Ankle-Brachial Index(ABI) / Toe-Brachial Index(TBI) Test

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Ankle-Brachial Index (ABI) test

The ankle-brachial index (ABI) is used to diagnose P.A.D. The ABI compares blood pressure in your ankle to blood pressure in your arm. This test shows how well blood is flowing in your limbs.

ABI can show whether P.A.D. is affecting your limbs, but it won’t show which blood vessels are narrowed or blocked.

Peripheral Arterial Disease(P.A.D) occurs when the arteries in patient's legs become narrowed or clogged with fatty deposits, or plaque. The buildup of plaque causes the arteries to harden and narrow, which is called atherosclerosis. When leg arteries are hardened and clogged, blood flow to the legs and feet is reduced.

P.A.D. occurs most often in the arteries in the legs, but it also can affect other arteries that carry blood outside the heart. This includes arteries that go to the aorta, the brain, the arms, the kidneys and the stomach. When arteries inside the heart are hardened or narrowed, it is called coronary artery disease or cardiovascular disease.

The ABI test is done by measuring blood pressure at the ankle and in the arm while a person is at rest. Measurements are then repeated at both sites after 5 minutes of walking on a treadmill.
By dividing the highest blood pressure at the ankle by the highest recorded pressure in either arm, the ankle-brachial index (ABI) can be calculated. The ABI result is used to predict the severity of peripheral arterial disease (PAD) that may be present. A decrease in the ABI result with exercise is a sensitive indicator that significant PAD is probably present.
Why It Is Done:
This test is done to screen for peripheral arterial disease of the legs.
The resting ABI result can help diagnose peripheral arterial disease (PAD). If the index number drops after exercise, this may indicate that significant PAD is present.
A normal resting ankle-brachial index is 1 or 1.1. This means that your blood pressure at your ankle is the same or greater than the pressure at your arm and there is no significant narrowing or blockage of blood flow.
A resting ankle-brachial index of less than 1 is abnormal. If the ABI is:
      •          Less than 0.95, significant narrowing of one or more blood vessels in the legs is indicated.
      •          Less than 0.8, pain in the foot, leg, or buttock may occur during exercise (intermittent    claudication).
      •          Less than 0.4, symptoms may occur when at rest.
      •          0.25 or below, severe limb-threatening PAD is probably present.
What To Think About
You may experience leg pain during the treadmill portion of the test if you have peripheral arterial disease (PAD).
Undiagnosed arterial disease in the arms can cause inaccurate test results.
Blood pressure readings may not be accurate when the blood vessel being measured is hardened by calcium (calcified). Arteries may calcify more than usual if you have diabetes or kidney problems (renal insufficiency). 1
A very abnormal ABI test result may require more testing to determine the location and severity of PAD that might be present
The Toe Brachial Index
Purpose: Assess presence or severity of peripheral arterial disease (PVD) of lower extremity.
Toe brachial index (TBI) and is a calculation based on the systolic blood pressures of the arm and the systolic blood pressures of the toes.  The examination  is performed with a photoplethysmograph (PPG) infrared light sensor and  a very small blood pressure cuff placed around the toe.
How is the exam given?
Patient will be asked to lie on the back while standard blood pressure cuffs are placed around the arm and big toe.  These cuffs will be inflated briefly above your normal systolic blood pressure.  Once the cuff is  deflated, blood pressure measurements are taken using the Doppler instrument (PPG). .  The arm and  big toe  systolic blood pressure measurements are recorded.  Then the big toe  systolic pressures are divided by the highest arm pressure to establish an TBI measurement for each leg. A TBI of .75 or greater is consider normal.
What is Peripheral Arterial Disease(PVD)
Peripheral Arterial Disease (PAD) is also known as atherosclerosis, poor circulation, or hardening of the arteries. PAD progresses over time at variable rates in each individual depending on the area of circulation effected and one's health and family history. The signs and symptoms of PAD may not arise until later in life. For many, the outward indications will not appear until the artery has narrowed by 60 percent or more.
One method the body uses to adapt to the narrowed arteries is the development of smaller peripheral arteries that allow blood flow around the narrowed area. This process is known as collateral circulation and may help explain why many can have PAD without feeling any symptoms.
When a piece of cholesterol, calcium or blood clot abruptly breaks from the lining of the artery or a narrowed artery blocks off completely, blood flow will be totally obstructed and the organ supplied by that artery will suffer damage. The organs in PAD most commonly affected and researched are the legs.
What happen if the disease worsens?

The severity of PAD depends on when it is detected and any pre-existing health factors; especially smoking, high cholesterol, heart disease or diabetes. In the later stages, leg circulation may be so poor that pain occurs in the toes and feet during periods of inactivity or rest.  This is especially true at night. This is known as rest

pain, which usually worsens when the legs are elevated and is often relieved by lowering the legs (due to the effects of gravity on the blood flow).
Critical Limb Ischemia
The most advanced stages of PAD can lead to Critical Limb Ischemia (CLI) . Here the legs and feet have such severe blockage that they do not receive the oxygen rich blood required for growth and repair of painful sores and even gangrene (dead tissue). This condition, if left untreated, may require amputation
What is the first thing patient might notice If he has Peripheral Arterial Disease?
For many, the first noticeable symptom of PAD is a painful cramping of leg muscles during walking called intermittent claudication.  When a person rests, the cramping goes away.  This leg pain can be severe enough to deter a person from normal walking.
Some individuals will not feel cramping or pain but might feel a numbness, weakness or heaviness in the muscles.
What are some other symptoms?
In patients whose PAD is more severe, insufficient blood flow to the feet and legs may cause a burning/aching pain in the feet and toes while resting. The pain will occur particularly at night while lying flat. Other symptoms include
  • Cooling of skin in specific areas of legs or feet
  • Color changes in the skin and loss of hair
  • Toe and foot sores that do not heal
Silent PDA
Many people are affected by PAD yet they do not symptoms. These individuals are at high risk for suffering an early heart attack or stroke. Research has proven that the life expectancy for a person with PAD is greatly reduced. For example, the risk of dying from heart disease is six times higher for those with PAD compared without. Therefore, it is important to examined patient properly if patient has several of the risk factors for PAD.
                                                 Risk factors
An individual is at risk for developing PAD when one or more of these risk factors are present:

This is the number one risk factor for PAD. Those that smoke not only put 

  • themselves at risk for developing arterial disease but also undermine attempts at treatment. For more on "Smoking and PAD" 
  • Diabetes
    Individuals with diabetes are at a greater risk for developing PAD due to its effect on blood vessels.  
  • Age
    In the United States, those 50 years or older are at greater risk to develop PAD. PAD affects both men and women, but occurs slightly more in men.
  • History of Heart Disease
    A family history of cardiovascular disease is an indicator for risk at developing PAD.
  • Hypertension (high blood pressure)
    When blood pressure remains high, the lining of the artery walls becomes damaged. Many PAD patients also have high blood pressure.
  • High levels of Homocysteine
    This is an amino acid found in plasma (blood). Some recent studies show higher levels are associated with PAD.
Diagnostic test which can be done in our office to determent PAD
 -TBI-Toe Brachial Index     ( can be done by MA, or ultrasound technician)
 -ABI- Ankle Brachial Index  (done by ultrasound technician)
 -Arterial Duplex ultrasound (done by ultrasound technician)