|
Classification | Velocity (cm/sec) | Image characteristics |
|
Normal | Mid graft PSV > 150 cm/sec | No visible narrowing |
Distended outflow veins |
Anastamosis PSV > 300 cm/sec, chaotic, disorganized flow | Aneurysms, puncture sites, perigraft |
fluid may be visible |
|
Moderate stenosis | Ratio of PSV at stenosis to PSV at 2 cm | Decrease in lumen diameter |
beyond anastamosis if normal-appearing <3 | Echogenic narrowing |
Wall abnormalities |
|
Severe stenosis | Marked velocity acceleration at stenotic area | Intraluminal echogenicity < 2 mm |
lumen >50% diameter reduction |
Ratio of PSV at stenosis to PSV at 2 cm | Marked reduction in lumen |
beyond anastamosis if normal-appearing >3 | diameter with color doppler |
|
Inflow Stenosis | Peak systolic velocities will increase at the site of | Intraluminal echogenicity |
stenosis with monophasic and diminished | < 2 mm lumen at velocity acceleration |
waveforms distal |
Flow acceleration with graft compression at |
outflow anastamosis |
|
Outflow stenosis | Mid graft PSV < 100 cm/s | Intraluminal echogenicity |
Distal vein > 300 cm/sec | < 2 mm lumen velocity acceleration |
Velocity at the proximal anastamosis will diminish | Prominent collateral veins around outflow |
in proportion to severity of venous outflow stenosis |
|
Occlusion | No doppler signal | Intraluminal echogenicity |
Graft walls appear collapsed |
Occluded vein may not be visible |
|