## First-Line Thrombolytic for Acute Limb Ischemia **Key Point:** Alteplase (recombinant tissue plasminogen activator, rt-PA) is the preferred thrombolytic agent for acute arterial thromboembolism and acute limb ischemia in contemporary clinical practice, owing to its fibrin selectivity, established efficacy in catheter-directed thrombolysis (CDT), and favorable safety profile. ## Mechanism & Rationale Alteplase is a fibrin-selective, recombinant tissue plasminogen activator. It preferentially binds fibrin within the thrombus and locally converts plasminogen to plasmin, resulting in: - **Targeted clot lysis** with minimal systemic plasminogen activation - Lower risk of systemic bleeding compared to non-selective agents (streptokinase) - Rapid onset of action suitable for the 6-hour therapeutic window - Established use in catheter-directed thrombolysis (CDT) for peripheral arterial occlusion ## Comparison of Thrombolytics in Peripheral Arterial Thrombosis | Agent | Mechanism | Use in Limb Ischemia | Systemic Fibrinolysis | | --- | --- | --- | --- | | **Alteplase (tPA)** | Fibrin-selective direct plasminogen activator | **First-line (CDT)** | Low–Moderate | | Urokinase | Direct (non-selective) plasminogen activator | Alternative; less preferred in current guidelines | Moderate | | Streptokinase | Indirect (SK-plasminogen complex) | Not preferred; high systemic effects, antigenic | High | | Tenecteplase | Fibrin-selective tPA variant | Not standard for peripheral thrombosis | Low–Moderate | ## Clinical Pearl **High-Yield:** Current TASC II guidelines and ACC/AHA peripheral vascular disease guidelines recommend catheter-directed thrombolysis (CDT) with **alteplase** as the preferred pharmacological approach for acute limb ischemia (Rutherford category I–IIa) presenting within 14 days. Urokinase, while historically used, has been largely supplanted by alteplase due to the latter's superior fibrin selectivity and robust evidence base. Streptokinase is avoided due to antigenicity and excessive systemic fibrinolysis. ## Dosing & Administration Alteplase for peripheral arterial CDT is typically administered as: 1. **Intra-arterial infusion** (preferred route) — 0.05 mg/kg/hr via catheter embedded in the thrombus, for up to 24–48 hours 2. Concurrent systemic anticoagulation with heparin to prevent peri-catheter thrombosis **Warning:** Contraindications include active internal bleeding, recent (within 3 months) intracranial surgery or trauma, and intracranial neoplasm. The 6-hour presentation window in this case is well within the therapeutic window for CDT. [cite: Rutherford's Vascular Surgery 8e; ACC/AHA Guidelines on Peripheral Artery Disease; Harrison's Principles of Internal Medicine 20e Ch 275]
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