Segmental arterial Doppler pressures: A test that measures the blood pressures in the legs to make sure there is normal blood flow. The test is usually done when there is intermittent claudication (leg pain on exercise).
Normally the blood pressures in the legs are similar to those in the arms. Lower pressures in the legs usually mean there are plaques (cholesterol deposits) in the leg arteries compromising the circulation. Blood pressure measurements are therefore made at different locations on the legs to see if there is narrowing of the arteries and where the blocks are in the legs. The test is often done in diabetics because diabetes tends to cause small vessel disease.
Doppler ultrasound replaces the stethoscope usually used to take the blood pressure. The Doppler ultrasound is more accurate. It employs sound waves and a sonar detection system to detect and measure blood flow.
In the test the patient lies on a table and blood pressure cuffs are wrapped around the leg in four or five locations. Clear jelly is put on the skin to help the Doppler sensor slide around easily like a wand and conduct sound waves through the skin. Each blood pressure cuff is inflated twice. The first time it is inflated part way to send a signal to a machine about the size of the leg and the elasticity of the arteries in the leg. A wavy line that signifies blood flow appears on a screen. The second time each cuff is inflated, it is inflated to a higher pressure. As the cuff is deflated, the Doppler sensor on the foot detects the moment when blood flow starts up again by making a noise that sounds like the heartbeat. Checking the air pressure of the deflating cuff at this time shows the leg blood pressure. After all the cuffs on one side have been tested, the other leg is checked the same way. For comparison, a blood pressure is checked in the brachial artery in each arm using the Doppler technique.
The pressure in the ankle is normally slightly higher than that in the brachial artery in the arm. Therefore, the normal ankle/brachial index (the ratio of the ankle pressure to the brachial pressure) is greater than 1.0. The degree to which the ankle/brachial index is reduced correlates with the degree of clinical arterial insufficiency and the severity of symptoms: - Ankle/brachial index >1.0 Normal (no symptoms)
- Ankle/brachial index 0.9-1.0 Minimal ischemic disease (minimal symptoms)
- Ankle/brachial index 0.5-0.9 Mild-to-moderate disease (symptoms of intermittent claudication)
- Ankle/brachial index 0.3-0.5 Moderate-to-severe disease (symptoms of ischemic pain in leg at rest)
- Ankle/brachial index <0.3 Severe disease (danger to the leg)
The test usually requires about three quarters of an hour. If the test is done both before and after exercise on a treadmill, it takes longer. The test is non-invasive and virtually painless. |
