Vascular Technology

Question 1

What two arteries serve as collateral pathways between the SMA and IMA?

Answer 1

Marginal artery of the Colon (also known as the Marginal Artery of Drummond).
Arc of Riolan.
Note: the IMA may also serve as a collateral to the floor of the pelvis and the lower extremity via connections with the internal iliac artery.

Question 2

You find this waveform in a popliteal artery. Where is the disease, proximal or distal and why?

Answer 2

Proximal – note the delayed systolic upstroke – this suggests a stenosis proximal to where the waveform was obtained. The low resistance flow pattern (presence of diastolic flow) is consistent with vasodilatation due to limited blood flow to the distal leg.

Question 3

A 57 y/o male presents with a sudden onset of severe pain and massive left leg swelling. He does admit to a 2-year history of dependent left leg edema that typically resolved during the night. The most likely etiology would be:

1. Superficial venous insufficiency
2. Deep venous insufficiency
3. Acute venous thrombosis of a proximal vein on the left
4. Chronic deep vein occlusion
5. Iliac compression syndrome (May Thurner Syndrome)

Answer 3

3.** Acute deep vein thrombosis**. Sudden / Acute onset is the key clinical finding. Given the history, iliac compression syndrome is also highly suspect however this could explain the history of left leg symptoms and perhaps be the cause of the DVT but alone does not explain the acute onset. The diagnostic workup for possible iliac compression should be considered in this patient.

Question 4

Describe the how to calculate and characterize normal versus abnormal values for (Systolic) Acceleration Time (AT) for extremity arterial evaluations.

Answer 4

Simply a measure of time from onset of systole to peak velocity. Proximal obstruction results in delayed time interval between onset of systole and peak velocity

• Normal AT <133 milliseconds
• Abnormal AT > 133 milliseconds = proximal obstruction

Note there are some minor variations in the AT criteria. Also, remember that other vessels may have different AT values - for example AT in renal arteries should be <100ms.

Question 5

What are the three components of Virchow’s Triad?

Answer 5

1. Trauma to the vessel / endothelial damage
2. Venous Stasis – decreased venous return
   * Immobility, obesity, pregnancy, COPD, extrinsic compression of the vein, long flight (coach class syndrome)
   * Previous deep vein thrombosis (DVT)
3. Hypercoagulability

Example: certain protein deficiencies, pregnancy, malignancy, hormones (estrogen intake)