## Fibrinolytic Therapy in STEMI **Key Point:** Alteplase (tissue plasminogen activator, tPA) is the preferred fibrinolytic agent for acute STEMI in non-PCI-capable hospitals when primary PCI cannot be performed within 120 minutes of first medical contact. ### Mechanism of Action Alteplase is a recombinant tissue plasminogen activator that: - Directly activates plasminogen to plasmin - Exhibits fibrin-selectivity (preferentially binds to fibrin in thrombi) - Achieves TIMI 3 flow in ~50–60% of patients when given within 12 hours of symptom onset ### Dosing in Acute MI - **Bolus:** 15 mg IV over 1–2 minutes - **Infusion:** 0.75 mg/kg over 30 minutes (max 50 mg), then 0.5 mg/kg over 60 minutes (max 35 mg) - Total dose should not exceed 100 mg ### Comparison of Fibrinolytic Agents | Agent | Fibrin-Selectivity | TIMI 3 Flow | Bleeding Risk | Reperfusion Arrhythmia | | --- | --- | --- | --- | --- | | **Alteplase (tPA)** | High | 50–60% | Moderate | Common | | **Reteplase (rPA)** | High | 60% | Moderate | Common | | **Tenecteplase (TNK)** | Very high | 65% | Lower | Common | | **Streptokinase** | Low | 40–50% | Higher | Common | **High-Yield:** Alteplase is preferred in anterior MI and in patients <75 years with symptom onset <3 hours because it achieves superior patency rates compared to streptokinase. ### Clinical Pearl Reperfusion arrhythmias (accelerated idioventricular rhythm, ventricular tachycardia) indicate successful coronary recanalization and are a favorable prognostic sign. ### Contraindications to Fibrinolysis - Active internal bleeding - Recent intracranial hemorrhage or stroke (within 3 months) - Intracranial neoplasm or AVM - Severe uncontrolled hypertension (SBP >180 mmHg, DBP >110 mmHg) - Recent major surgery or trauma (within 2–4 weeks) **Warning:** Do NOT confuse fibrinolytic choice with antiplatelet/anticoagulant adjuncts. Aspirin and clopidogrel are given alongside fibrinolysis, not instead of it.
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