Acute Limb Ischemia
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Acute limb ischemia is a sudden decrease in blood flow to a limb that threatens viability. It requires urgent evaluation and management to determine if the limb is viable, threatened, or irreversibly damaged. Prompt diagnosis and revascularization through catheter-based thrombolysis, thrombectomy, or surgery can reduce limb loss risk. Treatment approaches depend on the severity of ischemia and limb threat.
Acute Limb Ischemia
- 1. Acute Limb Ischemia N Engl J Med 2012;366:2198-206
- 2. Key Clinical Points Acute limb ischemia is a sudden decrease in limb perfusion that threatens limb viability and requires urgent evaluationand management. Causes of acute limb ischemia include acute thrombosis of a limb artery or bypass graft, embolism from the heart or a diseased artery, dissection, and trauma. Assessment of limb appearance, temperature, pulses (including by Doppler), sensation, and strength is used to determine whether the limb is viable, threatened, or irreversibly damaged.
- 3. Key Clinical Points Prompt diagnosis and revascularization by means of catheter-based thrombolysis or thrombectomy or by surgical reconstruction reduce the risk of limb loss. Catheter-directed thrombolysis is the preferred treatment for a viable or marginally threatened limb, recent occlusion, thrombosis of synthetic grafts, and occluded stents. Surgical revascularization is generally preferred for an immediately threatened limb or occlusion of more than 2 weeks’ duration. Amputation is performed in patients with irreversible damage.
- 4. In contrast to chronic limb ischemia, in which collateral blood vessels may circumvent an occluded artery, acute ischemia threatens limb viability because there is insufficient time for new blood-vessel growth to compensate for loss of perfusion.
- 5. Despite urgent revascularization with thrombolytic agents or surgery, amputation occurs in 10 to 15% of patients during hospitalization. A majority of amputations are above the knee. Approximately 15 to 20% of patients die within 1 year after presentation, often from coexisting conditions that predisposed them to acute limb ischemia.
- 6. 6 Ps Paresthesia Poikilothermia Pain impaired regulation of Pallor body temperature, with Pulselessness the temperature of the limb usually cool, reflecting the ambient temperature Paralysis
- 7. Symptoms Potential Causes – Pain – Thrombosis of artery – Paresthesia or bypass graft – Weakness or paralysis – Embolism from heart or proximal vessel – Dissection Signs – Trauma – Absent pulses – Pallor – Cool skin – Decreased sensation – Decreased strength – Limb blood pressure <50 mm Hg
- 8. 3D Reconstruction of a CTA in a Patient with a 3-Day History of Pain and Numbness in the Right Foot. This posterior view shows a focal occlusion of the right popliteal artery (arrow) with surrounding enlarged collateral vessels. The patient underwent surgical bypass with a reversed saphenous vein graft to the posterior tibial artery.
- 9. Stages of Acute Limb Ischemia Description and Stage Findings Doppler Signal Prognosis Sensory Muscle Arterial Venous Loss Weakness Limb viable, not I immediately threatened None None Audible Audible II Limb threatened Marginally threatened, Minimal (toes) IIa salvageable if or none None Often inaudible Audible Immediately threatened, More than Usually IIb salvageable with immediate toes, Mild or moderate inaudible Audible revascularization associated Limb irreversibly damaged, major tissue loss or Profound, Profound, Inaudible Inaudible III permanent nerve damage anesthetic paralysis (rigor) inevitable
- 10. Treatment Endovascular Revascularization Surgical Revascularization
- 11. Endovascular Revascularization The goal of catheter-based endovascular revascularization is to restore blood flow as rapidly as possible to a viable or threatened limb with the use of drugs, mechanical devices, or both. Patients in whom ischemia for 12 to 24 hours would not be safe and those with a nonviable limb, bypass graft with suspected infection, or contraindication to thrombolysis (e.g., recent intracranial hemorrhage, recent major surgery, vascular brain neoplasm, or active bleeding) should not undergo catheter-directed therapies.
- 12. Thrombolytic Agents Alteplase (Genentech) Reteplase (EKR Therapeutics) Tenecteplase(Genentech)
- 13. Acute ischemia of the left leg in a 68 y/o woman with chronic renal failure occlusion of the proximal superficial femoral artery intraluminal filling defect in tPA was infused directly into the the proximal thrombosed segment through a superficial multi-side-hole infusion catheter. femoral artery After angioplasty and placement of a self-expanding stent, shows a widely patent artery
- 14. Surgical Revascularization Surgical approaches to the treatment of acute limb ischemia include thromboembolectomy with a balloon catheter, bypass surgery, and adjuncts such as endarterectomy, patch angioplasty, and intraoperative thrombolysis.
- 15. 3D Reconstruction of CTA Showing Runoff in the Left Leg. A patent bypass graft (arrow) to the anterior tibial artery, performed to repair an aneurysm in a popliteal artery with acute thrombosis.
- 16. Endovascular versus Surgical Revascularization The Surgery versus Thrombolysis for Ischemia of the Lower Extremity (STILE) trial was halted early because of higher rates of ischemia, amputation, and complications among patients undergoing thrombolysis than among those undergoing surgery. In the Thrombolysis or Peripheral Arterial Surgery (TOPAS) trial, the rates of limb salvage and survival did not differ significantly between the thrombolysis and surgery groups, but complication rates were higher in the thrombolysis group.
- 17. Endovascular versus Surgical Revascularization Catheter-directed thrombolysis has the best results in patients with a viable or marginally threatened limb, recent occlusion (no more than 2 weeks’ duration), thrombosis of a synthetic graft or an occluded stent, and at least one identifiable distal runoff vessel. Surgical revascularization is generally preferred for patients with an immediately threatened limb or with symptoms of occlusion for more than 2 weeks.
- 18. Initial treatment with intravenous heparin Imaging and treatment according to severity Stage I Stage IIa Stage IIb Stage III Viable limb Marginally threatened Immediately threatened Irreversible damage Not immediately threatened Imaging Imaging Imaging if no delay in emergency revascularization Revascularization Amputation Endovascular, surgical, or hybrid Algorithm for the Diagnosis and Treatment of Acute Limb Ischemia
- 19. Conclusions and Recommendations Heparin should be administered as soon as the diagnosis has been made. In a patient with a viable or marginally threatened limb, imaging studies (duplex ultrasonography, CTA, or MRA) can be obtained to guide therapeutic decisions. In a patient with an immediately threatened limb, such as the patient described in the vignette, emergency angiography followed by catheter- based thrombolysis or thrombectomy or open surgical revascularization is indicated to restore blood flow and preserve limb viability.