Transcranial Doppler criteria for decision making in treatment of Carotid Stenosis

1. Combination Of Carotid Duplex And
Transcranial Doppler For The
Assessment Of Carotid Stenosis
Roberto Hirsch*, Donald H. Lee**, Milberto Scaff*
*Department of Neurology of the Hospital das Clínicas da
Faculdade de Medicina da Universidade de São Paulo,
Brazil
**Department of Neuroradiology of the University Hospital
of the University of Western Ontario, London, Canada

2. Background
NASCET published
data from the severe
stenosis randomization
phase
70% ICA stenosis
arbitrary cutoff
“Poor results” achieved
by ultrasound in
correlating with angio
measurements
Why should this
threshold represent
a greater risk for
stroke if not
corrected by
endarterectomy
Can TCD and DCU
address this
question?

3. Background
Is there a
physiological
phenomenon at this
boundary that might
be detected by
physiological
approach?
Is there room for
non invasive
approach for the
assessment of ICA
stenosis?

4. Background
Can TCD provide additional information
in order to optimize DCU results in
determining ICA degree of stenosis?
Is the combination TCD/DCU more
reliable than carotid ultrasound alone in
determining severe stenosis?

5. NASCET angiographic criteria
Bulbo de ACI
Diâmetro da luz
Diâmetro distal
Método NASCET angiográfico
%= 1- luz/luz distal
The NASCET angio
measurement
technique brought
clear standards
reducing
interobserver
variation, unlike
ultrasound at the
beggining

6. Methods
67 out of 72 (42 NASCET and 8 ACAS)
consecutive patients were studied by
CA, TCD and DCU performed closest
possible to concurrent. We estimated
the degree of proximal ICA stenosis
with CA according to NASCET criteria
Best images were selected for study, 3
TCD “no shows” ruled out

7. Methods
134 arteries were randomized according to
angio degree of ICA stenosis into below and
over 70% stenosis and ICA occlusion, and
had their TCD and DCU readings compared
Multivariate and univariate analysis with
logistic regression and chi-square and T-
student test performed for each and total of
TCD and DCU parameters having angiogram
as gold standard

8. Methods
TCD parameters:
MCA velocities,
presence of
collateral circulation,
pulsatility index, flow
acceleration
DCU parameters:
ICA peak systolic
velocity, ICA/CCA
ratio, turbulence,
ultrasound stenosis,
CCA asymmetry or
CCA damping

9. Upstroke time fraction
x
y
UST-F = x/y
ACI
Normal
B
MCA reading distal
and ipsilateral to
normal ICA. Note
the flow acceleration
showing steep
elevation of systolic
flow velocity
reaching its peak
early in the cardiac
cycle

10. Upstroke time fraction
x
y
UST-F = x/y
cas o de s ub-oclus ão
A
MCA reading distal
and ipsilateral to a
near-occluded ICA
bulb. Note that peak
systolic flow velocity
is reached later in
the cardiac cycle.

11. Upstroke time fraction
x
y
UST-F = x/y
cas o de s ub-oclus ão
A
UST-f was taken
measuring the
linear distance
(time) for systolic
velocity to be first
achieved (x) and
dividing it by the
linear distance
that represents
one cardiac cycle.

12. Reproducibility of UST-f
Patient presenting ICA near-occlusion, being the
only conflictive result among the two readings
(D.Lee = 7,82 ; RH = 15,92)

13. Reproducibility of UST-f
By shifting background colour one can identify 2
spectra

14. Reproducibility of UST-f
Superimposed retrograde ACA showing quicker flow
acceleration time and underlying MCA affected by proximal ICA
near-occlusion

15. Univariate analysis of TCD and DCU
parameters - under 70% angio
Mean SD p
MCA mfv 48.5 10.62 0.0014
MCA UST-f 8.7 1.37 0.0001
ECICA psv 158.2 97.68 0.0000
ICA/CCA
ratio
2.05 1.38 0.0001
CCA
damp/asym
79.81 19.03 0.0000

16. Univariate analysis of TCD and DCU
parameters - over 70% angio, excluding ICA
occlusion
Mean SD p
MCA mfv 41.32 11.1 0.0014
MCA UST-f 19.8 3.42 0.0001
ECICA psv 338.89 125.43 0.0000
ICA/CCA
ratio
6.63 4.16 0.0001
CCA
damp/asym
57.52 19.92 0.0000

17. Most important TCD parameters -
UST-f
Upstroke time
fraction could
not be predictive
in multivariate
analysis because
of the wide SD,
but in univariate
analysis was
predictive with
100% of both
specificity and
sensitivity,
provided there
were no proximal
ICA occlusion
Ust-f
<70%
Ust-f
>70%
Occl
< 70% 103 0 0
>70% 0 31 0
Occl 0 0 10

18. Most important TCD parameters -
presence of collateral circulation
Presence of
collaterals in
all patients with
severe stenosis
except when
more severe
stenosis or
occlusion was
present in
contralateral side
(p=0.000)
Yes no total
< 70% 98
95.15%
5
4.85%
103
> 70% 4
12.90%
27
87.10%
31
total 102 32 134

19. Multivariate analysis
Logistic regression, with analysis of
maximum likelihood estimates, shows that
CCA damp/asymmetry has 101.686 odds
ratio and 95% confidence limits. This
parameter was arbitrarily defined as a more
than 14 cm/s velocity reduction below the
stenotic site or spectral damping. It may be
jeopardized when contralateral to an ICA
severe stenosis or occlusion

20. Probability of peak systolic extra-cranial ICA
velocity to determine severe ICA stenosis
0
0,1
0,2
0,3
0,4
0,5
0,6
0,7
0,8
0,9
1
0 100 200 300 400 500
EC_ICA
Probability
CCADAMP=N
CCADAMP=S

21. Sensitivity and specificity for CCA
asymmetry to determine severe ICA stenosis
0
20
40
60
80
100
0 0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,8 0,9 1
PROBABILITY
SENSIBILIDADE
ESPECIFICIDADE
This model gives 90% of both sensitivity and
specificity for CCA asymmetry presence to
indicate severe stenosis

22. Conclusion
Combined TCD and
DCU parameters
can reliably predict
ICA proximal
stenosis greater
than 70% according
to NASCET
angiographic
criteria.
If indication of
endarterectomy in a
symptomatic patient is
to be based only upon
degree of stenosis, it
can safely be done
solely on non-invasive
combined transcranial
and cervical
ultrasound approach

23. Conclusion
These findings may bring us to the point
that hemodynamic features, detectable
by physiological methods, may play an
important additional role in the genesys
of ischemic events in symptomatic
patients suffering from ICA stenosis
along with embolic risk of a given
plaque.