all patients without contraindications. 1 The dose is 160-325 mg initially, then continued indefinitely at 75-100 mg daily. 1
Clopidogrel is indicated in addition to aspirin for all patients receiving fibrinolytic therapy. 1
Anticoagulation is mandatory in patients treated with alteplase and should continue until revascularization or for the duration of hospital stay up to 8 days: 1
- Enoxaparin IV bolus followed by subcutaneous dosing (preferred over unfractionated heparin) 1
- Unfractionated heparin as weight-adjusted IV bolus followed by infusion (alternative option) 1
Current practice dictates continuing IV heparin for an additional 48 hours specifically when alteplase is used, as this fibrin-specific agent requires more aggressive anticoagulation than streptokinase. 1, 4
Timing Considerations
Initiate fibrinolytic therapy as soon as possible after STEMI diagnosis, preferably in the pre-hospital setting. 1 The benefit of reperfusion is highly time-dependent, with greatest mortality reduction occurring within the first 3 hours of symptom onset. 5 However, survival benefit persists when alteplase is administered up to 12 hours after symptom onset. 1, 4
Mandatory Post-Fibrinolysis Management
All patients receiving fibrinolytic therapy must be transferred to a PCI-capable center immediately after fibrinolysis. 1 This is a Class I recommendation regardless of whether fibrinolysis appears successful. 1
Angiography with PCI of the infarct-related artery should be performed between 2-24 hours after successful fibrinolysis. 1 The optimal timing for stable patients is 3-24 hours. 1
Rescue PCI must be performed immediately when fibrinolysis has failed, defined as <50% ST-segment resolution at 60-90 minutes after treatment. 1
Emergency angiography with PCI is indicated at any time for: 1
- Heart failure or cardiogenic shock
- Hemodynamic or electrical instability
- Worsening ischemia
- Recurrent ischemia or evidence of reocclusion after initial successful fibrinolysis
Monitoring Requirements
After alteplase administration, patients require intensive monitoring: 1
- Admit to intensive care or stroke unit
- Monitor blood pressure and perform neurological assessments every 15 minutes during and for 2 hours after infusion
- Then every 30 minutes for 6 hours
- Then hourly until 24 hours after treatment
If severe headache, acute hypertension, nausea, vomiting, or worsening clinical status develops, discontinue the infusion immediately and obtain emergency head CT. 1
Critical Contraindications and Precautions
Active internal bleeding or recent (within 21 days) gastrointestinal or urinary tract hemorrhage are absolute contraindications. 1 Coagulopathy (platelets <100,000/mm³, INR >1.7, aPTT >40 seconds, or PT >15 seconds) also contraindicates fibrinolytic therapy. 1
Delay placement of nasogastric tubes, indwelling bladder catheters, or intra-arterial pressure catheters if the patient can be safely managed without them. 1
Common Pitfalls to Avoid
Never use the stroke dosing protocol (0.9 mg/kg) for myocardial infarction—this is the most critical error to avoid, as MI requires the 100 mg accelerated regimen over 90 minutes. 2, 3, 4
Do not delay transfer to a PCI-capable center after fibrinolysis, even if the patient appears stable—this is a Class I recommendation for all patients. 1
Recognize that alteplase has higher reocclusion rates than non-fibrin-specific agents, which is why aggressive anticoagulation with heparin and early angiography are essential. 4, 6
The risk of hemorrhagic stroke is higher with alteplase than streptokinase, though major bleeding rates are similar. 4 This reinforces the importance of strict adherence to contraindications and monitoring protocols.
Adjunctive Medications
Intravenous nitroglycerin should be infused for 24-48 hours after hospitalization in patients without hypotension, bradycardia, or excessive tachycardia. 1 However, nitrates should never substitute for narcotic analgesics when pain control is needed. 1
Intravenous beta-blocker therapy should be initiated early, followed by oral therapy for at least 6 weeks, provided there are no contraindications. 1 This reduces morbidity and mortality regardless of whether reperfusion therapy was given. 1