Critical Limb Ischemia - Risk Factors, Symptoms, Diagnosis, and Management

What Is Critical Limb Ischemia?

Critical Limb Ischemia(CLI) is the most severe form of peripheral artery disease(PAD), characterized by the presence of foot ulcer or gangrene and chronic ischemic(due to impaired blood supply) rest pain. All PAD( peripheral artery disease), including CLI, occurs as a result of atherosclerosis, a condition in which atherosclerotic plaque(plaque is made of fatty deposits, calcium, and fibrin) occludes the blood vessels. This restricts the blood flow to the extremities, the legs, and arms.

CLI presents with a high risk of amputation, cardiovascular complications, and even death. It can result in lower limb amputation in 10 to 40 % of the cases. The mortality rate is 20 % within six months after diagnosis and reaches 50 % in five years after diagnosis.

What Are the Risk Factors?

CLI is considered an advanced stage of PAD, so it is the result of atherosclerosis. So, those having atherosclerosis and having a risk for atherosclerosis are also at risk for CLI. The risk groups include:

• Smokers.

• Alcoholics.

• Hypertensive patients.

• Patients having high C-reactive protein levels.

• Chronic kidney disease.

• Dyslipidemia.

• Age.

• Obesity.

• Family history of atherosclerosis.

• Sedentary lifestyle.

• Hyper homocysteinemia.

Other low-risk factors include:

• Buerger’s disease.

• Thromboangitis obliterans.

What Are the Symptoms?

CLI is the most severe form of PAD and presents with the following symptoms:

• Chronic ischemic rest pain for more than two weeks. The pain is experienced as severe burning pain in the extremities when the person is at rest. Pain is usually experienced when the person is sleeping at night and may keep the person awake. The patient’s pain gets relieved when sleeping in a reclining position or when they dangle their legs over the bedside.

• Presence of nonhealing foot ulcer or gangrene.

• Thickening of toenails.

• Pale smooth, shiny, dry skin of legs.

• Numbness in the feet.

• Diminished pulse in legs and feet.

• Shortness of breath.

• Swelling in legs and feet.

• The affected part (feet/leg) is colder when compared to the overall body temperature.

How Is the Condition Diagnosed?

The condition is mainly diagnosed by the physician on clinical evaluation based on the symptoms and patient history. The patient presents with chronic ischemic rest pain with ankle pressure of less than 50 mm Hg or toe pressure of less than 30 mm Hg. In patients who present with foot ulcer or gangrene and ankle pressure lesser than 70 mm Hg and transcutaneous oxygen pressure(TcPO2) lesser than 50 mm Hg, CLI is diagnosed. Foot ulcer or gangrene with TcPO2 less than 30 mm Hg also indicates CLI.

In some patients, the condition may be asymptomatic, as is the case of diabetic patients with diabetic neuropathy due to loss of sensations. Another parameter considered for diagnosis is ABI(Ankle-Brachial Index); ABI is the ratio of systolic pressure at the dorsalis pedis or post-tibial artery divided by systolic pressure at the brachial artery. An ABI value of 0.4 or less indicates CLI. On auscultation, a bruit is present in the arteries of the leg. A Doppler ultrasound is also used for diagnosis. Changes in Doppler waveform are used for the identification of arterial blockage sites. As a second level of examination, CT (computed tomography)and MR (magnetic resonance) angiography may also be used.

What Is the Differential Diagnosis?

CLI should be differentiated from the following conditions:

• Night Cramps: Night cramps usually affect the calf muscles(muscle on the posterior part of the lower leg) and can keep the person awake. But the pain gets relieved by massaging the muscle or by walking.

• Arthritis: Arthritis of the metatarsal bone can also cause pain in the foot. But the pain is intermittent and gets relieved on standing.

• Diabetic Neuropathy: Diabetic neuropathy can also result in skin changes, pain, and diminished pulse in the foot, similar to CLI. But diabetic neuropathy is also characterized by reduced vibratory sense and loss of light touch.

• Spinal Stenosis: Spinal stenosis is a condition characterized by back pain radiating to the legs.

• Acute Limb Ischemia: In acute limb ischemia, the clinical features last for less than two weeks duration and occur immediately.

How Is the Condition Managed?

Management of CLI requires a holistic approach that focuses on pain management, wound healing, reducing mortality, preventing amputation, and improving patients’ quality of life.

The first line of treatment option is revascularization. The management involves the following:

• Pain Management: Peripheral revascularization provides pain relief. In patients where revascularization is not possible or a failure, medical therapy is done. NSAIDS(non-steroidal anti-inflammatory drugs) and Paracetamol are used for managing pain. Opioids may also be used for pain management.

• Smoking Cessation: As smoking can increase the mortality rate and increase the risk of revascularization failure, smoking cessation is essential.

• Management of Dyslipidemia: In the case of patients with dyslipidemia, LDL-C(Low-density lipoprotein cholesterol) should be bought below 70 mg/dL. Statins are used for management.

• Management of Diabetic: Diabetes is an important risk factor for CLI. The glycemic level should be bought under control as diabetes increase the risk of ulcers and infection.

• Management of Hypertension: The blood pressure should be bought to less than 140/90 mm Hg in hypertensive patients and less than 130/80 mm Hg in patients having both diabetes and hypertension. Any antihypertensive drugs like Thiazide, calcium channel blockers, beta-blockers, etc., can be used for treatment.

• Antiplatelet Therapy: Aspirin(75-160 mg) or Clopidogrel is used for antiplatelet therapy.

• Revascularization: Revascularization is the first line of treatment. Revascularization can be done as an endovascular technique or as surgery through the bypass. Bypass surgery provides long-term patency but is unsuitable in some cases, like those patients in which several other medical conditions are present, or unavailability of a vein is present, reduced life expectancy, etc. Endovascular treatment options include angioplasty(the procedure involves inserting a tiny balloon that is inflated to open an artery), stents, laser atherectomy (using a laser probe, plaque is vaporized), and directional atherectomy(catheter with blades used to remove plaque).

Conclusion

Critical limb ischemia is the severe advanced stage of peripheral artery disease that poses a high risk of amputation, cardiovascular complications, and death. The mortality rate is high, and management involves a holistic approach that takes into account all the contributing risk factors. It is a condition that requires immediate medical attention and treatment.