Acute Limb Ischemia

Introduction
Acute limb ischemia can be embolic, thrombotic, or traumatic. Symptoms and signs are related to the location of the occlusion, the duration of ischemia, and the degree of development of collateral circulation. Baseline pulse examination and assessment of motor and sensory function are imperative. Characteristically, acute ischemia is described by the six Ps: pain, pallor, pulselessness, paresthesias, poikilothermia, and paralysis. Pain and paresthesias are the most common early symptoms.

The following differential points should be considered: (1) Are there manifestations of advanced occlusive arterial disease in other areas, especially the opposite extremity (bruit, absent pulses, secondary skin changes), and is there a history of intermittent claudication? These findings suggest primary arterial thrombosis. (2) Is there a history of rheumatic heart disease, atrial fibrillation, or myocardial infarction? These findings suggest embolism.

1. Arterial Embolism

Introduction

Eighty to 90 percent of arterial emboli arise from the heart. Atrial fibrillation is present in 60-70% of patients with arterial emboli and is associated with formation of thrombus in the left atrial appendage. Thrombus within a postinfarct ventricular aneurysm may also be a potential embolic source. Emboli arising from rheumatic heart disease are decreasing in incidence and now comprise less than 20% of arterial emboli. Cardiac valvular prostheses and cardiac tumors (myxomas) can also produce emboli. Noncardiac emboli arise from atherosclerotic lesions in proximal vessels, tumors, and foreign bodies. Paradoxical emboli deriving from deep venous thrombosis in the leg can also occur.

Emboli tend to lodge at the bifurcation of major arteries, with 40% going to the aortic, femoral, or popliteal bifurcations. Thirty percent lodge in the cerebrovascular vessels, 10% in the visceral vessels, and 15% in the upper extremity vessels. Noncardiac emboli from arterial ulcerations are usually small (< 400 um), giving rise to peripheral ulceration and digital ischemia or occasionally to a systemic illness resembling vasculitis.

Treatment
Heparin sodium should be given as soon as the diagnosis of acute arterial occlusion is made and continued intraoperatively to prevent distal thrombosis. Emergent embolectomy is performed by introducing a balloon catheter through a small arteriotomy. An embolus at the aortic bifurcation or in the iliac artery can often be removed under local anesthesia through unilateral or bilateral common femoral arteriotomies. Smaller balloon catheters passed distally from the femoral artery can be used to extract popliteal or tibial emboli, though these often require popliteal arteriotomy. Percutaneous catheter techniques (aspiration, mechanical thrombolysis, or thrombolytic therapy) have some reported success in treatment of peripheral embolic disease. Lifelong anticoagulation is recommended because of the high frequency of recurrent emboli. Surface or transesophageal echocardiography should be performed to exclude the possibility of atrial thrombus, valvular disease, or cardiac tumor.