Ankle–brachial pressure index

Ankle–brachial pressure index
Measuring the ankle-brachial index
Synonyms	Ankle-brachial index
Purpose	Detection of peripheral artery disease

The ankle-brachial pressure index (ABPI) or ankle-brachial index (ABI) is the ratio of the

The patient must be placed supine, without the head or any extremities dangling over the edge of the table. Measurement of ankle blood pressures in a seated position will grossly overestimate the ABI (by approximately 0.3).^[citation needed]

A

${\displaystyle ABPI_{Leg}={\frac {P_{Leg}}{P_{Arm}}}}$

Where P_Leg is the systolic blood pressure of dorsalis pedis or posterior tibial arteries

and P_Arm is the highest of the left and right arm brachial systolic blood pressure

The ABPI test is a popular tool for the non-invasive assessment of

• ABPI is known to be unreliable on patients with arterial
  peripheral arterial disease (PAD) have diabetes^[7]), kidney failure or heavy smokers
  . ABPI values below 0.9 or above 1.3 should be investigated further regardless.
• Resting ABPI is insensitive to mild PAD.[8] Treadmill tests (6 minute) are sometimes used to increase ABPI sensitivity,^[9] but this is unsuitable for patients who are obese or have co-morbidities such as Aortic aneurysm, and increases assessment duration.
• Lack of protocol standardisation,^[10] which reduces intra-observer reliability.^[11]
• Skilled operators are required for consistent,
  accurate results.^[12]

When performed in an accredited diagnostic laboratory, 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. Technology is emerging that allows for the oscillometric calculation of ABI, in which simultaneous readings of blood pressure at the levels of the ankle and upper arm are taken using specially calibrated oscillometric machines.^{[citation needed]}

Interpretation of results

In a normal subject the pressure at the ankle is slightly higher than at the elbow (there is reflection of the pulse pressure from the vascular bed of the feet, whereas at the elbow the artery continues on some distance to the wrist).^{[citation needed]}

The ABPI is the ratio of the highest ankle to brachial artery pressure. An ABPI between and including 0.90 and 1.29 considered normal (free from significant

Studies in 2006 suggests that an abnormal ABPI may be an independent predictor of mortality, as it reflects the burden of atherosclerosis.^[16][17] It thus has potential for screening for coronary artery disease,^[18] although no evidence-based recommendations can be made about screening in low-risk patients because clinical trials are lacking.^[18] It is noteworthy that abnormal values of ABI predispose to development of the frailty syndrome.^[19]

See also

• Peripheral vascular examination
• Intermittent claudication

References