What Is the Difference Between Critical Limb Ischemia and Acute Limb Ischemia?

The difference between critical limb ischemia (CLI) and acute limb ischemia (ALI) is the duration of symptoms. CLI develops over time, and ALI is sudden

The main difference between critical limb ischemia (CLI) and acute limb ischemia (ALI) is the duration of symptoms. CLI symptoms develop over a longer period of time, whereas ALI symptoms develop suddenly.

Learn about symptoms, causes, risk factors, and treatment.

Table 1: Critical limb ischemia vs. acute limb ischemia Clinical features Critical limb ischemia Acute limb ischemia

Definition
Severe blockage in the arteries that reduces blood flow to the hands, legs, and feet; may be acute or chronic
Sudden decrease in blood flow to the limb

Onset
Develops over time (2 weeks or more)
Occurs within 14 days after symptoms start

Symptoms

• Ischemic rest pain
• Ulcers and sores in the feet
• Non-healing sores
• Gangrene
• Legs may be warm and pink
• Reduced or absent pulse

• Limb pain
• Pulselessness in the limb
• Pallor
• Tingling sensation in the legs
• Paralysis (late sign)
• Legs may be cold

Causes
Occurs due to blockage of the arteries or narrowing of the arteries in the lower extremities
Occurs due to the formation of clots or blood vessel blockage

Physical appearance
Pink
Pale, marble white

Emergency
No
Yes

Pain
Gradual, at rest
Sudden, at rest, calf tenderness

Treatment

• Surgery
• Medications
• Thrombolysis

• Surgery
• Medications

What is critical limb ischemia?

Critical limb ischemia is a severe blockage in the arteries that reduces blood flow to the hands, feet, and legs. It can cause severe pain, non-healing skin ulcers, and gangrene.

The main cause of CLI is atherosclerosis, in which plaques build up in the arteries, causing narrowing and reduced blood supply. When atherosclerosis affects the arteries that supply blood to the lower extremities, the condition is called CLI.

What is acute limb ischemia?

Acute limb ischemia is sudden decrease in the blood flow to the legs that poses a threat to the limbs. It is an emergency because there is a high risk of amputation and even death if left untreated.

Main causes of ALI include:

• Thrombosis (atherosclerosis that leads to blood vessel blockage)
• Embolism (blood clots of cardiac origin)
• Trauma (injury due to previous heart surgery such as percutaneous coronary intervention)

Stages of ALI are as follows:

• Class I: Limbs are not threatened. Restoration of blood flow may or may not be necessary.
• Class II: Limb viability is threatened. Restoration of blood flow is needed to prevent tissue death.
• Class III: Irreversible ischemia. Saving the legs is impossible.

Table 2: Clinical classification of acute limb ischemia Category Sensory change Motor change Arterial Doppler signals Venous Doppler signals

Viable
None
None
Audible
Audible

Threatened
Rest pain
Moderate
Inaudible
Audible

Irreversible
Anesthetic
Paralysis
Inaudible
Inaudible

What are risk factors for both CLI and ALI?

Risk factors for both critical limb ischemia and acute limb ischemia are similar:

• Obesity
• Diabetes
• High blood pressure
• High cholesterol levels
• Smoking
• Age (over age 65)
• Family history of critical limb ischemia, heart disease, or stroke
• High levels of homocysteine