Ankle Brachial Index

Ankle brachial index is a simple and useful test to assess lower extremity arterial perfusion. It is being performed by using handheld Doppler device and blood pressure cuff

It is very crucial as peripheral vascular disease is a risk marker for a number of conditions, including: coronary disease, cerebrovascular disease, aneurysmal disease, diabetes, and hypertension. Documented PVD increases the risk of cardiovascular mortality 4-6 times over healthy age-matched individuals

Ankle Branchial Index is also useful indicator in deciding the type of amputation requires in managing the diabetic foot complication.

The proper technique to use is as follows:

1. Put the patient in supine position to measure the brachial pressure in both arms using Doppler ultrasound. Take two readings for each arm and select the highest reading for calculating the index. We can only allow differences of less than 10 mm Hg between each brachial pressure measurement.
2. Place the Blood pressure cuff on patient's leg just above the mallelous. Measure the anterior tibial and posterior tibial arterial systolic pressures. Select the higher of these two values as the ankle pressure measurement to be used for the ankle systolic pressure in the ABI calculation.
3. ABI is calculated by dividing the ankle systolic pressure by brachial systolic pressure

Interpreting the results

1) ABIs as high as 1.10 are normal

2) abnormal values are those less than 1.0

3) majority of patients with claudication have ABIs ranging from 0.3 to 0.9

4) Rest pain or severe occlusive disease typically occurs with an ABI lower than 0.50

5) Indexes lower than 0.20 are associated with ischemic or gangrenous extremities.

Notes

1) ABI of less than 0.6 to 0.8 is a contraindication for pressure dressing as in increases further risk of ulceration.

2) Stiff or calcified arterial wall in diabetes patient may give false high ABI. Therefore, it is a good habit to consult this matter with vascular surgeon