Fistulas
What are some factors that influence where they place a fistula?
Dominant arm, vessel diameter, vessel depth, atherosclerosis, abnormal anatomy.
Where are the most common sites for stenosis with a graft?
Venous anastomosis and outflow vein due to the increased pressure from the arterial flow.
What fluid collection may present immediatley post op of a graft and persist up to 1 week?
Perigraft fluid collection
Do we use angles when scanning fistulas and/or grafts?
Yes. Only removed when we Doppler native veins.
What is the flow volume method formula?
Q (mL/minute) = graft area x TAV x 60 seconds.
What is the Brescia Cimino AVF type?
Radial to cephalic.
What is the minimum diameter for a preoperative vein for a graft?
>4 mm
What is a type II endoleak?
A leak that originates from the branches.
Explain the protocol modifications for scanning a graft.
Native inflow, proximal anastomosis, proximal graft, middle graft, distal graft, distal anastamosis, native outflow.
What is the rule of 6’s?
After AVF placement we want >600 mL/min flow volume, >6 mm diameter, and <6 mm in depth.
Vascular surgeons like to place fistulas/grafts more _______________ (proximal/distal) in the arm.
Distal.
Low PSV in the access graft could indicate....
Arterial inflow problems.
Why would an endograft be used?
AAA repair.
What is the preparation and protocol for preoperative mapping?
Room temperature should be warm, patient in upright position, evaluate diameter of wall thickness of vessels, vein compression to assess patency, and assess forearm vessels.
What is the most common endovascular complication?
Endoleak.
What is the minimum diameter for a preoperative vein for a fistula?
>2.5 mm
What materials can be used for a graft?
PFTE, Dacron, xenograft (other species), or cryograft (frozen allograft).
What are some complications of a AAA repair?
Hematoma, infection, pseudoaneurysm, true aneurysm, and occlusion.
What is the velocity ratio formula?
PSV at anastomosis or stenosis/PSV prox to anastomosis or stenosis.
What is Type 1A and 1B of an endoleak?
1A - Proximal end of graft.
1B - Distal end of graft.
What causes the vein to enlarge and thicken during fistula maturation?
Increased blood flow from the artery.
What are the risks associated with AV grafts? (3)
Thrombus, aneurysms, and infections.
What is steal syndrome?
When blood flow is redirected or "stolen" by the fistula because of the high arterial to low venous pressure flow, starving the hand of blood.
What should the gate size be when measuring flow in the AV access vein?
Entire lumen width to calculate flow volume.
What do we need to obtain to get the flow volume through an AVF?
Measurements of the vessel's cross-sectional area and the time-averaged velocity (TAV) of blood flow.