ACTIVITY 3.1Our Departmental measurement criteria- uses the ASUM

guide lines below

Stenosis Grade Ultrasound Criteria- ICA

0 Normal wave form and image

15% diameter reduction Deceleration spectral broadening PSV < 125cm/sec

16- 49% diameter reduction Pansystolic spectral broadening PSV < 125cm/sec

50-69% diameter reduction -Pansystolic spectral broadening-PSV >125cm/sec and EDV<110cm/sec or-ICA/CCA>2

70-79% diameter reduction -Pansystolic spectral broadening-PSV>270cm/sec or-EDV>110cm/sec orICA/CCA>4

80-99% diameter reduction As above plus-EDV > 140cm/sec

Occludes No flow Terminal thump

• However there is emphasis on the need to be consistent in cases of <50% stenosis, by accurately placing the curser in mid stream to obtain a good clear spectral window-because spectral broadening can occur with increased transducer pressure and when the curser or sample volume is placed near the vessel wall as shown below.

Standard –curser in mid stream shows clear spectral window

Curser in mid stream with increased transducer pressure causing spectral

broadening

Curser placed near the vessel wall again shows spectral broadening

NASCET CRITERIA Minimum residual lumen at the point of maximum stenosis referenced to the diameter of distal lumen for the internal carotid artery at the first point at which the arterial walls become parallel. The image below show plague of the ICA bulb, the residual lumen was measured as well as the normal ICA distal to the bulb.

Relationship to the NASCET CRITERIA

Calculation• A= 4.7 B=5.6 therefore 1-4.7 5.0x100=0.6%

Minimal stenosis- there will be no significant increase in peak systolic velocity until >50%

• NASCET is more straight forward indicator of the degree to which the ICA is narrowed by the stenosis, in that it compares the stenosis to the distal lumen of the artery and is reproducible and reliably measured from the angiograms . Uses the diameter of the disease free point in ICA as the denominator

• The ECST method gives a better indication of plague burden at the sight of the stenosis but uses the artery diameter as the denominator at the same point

THE ECST CRITERIA

• Uses a different method

• I think that the ECST criteria is no longer popular because it produces higher values for modest and significant benefit being between70-99% equivalent to NASCET of 50-69%. A ECST 50% stenosis within the carotid bulb may yield 0% using the NASCET method, that is very risky to the patient ‘s treatment plan.`