Diagnostic Studies: ABI Vascular Study

The 26 Review

  • What is the ABI vascular study The ankle brachial index, or ABI, is a simple test that compares the blood pressure in the lower and upper limbs
  • How The ABI is calculated by dividing the blood pressure in the arm by the blood pressure in the ankle
  • Why  This test aids in determining whether a patient may be suffering from PAD, as well as aid in identifying those who are at high risk of coronary artery disease
  • What is PAD Peripheral artery disease includes plaque build up in the arteries that bring blood to the legs. PAD can also increase the risk of heart attack or stroke
  • Symptoms  Reduced blood flow causes pain, numbness, and decreased healing within the legs and feet
  • Recommended For  Patients experiencing PAD symptoms and those with a history of PAD
26 Foot and Ankle ABI Vascular Studies

Let’s take a closer look…

As mentioned previously, the ankle brachial index test is a quick, simple way to check for PAD or peripheral artery disease. The ABI test compares the blood pressure measured at the arm with the blood pressure measured at the ankle. A low ABI number can indicate the blockage or narrowing of the arteries in the legs. Typically if a ratio is less than 0.9, it could mean that a patient has PAD in the blood vessels in their legs. The reduced blood flow can cause numbness and pain within patients. Low ABI may mean that a patient’s legs and feet are not getting as much blood as they need. However, an ABI test will not show exactly which blood vessels have become blocked or narrowed. Patients experiencing any PAD symptoms should consider speaking with a Podiatrist to determine if an ABI study is right for them. 

Why the ABI Vascular Study

The ankle brachial index test can be useful for people who have persistent leg pain while walking. This test has proven beneficial for people who have risk factors for PAD. Additionally, the test is important for those with slow healing or complete lack of healing to cuts or wounds in their feet and ankles.

Some common factors that can increase a patient’s risk of PAD can include; history of tobacco use, diabetes, high blood pressure, high cholesterol, high levels of lipids, abnormal pulses in the lower leg, and known plaque formations in other arteries. A healthcare provider might also use the ABI test to check the severity of a patient’s PAD. The healthcare provider might order this test annually to check if a patient’s condition is getting worse. If a patient has had surgery on the blood vessels within their legs, a doctor might want an ABI test to see how well blood is flowing into the leg. Lastly, sometimes doctors use the ABI test to assess a patient’s risk of future heart attack or stroke.

How: Steps of the ABI Vascular Study

In preparation for the ABI there is very little a patient is required to do. Patients can follow a normal diet on the day of the test. In conjunction with the previous statement, patients shouldn’t need to stop taking any medications prior to the procedure. It is suggested to wear loose, comfortable clothing to allow the technician to easily place the blood pressure cuffs on the arms and ankles. Patients will need to rest for at least 15 to 30 minutes prior to the procedure. As the procedure begins, patients will lie flat as the cuffs are placed just above the ankle. The technician will then place an ultrasound probe over the artery, so that they can listen to the blood flowing through the vessel. The blood pressure cuff will then inflate until the blood flow halts through the vessel. As the pressure is slowly released the doctor will wait for the systolic pressure, which is the pressure at which the blood flow is heard again. That is the part of the blood pressure measurement needed for the ABI. The healthcare professional will repeat this process on the remaining ankles and arms. 

Once the procedure has finished, the technician will calculate the ABI by dividing the blood pressure in the arms by the blood pressure found in the legs. The numerator is the highest systolic blood pressure found in the ankles, while the denominator is the highest systolic blood pressure found in the arms. Based on the number calculated, a patient’s ABI may show a few different things. If there is no blockage detected that number will fall between 1.0 to 1.4. An ABI number within this range suggests that there is no PAD detected, however if a patient has symptoms of PAD an exercise ABI test may be conducted. A borderline blockage will fall between 0.9 to 0.99, meaning this range is indicative of PAD. Patients in this number range may also be suggested an exercise ABI test. If an ABI number is less than 0.9 it indicates a diagnosis of PAD. Patients may have more testing done, such as an ultrasound or angiography, to view the arteries in the leg. As mentioned previously, there is an exercise ABI test. This entails an ABI test followed by an exercise session, which is then followed up by a final ABI test. This variance allows for a doctor to observe the change in the ABI number to determine whether a patient has PAD. If you’re currently experiencing pain or numbness in the legs, consider setting up an appointment with a Podiatrist to learn whether PAD may be affecting you. 

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