Peripheral arterial disease is defined as an ankle-brachial index (ABI) of <0.9 (see ABI definition below). The disease prevalence is 4.3% in Americans under age 40 years, and prevalence climbs to 15.5% in those over 70 years of age. High-risk individuals (such as those over 70 years, or those over 50 years with risk factors such as diabetes) should be evaluated carefully when complaints are indicative of possible occlusive arterial disease. Tobacco use significantly increases the risks that an individual will develop peripheral arterial disease. Limb ischemia from an acute arterial occlusion can lead to irreversible changes in peripheral nerves and skeletal muscle tissue in 4 to 6 hours. The most frequently diseased arteries leading to limb ischemia are the femoropopliteal, tibial, aortoiliac, and brachiocephalic. The common femoral and popliteal arteries are the most common sites of arterial embolism.
Patients with acute arterial limb ischemia typically present with one or more of the “six Ps”: pain, pallor, poikilothermia (coldness), pulselessness, paresthesias, and paralysis. Pain is the earliest symptom and may increase with elevation of the limb. Changes in skin color with mottling, splotchiness, and cool temperature are common. Patients may present with muscle weakness as one early sign of limb ischemia, and the presence of acute anesthesia progressing to paralysis is concerning for acute ischemia that may negatively impact limb viability. A decreased pulse palpated distal to a vascular obstruction is an unreliable finding for early ischemia, especially in patients with chronic peripheral vascular disease and well-developed collateral circulation. Claudication is a cramping pain, ache, or tiredness in an ischemic limb that is brought on by exercise and relieved by rest. It is reproducible, resolves within 2 to 5 minutes of rest, and reoccurs at consistent walking distances. Claudication is a classically described symptom of peripheral vascular disease, but may only be present in 20% to 30% of patients with significant disease. These symptoms are contrasted with the pain of an acute episode of limb ischemia which is not well localized, is unrelieved by rest or gravity, and can present as a worsening of chronic pain when caused by an acute thrombotic event.
DIAGNOSIS AND DIFFERENTIAL
Although thromboembolic disease is the most common cause of acute arterial occlusion, the differential diagnosis for some of the presenting symptoms may include catheterization complications, vasculitis, Raynaud disease, thromboangiitis obliterans, blunt or penetrating trauma, or low-flow shock states such as sepsis. Vasospasm caused by intentional or accidental intraarterial drug injections may present as acute ischemic digits. Most commonly, a history of an abruptly ischemic limb in a patient with atrial fibrillation or recent myocardial infarction is strongly suggestive of an embolus. A history of chronic claudication suggests the presence of peripheral vascular disease, and an acute episode is likely caused by thrombosis and worsening limb ischemia. Examine the patient for differences in peripheral pulses, capillary refill, and skin findings on the extremities.
Objective bedside testing with a handheld Doppler can document the presence or absence of blood flow in an affected limb. Duplex ultrasonography can further be used to detect an obstruction to flow with sensitivity greater than 85%. In addition, the ABI can be easily measured in the emergency department using a blood pressure cuff and Doppler ultrasound to measure the systolic pressure of occlusion at the brachial artery and posterior tibial or dorsalis pedis arteries. The ABI is the leg occlusion pressure divided by the arm occlusion pressure and a normal ABI is >0.9. An abnormal ABI suggests peripheral vascular disease, and a ratio lower than 0.41:1 is concerning for critical limb ischemia. A CT angiogram is a diagnostic option that can be ...