Evaluating stents and bypass grafts

Knowing how to evaluate and recognize a stent or bypass graft in patients who've had them is a critical skill all clinicians should have. In this video, from our Ultrasound Masterclass: Arteries of the Legs course, we'll show you how to identify and assess them, and differentiate between the artery and the graft.

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Often patients will have stents or stent grafts or a bypass graft placed as part of treatment, so it's important to evaluate and recognize them. 

How to identify a stent on ultrasound

[0:13]
Here is a stent in the SFA [superficial femoral artery], notice its bright, echogenic borders. Stents are most easily recognized at the proximal attachment. Occasionally, they can be difficult to evaluate for both presence and patency due to the calcific shadow from atherosclerotic plaque pushed up against the walls. When off axis you can usually recognize a stent by identifying the mesh pattern. 

Measuring stent velocities

[0:38]
Evaluation of a stent follows a standard protocol that is the same for a bypass graft. Measure velocity just proximal to the proximal attachment, which is known as inflow and serves as a velocity reference. Next, take a velocity in the proximal attachment, as well as the proximal, mid, and distal portions of the stent. The distal attachment and outflow are the final measurements.

Assessing synthetic bypass grafts

[0:59]
The synthetic bypass grafts are usually pretty easy to recognize on ultrasound. For example, notice the synthetic graft on this ultrasound, they are interrogated the same way as stents. The only difference is that we use slightly different terminology, we use the terms proximal and distal anastomosis for the grafts instead of attachments. 

Recognizing a bypass graft on ultrasound

[1:26]
The bPg, or bypass graft, looks like a vessel with the same color fill and waveforms as a normal healthy artery. However, it has a pattern edge and often has a more superficial path compared to the SFA. 

Identifying autologous vein grafts on ultrasound

[1:39]
If the graft is autologous, or taken from the patient's body from a reverse saphenous vein, there is nothing remarkable about the appearance of the walls. In this case, it is best identified by its pulsating color and location down the length of the medial thigh. In some rare instances, they can go down the outer thigh to get to the anterior tibial artery. 

When a normal-looking artery is actually a graft

[2:01]
An important note: the bypass graft passes by a very diseased vessel. If the bypass graft isn't identified, but the artery looks wildly patent, it's likely that it is the bypass graft that's being imaged.

Finding and following a bypass graft

[2:13]
Some surgeons tend to place the graft in the native arteries anatomical location, which can be confusing at first. Sometimes you can see the disease vessel, but this might be difficult if it is chronically occluded. It's easiest to locate the bPg at the proximal anastomosis, most often in the groin, and follow it continuously like a regular artery. If you get lost, go back in transverse orientation with color and relocate it.