Peripheral Arterial Embolism

What happens in a peripheral arterial embolism

An embolus is material that breaks off, travels in the bloodstream and wedges in an artery too narrow for it to pass. In peripheral arterial embolism it lodges in a limb artery, often where an artery divides: the femoral artery in the groin, the popliteal artery behind the knee, or the brachial artery at the elbow.

Because the blockage is sudden, the limb has had no time to grow bypass vessels (collaterals). Muscle can tolerate a total lack of blood flow for only about 4 to 6 hours before irreversible damage begins. Nerves are even more sensitive.

This differs from a clot forming on top of long-standing narrowing (arterial thrombosis) in a person with peripheral artery disease. Thrombosis tends to cause slightly less sudden symptoms because collaterals already exist.

Symptoms: the 6 Ps

Doctors remember the signs of acute limb ischemia as the six Ps:

1. Pain: sudden, severe and constant, often in the calf or forearm.
2. Pallor: the skin turns white or mottled, later bluish.
3. Pulselessness: no pulse below the blockage.
4. Poikilothermia: the limb feels cold compared with the other side.
5. Paresthesia: numbness, pins and needles or loss of feeling.
6. Paralysis: weakness or inability to move. This is a late sign of severe damage.

The legs are affected far more often than the arms. Small emboli can lodge in the toes, causing sudden painful blue or black spots ("blue toe syndrome"), usually from cholesterol debris breaking off plaque.

Causes and risk factors

• Atrial fibrillation: the most common source. Blood pools in the left atrium and forms clots.
• Recent heart attack: a clot can form on damaged heart muscle.
• Heart valve disease and artificial valves.
• Endocarditis: infected material on a valve breaks off.
• Aneurysms: clots inside an aortic or popliteal aneurysm can travel downstream.
• Atherosclerotic plaque in the aorta, releasing cholesterol crystals.
• Paradoxical embolism: rarely, a vein clot crosses a hole in the heart into the arterial circulation.
• After procedures: heart catheterization or vascular surgery can dislodge material.

How it is diagnosed

Diagnosis begins at the bedside, because time matters. The doctor compares both limbs for color, temperature, pulses, sensation and movement, and uses a handheld Doppler to listen for blood flow in the foot or hand arteries. The severity is graded to decide how urgently to operate.

Imaging, usually CT angiography, shows the exact site of the blockage. An ECG looks for atrial fibrillation, and an echocardiogram later looks for a source in the heart. Blood tests check kidney function, muscle damage (creatine kinase) and clotting.

Treatment

• Heparin: an intravenous blood thinner is started immediately to stop the clot spreading.
• Embolectomy: a surgeon opens the artery and pulls the clot out with a balloon catheter. This is the standard approach for embolism.
• Catheter-directed treatment: clot-dissolving drugs (thrombolysis) or devices that suck out the clot, delivered through a catheter. Used for some patients when the limb can tolerate a slightly longer time to reopen.
• Bypass surgery when there is underlying artery disease.
• Fasciotomy: if the muscles swell after blood flow returns (compartment syndrome), the surgeon cuts the tight tissue around the muscles to relieve pressure.
• Amputation: when the limb is no longer viable.

After treatment, most people need long-term anticoagulants to prevent another embolism, plus treatment of the source, such as rhythm control in atrial fibrillation.

Complications

• Reperfusion injury: toxins and potassium released from damaged muscle when flow returns can cause kidney failure and dangerous heart rhythms.
• Compartment syndrome.
• Limb loss.
• Further emboli to the brain (stroke), gut or kidneys from the same source.

Prognosis

The outlook depends mostly on how quickly blood flow is restored and on the person's general health. Treated within about 6 hours, most limbs are saved. After 12 to 24 hours the chance of permanent damage and amputation rises sharply. Even with good treatment, acute limb ischemia carries a significant risk of amputation and death within the following year, mainly because people affected often have serious heart disease. Taking blood thinners as prescribed and treating atrial fibrillation greatly reduce the chance of recurrence.

Prevention

• Take anticoagulants if prescribed for atrial fibrillation or a mechanical valve.
• Control blood pressure, cholesterol and diabetes, and stop smoking to limit plaque.
• Seek care quickly for symptoms of atrial fibrillation, such as an irregular racing heartbeat.

Frequently asked questions

What is a peripheral embolism?

It is a blockage of an artery in an arm or leg by a clot or other debris that traveled from elsewhere, usually the heart. It cuts off blood flow suddenly, causing a painful, pale, cold and numb limb. It needs emergency treatment to restore blood flow.

What is the prognosis of a peripheral arterial embolism?

With treatment within about 6 hours, most limbs are saved. Delays increase the risk of permanent nerve and muscle damage and amputation. Overall survival depends largely on underlying heart disease. Long-term blood thinners reduce the chance of another embolism.

What are the symptoms of a peripheral arterial embolism?

The classic symptoms are the six Ps: sudden pain, pallor, no pulse, coldness, pins and needles or numbness, and paralysis. They appear over minutes to hours, usually in one leg. Weakness or loss of sensation means the limb is at immediate risk.

How is a peripheral embolism different from a DVT?

A DVT is a clot in a vein, which causes a swollen, warm, red and aching leg. A peripheral arterial embolism blocks an artery, so the limb becomes pale, cold, numb and painful. Both are serious, but an arterial embolism threatens the limb within hours.

Can atrial fibrillation cause a clot in the leg?

Yes. In atrial fibrillation, blood can pool and clot in the heart. A piece can travel to the brain, causing a stroke, or to a leg or arm artery, causing acute limb ischemia. Anticoagulant medicine greatly lowers this risk.