Cardiology > Acute Limb Ischemia

Background

Acute Limb Ischemia (ALI) is a sudden decrease in arterial perfusion to a limb, typically occurring over hours to days, threatening limb viability. It results from an abrupt interruption of blood flow, most commonly due to thromboembolism or in situ thrombosis in the setting of peripheral artery disease (PAD). Without timely intervention, ALI can lead to tissue necrosis, limb loss, or death. 

I) Classification/Types 

A) By Etiology: 

• • Embolic ALI – Sudden occlusion from an embolus (e.g., atrial fibrillation, mural thrombus, cardiac vegetations). 

• • Thrombotic ALI – In situ thrombosis over atherosclerotic plaque or stent, often in patients with chronic PAD. 

• • Traumatic ALI – Direct vascular injury (blunt, penetrating trauma, iatrogenic). 

• • Dissection-related – Acute occlusion secondary to arterial dissection (e.g., aortic dissection). 

B) By Rutherford Classification (Severity): 

• • Category I (Viable): No immediate threat. 

• • Category IIa (Marginally threatened): Salvageable if promptly treated. 

• • Category IIb (Immediately threatened): Requires urgent revascularization. 

• • Category III (Irreversible): Major tissue loss inevitable; amputation likely. 

II) Pathophysiology 

ALI causes an abrupt cessation of arterial blood flow, depriving tissue of oxygen and nutrients. Ischemia leads to: 

• • Metabolic acidosis 

• • Increased vascular permeability 

• • Muscle necrosis and reperfusion injury (if restored) 

• • Potential for hyperkalemia, renal failure, systemic inflammatory response 

III) Epidemiology 

• • Sex: Slight male predominance 

• • Age: Most common in patients >60 years 

• • Geography: Higher prevalence in regions with high cardiovascular risk burden 

• • Comorbidities: Strongly associated with atrial fibrillation, CAD, PAD, diabetes, hypertension, and smoking 

Etiology

I) Causes 

• • Cardiac embolism (AFib, recent MI, valvular disease, endocarditis) 

• • In situ thrombosis (advanced PAD, bypass graft occlusion, stent thrombosis) 

• • Aneurysmal disease (popliteal or femoral aneurysms with thrombosis) 

• • Aortic dissection 

• • Iatrogenic (catheterization, endovascular procedures) 

• • Hypercoagulable states (malignancy, antiphospholipid syndrome) 

II) Risk Factors 

• • Atrial fibrillation 

• • Coronary artery disease 

• • Peripheral artery disease 

• • Diabetes mellitus 

• • Smoking 

• • Recent surgery or trauma 

• • Hypercoagulable disorders 

• • Prior vascular interventions 

Clinical Presentation

I) History (Symptoms) – The 6 P’s 

• • Pain (sudden onset, severe distal limb pain) 

• • Pallor 

• • Pulselessness 

• • Paresthesia (early sign of neurologic involvement) 

• • Paralysis (late sign, suggests irreversible damage) 

• • Poikilothermia (cool limb) 

Onset: Abrupt and dramatic in embolic cases; gradual worsening in thrombotic cases on background of claudication 

II) Physical Exam (Signs) 

Vascular: 

• • Absent distal pulses 

• • Bruits (in chronic PAD) 

• • Cool, pale extremity with delayed capillary refill 

Neurologic: 

• • Decreased sensation 

• • Muscle weakness or paralysis (severe ischemia) 

Note: Compare to contralateral limb for asymmetry 

Differential Diagnosis (DDx)

• • Deep vein thrombosis (DVT) 

• • Chronic critical limb ischemia 

• • Compartment syndrome 

• • Cellulitis or necrotizing fasciitis 

• • Acute peripheral neuropathy 

• • Spinal cord compression 

Diagnostic Tests

Initial Tests: 

• • Bedside Doppler: Assess arterial and venous signals 

• • Ankle-Brachial Index (ABI): Often unmeasurable in ALI 

• • ECG: Look for atrial fibrillation, MI 

• • CBC, PT/INR, aPTT, renal function, lactate: Evaluate for systemic effects and bleeding risk 

Imaging: 

• • CT Angiography (CTA): First-line imaging to localize occlusion and plan intervention 

• • Duplex ultrasonography: Noninvasive assessment of flow 

• • Conventional angiography: Gold standard, often combined with endovascular therapy 

Treatment

I) Medical Management 

Immediate Measures: 

• • Anticoagulation: Start IV heparin immediately (bolus + infusion) to prevent clot propagation 

• • Analgesia: For severe pain 

• • IV fluids: Prevent contrast-induced nephropathy and support perfusion 

• • Limb positioning: Keep at neutral or slightly dependent position 

• • Avoid cold exposure 

II) Interventional/Surgical 

Revascularization Options (based on severity and anatomy): 

• • Endovascular therapy: Catheter-directed thrombolysis, percutaneous thrombectomy 

• • Surgical embolectomy/thrombectomy: Preferred in embolic ALI or large clot burden 

• • Bypass surgery: In extensive arterial occlusion with underlying PAD 

• • Amputation: Required in Rutherford category III (irreversible ischemia) 

Adjuncts: 

• • Fasciotomy: If compartment syndrome or prolonged ischemia 

• • Management of underlying cause (e.g., anticoagulation for AFib) 

Patient Education

• • Educate on symptoms of recurrent ischemia 

• • Emphasize importance of medication adherence (anticoagulation, antiplatelets) 

• • Smoking cessation 

• • Control risk factors: hypertension, diabetes, lipids 

• • Monitor for signs of compartment syndrome after revascularization 

• • Encourage PAD screening in at-risk individuals 

Vaccinations: 

• • Influenza annually 

• • Pneumococcal vaccine 

• • COVID-19 vaccination 

Consults

• • Vascular Surgery: Immediate involvement for all ALI cases 

• • Interventional Radiology: For catheter-directed therapy 

• • Cardiology: If embolic etiology suspected (e.g., AFib) 

• • Hematology: If hypercoagulability suspected 

• • Internal Medicine/Primary Care: For long-term vascular risk factor control 

Follow-Up

• • Post-procedure monitoring: Limb perfusion, renal function, CK levels 

• • Anticoagulation monitoring: Adjust warfarin or DOACs based on etiology 

• • ABI testing and vascular imaging: To assess long-term patency 

• • Long-term vascular follow-up: Evaluate for recurrence, PAD progression 

• • Lifestyle counseling and secondary prevention (e.g., statins, aspirin, supervised exercise)