Ankle Brachial Index

 

Ankle Brachial pressure index

The ankle-brachial index (ABI) is used for the diagnosis of lower-extremity peripheral arterial disease (PAD). It is a simple, and inexpensive assessment that can be used to detect lower-extremity arterial stenosis (blockage) in the primary care setting. This can be carried out in symptomatic or asymptomatic patients for the diagnosis of PAD as well as assessment of vascular risk for PAD.

This test is contraindicated for patients who are unable to lie flat on their back for the duration of the examination. ABI measurement is also contraindicated in a patient in whom the use of an occlusive sphygmomanometer cuff may worsen the extremity injury.

Risk factors for PAD are:

  • -High cholesterol
  • -Smoking
  • -High blood pressure
  • -Diabetes

Peripheral artery disease (PAD) risk increases progressively with age, beginning after the age 40.Thus when assessing patients over 40 years of age we should enquire about symptoms related to walking, pain in lower extremity that might be due to poor blood supply and non-healing wounds. If patients are asymptomatic, then we should assess for loss of functional capacity over time.

Patients with PAD can present with pain in one or more muscle groups, atypical pain or with no symptoms.

Intermittent claudication is defined as a reproducible discomfort of a defined group of muscles that is induced by exercise and relieved with rest. This disorder results from an imbalance between supply and demand of blood flow that fails to satisfy  metabolic requirements.

Classic claudication is characterized by leg pain that is consistently reproduced with exercise and relieved with rest. The degree of symptoms of claudication depends upon the severity of blockage, the presence of collateral circulation, and the intensity of exercise. Patients with claudication can present with buttock, hip, thigh, calf, or foot pain, alone or in combination.

Patients with severe PAD will present with rest pain which involves digits and forefoot. This pain would typically occur at night. A more localized pain can be indicative of future development of ischemic ulcer or gangrenous toe.

ABI should be performed in patients with lower extremity exertional symptoms and in those patients with risk factors for PAD. An ABI of ≤0.90 has a high degree of sensitivity and specificity for a diagnosis of PAD.

Other conditions that can lead to arterial stenosis (blockage) can be:

-Arterial            -Arterial aneurysm, arterial dissection, and arterial embolism

-Non-arterial   -Neurological disorders, musculoskeletal disorders, and acute and chronic venous                                     disease(DVT)

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