0:00

Moving on to the next set of cases, which are looking at cases

0:04

that are post-intervention.

0:07

So once we've looked at what the patterns look like in peripheral arterial

0:11

disease, it's important to know what it looks like after it's been fixed.

0:15

And one of the most common ways to treat peripheral arterial disease

0:19

nowadays is by undergoing a bypass graft, which is commonly used to treat acute

0:23

or chronic limb-threatening ischemia.

0:25

Often, they can be combined with other surgical interventions, such as a

0:28

thromboembolectomy. These grafts can either use synthetic materials

0:32

or you use vein grafts. Now, depending on what is

0:36

occluded, different parts need to be bypassed.

0:40

So in a patient who has extensive aortobiliac

0:44

occlusion or stenosis, they might need an

0:46

aortobifemoral bypass graft as seen here.

0:49

So the native is all the way at the back and it's non-opacified, and the

0:53

aortobypass graft looks like this anteriorly

0:57

oriented vascular channel that mimics the path of

1:01

aorta iliac arteries that one might have in a native setting.

1:05

If only one of the vessels is diseased and the

1:09

other iliac limb is okay, then

1:12

one might consider doing a femorofemoral bypass graft.

1:15

So then the contrast column goes all the way from the aorta to that iliac artery

1:18

and then supplies both the ipsilateral as well as that contralateral

1:22

limb.

1:23

When really none of these are the targets, one of the last

1:27

resorts that one might employ is using an axillofemoral bypass graft,

1:31

which means they create a vascular channel all the way from the axillary artery,

1:35

all the way in the chest that travels down through the chest and abdomen and then

1:39

comes down to the pelvis and is anastomosed with the femoral artery.

1:43

In the leg, you can have femoral popliteal bypass grafts or

1:47

popliteal to a tibial artery bypass grafts.

1:50

It really all depends which area we're trying to bypass.

1:53

Stents offer a minimally invasive alternative to bypass grafts,

1:57

particularly when there are shorter segment involvement, less extensive

2:01

PAD, with lack of suitable veins that might be needed for

2:04

grafting. They are, however, less suited when it's a long

2:09

segment

2:10

stenosis or a long segment disease, and if there are heavy

2:13

calcifications or at levels of joints where mechanical

2:17

forces may lead to a stent fracture.

2:21

So other than looking at the bypass graft itself and whether it's

2:24

patent, we also need to look at complications.

2:27

So are there any procedural complications such as a bleed,

2:31

pseudo aneurysms, arteriovenous fistulae?

2:34

We look at distal vessels. Have they undergone a trauma during this procedure?

2:37

So is there a dissection? Has there been a distal embolization of a clot during

2:41

the procedure? We look at whether that bypass graft itself is

2:45

stenosed or not. We look at whether it is infected or not in an appropriate

2:49

setting. And so depending on the indication, we may need to tailor our

2:53

imaging. You've seen by now that typically the I-minus or the

2:57

non-contrast in the arterial phase are necessary, but we don't typically

3:01

obtain a venous phase imaging. However, if the

3:04

concern is dropping hematocrit, we're thinking of a bleed, then

3:08

we might need to consider adding a venous phase.

3:11

If the indication is infection, having that venous phase really helps assess

3:15

rim enhancement around a connection and definitively calling something as

3:19

an abscess. Additional reconstructions that you might need depending on

3:23

indication is that if you know that there are stents, you may have to

3:27

call the scanner or call your tech and get sharper imaging kernels so

3:31

that we are giving a better assessment of stent patency and

3:35

not over-calling in-stent restenosis.

3:39

We want to avoid interpreting just on the MIPs and relying source data is

3:43

key because a stent might just look like a contrast

3:47

column with stent, and you might misinterpret

3:50

and miss in-stent restenosis.