Ankle-brachial Index (also called ABI)
What is the Ankl-brachial Index?
Measuring ankle-brachial index (ABI) is a simple, easily reproducible and accessible test that can accurately highlight the presence of peripheral artery disease.
Peripheral artery disease is a condition in which the arteries of the legs or the upper extremities are narrowed. Studies show that patients with peripheral artery disease have an increased risk of developing cardiac events and stroke.
How is the test performed?
During the test, blood pressure is measured at the upper and lower extremities. This presupposes that the examined person is lying down. Blood pressure is then measured at all four extremities, using a cuff and a doppler device. In some cases it may be useful to measure pressure after exercise in a treadmill. When the measurements are taken, the subject’s ankle-brachial index is calculated. An ABI of less than 0.9 is considered abnormal and may indicate the presence of stenosis in the lower limb arteries.
In which cases is it necessary to measure the ankle-brachial index?
Peripheral artery disease, like coronary artery disease, may have symptoms only when it is at an advanced stage. It is therefore necessary to look for those who have an increased risk of developing it.
- Smokers or ex-smokers over 50 years of age
- Patients with arterial hypertension
- Those with elevated lipids
- People over 70 years of age
And of course patients reporting symptoms suspected of peripheral artery disease. These may be pain or cramps in the legs during walking that disappear in rest (also called intermittent claudication). Even sores in the legs that do not heal easily or not at all. Cold lower extremities compared to the rest of the body.
What do the results show?
An ankle-brachial index value between 0.9 and 1.3 is considered normal.
Values below 0.9 indicate peripheral artery disease. Specifically, values below 0.4 indicate a significant degree of peripheral angiopathy. While values from 0.41 – 0.9 are indicative of small or moderate degree of peripheral angiopathy and may be accompanied by intermittent claudication.
Values from 0.91 to 0.99 are considered to be to the limits, and in the presence of indications, it may be required to measure the ankle-brachial index after exercise.
Finally, values above 1.3 (or 1.4 by other researchers) show hard vessels and usually occur in patients with diabetes or chronic renal failure.
What are the next steps?
The measurement of abnormal ankle-brachial index is the trigger for further control of the cardiovascular system and risk factors. As mentioned above, patients suffering from peripheral artery disease are more likely to develop coronary artery disease or stroke. Therefore, a full cardiac check up is necessary to assess the presence of coronary heart disease or the presence of angiopathy in other parts of the vascular system.In addition, cardiac risk factors (arterial hypertension, dyslipidaemia, smoking, obesity, sedentary lifestyle) should be sought and evaluated and appropriate guidance given. Finally, further angiological testing is likely to be required to better assess the extent of angiopathy.