A 72-year-old woman with a prosthetic mechanical mitral valve (on warfarin with INR 2.5) presents with acute onset right lower limb pain, coolness, and absent femoral pulse. Doppler ultrasound confirms acute thrombosis of the right femoral artery. What is the most appropriate immediate management?

Explanation

## Clinical Context This is acute arterial thrombosis in a patient with a mechanical prosthetic valve on anticoagulation. Despite therapeutic INR, thrombosis has occurred—likely due to valve thrombosis with subsequent embolization or in situ arterial thrombosis. This is a limb-threatening emergency. ## Pathophysiology of Prosthetic Valve Thrombosis **Key Point:** Mechanical prosthetic valves are highly thrombogenic due to their non-endothelialized surface and flow disturbance. Even with adequate anticoagulation (INR 2.5), thrombosis can occur, especially if compliance is poor or INR fluctuates. **Mnemonic: CLOT in prosthetic valves** — **C**irculation disruption, **L**ow endothelialization, **O**bstruction risk, **T**hrombogenicity high ## Management Algorithm for Acute Arterial Thrombosis ```mermaid flowchart TD A[Acute arterial thrombosis with absent pulse]:::outcome --> B{Limb viability?}:::decision B -->|Viable/threatened| C[Immediate anticoagulation with UFH]:::action B -->|Irreversible ischemia| D[Amputation consideration]:::urgent C --> E{Thrombus age < 14 days?}:::decision E -->|Yes| F[Thrombolysis or thrombectomy]:::action E -->|No| G[Surgical thrombectomy]:::action F --> H[Vascular surgery consultation]:::action G --> H H --> I[Restore limb perfusion]:::outcome ``` ## Why Anticoagulation + Urgent Vascular Surgery is Correct **High-Yield:** Acute arterial thrombosis is a surgical emergency. The immediate steps are: 1. **Anticoagulation:** UFH prevents thrombus propagation and recurrent embolism 2. **Urgent vascular surgery consultation:** For thrombectomy (Fogarty catheter) or catheter-directed thrombolysis 3. **Time is critical:** Muscle necrosis begins at 4–6 hours of ischemia; irreversible damage at 8–12 hours **Clinical Pearl:** In a patient with a mechanical valve and acute arterial thrombosis, the source is likely valve thrombosis with embolization. Restoring anticoagulation alone is insufficient; mechanical intervention (thrombectomy) is mandatory. ## Mechanism of UFH in Acute Thrombosis UFH inhibits thrombin (Factor IIa) and Factor Xa, preventing further thrombus propagation while allowing time for mechanical intervention. ## Distinction: Anticoagulation vs. Intervention | Intervention | Indication | Timing | |---|---|---| | UFH anticoagulation | All acute arterial thrombosis | Immediate | | Thrombectomy | Thrombus < 14 days old, viable limb | Within 6–8 hours | | Thrombolysis | Thrombus < 14 days, no contraindications | Within 6–8 hours | | Amputation | Irreversible ischemia (> 12 hrs) | After viability assessment | **Key Point:** Anticoagulation alone does NOT restore limb perfusion in acute arterial thrombosis. Mechanical intervention is essential.