Ankle brachial pressure index

The Ankle Brachial Pressure Index (ABPI) is a measure of the reduction in arterial blood pressure of the legs and as such is used to detect evidence of blockages (peripheral vascular disease). It is calculated by dividing the highest systolic blood pressure in the arteries at the ankle and foot by the higher of the two systolic blood pressures in the arms.

Method

A Doppler probe is used, through a device called the Pulse Volume Recorder (some variances may apply depending on the physician), to monitor the pulse while a sphygmomanometer (blood pressure cuff) is inflated above the artery. The cuff is deflated and the pressure at which the pulse returns gives the systolic pulse pressure reading for the given artery.

The higher of the left and right arm brachial artery pressure is used in the assessment. The pressures in each foot's posterior tibial artery and dorsalis pedis artery are measured with the higher of the two values used as the ABPI for that leg.cite journal |author=Vowden P, Vowden K |title=Doppler assessment and ABPI: Interpretation in the management of leg ulceration |journal=Worldwide Wounds |month=March |year=2001 |url=http://www.worldwidewounds.com/2001/march/Vowden/Doppler-assessment-and-ABPI.html - describes ABPI procedure, interpretation of results, and notes the somewhat arbitrary selection of "ABPI of 0.8 has become the accepted endpoint for high compression therapy, the trigger for referral for a vascular surgical opinion and the defining upper marker for an ulcer of mixed aetiology"]

:$ABPI\_\{Leg\}\; =\; frac\; \{\; P\_\{Leg\}\; \}\{\; P\_\{Arm\}\; \}$::Where P_Leg is the highest systolic pressure of dorsalis pedis and posterior tibial arteries::and P_Arm is the highest of the left and right arm brachial artery pulse pressure

Interpretation of results

In a normal subject the pressure at the ankle pulses 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). The ABPI is the ratio of the highest ankle to brachial artery pressure and an ABPI of greater than 0.9 is considered normal.

However, a value greater than 1.3 is considered abnormal, and suggests calcification of the walls of the arteries and noncompressible vessels, reflecting severe peripheral vascular disease.

Provided that there are no other significant conditions affecting the arteries of the leg, the following ABPI ratios can be used to predict the severity of PAD as well as assess the nature and best management of various types of leg ulcers:

Predictor of atherosclerosis mortality

Studies in 2006 suggests that an abnormal ABPI may be an independent predictor of mortality, as it reflects the burden of atherosclerosis.cite journal |author=Feringa HH, Bax JJ, van Waning VH, "et al" |title=The long-term prognostic value of the resting and postexercise ankle-brachial index |journal=Arch. Intern. Med. |volume=166 |issue=5 |pages=529–35 |year=2006 |month=March |pmid=16534039 |doi=10.1001/archinte.166.5.529 |url=] cite journal |author=Wild SH, Byrne CD, Smith FB, Lee AJ, Fowkes FG |title=Low ankle-brachial pressure index predicts increased risk of cardiovascular disease independent of the metabolic syndrome and conventional cardiovascular risk factors in the Edinburgh Artery Study |journal=Diabetes Care |volume=29 |issue=3 |pages=637–42 |year=2006 |month=March |pmid=16505519 |doi= |url=http://care.diabetesjournals.org/cgi/content/full/29/3/637]

ee also

*Peripheral vascular disease
*Peripheral vascular examination

References