What is Ankle Brachial Blood Pressure Index (ABI)?
ABI (Ankle Brachial Blood Pressure Index) is a measurement that compares the blood pressure ratio of the arteries at the ankle with the blood pressure of the arteries at the arm (brachial artery) on the same side, i.e., right leg compared to right arm and left leg compared to left arm, to assess peripheral arterial stiffness or narrowing (Peripheral Arterial Disease).
Arterial stiffness usually begins with fat deposits on the arterial walls, causing inflammation, fibrosis, and calcium accumulation, or blood clots blocking the arteries. This thickens the arterial walls and narrows the arteries, resulting in insufficient blood supply to the legs and feet. It is commonly found in elderly patients with coronary artery disease and cerebrovascular disease because they have similar arterial abnormalities, and it is also common in diabetic patients.
Who should have the Ankle Brachial Blood Pressure Index (ABI) test?
Those who should undergo ABI testing are individuals at risk of arterial stiffness as follows:
- Age 50 years and older
- Those at risk or with conditions such as diabetes, obesity, coronary artery disease, cerebrovascular disease, high blood pressure, or high blood cholesterol
- Those with a family history of peripheral arterial disease or premature coronary artery disease and cerebrovascular disease
- Those with high levels of homocysteine or lipoprotein
- Heavy smokers or those who have smoked for more than 10 years, and those regularly exposed to secondhand smoke
- Bedridden patients
Procedure for Ankle Brachial Blood Pressure Index (ABI) measurement
The patient lies supine on a bed with a pillow. The doctor or specialist will use a blood pressure cuff wrapped around the ankles and arms on both sides, similar to a regular blood pressure measurement. The procedure is risk-free and painless.
Preparation before Ankle Brachial Blood Pressure Index (ABI) measurement
- You can undergo the test without fasting or stopping any medications
- Wear loose-fitting clothing on the day of the test
Interpretation and evaluation of Ankle Brachial Blood Pressure Index (ABI) results
The doctor will interpret the ABI results based on the ratio of ankle blood pressure to brachial blood pressure with the following criteria:
- > 0.9 indicates normal peripheral blood flow in the legs
- < or = 0.9 indicates peripheral blood flow problems in the legs; the lower the value, the more severe the arterial blockage, possibly at multiple sites
- < 0.6 indicates arterial narrowing with symptoms of leg ischemia
- < 0.3 indicates severe arterial narrowing in the legs requiring immediate treatment
- < 0.26 indicates leg pain due to arterial narrowing
- < 0.2 indicates tissue and muscle cell death in the leg area caused by ischemia from arterial narrowing
Arterial stiffness or narrowing in the legs often occurs in diabetic patients, and the disease usually progresses slowly and chronically, causing patients to neglect it. When arterial narrowing exceeds 70-80%, patients experience leg pain, slow-healing wounds, and black tissue necrosis on the feet, which may require amputation. In some cases, acute symptoms may require amputation of the affected limb, resulting in disability. Additionally, it increases the risk of death from myocardial infarction by 4-5 times and stroke by 2-3 times compared to those without peripheral arterial disease.
Therefore, diabetic patients or those at risk should have early blood flow assessment in the lower extremities to receive appropriate care, which helps prevent wounds and loss of toes, feet, and legs.