1. Interventional Procedures: lower extremities
Bypass graft
Synthetic: Polytetrafluoroethylene (PTFE) , Dacron
Autogenous vein grafts
Reversed
In situ
Percutaneous angioplasty (PTA)
Stents
Synthetic grafts are favored in the abdomen, and in the thigh, but not below the knee. PTFE is a form of Teflon. “Autogenous” (aw-tojen us) means the patient’s own veins.

2. Aorto-femoral grafts
Above Inguinal Ligament Grafts
1) Aorto-bifemoral graft ("aortoiliac", if the distal end of the graft is connected above the inguinal ligament).
Used to bypass a diseased distal aorta and/or iliac arteries.
Patient will have a scar near the umbilicus, and one in each groin region.
2) Femoral to femoral “jump” graft.
Scar at each groin, although this can result from endovascular aneurysm stent repair (EVAR) of aortic aneurysm.
Used to bypass a single iliac artery. Intended flow direction should be from asymptomatic leg to preoperative symptomatic leg.
3) Axillo-femoral, fem-fem bypass.
Used to bypass the abdominal aorta. Proximal anastomosis is at the axillary artery. Less frequently used these days.
The entire graft, as well as the graft inflow and outflow, should be evaluated for stenosis Careful attention should be given to the anastomotic sites as technical problems, graft failure and infection are more likely to occur in these regions.

3. Below Inguinal Ligament Grafts
1) Synthetic polytetrafluoroethylene (PTFE) graft.
Common femoral artery (CFA) to distal superficial femoral artery (SFA) or proximal popliteal a.
Newer flexible fabrication may allow placement to extend below knee.
The patency rates of PTFE grafts, when coursing past the knee joint, are limited. Graft kinking is a complication of this type of graft if it extends below knee.

4. PTFE Graft
PTFE grafts have a “double-walled” appearance on ultrasound.

5. Below Inguinal Ligament Grafts
2) Synthetic Dacron.
Often used for fem-fem, and iliac grafts.
Advances in Dacron material is now allowing femoral-distal bypass grafts.
Dacron grafts look slightly like a vacuum cleaner hose.

6. Below Inguinal Ligament Grafts Autogenous vein grafts
3) In situ vein graft
Used to bypass femoro-popliteal occlusion.
Graft often extended from CFA to distal tibial artery (aka, fem-distal graft).
Vein grafts appear to have better patency rates than synthetic grafts in the legs.

7. In situ vein graft
Uses great saphenous vein (GSV) in it’s native bed. It’s not removed.
Valve leaflets are excised with a valvulatome.
Perforators / tributaries are ligated.
Proximal and distal ends of the vein are connected to artery.
The graft lies superficial in the proximal section, but courses deep towards the SFA, popliteal or tibial anastomosis.
The proximal anastomosis is usually at the CFA, but the graft may originate at the profunda femoris artery (PFA) or the proximal SFA.

8. Valvulatome for in situ method
Used to cut and remove valves so blood can flow down the vessel.

9. Occluded SFA In situ vein graft CFA GSV ligated perforators CFV CFA
Valves
CFV
CFA
PFA
SFA
GSV
Pre-op on left, post op on right with in-situ vein graft. A potential complication of this method: partially excised valve leaflets. These leaflets act as a stenosis within the graft and may reduce blood flow distally.

10. Vein Graft Evaluation Potential complication
A-V fistula due to a non-ligated perforator vein (in situ only). Can’t happen in a reverse vein bypass
Blood destined for foot can be diverted into a vein.

11. Other grafts Veins and arteries harvested from cadavers are also used.
The small saphenous vein (SSV) is used for small segments or for graft revisions.
The cephalic or basilic veins in the arm may be used for small graft extensions or revisions.

12. Below Inguinal Ligament Grafts Autogenous vein grafts
CFA
SFA
Vein
graft
4) Reversed-vein bypass
Perforating veins and tributaries are ligated and cut
GSV is removed
Vein is reversed and implanted as bypass.
Valves are not excised
Can be used in contralateral leg.
In this procedure the GSV is removed, turned upside down, and sewn back in.
The valves are not removed or excised as in the in situ method.
All perforating veins/ communicators are ligated and cut.
This graft is smaller proximally, larger distally due to the diameter of the reversed vein.
Some surgeons prefer this bypass method, as distal anastomotic stenosis (by neointimal hyperplasia) has less of an effect due to the wide bore of the vein.
The vein for this procedure may be harvested from the contralateral or ipsilateral limb.

13. Reverse vein graft stenosis
Valve cusp
Transverse vein graft
In all vein grafts intimal hyperplasia can occur and cause stenosis. Also, kinking and twisting can be problems in both types of vein grafts.

14. In situ fem-tibial graft
femoro-popliteal
graft

15. Follow-up Surveillance of Bypass Grafts-Rationale
Allows the surgeon to detect early graft stenosis prior to thrombosis and occlusion.
Thrombosed grafts are prone to early failure following thrombectomy.
Graft defects and stenosis may be followed for progression or resolution.
Intervention can be initiated with onset of symptoms and confirmation of progressive occlusive disease.

16. Graft surveillance 20-30 % stenosis rate within 1 year
High failure rate if graft undergoes thrombectomy.
60% of graft stenoses are ASX, due to limited ambulation -
Many grafts are performed for limb salvage.
If a graft occludes, there is a 50-80% chance of re-thrombosis following thrombectomy.
Amputation is likely if the graft fails again.

17. Bypass graft scan method
Identify graft type & location. Any revisions?
Perform ABI
Use image, color and spectral Doppler
If possible, obtain information from the surgeon’s office or medical record regarding the type and the anatomical placement of the graft. A drop of 0.15 in the ABI from the previous exam suggests progressive graft stenosis.

18. Graft evaluation Graft inflow and anastomosis Entire graft for:
Stenosis
Wall irregularity
Aneurysm, pseudoaneurysm
A-V in non-ligated perforators (in situ only)
Partially excised valve leaflets

19. Graft evaluation Distal anastomosis Run-off (graft outflow vessel)
Assess profunda femoral artery origin
3.The anastomoses for stenosis or defects. The proximal vein graft often develops neo-intimal hyperplasia due to the shear stress of arterial flow on a thin vein wall. Intimal hyperplasia is a rapid proliferation of intimal cells causing wall thickening and lumen encroachment
Vein graft aneurysm

20. Distal anastomosis is often difficult to assess due to weird angles.
High frequency
Velocity ratios may be unreliable in regions of anastomoses as the vein and the runoff vessel diameters are often of different size. Look for velocity changes over time in these specific areas during serial follow-up exams.
Stenosis has an abrupt increase in velocity

21. Obtain and record peak systolic velocities from the following locations:
Proximal to, at and distal to a stenotic segment.
The artery segment proximal to the graft.
Within the graft:
Proximal graft
Mid graft
Distal graft segments.
The artery segment distal to the graft.
TIP: If a specific stenosis is being serially evaluated, place a tape measure on the thigh/calf along the course of the graft and identify its location relative to a major branch vessel. New stenoses can be differentiated from a known stenosis in this fashion.

22. In situ graft stenosis
Use color Doppler to identify stenosis, then measure velocities with spectral Doppler. Note the “color bruit” above. Energy is released as flow comes through the stenosis; local tissue distal to stenosis vibrates and caused a color shift in the tissue.

23. In situ graft stenosis
PSV 775 cm/sec = severe graft stenosis.

24. Graft waveform 1 week post op
Courtesy of J. Primozich
Doppler waveforms of blood flow in "mature" bypass grafts resemble that of native vessels, i.e., high resistance flow presented as a triphasic waveform. However, In the early post-operative period (less than 45 days), the Doppler flow pattern may not be triphasic and may exhibit antegrade flow throughout the cardiac cycle. Chronic vasodilation that occurred before the graft or PTA will persist for some weeks and cause the hyperemic flow. After the hyperemic response subsides, the graft waveforms should be triphasic and consistent with normal outflow resistance.
Hyperemia will usually occur in normal, patent grafts in the early post op period.

25. Interpretation Graft velocities should be above 40 cm/sec.
Velocities in normal reversed vein grafts will decrease distally as the diameter becomes larger.

26. Interpretation > 50% graft stenosis
Focal velocity acceleration followed by post stenotic turbulence.
PSV ≥150 cm/sec and velocity ratio of ≥ 2.0
If velocity ratios are ≥ 3.5 and peak systolic velocities exceed 300 cm/sec, the stenosis is unlikely to regress and intervention is recommended to prolong graft patency.

27. Pt. #1 Recent in-situ femoro-popliteal vein bypass graft.
No increase post-op in ABI. Cause for concern so a STAT color duplex scan was ordered.

28. Vein graft stenosis
Stenosis not seen in B-mode

29. Graft - valve stenosis Graft stenosis
Not seen, but there’s a valve sticking straight up.
Graft stenosis

30. Vein graft -pre stenosis
PSV 39 cm/s

31. Vein graft, max stenosis
PSV 504 cm/s

32. Graft- Post stenosis
PSV 120cm/s

33. Distal vein graft PSV 49 cm/s
Non-ligated venous valve was the problem. It was fixed surgically with good result.
PSV 49 cm/s

34. Stents Palmaz - balloon deployed Wallstent - self expanding
Stents for peripheral arterial disease are either balloon-deployed or self expanding.
Stents are made of titanium, nitinol or similar material and can be either open or covered.

35. Angioplasty with stent placement
Vascular stenting, used in combination with percutaneous angioplasty, has been successful in the treatment of coronary artery stenosis. The diseased segment of the artery is initially dilated with the angioplasty balloon. The stent is then introduced within a catheter sleeve, the sleeve is removed, and the stent is expanded with the underlying balloon catheter. The stent mechanically holds the artery open and improves patency rates compared to angioplasty alone.

36. Palmaz stent - non-expanded
Palmaz stent expanded on PTA balloon

37. Stent sites: peripheral vascular
Aorta
Renals
Iliacs
Femoral - popliteal
At the time of this writing, there are no established velocity criteria for peripheral arterial stent stenosis. As with carotid stents, it is recommended that post stent velocities be recorded and used as a reference for follow-up examinations.
Open stent

38. Covered Stent

39. Peripheral stent criteria
Obtain post operative velocity within stent.
Use this as a reference during follow-up exams

40. Endoluminal AAA Repair with covered stents-EVAR

41. Stent graft for AAA
Endovascular treatment of abdominal aortic aneurysm (EVAR) involves the percutaneous placement of a thin Teflon covered stent graft within the aortic aneurysm. The graft is anchored at each end by stents against the normal vessel wall. The risk of aneurysm rupture, thrombosis, and embolization appears to be significantly reduced. It is a relatively minor procedure, requiring much less recovery time, and a shorter hospital stay compared to AAA resection.

42. Endoluminal AAA stent
Courtesy of Philips Ultrasound

43. Another method of Endoluminal AAA repair with covered stent
Fem-fem bypass

44. AAA -EVAR Complications include: Graft infection.
Vessel rupture during deployment.
Distal embolization.
Endoleak.

45. Endo-leak Aneurysm Stent
Endoleak - an inadequate seal of the proximal or distal wall that allows blood flow into the perigraft region. Or, from back flow from the inferior mesenteric artery (IMA) or lumber arteries.This can increase the size of the aneurysm.

46. Pre-stent (AAA) evaluation
Obtain pressure measurements and calculate an ankle to brachial index (ABI).
Carefully assess the aorta from the diaphragm to the bifurcation of iliac arteries, and to the CFA bilaterally.
Measure aneurysm outside diameter, its length, and residual lumen. Does the aneurysm extend above the renal arteries (RA)?

47. Pre-stent (AAA) evaluation
Measure the diameter of the aorta proximal to the aneurysm, and if possible, the distance between the left RA and the aneurysm.
To allow for proper stent anchoring, there should be at least 1 cm of normal aorta between the left RA and the aneurysm.
Measure the diameter of the iliac arteries. Measurements of the proximal and distal anchoring sites will enable the correct size selection of stent.

48. Post op evaluation ABIs. Monitor stent for patency.
Is the graft in the same position or has it moved proximally or distally?
Look carefully for low velocity endoleaks into the aneurysm sac.

49. Post-op eval.
Look for retroperitoneal fluid that may represent a leak outside of the aorta.
Measure diameter of aorta.
DO NOT OBTAIN A SEGMENTAL PRESSURE WITH THE CUFF OVER A FEMORAL, POPLITEAL OR TIBIAL STENT.