The ankle-brachial index (ABI) is a simple, noninvasive test used to detect peripheral arterial disease (PAD) in the legs. It is the ratio of the ankle systolic blood pressure to the brachial systolic blood pressure. An ABI below 0.9 suggests significant narrowing of leg blood vessels. The ABI test involves measuring blood pressure in the ankle and arm with a blood pressure cuff and Doppler ultrasound. It provides information on the severity and extent of PAD.

1. Edited on June 25, 2016
Ankle-Brachial Index (ABI)
No financial relationships with commercial entities to disclose.
INTRODUCTION
The anklebrachial pressure index (ABPI) or anklebrachial index (ABI) is the ratio of the blood
pressure at the ankle to the higher of the brachial systolic blood pressures, which is the
best estimate of central systolic blood pressure.
It is a noninvasive, simple, valid, reliable and cot effective test wich is used to detect
lower extremity peripheral arterial disease (PAD), to measure the severity of
atherosclerosis in the legs but is also an independent predictor of mortality, as it
reflects the burden of atherosclerosis (5,16,17). However, alone it is not appropriate to
detect PAD (Peripheral Arterial Disease) because of possibility of false-negative
findings and does not give enough directions for revascularisation in term of
localization and characterization.
Lower extremity peripheral arterial disease (PAD) is a frequent, chronic, progressive
vascular disease and associated with significant morbidity and mortality (18).
Risk factors for PAD (2,12) are Advanced age (> 70yr). Smoking, past and present
diabetes, dyslipidemia, hypertension, hyperhomocysteinemia, chronic renal
insufficiency, family history of cardiovascular disease.
A lot of persons with APAD are undiagnosed because they are asymptomatic or
have atypical symptoms.
The ABI is also used as a prognostic marker for cardiovascular events, even in
the absence of symptoms of PAD.

2. INDICATIONS
1- Detection of PAD in all all patients who present with symptoms (pain that restrict
walking, ischemic pain at rest) and signs (reduced or absent pedal pulses on palpation,
skin that is cool, shiny, hairless or thin, thickening of the nails, abnormal capillary refill
time, pallor of distal extremities on elevation, leg pain and tissue ulceration or necrosis)
(12) suggestive of peripheral artery disease.
Measuring ABI to detect peripheral artery disease is a more sensitive and reliable test
compared to palpation of a pedal pulse, especially in patients who are obese or who
have significant oedema (12).
The ABI can provide also provide reliable information about the severity of the disease.
It can exclude other causes of calf pain : Spinal Stenosis, Venous, Raynaud
Phenomena and popliteal artery entrapment.
2- In the absence of revascularisation, ABI can be used as a Marker of PAD
Progression and clinical deterioration. It is not however correlate with clinical
amelioration (5).
3- Detection of PAD in asymptomatic patients
Patients with PAD are frequently asymptomatic. Most commonly, they have atypical leg
pain and a few present with typical claudication (12) .
There is currently insufficient evidence to recommend population screening for
peripheral artery disease using ABPI 3in 12. However, an ABI should be conducted on
patients presenting with risk factors to detect PAD, so that therapeutic interventions
known to diminish their increased risk of myocardial infarction (MI), stroke, and death
may be offered (2 in 2) .
Screening of PAD is recommended for patients presenting with risk factors (12):
- > 65-70 ans regardless of risk-factor status
- ⩾ 50 ans + 1 FRCV ( particularly for tabaccos and diabetes)

3. - ⩾ 40 ans + diabètes + 1 other Risk Factor.
- All people with a Framingham risk score (age, Total CT, cigarette smoking, HDL CT, Systolic
blood pressure) > 10%
- Other atherosclerosis location ( coronary a. , carotids, Renal a.…).
- Absence of Tibial posterior pulse.
4- ABI prior to surgery: Before leg or foot surgery (12) to exclude PAD that may result
in vascular complications and before wound debridement to determine adequate
arterial blood flow (1).
5- ABI prior to compression therapy for patients with venous disease or ulceration, to
exclude peripheral artery disease wich will induce complications.
- If the ABI is less than 0.8, le degré de compression devrait être réduit et la
compression contre indiquée si l’ABI is less than 0,5 (1).
6- ABPI can be used as a marker of cardiovascular risk both in the general
population free of clinical CVD and in patients with established CVD (5,12).
7- ABI is useful in the setting of lower extremity traumatism with suspiction of
arterial injury (10) :
An ABI less than 0.90, require CTA or Angiography or operative exploration in an
unstable patient.
An ABI greater than 0.90 decreases the likelihood of an arterial injury: F/U by serial ABI
vs Delayed Vascular Imaging.
Contre-Indications
1- Patients who are unable to remain supine for the duration of the examination.
2- Treadmill testing may be inappropriate for people who are obese, need assistance
to walk or limited by comorbidities such as Aortic aneurysm.
3- ABI measurement is also contraindicated in a patient in whom the use of an
occlusive sphygmomanometer cuff may worsen the extremity injury.

4. 4- Bilateral subclavian stenosis.
5- The use of the cuff over a distal bypass should be avoided (risk of bypass
thrombosis).
ABI PROCEDURE With the Doppler Method
Courtesy of Wikipedia, the free encyclopedia (Anklebrachial pressure index).
See also Images at : http://emedicine.medscape.com/article/1839449-overview#a3
* An ABI measurement can usually be performed in less than 10 minutes.
Standardisation of the technique used to measure the ABI was juged necessary because the
result may vary and hence the estimate prevalence of PAD (5).
* Before performing ABI, it is important to obtain a thorough history, symptoms and
clinical signs.
* Material:
Hand-held portable Doppler device with a frequency of 8 – 10 MHz; although 5 MHz
probes may be better for patients with significant ankle oedema.
Appropriately sized sphygmomanometer (blood pressure cuff) for the upper and lower
extremities. The cuff width should be, at a minimum, 40 % greater than the diameter of
the extremity (5).
And Ultrasonographic gel.

5. * Patient in supine position, with the arms and legs at the same level as the heart,
relaxed for a minimum of 10 minutes before measurement.
The patient should not smoke at least 2 hours before the ABI measurement.
Ideally, the ABI must be performed in a quiet, warm environment to prevent
vasconstriction of the arteries. If the room is cold, warm the patient with blankets.
The patient should stay still during the pressure measurement. If the patient is unable
to not move his/her limbs (eg, tremor), other methods should be considered.
The ABI procedure may cause discomfort for patients with lower leg pain or cellulitis. If
ulcers or wounds are present on the ankle then a protective barrier, e.g. a plastic wrap,
should
be placed over the affected area before the cuff is applied.
* The ankle cuff should go on the leg between the malleolus and the calf. Enough room
should be left below both cuffs (approximately five centimetres above the medial
malleolus and approximately two to three centimetres above the antecubital fossa for
the brachial pressure).
Make sure that cuff completely encircles lower extremity and wrapped without wrinkles
and placed securely to prevent slipping and movement during the test.
* Artery is palpated by hand before Doppler device is used. Place small amount of
ultrasound transmission gel at landmark where artery was located. Identify artery with
Doppler device. Upon application of Doppler probe, arterial pulsations should be
clearly audible before cuff is inflated. If they are not, reposition probe until appropriate
sound is obtained. Typically, Doppler probe must be positioned at 45- 60 degrees, not
at 90 degrees.
* The blood pressure cuff is inflated proximal to the artery in question. The inflation continues
20- 30mm above the pressure at wich the brachial pulse becomes inaudible by Doppler. The
blood pressure cuff is then slowly deflated (2–3 mm Hg per heartbeat). When the artery's
pulse is redetected through the Doppler probe, the pressure in the cuff at that moment indicates
the systolic pressure of that artery.
The maximum inflation is 300 mm Hg. If the flow is still detected, the cuff should be
deflated rapidly to avoid pain.

6. * The higher systolic reading of the left and right arm brachial artery is generally used
in the assessment.
* The pressures in each foot's posterior tibial artery and dorsalis pedis artery are
measured. Obtain the anterior tibial and posterior tibial systolic pressures of the
extremity in question, and select the higher of the 2 values as the ankle pressure
measurement. The posterior tibial pulse is best appreciated just dorsal and inferior to
the medial malleolus. The dorsalis pedis pulse is best appreciated on the dorsum of the
foot between the proximal section of the first and second metatarsals, usually above
the navicular bone.
The measurement of the systolic pressure of the dorsalis pedis arteries may not be
possible in all patients as 12% of the general population has a congenital absence of
the dorsalis pedis pulse
* Some (11) advocate to repeat each measure 2-3 times, especially for people who
have little experience with the handling of Doppler probes and measuring the ABI.
However, the Scientific Statement of the AHA (5) states to wait one minute at least
before reinflating the cuff because the accuracy of measurement of ABI depend on the
number of measurements.
* ABI for each leg is obtained by dividing the highest ankle systolic blood pressure
of dorsalis pedis or posterior tibial artery by the highest of the left and right arm
brachial systolic blood pressure.
The ABI must be calculated separately for each leg.
ABI =
Higher of either the dorsalis pedis or posterior tibial pressures
Higher of the brachial pressures
* Usually, the systolic pressure is first measured at the arm and ankle and
subsequently at ankles. However, the AHA recommends (5), for standardization
purpose, that the measurement sequence must be looped in clockwise or in

7. counterclockwise starting with an arm and ending by it ( e.g. Right Arm- Right Ankle-
Left Ankle- Left Arm- Right Arm) to reduce the effect of "white coat" on the first
measure. The average of the 2 measurements is to retain unless the difference
between the two (for the 1st arm) exceeds 10mmHg which case the 2nd measure is
only retained.
* For any situation, when the ABI is initially determined to be between 0.80 and 1.00, it
is reasonable to repeat the measurement. The measurements should be repeated
then in the reverse order of the first sequence starting with opposite arm (5).
* Postexercise ABI
This test is indicated for borderline ABI.
It usually lasts 5 to 15 minutes, sometimes less (15), depending on the importance of
any discomfort but for some (8), patient should not exercise for longer than 5 minutes.
Anyway, the patient must exercice only to the point of claudication.
Ankle pressures are then measured immediately after the exercise and at 3minute
intervals until the pressures return to preexercise levels (8).
The walk is usually undertaken with a small incline (10%). The speed is usually from
3km per H. and can vary from 2 to 5 km / h. This elevation and speed simulate the
circulatory response induced by normal ambulation (8). It is important that the same
speed and elevation are consistent for each patient on followup (8).
Treadmill testing may be inappropriate for people who need assistance to walk or who are
limited by other medical conditions.
In addition to evaluating the effect of exercise on the ankle level blood pressure,
treadmill exercise testing also offers a means to characterize the functional impact of
claudication symptoms. The distance walked before the onset of symptoms (painfree
walking distance) and the maximum distance that can be walked can be measured
using a standardized speed and grade on the treadmill. These values establish a
baseline for comparison, allowing objective assessment of change in walking
performance with medical therapy or interventions.

8. An alternative method simple method wich doesn’t need special equipment, the active
pedal plantar flexion technique, has been assessed for office purpose. It consists of
heel raising while standing. Excellent correlation of this method have been obtained in
correlation with treadmill test (5).
* Toe -Brachial Pressure Index (8, 13)
Compares the toe pressure to the arm pressure and is derived by dividing the toe
systolic pressure by the higher of the right and left arm’s systolic pressures.
Continuous wave Dopplers are not reliable to measure toe pressures due to the small
size of digital arteries and vasospasms if toes are cold.
Toe pressures, when indicated ( see below) are commonly measured in the vascular
laboratory by vascular technicians using standard laboratory photoplethysmography
(PPG) equipment. Toe pressures can be also measured by clinicians using a portable
PPG if the clinician is educated/skilled in the use of the equipment and it is available.
RESULTS INTERPRETATION.
*
ABI------------------------------------------------------- Perfusion Status
> 1.3 -----------------------------------------------Elevated, incompressible vessels
> 1.0 -----------------------------------------------------------Normal
0.99- 0.91 ------------------------------------------------------ Borderline values
< 0.9----------------------------------------------------- PAD= Lower extremity arterial disease

9. - An ABI <0.9 suggests significant narrowing of one or more blood vessels in the leg.
- The majority of patients with claudication have ABIs ranging from 0.3 to 0.9.
- IPS entre 0.7 et 0.9 : Low intensity well compensated arterial disease. Stenosis> 50%
at this stage. Cardiovascular risk would be the same in a limping and in an
asymptomatic patient with IPS <0.9 (6).
- IPS entre 0.5 et 0.7 : Moderately Compensated Arterial Disease (6).
- Rest pain or severe occlusive disease typically occurs with an ABI <0.5. This is a
critical ischemia. Patients have pretty high likelihood of developing ischemic leg pain,
to have ulcers that do not heal and large rate of death and amputation (6).
- ABIs <0.2 are associated with ischemic or gangrenous extremities.
- IPS > 1.3 : Médiacalcosis. The arteries are incompressible. It’s another
cardiovascular risk marker. Often in the setting of diabetes, advanced age and renal
failure. Referral to a vascular laboratory shoulds be regarded, as this result is
Clinically inconclusive.
* ABI in Case of Clinical Presentation of PAD
- The ABI test approaches 95% accuracy in detecting PAD. However, a normal ABI
value does not absolutely rule out the possibility of PAD. So, when the ABI is >0.90 but
there is clinical suspicion of PAD, postexercise ABI or other noninvasive tests, which
may include imaging, should be considered (5).
* Postexercise ABI
An ABI of 0.91-0.99 is considered borderline. The patient may be asymptomatic at rest
but may experience symptoms when ambulating. When there is an additional reasons
to suspect peripheral artery disease, e.g. symptoms and risk factors, further
investigations, such Treadmill testing wich rises the sensitivity of the ABI to detect PAD,
may be recommended (10).
In Healthy patients: There is Mild decrease in the ABI (average of 5%) when measured
immediately after exercise cessation. The ankle pressure then increases rapidly and reaches the

10. pre-exercise values within 1 to 2 minutes. A recovery of at least 90% of the ABI to baseline
value within the first 3 minutes after exercise was found to have a high specificity to rule out
PAD (5).
In the case of even moderate occlusive PAD (typically in the proximal vessels), the ankle
pressure decreases of more than 30 mm Hg during exercice or a postexercise, ABI
decreases of >20% and the recovery time to the pre-exercise value after exercise cessation is
prolonged, proportional to the severity of PAD (5). Critical ischemia and vascular
claudication cause a dramatic decrease in the postexercise ankle pressure to 60
mmHg or less (8).
When postexercise ankle pressures initially decrease but return to baseline values
within 3- 5 minutes, a single segment lesion is most often indicated (8).
Reconstitution of distal vessels is significantly delayed when multisegmental disease
is present. In such cases, ankle pressures return to baseline values within 10-12
minutes dependent on the extent of collateral compensatory flow (8).
* ABI as a Marker of PAD Progression.
In the absence of revascularization, an ABI decrease is correlated with clinical
deterioration. Clinical improvement in terms of an increased walking distance, however,
is not correlated with an ABI increase
Clinical prognosis of the limb is better predicted by ankle pressure rather than the ABI.
An ankle pressure < 50 mm Hg has been reported to be associated with higher risk
for amputation (19).
* ABI is a Marker of Cardiovascular Risk and Atherosclerosis
Un ABI <0.90 or >1.40 are considered at increased risk of cardiovascular events and mortality
independently of the presence of symptoms of PAD and other cardiovascular risk factors (5).
The ABS improves Framingham score's ability to predict CV complications for patients
classified at "low risk or intermediate" (11).
* After performing a vascular examination, criteria that would indicate an increased
urgency of referral to a vascular surgeon include:
- An ABPI < 0.5

11. - Known peripheral artery disease presenting with a new ulcer or area of necrotic
tissue
- An ulcer that is not responding to treatment
- Intermittent claudication when walking for less than 200 m
- Young and otherwise healthy patients with claudication to rule-out rare causes,
e.g. popliteal artery entrapment
* Discussion with a vascular surgeon should also be considered when:
There is doubt concerning the patient’s diagnosis
There is uncertainty around the significance of an ABPI result
There is doubt about the need for treatment or what treatment options are available
METHOD LIMITATIONS
* ABPI is known to be unreliable on patients with arterial calcification (hardening of the
arteries) which results in less or incompressible arteries, as the stiff arteries produce
falsely elevated ankle pressure, giving false negatives. This is often found in patients
with diabetes mellitus, renal failure, rheumatoid arthritis or heavy smokers. Vascular
Calcifications doesn’t mean that there is underlying stenotic or occlusion lesion but
stenosis is frequently present and can’t be excluded by normal ABI but ABI values
above 1.3 should be investigated further. This may be obvious (ABI above 1.3) but
when the arteries are partially calcified it can simulate normal ABI but actually the
values are decreased . So, Toe pressures/ brachial index are recommended if the
ABI is > 1.3 because the digital arteries are generally less affected by
calcifications than the ankle arteries and Comparison with pedal artery velocity
waveform shape is prudent.
* False negative can be induced by large collateral circulation supplying downstream
arterial stenosis or occlusion. ABI can be normal while patient experience claudication
with activity. Further vascular evaluation is then needed (Treadmill test, Doppler).
* Resting ABI is insensitive to mild PAD. Treadmill tests is then indicated to increase
ABI sensitivity, but this is unsuitable for patients who are obese or have comorbidities
such as Aortic aneurysm.
* ABI correlates poorly with result after revascularisation so it is not reliable method
alone of surveillance.

12. * The exact location of the stenosis or occlusion cannot be determined by ABI alone.
* Lack of complete protocol standardisation reduces intraobserver reliability.
* Skilled operators are required for consistent, accurate results. An incorrectly
performed test may lead to a false negative or a false positive result and thereby delay
the diagnosis or prompt unnecessary further testing.
* When performed in an accredited lab, the ABI is a fast, accurate, and painless exam,
however these issues have rendered ABI unpopular in primary care offices and
symptomatic patients are often referred to specialty clinics (13) due to the perceived
difficulties.
CONCLUSION
ABI It is a noninvasive, cost effective and reliable test used to detect lower extremity
peripheral arterial disease (PAD), to measure the severity of atherosclerosis in the legs
but is also an independent predictor of cardiovascular events and mortality. However,
alone this test is not appropriate to investigate PAD because of possibility of false-
negative findings and does not give enough directions for revascularisation in term of
localization and characterization.
Few contreIndications must be considered, especially in the setting of distal bypass.
Standardization of the technic is recommended as in AHA Scientific Statement (5).
Because of several limitations, Complementary tests are sometimes necessary to
detect PAD as Post Exercice ABI ( if borderline ABI values), Toe-Brachial Pression
Index (for incompressible arteries) and Doppler in inconclusive pressions Tests.
EXTERNAL LINK:
1- Stanford Medicine 25: Ankle Brachial Index
https://www.youtube.com/watch?v=KnJDrmfIXGw
2-Ankle--Brachial Index for Assessment of Peripheral Arterial Disease. SECEI ESCS.
https://www.youtube.com/watch?v=8q4Cz-a6zkQ

13. 3- Victor Aboyans et co, Measurement and Interpretation of the Ankle-Brachial Index. A
Scientific Statement From the American Heart Association.
http://circ.ahajournals.org/content/126/24/2890.full
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