Ankle Brachial Index
The ankle-brachial index (ABI) is a non-invasive tool for the assessment of vascular status. It consists of the ratio between the systolic blood pressure of the lower extremity, specifically the ankle, and the upper extremity. This ratio compares the resistance of the blood vessels, with one of the primary factors being the diameter of the vessels. This diameter is narrowed either from internal factors (plaque, intimal tear) or external factors such as compression by soft tissues.
Anatomy and Physiology
Earn CME credit as you help guide your clinical decisions.
The ankle-brachial index is measured using three arteries: the brachial artery for the upper extremity and the dorsalis pedis and or posterior tibial artery at the ankle.
Dorsalis pedis artery: The dorsalis pedis artery arises primarily from the anterior tibial artery and starts higher in the anterior compartment of the leg between the tibialis anterior and extensor hallucis longus (EHL). In most cases, the vessel above the ankle passes under the EHL to reside between EHL and the extensor digitorum longus (EDL). Other variations include later crossing sites either at the ankle or distal. Ranging the great toe can help identify the EHL for guidance about finding the dorsalis pedis pulse, especially in a patient with faint pulses. Additionally, the artery can be traced proximally from the first dorsal metatarsal artery extending into the great toe webspace or distally from the supplying artery.
Posterior tibial artery: The posterior tibial artery passes posterior to medial malleolus at the ankle between the tibialis posterior and flexor digitorum longus tendons.
Brachial artery: The brachial artery is palpable medial to biceps tendon in the antecubital fossa.
The ankle-brachial index has uses in screening, diagnosis, treatment, guidance, and prognosis. See the clinical relevance section for further information.
Deep vein thrombosis (DVT): The American Heart Association guidelines recommend avoiding compression of the extremity with known or suspected DVT due to concern for breaking and embolizing a thrombus.
Severe leg pain: Performing ABI measurement requires significant pressure to be applied to the leg. Whether related to leg ischemia, fracture/swelling, or wounds, this procedure can cause significant pain for the patient.
Compression device: Blood pressure cuff (sphygmomanometer). The appropriate size is a “width at least 40% of the limb circumference”.
Pulse detection device: doppler or stethoscope
Oscillometer: Use regular cuff for calf diameter less than 35cm and large cuff for over 35 cm. Take note; there are limits to using an automated device as the device has difficulty reading low blood pressures. Also, there is a concern the value is less accurate as the device detects the point of maximum impulse, which is more consistent with the mean arterial pressure.
An ankle-brachial index is a tool that can be used by many medical providers, including physicians, nurse practitioners/physician extenders, and nurses. One study showed in the general practice setting that nurses were the highest utilizer of this diagnostic tool.
This tool plays a valuable clinical role across many specialties, including:
- Primary care
- Vascular surgery
- Plastic surgery
- Orthopedic surgery
- Emergency medicine
- Wound care
- Rest patient. Different guidelines suggest the patient should have a specific rest period before assessing ABI, ranging from 10 to 30 minutes.
- Avoid nicotine. Studies show that smoking selectively affects the ankle but not the brachial systolic pressure resulting in artificially elevated values.
- Supine position. There is a documented increase in the ABI value by approximately 0.3 with sitting instead of the supine position.
- Quiet space: Avoid underestimating systolic pressure due to difficulty with the audibility of systolic sounds.
- Supported limbs: Reduces motion, and the patient is more likely to be relaxed.
- Cover wounds: Reduce the risk of contaminating wounds or equipment.
Technique or Treatment
Cuff Application Sites
Ankle: Above level of malleoli
For the manual method, apply a stethoscope or doppler to sites of brachial, dorsalis pedis, and posterior arteries as described in the anatomy section.
Inflate cuff 20 to 30mm Hg above the last heard sound, then slowly release pressure. The first heart sound is the pressure that should be recorded as the systolic pressure at that site.
Order: The AHA suggests performing the order of measurements as follows: First arm, same side ankle (both PT and DP), opposite leg, and opposite arm.
If there is a 10m Hg difference in the arm, it is recommended to recheck the initial arm to address the “white coat effect” of blood pressure measurement.
Calculation: The calculation is the ratio of the systolic pressure at the ankle over the systolic pressure at the arm. The appropriate value to use for the systolic ankle pressure has been a subject of debate. The most commonly used is the highest value of the ankle values. One study looked at alternative methods, including averaging values, dorsalis pedis only, posterior tibial only, and lowest value. This study suggests all have prognostic value. The difference is the “threshold” for abnormal values and varies slightly (0.87 to 0.95).
Studies demonstrate value variability based on experience and the same patient on different days and between offices/ specialties. One study suggests repeatability is the best using high ankle/highest arm. A suggested minimal significant difference between recorded ABI values is 0.15. Also, consider training. About one-third of providers who reported performing procedures demonstrated “correct” use per study.
- Normal: 0.9 to 1.4 
- High: greater than 1.4, typically indicative of vessel stiffening
- Low: less than 0.9 - narrowing of vessels
- Non-measurable: Unable to occlude blood vessel at 300mmHg of pressure application.
Special considerations for the pediatric population: In early infancy, ABI values average lower values than adults (58% below 0.9); however, ABI reaches normal values after 12 months. Studies support use in the pediatric population to reduce radiation exposure to more invasive tests with good reliability.
In general, the variation in measurements is less in young, healthy individuals.
Peripheral Arterial Disease (PAD)
The AHA suggests clinicians consider evaluating patients who smoke over 50, patients with diabetes, or over age 70 for peripheral arterial disease. In one screening study involving asymptomatic 50 years old patients, 20% were identified to have PAD. One study suggested that providers in the general medical community use the information to initiate cardiovascular risk reduction interventions. Peripheral arterial disease results suggest that ABI is better at detecting greater than 50% stenosis and proximal lesions better than distal lesions. Both low and high ABI values have an independent association with cardiovascular events. Also, abnormal ABI correlates with the risk of chronic kidney disease.
Several studies have used ABI for predicting additional risk due to low invasiveness and relative ease of performance to the test:
- Studies show correlations of ABI less than 0.9 with increased risk for PVD, MI, renal disease, HTN.
- Lower ABI also correlates with a high carotid plaque score.
- There is a higher risk of recurrent stroke (HR 1.7) and vascular evens/ death (2.22).
Traditionally ABI was thought to have a role in wound healing. One study evaluating heel wounds showed ABI was not reliable for heel pressure sores. Another study suggested that ABI is predictive of further need for amputation in diabetic wounds, but not in wound healing itself. An ABI under 0.5 increased the likelihood of amputation by 40%.
ABI is useful in the evaluation of critical limb ischemia. One management protocol suggests that a normal or inability to perform ABI warrants more invasive evaluation in the setting of critical limb ischemia. If there is an abnormality in the ABI, promote surveillance if no tissue loss/gangrene and revascularization in the case of tissue loss or gangrene.
After revascularization, there is a correlation between change in ABI value and ulcer wound healing (ABI delta greater than or equal to 0.23, HR 1.87 for wound healing).
Surgical healing prediction:
- ABI has been reported useful in total knee arthroplasty procedures. Lower ABI (less than 0.7) shows an increased chance of total knee arthroplasty failure.
- Patients with lower ABI more likely to have delayed healing when undergoing heart surgery.
- Evaluation of flap placement in foot/ankle trauma 0.9 to 1.2.
ABI has a role in the initial evaluation and management of blunt trauma and knee dislocations as a method of assessing for vascular injury. The widely used criteria is an ABI less than 0.9 as an abnormal value for knee dislocations. For low values (less than 0.9), further evaluation is warranted, including methods such as ultrasound, MRI, CT, and angiography. For values greater than 0.9, serial monitoring is the recommendation (48 to 72 hours). ABI can be correlated with physical exam monitoring, exhibiting good reliability (sensitivity ABI 49.5 % vs. ABI + exam 100%); however, if the two do not agree, further evaluation may be warranted.
Occult PAD in 20% of patients referred to orthopedic surgery for leg pain in patients over 50 years old.
One study found that the value of the ABI was not necessarily predictive of current functional status. Still, there is a prognostic value with a greater likelihood to have decreased functional status over time with lower baseline values.
Also, there are conditions associated with claudication unrelated to arterial disease. These conditions include functional popliteal syndrome and exercise-induced leg pain. In these individuals, muscle hypertrophy of the soft tissues can lead to vessel occlusion, which is important to note/consider when evaluating a patient for exertional compartment syndrome as these patients would not be expected to improve after fasciotomy.
Enhancing Healthcare Team Outcomes
The use of ABI for patient care requires knowledgeable individuals who are trained to do so. Training is necessary for the full team of providers from the clinicians, mid-level practitioners, nurses, and ultrasonographers. One randomized control trial evaluated the optimal way to teach the ABI procedure to medical students. The study compared didactic versus experiential learning. Results showed that experiential learning significantly improved the ability to perform the test correctly accurately. [Level 2: small randomized control trial]
Performance, application, and interpretation of ABI require an interprofessional team approach, including physicians, specialists, specialty-trained nurses, and ultrasound techs, all collaborating across disciplines to achieve optimal patient results. [Level 5]
Nursing, Allied Health, and Interprofessional Team Interventions
Performing an ABI assessment does take time; the estimated time is 15 minutes. As such, it will often fall on the duty of the nurse or ultrasound technician to perform the test to assist in clinical flow.
Wound Care Providers
- Avoid compression dressing with ABI 0.5 and refer to the specialist/supervising provider
- Values 0.5 to 0.8 apply low compression only
- Greater than 0.8 may apply high compression
Nursing, Allied Health, and Interprofessional Team Monitoring
The key to monitoring is establishing protocols for ABI.
An appropriate protocol for nursing monitoring should address the following three questions: Which values should I use? What periods to perform the test? When should I notify someone? Routine trauma monitoring for injuries such as knee dislocations has been suggested at intervals of every 2 hours. This approach should consist of clinical assessment and determination if ABI is necessary at the same time with every clinical evaluation. Other options include ABI at specific periods (i.e., a clinical exam every 2 hours and ABI every 4 hours) or only if there is a change in the clinical exam.
Yamada T,Gloviczki P,Bower TC,Naessens JM,Carmichael SW, Variations of the arterial anatomy of the foot. American journal of surgery. 1993 Aug; [PubMed PMID: 8352403]
Azam M,Shaw PM, Anatomy, Bony Pelvis and Lower Limb, Tibial Artery 2019 Jan; [PubMed PMID: 30422466]
Bains KNS,Lappin SL, Anatomy, Shoulder and Upper Limb, Elbow Cubital Fossa 2019 Jan; [PubMed PMID: 29083694]
Aboyans V,Criqui MH,Abraham P,Allison MA,Creager MA,Diehm C,Fowkes FG,Hiatt WR,Jönsson B,Lacroix P,Marin B,McDermott MM,Norgren L,Pande RL,Preux PM,Stoffers HE,Treat-Jacobson D, Measurement and interpretation of the ankle-brachial index: a scientific statement from the American Heart Association. Circulation. 2012 Dec 11; [PubMed PMID: 23159553]
MacDougall AM,Tandon V,Wilson MP,Wilson TW, Oscillometric measurement of ankle-brachial index. The Canadian journal of cardiology. 2008 Jan; [PubMed PMID: 18209769]
Gibb MA,Edwards HE,Gardner GE, Scoping study into wound management nurse practitioner models of practice. Australian health review : a publication of the Australian Hospital Association. 2015 Apr; [PubMed PMID: 25493448]Level 2 (mid-level) evidence
Davies JH,Kenkre J,Williams EM, Current utility of the ankle-brachial index (ABI) in general practice: implications for its use in cardiovascular disease screening. BMC family practice. 2014 Apr 17; [PubMed PMID: 24742018]
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; [PubMed PMID: 31045795]Level 1 (high-level) evidence
Böhrer H,Schick M,Schönstedt R,Bach A, Marked decrease in arterial oxygen tension associated with continuous intravenous nifedipine administration. Anaesthesia. 1991 Oct; [PubMed PMID: 1952002]
Le Bivic L,Magne J,Guy-Moyat B,Wojtyna H,Lacroix P,Blossier JD,Le Guyader A,Desormais I,Aboyans V, The intrinsic prognostic value of the ankle-brachial index is independent from its mode of calculation. Vascular medicine (London, England). 2019 Feb; [PubMed PMID: 30426857]
Nicolaï SP,Kruidenier LM,Rouwet EV,Bartelink ML,Prins MH,Teijink JA, Ankle brachial index measurement in primary care: are we doing it right? The British journal of general practice : the journal of the Royal College of General Practitioners. 2009 Jun; [PubMed PMID: 19520025]
Atsma F,Bartelink ML,Grobbee DE,van der Schouw YT, Best reproducibility of the ankle-arm index was calculated using Doppler and dividing highest ankle pressure by highest arm pressure. Journal of clinical epidemiology. 2005 Dec; [PubMed PMID: 16291473]
Rac-Albu M,Iliuta L,Guberna SM,Sinescu C, The role of ankle-brachial index for predicting peripheral arterial disease. Maedica. 2014 Sep; [PubMed PMID: 25705296]
Criqui MH,McClelland RL,McDermott MM,Allison MA,Blumenthal RS,Aboyans V,Ix JH,Burke GL,Liu K,Shea S, The ankle-brachial index and incident cardiovascular events in the MESA (Multi-Ethnic Study of Atherosclerosis). Journal of the American College of Cardiology. 2010 Oct 26; [PubMed PMID: 20951328]
Katz S,Globerman A,Avitzour M,Dolfin T, The ankle-brachial index in normal neonates and infants is significantly lower than in older children and adults. Journal of pediatric surgery. 1997 Feb; [PubMed PMID: 9044135]
Dean EM,Rogers K,Thacker MM,Kruse RW, Inter-observer reliability of the ankle-brachial index in a pediatric setting. Delaware medical journal. 2015 Mar; [PubMed PMID: 25985540]
Bernstein J,Esterhai JL,Staska M,Reinhardt S,Mitchell ME, The prevalence of occult peripheral arterial disease among patients referred for orthopedic evaluation of leg pain. Vascular medicine (London, England). 2008 Aug; [PubMed PMID: 18687760]
Semba M,Inui N, Inhibition of 12-O-tetradecanoylphorbol-13-acetate-enhanced transformation in vitro by inhibitors of phospholipid metabolism. Toxicology letters. 1990 Mar; [PubMed PMID: 2315953]Level 3 (low-level) evidence
Sonoda H,Nakamura K,Tamakoshi A, Ankle-Brachial Index is a Predictor of Future Incident Chronic Kidney Disease in a General Japanese Population. Journal of atherosclerosis and thrombosis. 2019 Apr 30; [PubMed PMID: 31061261]
Królczyk J,Piotrowicz K,Chudek J,Puzianowska-Kuźnicka M,Mossakowska M,Szybalska A,Grodzicki T,Skalska A,Gąsowski J, Clinical examination of peripheral arterial disease and ankle-brachial index in a nationwide cohort of older subjects: practical implications. Aging clinical and experimental research. 2018 Dec 17; [PubMed PMID: 30560433]
Alizargar J,Bai CH, Value of the arterial stiffness index and ankle brachial index in subclinical atherosclerosis screening in healthy community-dwelling individuals. BMC public health. 2019 Jan 15; [PubMed PMID: 30646893]
Hong JB,Leonards CO,Endres M,Siegerink B,Liman TG, Ankle-Brachial Index and Recurrent Stroke Risk: Meta-Analysis. Stroke. 2016 Feb; [PubMed PMID: 26658450]Level 1 (high-level) evidence
Crowell A,Meyr AJ, Accuracy of the Ankle-brachial Index in the Assessment of Arterial Perfusion of Heel Pressure Injuries. Wounds : a compendium of clinical research and practice. 2017 Feb; [PubMed PMID: 28272012]
Wang Z,Hasan R,Firwana B,Elraiyah T,Tsapas A,Prokop L,Mills JL Sr,Murad MH, A systematic review and meta-analysis of tests to predict wound healing in diabetic foot. Journal of vascular surgery. 2016 Feb; [PubMed PMID: 26804365]Level 1 (high-level) evidence
Brownrigg JR,Hinchliffe RJ,Apelqvist J,Boyko EJ,Fitridge R,Mills JL,Reekers J,Shearman CP,Zierler RE,Schaper NC, Performance of prognostic markers in the prediction of wound healing or amputation among patients with foot ulcers in diabetes: a systematic review. Diabetes/metabolism research and reviews. 2016 Jan; [PubMed PMID: 26342129]Level 1 (high-level) evidence
Shishehbor MH,White CJ,Gray BH,Menard MT,Lookstein R,Rosenfield K,Jaff MR, Critical Limb Ischemia: An Expert Statement. Journal of the American College of Cardiology. 2016 Nov 1; [PubMed PMID: 27692726]
Reed GW,Young L,Bagh I,Maier M,Shishehbor MH, Hemodynamic Assessment Before and After Endovascular Therapy for Critical Limb Ischemia and Association With Clinical Outcomes. JACC. Cardiovascular interventions. 2017 Dec 11; [PubMed PMID: 29153498]Level 2 (mid-level) evidence
Gad BV,Langfitt MK,Robbins CE,Talmo CT,Bono OJ,Bono JV, Factors Influencing Survivorship in Vasculopathic Patients. The journal of knee surgery. 2019 May 23; [PubMed PMID: 31121629]
Boffa GM,Faggian G,Buja G,Livi U,Bortolotti U,Stellin G,Razzolini R,Stritoni P,Mazzucco A,Thiene G, Coronary artery spasm in heart transplant recipients. The Journal of heart transplantation. 1989 Mar-Apr; [PubMed PMID: 2651619]
Tsai J,Liao HT,Wang PF,Chen CT,Lin CH, Increasing the success of reverse sural flap from proximal part of posterior calf for traumatic foot and ankle reconstruction: patient selection and surgical refinement. Microsurgery. 2013 Jul; [PubMed PMID: 23653382]
Ko SH,Bandyk DF, Interpretation and significance of ankle-brachial systolic pressure index. Seminars in vascular surgery. 2013 Jun-Sep; [PubMed PMID: 24636605]
Perron AD,Brady WJ,Sing RF, Orthopedic pitfalls in the ED: vascular injury associated with knee dislocation. The American journal of emergency medicine. 2001 Nov; [PubMed PMID: 11699005]
Mills WJ,Barei DP,McNair P, The value of the ankle-brachial index for diagnosing arterial injury after knee dislocation: a prospective study. The Journal of trauma. 2004 Jun; [PubMed PMID: 15211135]
Klineberg EO,Crites BM,Flinn WR,Archibald JD,Moorman CT 3rd, The role of arteriography in assessing popliteal artery injury in knee dislocations. The Journal of trauma. 2004 Apr; [PubMed PMID: 15187743]
Pardiwala DN,Rao NN,Anand K,Raut A, Knee Dislocations in Sports Injuries. Indian journal of orthopaedics. 2017 Sep-Oct; [PubMed PMID: 28966379]
Medina O,Arom GA,Yeranosian MG,Petrigliano FA,McAllister DR, Vascular and nerve injury after knee dislocation: a systematic review. Clinical orthopaedics and related research. 2014 Sep; [PubMed PMID: 24554457]Level 1 (high-level) evidence
Long B,April MD, What Is the Utility of Physical Examination, Ankle-Brachial Index, and Ultrasonography for the Diagnosis of Arterial Injury in Patients With Penetrating Extremity Trauma? Annals of emergency medicine. 2018 Apr; [PubMed PMID: 28967515]
deSouza IS,Benabbas R,McKee S,Zangbar B,Jain A,Paladino L,Boudourakis L,Sinert R, Accuracy of Physical Examination, Ankle-Brachial Index, and Ultrasonography in the Diagnosis of Arterial Injury in Patients With Penetrating Extremity Trauma: A Systematic Review and Meta-analysis. Academic emergency medicine : official journal of the Society for Academic Emergency Medicine. 2017 Aug; [PubMed PMID: 28493614]Level 1 (high-level) evidence
Wassel CL,Allison MA,Ix JH,Rifkin DE,Forbang NI,Denenberg JO,Criqui MH, Ankle-brachial index predicts change over time in functional status in the San Diego Population Study. Journal of vascular surgery. 2016 Sep; [PubMed PMID: 27139783]
Lane R,Nguyen T,Cuzzilla M,Oomens D,Mohabbat W,Hazelton S, Functional popliteal entrapment syndrome in the sportsperson. European journal of vascular and endovascular surgery : the official journal of the European Society for Vascular Surgery. 2012 Jan; [PubMed PMID: 22123206]
Taylor AJ,George KP, Ankle to brachial pressure index in normal subjects and trained cyclists with exercise-induced leg pain. Medicine and science in sports and exercise. 2001 Nov; [PubMed PMID: 11689736]
Donnou C,Chaudru S,Stivalet O,Paul E,Charasson M,Selli JM,Mauger C,Chapron A,Le Faucheur A,Jaquinandi V,Mahé G, How to become proficient in performance of the resting ankle-brachial index: Results of the first randomized controlled trial. Vascular medicine (London, England). 2018 Apr; [PubMed PMID: 29125051]Level 1 (high-level) evidence