From the Guidelines
Thrombolysis should be administered in cases of ST-Elevation Myocardial Infarction (STEMI) when primary percutaneous coronary intervention (PCI) cannot be performed within 120 minutes of first medical contact, and the onset of ischemic symptoms is within the previous 12 hours. The optimal timing for thrombolysis is within 12 hours of symptom onset, with the greatest benefit when administered within the first 3 hours 1. Common thrombolytic agents include alteplase (tPA) at 15 mg IV bolus, then 0.75 mg/kg over 30 minutes (maximum 50 mg), then 0.5 mg/kg over 60 minutes (maximum 35 mg); or tenecteplase (TNK) as a single weight-based bolus (30-50 mg) 1. Thrombolysis should be accompanied by dual antiplatelet therapy (aspirin 162-325 mg loading dose, then 81 mg daily, plus clopidogrel 300 mg loading dose, then 75 mg daily) and anticoagulation with unfractionated heparin or enoxaparin 1. Some key points to consider when administering thrombolysis include:
- Absolute contraindications, such as prior intracranial hemorrhage, known cerebral vascular lesion, ischemic stroke within 3 months, active bleeding, or suspected aortic dissection 1
- The need for transfer to a PCI-capable facility for either rescue PCI if thrombolysis fails (persistent chest pain, <50% ST resolution at 90 minutes) or routine angiography within 24 hours 1
- The mechanism of action of thrombolytics, which activate plasminogen to plasmin, degrading fibrin clots blocking coronary arteries, restoring blood flow, and limiting myocardial damage 1. It is essential to weigh the benefits and risks of thrombolysis in each individual patient, considering factors such as the time from symptom onset, the presence of contraindications, and the anticipated delay to primary PCI 1.
From the FDA Drug Label
Initiate treatment as soon as possible after the onset of STEMI symptoms.
Thrombolysis with tenecteplase should be administered as soon as possible after the onset of ST-Elevation Myocardial Infarction (STEMI) symptoms.
- The primary goal is to reduce the risk of death associated with acute STEMI.
- Key considerations include:
- Timing: Initiate treatment as soon as possible.
- Administration: Tenecteplase is for intravenous administration only, administered as a single bolus over 5 seconds.
- Dosage: Individualize dosage based on patient's weight. 2
From the Research
Thrombolysis Administration in STEMI Cases
Thrombolysis should be administered in cases of ST-Elevation Myocardial Infarction (STEMI) when primary percutaneous coronary intervention (PCI) is not possible within 120 minutes after first medical contact (FMC) 3, 4, 5.
- The American Heart Association (AHA) and the American College of Cardiology (ACC) favor the use of pre-hospital thrombolysis (PHT) over PCI, placing emphasis on the time factor rather than the method of reperfusion 4.
- If primary PCI is not feasible, thrombolysis must be initiated within 30 minutes after FMC, either in the emergency medical services (EMS) ambulance or in a nearby non-PCI hospital 3.
- Thrombolysis is almost always delivered to patients after arriving in hospital, losing valuable time, and PHT is significantly superior to in-hospital thrombolysis (IHT) 4.
- The National Institute for Clinical Excellence supports reperfusion with fibrinolytics, recommending PHT using newer agents such as reteplase and tenecteplase 4.
Time-Sensitive Thrombolysis
The efficacy of thrombolytic therapy in STEMI is highly time-dependent, with the best efficacy when given within the "golden hour" 6.
- Initial patency, ST-segment resolution (STR) before PCI, and the incidence of aborted myocardial infarction gradually increase with shorter time from symptom onset to first medical contact 6.
- Antiplatelet pretreatment before primary PCI, including a glycoprotein IIb/IIIa blocker, seems to be most effective when given shortly after symptom onset 6.
Combination Therapy
Thrombolytic therapy, even if "successful", is not the final therapy, and within 24 hours (but not before 3 hours) cardiac catheterization has to be performed with PCI, if applicable 3.