Ankle-Brachial Index (ABI):
Ratio of brachial systolic pressure and either or both of the posterior tibial or anterior tibial artery systolic pressure. Doppler is usually used to get a clearer sound of foot pressures
1) Record brachial systolic pressure
2) Record ankle systolic pressure
a) Inflate cuff above ankle and elevate until can hear no arterial pulse with Doppler over posterior tibial artery
b) When arterial sound returns systolic pressure
c) Repeat for dorsalis pedis artery
d) Use highest of PT & DP as ankle systolic pressure
e) Divide ankle by arm ABI
Normal = 1; >1 = ? calcified vessels; <1 arterial disease.
Can be problematic in disease with calcification of artery (Monckeberg’s sclerosis) giving a falsely high reading.
An ABI <0.9 is over 90% specific and sensitive in identifying angiographic arterial narrowing in symptomatic subjects