Arterial · IR Playbook

Endovascular Treatment of Acute Limb Ischemia (EVT for ALI)

Endovascular treatment of acute limb ischemia restores arterial perfusion using catheter-directed thrombolysis, aspiration thrombectomy, mechanical thrombectomy, pharmacomechanical thrombectomy or a combination of these techniques. Treatment must be selected according to Rutherford limb-viability class, thrombus age and burden, anatomy, bleeding risk and the time available for reperfusion. Contemporary thrombolysis series report technical success of approximately 80–90%, but major bleeding occurs in approximately 8–10%; rapidly progressive Rutherford IIb ischemia generally requires immediate thrombectomy or surgery rather than prolonged thrombolysis alone.

Learning objectives

• Classify acute limb ischemia using the Rutherford system and distinguish a viable, threatened and irreversible limb.
• Select catheter-directed thrombolysis, aspiration, mechanical thrombectomy or pharmacomechanical thrombectomy according to ischemia severity, thrombus characteristics and bleeding risk.
• Perform safe arterial access, thrombus crossing, debulking, thrombolytic infusion and treatment of the underlying causative lesion.
• Recognize bleeding, distal embolization, reperfusion injury, compartment syndrome, hemolysis and renal injury promptly.
• Define technical success and plan antithrombotic treatment and etiological evaluation after revascularization.

Indications

• Rutherford IIa acute limb ischemia from acute native-artery thrombosis, embolism, bypass-graft thrombosis or stent or stent-graft thrombosis when endovascular treatment can restore perfusion promptly.
• Selected Rutherford IIb acute limb ischemia when immediate endovascular thrombectomy can be performed, with catheter-directed thrombolysis used only as a rapid adjunct for residual thrombus.
• Acute or subacute thrombotic occlusion, usually with symptom duration less than 14 days, that can be crossed safely and treated within the time permitted by limb viability.
• Large thrombus burden requiring aspiration or mechanical debulking before angioplasty, stenting or surgical revision of the underlying lesion.
• Thrombotic occlusion in a patient at high operative risk or with anatomy in which an endovascular or hybrid strategy offers a reasonable likelihood of rapid limb salvage.
• Distal embolic occlusion or poor tibial runoff in selected patients, including before definitive repair of a thrombosed popliteal artery aneurysm.

Absolute contraindications

• Rutherford III irreversible ischemia with profound anesthesia, paralysis, muscle rigor and absent arterial and venous Doppler signals; revascularization of nonviable tissue risks fatal reperfusion injury and primary amputation is usually required.
• Established stroke or transient ischemic attack within the preceding 2 months when thrombolysis is planned.
• Active bleeding or an uncorrectable bleeding diathesis.
• Gastrointestinal bleeding within the preceding 10 days.
• Intracranial or spinal surgery within the preceding 3 months.
• Intracranial trauma within the preceding 3 months.
• Inability to provide the required monitored care during continuous thrombolytic infusion.

Relative contraindications

• Cardiopulmonary resuscitation, major nonvascular surgery or major trauma within the preceding 10 days.
• Uncontrolled hypertension greater than 180 mmHg systolic or 110 mmHg diastolic.
• Recent puncture of a noncompressible vessel, intracranial tumor or recent ophthalmic surgery.
• Pregnancy, bacterial endocarditis, hepatic failure with coagulopathy or diabetic hemorrhagic retinopathy.
• Rutherford IIb ischemia in which prolonged catheter-directed thrombolysis would delay the immediate reperfusion required to salvage the limb.
• Severe renal impairment, contrast allergy, severe anemia or thrombocytopenia; these may influence the technique but do not automatically preclude limb-saving mechanical treatment.
• Inability to cross the occlusion intraluminally, extensive chronic organized occlusion, severe calcification or anatomy incompatible with the available thrombectomy device.
• Severe inflow disease, common femoral disease requiring endarterectomy, infected graft, arterial trauma requiring repair or thrombosed popliteal aneurysm better managed by open or hybrid reconstruction.

Equipment

• Ultrasound machine with sterile probe cover and 21 G micropuncture access set with 0.018 inch wire.
• 4–6 Fr diagnostic catheters appropriate for aortoiliac and runoff angiography, such as pigtail, multipurpose, angled glide or vertebral configurations.
• 0.035 inch hydrophilic guidewire and support catheter for initial lesion traversal.
• 0.014 inch and 0.018 inch hydrophilic and supportive guidewires for distal and tibial intervention.
• 5–8 Fr standard or long reinforced arterial sheath for thrombolysis, aspiration or compatible mechanical devices.
• 4–5 Fr multi-side-hole infusion catheter with an infusion segment selected to cover approximately 5–50 cm of thrombus, with an occlusion wire when required.
• Alteplase preparation and programmable infusion pump; a commonly used low-dose regimen is 0.25–1.0 mg/hour with a maximum total catheter-directed dose of 40 mg.
• 50–60 mL locking syringe with detachable hemostatic valve and large-bore guiding or aspiration catheter for manual aspiration.
• Dedicated aspiration catheter and vacuum pump system, commonly requiring a 6–12 Fr sheath depending on vessel size and device instructions.
• Mechanical or pharmacomechanical thrombectomy system selected for vessel diameter, thrombus age, lesion length and compatible sheath size.
• Angioplasty balloons sized approximately 1:1 to the reference artery and appropriately sized bare, drug-eluting or covered stents for the underlying lesion when indicated.
• Microcatheter and 2–4 mm low-profile balloons for selective tibial or pedal treatment.
• Hemostasis equipment including manual compression materials, closure device where appropriate, covered stent and balloon tamponade equipment for access or target-vessel bleeding.
• Resuscitation equipment, blood products and reversal agents immediately available during thrombolysis.

Procedure steps

1. Confirm acute limb ischemia, document baseline sensory and motor findings and assign Rutherford class. Start intravenous unfractionated heparin unless contraindicated, provide analgesia and supportive care, and obtain immediate vascular-surgical involvement.Pearl: Motor weakness defines Rutherford IIb and sharply reduces the time available for revascularization.
2. Use thrombus age, Rutherford class, occlusion length, anatomy and bleeding risk to choose CDT, aspiration, mechanical thrombectomy, pharmacomechanical thrombectomy or a hybrid approach. Favor immediate thrombectomy or surgery for Rutherford IIb and low-dose CDT for stable Rutherford IIa disease.Pearl: A combination strategy often provides rapid initial flow and allows a lower total thrombolytic dose.
3. Puncture the common femoral artery under ultrasound using a single anterior-wall technique and insert the smallest sheath compatible with the planned treatment. Perform contralateral crossover or ipsilateral antegrade access according to lesion location and device support requirements.Pearl: Contralateral access allows the sheath to remain stable during overnight thrombolysis without obstructing or compressing the ischemic limb.
4. Perform low-volume angiography to identify the proximal cap, occlusion length, collateral circulation, distal reconstitution and runoff. Include inflow and the entire distal circulation rather than imaging only the obvious occlusion.Pearl: A discrete meniscus in a relatively normal artery suggests embolism, whereas long irregular occlusion with collaterals suggests thrombosis over chronic disease.
5. Advance a hydrophilic wire and support catheter gently through the thrombus, maintaining an intraluminal course when possible. Confirm distal intraluminal position with a small contrast injection through the catheter before advancing large-bore devices.Pearl: Easy wire passage through soft thrombus supports an acute component and permits intrathrombus catheter placement.
6. For aspiration, engage the thrombus with the largest safe catheter, apply continuous pump suction or a 50–60 mL syringe and withdraw slowly while maintaining aspiration. For mechanical or pharmacomechanical therapy, size the device to the vessel and use controlled passes according to its instructions, periodically reassessing flow and blood loss.Pearl: Remove bulky proximal thrombus before treating distal emboli or the underlying stenosis.
7. Place the multi-side-hole infusion segment across the residual thrombus and infuse alteplase, commonly at 0.25–1.0 mg/hour according to institutional protocol, without exceeding a total catheter-directed dose of 40 mg. Secure the sheath and catheter, label both clearly and maintain strict limb immobilization.Pearl: An infusion catheter buried throughout the thrombus is more effective than delivering alteplase only proximal to the occlusion.
8. Monitor vital signs, neurological status, access site and limb perfusion in a high-dependency or intensive-care setting. Repeat angiography after approximately 6–12 hours or earlier if symptoms worsen, bleeding occurs or flow is restored.Pearl: A change in pain, sensation, motor function or Doppler signals is more important than an isolated laboratory value.
9. After partial lysis, aspirate or mechanically remove residual focal thrombus and treat clinically important distal emboli. Selectively catheterize tibial vessels when needed to establish at least one continuous runoff artery to the foot.Pearl: Small distal emboli may respond to repositioning the infusion catheter into the embolized vessel when the limb remains stable.
10. Treat the unmasked inflow, native-artery, graft-anastomotic or stent-edge lesion using angioplasty, stenting, covered stenting, endarterectomy, bypass revision or another hybrid technique as appropriate. Use stents selectively where recoil, flow-limiting dissection or an appropriate structural lesion remains.Pearl: Successful thrombus removal reveals the lesion; durable limb salvage usually depends on correcting it.
11. Perform completion angiography from the treated inflow through the foot. Confirm brisk antegrade flow, correction of the causative lesion, acceptable residual stenosis, absence of flow-limiting dissection or extravasation and adequate distal runoff.Pearl: Compare completion angiography with the clinical endpoint because a warmer foot and improved Doppler signals may be meaningful even when distal angiography is imperfect.
12. Remove the sheath when anticoagulation and thrombolytic effects permit, using manual compression or an appropriate closure device. Immediately repeat the neurovascular examination and monitor for tense compartments, disproportionate pain, progressive swelling, hyperkalemia, acidosis, myoglobinuria and renal dysfunction.Pearl: Suspected post-ischemic compartment syndrome requires immediate four-compartment fasciotomy, preferably within 2 hours of diagnosis.

Complications

• Major bleeding, approximately 8–10% with catheter-directed thrombolysis
• Intracranial hemorrhage, usually approximately 1% or less
• Access-site hematoma, pseudoaneurysm or retroperitoneal hemorrhage
• Distal embolization, approximately 5–15% depending on technique and anatomy
• Arterial dissection, perforation or rupture
• Hemolysis, hemoglobinuria, hyperkalemia and acute kidney injury after mechanical thrombectomy
• Reperfusion injury and compartment syndrome, up to 25–30% after prolonged severe ischemia
• Recurrent thrombosis or failed revascularization

Exam pearls

• Acute limb ischemia is limb hypoperfusion of less than 2 weeks duration; neurological deficit determines urgency more reliably than absence of pulses alone.
• Rutherford IIa favors catheter-directed thrombolysis; Rutherford IIb requires immediate revascularization; Rutherford III generally requires primary amputation.
• Give unfractionated heparin immediately at diagnosis unless contraindicated: 5000 IU intravenously or approximately 70–100 IU/kg followed by an adjusted infusion.
• Low-dose alteplase for CDT is commonly 0.25–1.0 mg/hour, with a maximum recommended total catheter-directed dose of 40 mg.
• Continuous systemic therapeutic heparinization during CDT is not recommended.
• Thrombus removal is incomplete treatment unless the causative inflow, outflow, graft, stent or aneurysmal lesion is addressed.
• Restored pulses do not exclude compartment syndrome; a tense painful limb after reperfusion needs immediate surgical assessment.
• Stop thrombolysis for major bleeding or neurological symptoms and obtain urgent definitive evaluation.

Viva questions

How do you classify acute limb ischemia before treatment?

Use the Rutherford classification. Class I is viable without sensory or motor loss; IIa is marginally threatened with sensory loss limited to the toes but no weakness; IIb is immediately threatened with sensory loss beyond the toes and mild or moderate weakness; class III is irreversible with profound anesthesia and paralysis.

Which Rutherford class is the best indication for catheter-directed thrombolysis?

Rutherford IIa is the standard threatened-limb indication because sufficient time usually remains for thrombolysis. Selected IIb limbs may receive promptly initiated CDT only when combined with rapid aspiration or thrombectomy; prolonged lysis alone risks irreversible ischemia.

What is the commonly used alteplase dose for arterial catheter-directed thrombolysis?

A commonly used low-dose infusion is 0.25–1.0 mg/hour through an intrathrombus multi-side-hole catheter. ESVS cites a maximum recommended catheter-directed alteplase dose of 40 mg, although the exact protocol must follow institutional policy.

Should therapeutic heparin be continued during catheter-directed thrombolysis?

No. Unfractionated heparin is administered immediately on diagnosis, but continuous systemic therapeutic heparinization during CDT is not recommended because it increases major bleeding. A low-dose sheath infusion may be used according to local protocol.

What is the endpoint of endovascular treatment for acute limb ischemia?

The endpoint is removal of clinically important thrombus, brisk antegrade flow, correction of the causative lesion and adequate distal perfusion, ideally with at least one inline tibial artery to the foot. Clinical improvement in pain, temperature, neurological status and Doppler signals must accompany the angiographic result.

Why must the underlying lesion be treated after thrombolysis?

Thrombolysis removes the acute thrombus but frequently exposes the stenosis, graft-anastomotic lesion, stent failure or aneurysm that caused thrombosis. Failure to correct this lesion results in a high risk of early rethrombosis.

What findings suggest post-reperfusion compartment syndrome?

Disproportionate pain, pain on passive stretch, tense swelling and new or recurrent sensory or motor deficit are key findings. Pulses may remain present; clinically established compartment syndrome requires immediate four-compartment fasciotomy.

How do aspiration, mechanical and pharmacomechanical thrombectomy differ?

Aspiration removes thrombus using syringe or pump suction. Mechanical thrombectomy fragments and extracts thrombus using device-generated mechanical energy, while pharmacomechanical thrombectomy combines mechanical action with local thrombolytic delivery to accelerate clearance and reduce the required lytic dose.

References