Ankle-Brachial Index
Original Editor - Khloud Shreif
Top Contributors - Khloud Shreif, Chloe Waller, Vidya Acharya and Lucinda hampton
Introduction[edit | edit source]
The ankle-brachial index (ABI) is a quick, non-invasive technique used to check vascular status and for peripheral arterial disease (PAD)[1][2]. It was first described by Winsor in 1950[3].
The ABI is the ratio between the systolic blood pressure of the lower limb (specifically at the ankle) and the upper limb, to assess for narrowing or blockages in the arteries in the legs[1][4].
Indications[edit | edit source]
People presented with pain, cramps, or claudications in the calf, hamstring, G.max during walking.
Risk factors for PAD, such as:
- History of tobacco use
- High blood pressure
- High cholesterol
- Restricted blood flow (atherosclerosis) in other parts of your body.
Contraindications[edit | edit source]
- Patients with confirmed or suspected DVT, because of the possibility of breaking of the thrombus.
- Severe leg pain.
Procedures[edit | edit source]
Tools[edit | edit source]
Hand-held Doppler, or hand-held ultrasound device that's pressed on your skin
Inflated cuff
Preparation[edit | edit source]
- Rest for minutes before the measurements 10-30 minutes like normal blood pressure taken during normal visits.
- Loose, comfortable clothes will be a better choice for easily wearing the inflated cuff on the upper arm.
- Avoid nicotine/ smoking as it shows an increase in the peripheral systolic pressure resulting in elevated ABI value[2].
- Supported, comfortable position, and avoid limb movement during measurements.
- The supine position is the position of choice as the sitting position shows about 0.3 increase in the ABI[5],
Technique[edit | edit source]
The same procedures as in the measurement of normal blood pressure, with the patient in rested position, it is better to measure the brachial pressure before the ankle pressure:
1- Place the cuff around the patient's arm, use the hand-held ultrasound device or hand doppler and press against the skin at the level of the brachial artery in the arm in order to hear the waves of the systolic pressure, repeat on the other arm and record the highest measurement.
2- Place the cuff around the lower leg and use the hand-held ultrasound device to hear the waves of the systolic pressure at two levels :
- Dorsalis pedis, which is a branch from the anterior tibial artery, it is located between the tibialis anterior and extensor hallucis longus
- Posterior tibial pulse, that is behind the lateral malleoli.
3- Record the highest pulse between two measurements of dorsalis pedis and posterior tibial arteries.
4- The ankle-brachial index calculated by dividing the highest value of ankle systolic pressure between the two arteries by the highest brachial pressure between two sides.
5- Repeat the ankle measurement for the other leg in order to calculate its ABI.
6- The normal ABI is between 0.90 and 1.30, below indicate PAD, above may be a sign of arterial calcification.
Clinical Significance[edit | edit source]
The normal range is between 0.90 and 1.30. below 0.8 means there is a difficulty of blood flow to the foot and lower limb.
Below 0.7 means severe peripheral artery disease PAD and the patient may develop ulcer and gangrene[7].
Above the normal level, 1.30 is a sign of calcification of arterial walls that may happen in case of diabetic patients, chronic kidney disease, in this situation you need to measure the ankle pressure at distal digital arteries that is less likely to develop or be calcified
This ABI is not a confirmation for the diagnosis for arteries calcification[8][2].
General Considerations[edit | edit source]
- In normal healthy people, there is a slight decrease in ABI if measured immediately after lower limb exercises due to the decreased ankle systolic pressure because of vasodilation during lower limb exercises, and return to normal within about 3 min after rest.
- There is more decrease in ankle pressure after walking in case of moderate occlusive PAD specifically in the proximal vessels.
- The ABI has a high sensitivity, but these results came from one single study which may be included participants with critical limb ischemia[7] or diabetic patients.
- People with a history of PAD will demonstrate a continuous decrease of ABI over time, about 0.06 over 4.6 years. On the other side, there is a smaller decrease in the general population it's about 0.025 over 5 years[2].
- If the ankle pressure is less than 50 mm Hg it is associated with a higher risk of avascularity and amputation.
Resources[edit | edit source]
Mayo Clinic, Ankle- Brachial Index
References[edit | edit source]
- ↑ 1.0 1.1 McClary KN, Massey P. Ankle Brachial Index. 2022 Jan 21. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2022 Jan–
- ↑ 2.0 2.1 2.2 2.3 Aboyans V, Criqui MH, Abraham P, Allison MA, Creager MA, Diehm C, Fowkes FG, Hiatt WR, Jönsson B, Lacroix P, Marin B. Measurement and interpretation of the ankle-brachial index: a scientific statement from the American Heart Association. Circulation. 2012 Dec 11;126(24):2890-909.
- ↑ Winsor, T. Influence of arterial disease on the systolic blood pressure gradients of the extremity. Am J Med Sci. 1950 Aug;220(2):117-26.
- ↑ Mayo Clinic.Ankle Brachial Index. Available from:https://www.mayoclinic.org/tests-procedures/ankle-brachial-index/about/pac-20392934 (Last accessed 12/09/2022)
- ↑ Xu Y, Xu W, Wang A, Meng H, Wang Y, Liu S, Li R, Lu S, Peng J. Diagnosis and treatment of traumatic vascular injury of limbs in military and emergency medicine: A systematic review. Medicine. 2019 May;98(18).
- ↑ St. Michael's Hospital. How to perform an ankle brachial index. Available from: http://www.youtube.com/watch?v=ab_channel[last accessed 18/9/2020]
- ↑ 7.0 7.1 Crawford F, Welch K, Andras A, Chappell FM. Ankle brachial index for the diagnosis of lower limb peripheral arterial disease. Cochrane Database of Systematic Reviews. 2016(9).
- ↑ McClary KN, Massey P. Ankle Brachial Index (ABI). InStatPearls [Internet] 2020 May 21. StatPearls Publishing.
