About Vascular Laboratory Testing...

Duplex Scanning

A duplex scanner is a specialized ultrasound machine that creates images of structure in the body and simultaneously examines their blood flow. The ultrasound uses sound waves that are generated by a hand held probe. The probe is coupled to the skin by a gel, allowing the sound waves to pass into the body. 

The sound waves enter the body and are reflected back to the probe by the internal structures. The probe then relays the information to a computer that forms an image on a monitor. The image is an exact replication of what the sound waves encounter. 

If the sound waves encounter anything moving (such as blood), the returning sound waves are slightly altered. The probe and computer can detect these changes and calculate how fast the blood is flowing. The rate of blood flow can then be related to blockages. If a blood vessel narrows by half, the blood has to flow twice as fast for the same amount of blood to pass through. 

Duplex Scanning is painless and completely risk-free. It can be used to detect blockages in arteries of the neck (carotid), abdomen and legs. The test also examines veins for evidence of blood clots and maps their size prior to surgical procedures.

Segmental Pressures

In a normal exam, blood pressure in the legs should be equal to pressure taken in the arms. Blood pressure should not drop until blood reaches the smallest arteries (capillary level). 

The Segmental Pressures Test is performed by placing blood pressure cuffs on the thigh, calf, ankle and foot. Pressure is taken at every level using a special stethoscope at the foot and then inflating each cuff sequentially. 

A blockage and its position can be easily detected by an abnormal reading at any cuff position.

Pulse Volume Recordings (Plethysmography)

Each time the heart beats, both the arms and legs increase and decrease slightly in size, actually pulsating. Pulse Volume Recordings utilize these pulsations to examine blood flow. 

During Pulse Volume Recordings, blood pressure cuffs are placed on the legs at various levels and partially inflated to allow detection of blood flow without occluding it. The cuffs are then attached to a monitor that measures and records the small changes in volume as the heart beats. This information confirms the amount of blood flow in each segment of the leg. 

Pulse Volume Recordings are especially useful in the diagnosis and treatment of diabetic patients. These patients often have calcified arteries causing blood pressure to appear elevated because arteries cannot be effectively compressed by the cuff.

Exercise Testing

Some patients have partial leg artery blockages that only become significant upon exercise. This test first measures blood pressure in the feet at rest and compares it to pressure in the arms. The patient then performs monitored exercises on a treadmill and the test is repeated. 

Exercise Testing is useful for the detection of disease in patients who have normal test results at rest, but experience increased symptoms during activity. This result may strongly suggest peripheral vascular disease (PVD).