A 58-year-old woman with hypertension and hyperlipidaemia presents with acute onset of severe pain in her left foot with pallor, pulselessness, and coldness. Examination reveals mottled skin over the foot and calf. She has no prior history of claudication. Femoral pulse is palpable, but all distal pulses are absent. What is the most likely diagnosis, and what is the immediate management?

Explanation

## Clinical Presentation of Acute Limb Ischemia ### The Six Ps of Acute Limb Ischemia **Key Point:** This patient exhibits the classic triad of acute limb ischemia: - **Pain** — sudden onset, severe - **Pallor** — pale/mottled skin - **Pulselessness** — absent distal pulses with preserved femoral pulse (occlusion distal to femoral) - **Paresthesia** — implied by acute ischemia - **Paralysis** — may develop if ischemia progresses - **Perishing cold** — coldness of the limb ### Distinguishing Acute vs. Chronic Ischemia | Feature | Acute Ischemia | Chronic Ischemia | | --- | --- | --- | | **Onset** | Minutes to hours | Weeks to months | | **Prior claudication** | Absent (sudden onset) | Present (progressive) | | **Skin appearance** | Mottled, cyanotic acutely | Atrophic, hairless | | **Collateral circulation** | Absent/minimal | Well-developed | | **Urgency** | **Limb-threatening within hours** | Chronic, time for investigation | **High-Yield:** The absence of prior claudication history strongly suggests acute thromboembolism rather than chronic PAD with acute decompensation. ### Pathophysiology of Acute Limb Ischemia ```mermaid flowchart TD A[Acute arterial occlusion]:::outcome --> B{Etiology?}:::decision B -->|Embolism 80%| C[Cardiac source: AF, MI, valve disease]:::outcome B -->|Thrombosis 20%| D[In-situ thrombosis on atherosclerotic plaque]:::outcome C --> E[Sudden onset, no prior claudication]:::outcome D --> E E --> F[Immediate anticoagulation with IV heparin]:::action F --> G[Urgent vascular imaging: CT angiography or angiography]:::action G --> H{Viable limb?}:::decision H -->|Yes, within 6-8 hrs| I[Catheter-directed thrombolysis or surgical embolectomy]:::action H -->|No, >8 hrs or non-viable| J[Amputation consideration]:::urgent ``` ### Immediate Management Protocol 1. **Anticoagulation:** IV heparin bolus (80 U/kg) immediately — prevents propagation of thrombus and buys time for definitive intervention 2. **Vascular imaging:** CT angiography or conventional angiography to confirm diagnosis and define anatomy 3. **Urgent vascular surgery consultation:** Embolectomy (Fogarty catheter) or catheter-directed thrombolysis depending on: - Time since onset (<6–8 hours favors thrombolysis) - Limb viability - Cardiac source identified **Clinical Pearl:** The "golden window" for limb salvage is 6–8 hours from onset. Tissue becomes irreversibly damaged after 12–24 hours of complete ischemia. This patient requires **immediate intervention**, not outpatient imaging. **Warning:** Do NOT delay with outpatient duplex ultrasound or conservative management. Acute limb ischemia is a **surgical emergency**. ### Why This Is Thromboembolism, Not Chronic PAD - **No prior claudication** — suggests no pre-existing collateral circulation - **Sudden onset** — acute thromboembolism; chronic PAD is gradual - **Preserved femoral pulse** — occlusion is distal to femoral, typical of embolism lodging at arterial bifurcation - **Mottled skin** — acute ischemia with poor collateral perfusion