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Introduction
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Focus: Anticoagulation and thrombosis management in mechanical circulatory support (MCS), with emphasis on Impella devices and ECMO.
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Discusses anticoagulation strategies, management of pump thrombosis, and thrombolytic therapy in ECMO/PE.
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Impella Devices
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Continuous antegrade blood flow pumps unloading the LV, improving forward flow.
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Models: CP and 5.5 (most used for LV support), RP/RP Flex (RV support).
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Duration originally 14 days, but often extended to weeks/months.
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Anticoagulation & Purge Solutions
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Heparin purge (25 units/mL) traditionally used to protect motor housing from thrombus.
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Bicarbonate purge (25–50 mcg/mL NaHCO₃ in D5W): prevents protein denaturation/fibrin polymerization, reduces hemolysis, allows heparin-free strategy.
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Systemic anticoagulation: ACT 160–180, Anti-Xa 0.3–0.6, APTT ~45–90s.
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Survey Data (2019)
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Most high-volume centers used heparinized purge solutions.
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Alternatives: DTI (argatroban/bivalirudin) in purge or pure dextrose.
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Routine hemolysis monitoring underused (<50%).
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Heparin Exposure from Purge
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Purge flow may deliver therapeutic systemic heparin even without IV infusion.
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Strategies: adjust IV dose considering purge contribution, or manage IV infusion alone to avoid dosing errors.
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Evidence on Anticoagulation Intensity
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Lower APTT targets (40–60) reduced bleeding versus higher goals (60–80) without increasing thrombotic events.
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Institutional practice: systemic bivalirudin with bicarbonate purge (safer, less bleeding, good survival).
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Studies: Bivalirudin shows trend toward less bleeding and better therapeutic stability compared to heparin.
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Pump Thrombosis Management
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Signs: ↑ purge pressure, ↓ purge flow, ↑ motor current.
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Therapy: Alteplase (0.04–0.08 mg/mL) infused via purge restores flow.
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Institutional case series: 90% success, avg. 10 mg alteplase required.
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ECMO in Pulmonary Embolism
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VA ECMO used as a bridge to thrombectomy or CDT in massive PE/cardiac arrest.
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Strategies:
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Systemic thrombolysis + ECMO (higher bleeding risk).
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ECMO + catheter-directed thrombolysis/thrombectomy (increasingly preferred).
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Guidelines: CDT (fragmentation, aspiration, local lysis) reduces bleeding compared to systemic TPA.
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Mortality higher with anticoagulation alone; ECMO + CDT shows best outcomes.
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Emerging Concepts
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Novel approaches: instilling Alteplase into ECMO oxygenator to delay exchange (experimental).
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