High Rate of Recanalization of Middle Cerebral Artery
Occlusion During 2-MHz Transcranial Color-Coded Doppler
Continuous Monitoring Without Thrombolytic Drug
Pascal Cintas, MD; Anne Pavy Le Traon, MD, PhD; Vincent Larrue, MD
Background and Purpose—Experimental evidence indicates that ultrasound can accelerate thrombolysis. We report our
findings on early recanalization during transcranial color-coded Doppler (TCCD) continuous monitoring in acute stroke
patients with middle cerebral artery (MCA) main stem occlusion.
Methods—We performed continuous TCCD monitorings in 6 consecutive patients with acute MCA main stem occlusion
using a 2-MHz transducer. Patients were not treated with recombinant tissue plasminogen activator.
Results—Partial recanalization, defined as blunted waveforms, occurred during monitoring in 5 patients (83%). The mean
time to beginning of recanalization was 17.2⫾9.6 minutes. Complete recanalization at 24 hours occurred in only 1
patient. The mean National Institutes of Health Stroke Scale score in the patients who recanalized during monitoring was
21.2⫾4.1 at baseline, 19.2⫾5 at 2 hours, and 15.6⫾3.4 at 24 hours (P⫽0.1).
Conclusions—In this short series of patients with acute MCA main stem occlusion, not treated with recombinant tissue
plasminogen activator, we found a high rate of early partial recanalization during continuous exposure to 2-MHz
ultrasound. (Stroke. 2002;33:626-628.)
Key Words: middle cerebral artery 䡲 thrombolysis 䡲 ultrasonography, Doppler, transcranial
E
xperimental evidence indicates that low-intensity ultrasound, in the range of values used for diagnostic purposes, accelerates thrombolysis by enhancing plasminogen
activator-induced fibrinolysis.1,2 Recently, Alexandrov et al3
reported a high rate of recanalization in stroke patients treated
with intravenous recombinant tissue plasminogen activator
(rtPA) during 1-hour 2-MHz transcranial Doppler (TCD)
monitoring, suggesting that ultrasound might have enhanced
drug-induced fibrinolysis in these patients. We report our
findings on recanalization during 2-MHz transcranial colorcoded Doppler (TCCD) continuous monitoring in patients
with acute middle cerebral artery (MCA) main stem occlusion who were not treated with rtPA.
Subjects and Methods
This study included consecutive patients admitted to our stroke unit
with an acute ischemic stroke who could have a TCCD diagnosis of
MCA main stem occlusion within 6 hours from symptom onset. All
patients had a brain CT scan before inclusion to evaluate the
hyperdense MCA sign. Patients were not treated with intravenous
rtPA.
TCCD scannings were performed through the temporal bone
window with a 2-MHz transducer (ATL Ultramark 9 HDI). We first
used B-mode imaging to visualize the lateral fissure as a hyperechogenic structure, anterior and lateral to the hypoechogenic butterflyshaped mesencephalic brain stem, in the orbitomeatal plane. A
diagnosis of MCA main stem occlusion was made with the use of
both color-coded imaging and pulsed-wave Doppler in case of lack
of blood flow all along the lateral fissure, with persistent flow in both
the ipsilateral anterior cerebral artery and posterior cerebral artery.
Then the sample volume (10 mm in length) of the pulsed-wave
Doppler was positioned in the initial part of the lateral fissure, where
the MCA main stem runs (Figure 1). This allowed us to precisely
focus the ultrasound beam on occluded MCAs. In a preliminary
study, we found that this method could correctly identify the MCA
main stem in 31 of 37 patients (83.8%) without cerebral artery
occlusion and had 100% sensitivity compared with color-coded
Doppler imaging.
The transducer was fixed with a head set, and pulsed-wave
ultrasound was continuously delivered on the initial part of the MCA
main stem to evaluate possible changes in flow. The spatial-peak
temporal average intensity was 415 mW/cm2. The duration of
monitoring was 30 minutes in 5 patients and 45 minutes in the
remaining patient.
Other TCCD scannings (without monitoring) were performed 2 to
6 hours and 24 hours after the first one to evaluate possible delayed
recanalization.
The clinical severity of stroke was evaluated at baseline, 2 hours,
and 24 hours with the use of the National Institutes of Health Stroke
Scale.
Results
Six patients (5 men and 1 woman; mean age, 54.3⫾14.7
years) were included. Four patients had a hyperdense MCA
sign. All patients received aspirin 250 mg IV as part of their
initial treatment.
Received September 26, 2001; final revision received November 8, 2001; accepted November 14, 2001.
From the Department of Neurology, University of Toulouse (France).
Correspondence to Professor Vincent Larrue, Service de neurologie, Hopital de Rangueil, 1 avenue Jean Poulhes, 31403 Toulouse, France. E-mail
larrue.v@chu-toulouse.fr
© 2002 American Heart Association, Inc.
Stroke is available at http://www.strokeaha.org
626
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Cintas et al
TCCD in Acute Ischemic Stroke
627
Characteristics of Recanalization
Pt
Recanalization
During TCCD 1
1
⫺
Time to
Beginning of
Recanalization,
min
MCA Waveforms
TCCD 1
TCCD 2
TCCD 3
None
Blunted
Blunted
Blunted
2
⫹
䡠䡠䡠
23
Blunted
Blunted
3
⫹
16
Blunted
Blunted
ND
4
⫹
5
Blunted
Blunted
Blunted
5
⫹
12
Blunted
Stenotic
Stenotic
6
⫹
30
Blunted
Blunted
Blunted
TCCD 1 indicates initial monitoring; TCCD 2, 2 to 6 hours after initial monitoring; TCCD 3, 24 hours
after initial monitoring; and ND, not done.
The mean time from symptom onset to beginning of TCCD
monitoring was 210⫾86 minutes.
Recanalization of the initially occluded MCA main stem
occurred during monitoring in 5 patients. Time to beginning
of recanalization ranged from 5 to 30 minutes (mean,
17.2⫾9.6 minutes) after the beginning of monitoring. Peak
systolic velocities were reduced and waveforms were blunted
(rounded systolic complex) in all cases (Table and Figure 1),
suggesting that recanalization was only partial.4
On the second TCCD scan, performed 2 to 6 hours after
the first one, all arteries had recanalized. Peak systolic
velocities were reduced and waveforms were blunted in 5
patients, including the patient without recanalization during the monitoring. In the remaining patient, there was a
stenotic pattern (focally increased peak systolic velocity
and aliasing) of the initially occluded MCA (Table).
Figure 1. TCD focused on MCA main stem in the lateral fissure,
with the use of B-mode imaging. Note the partial recanalization
with localized color-coded blood flow and blunted waveforms
on Doppler.
Evolution of pulsed-wave Doppler in this patient is shown
in Figure 2.
A third TCCD scan performed 24 hours later in 5 patients
showed no further change. The mean National Institutes of
Health Stroke Scale score in the 5 patients with recanalization
during initial monitoring was 21.2⫾4.1 at baseline, 19.2⫾5 at
2 hours, and 15.6⫾3.4 at 24 hours (P⫽0.1, ANOVA).
Discussion
In this study of patients with acute MCA main stem occlusion, who were not treated with rtPA and who were scanned
within 6 hours of symptom onset, we could document early
recanalization in 5 of 6 patients (83%). Recanalization began
after a few minutes of continuous exposure to low-intensity
ultrasound. In previous studies of early spontaneous recanalization in similar patients not continuously exposed to
ultrasound, the rates of recanalization were much lower.
Thus, in a recent series of 32 patients with proximal MCA
occlusion first seen between 40 minutes and 5.3 hours from
the onset of symptoms, only 2 (6.3%) had recanalized on a
repeated TCD performed at 6 hours.5 Similarly, in the Duplex
Sonography in Acute Stroke (DIAS I) study, among 12
patients with M1 occlusion first scanned within 6 hours of
symptom onset, none had recanalized on a control TCCD
performed 2 hours after inclusion.6 Finally, in the Prolyse in
Acute Cerebral Thromboembolism (PROACT I and PROACT II) studies, which included patients with angiographically proven M1 or M2 occlusion within 6 hours of symptom
onset, the recanalization rates at 120 minutes for control
patients were 14.3% and 18%, respectively.7,8
Several in vitro studies have established that ultrasound at
low intensity enhances enzymatic fibrinolysis, while it has no
effect on clot dissolution without plasminogen activator.1,2,9
Figure 2. Evolution of recanalization in patient 5. a, Initial partial
recanalization 12 minutes after beginning of monitoring. b,
Increase in peak flow velocity with persistent blunted waveforms
30 seconds later. c, Stenotic flow signal 6 hours later with
increased peak systolic velocity up to 300 cm/s.
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628
Stroke
February 2002
Recently, in an in vitro model using the same 2-MHz
ultrasound system as in the present study, we found that
30-minute insonation of whole blood clots enhanced rtPAinduced thrombolysis by 47% (P⫽0.01).10 Mechanisms
whereby low-intensity ultrasound increases enzymatic fibrinolysis include acoustic microstreaming at clot/blood flow
boundary and reversible changes in fibrin structure, which
both result in increased plasminogen activator binding to
fibrin and transport into the clot.11
In the present study patients were not treated with rtPA.
Thus, if we assume that our findings are not coincidental, the
high rate of early recanalization and the close temporal
relationship between the beginning of continuous exposure to
ultrasound and recanalization suggest that low-intensity ultrasound focused on the occluded MCA main stem under
control by B-mode imaging may have enhanced endogenous
enzymatic fibrinolysis. However, early recanalization was
only partial in all patients. Previous work with angiographic
correlation suggests that blunted waveforms correspond, at
best, to partial deobstruction with delayed filling of distal
branches.4 This may explain, at least in part, why the clinical
improvement in patients with early recanalization did not
reach statistical significance in our study.
The present study has several limitations. The sample size
was small, we did not use a control group, and the assessment
of MCA patency at the end of monitoring was unblinded.
Thus, the findings should be interpreted with caution.
In conclusion, in a short series of consecutive patients with
acute MCA main stem occlusion, not treated with rtPA, we
found a high rate of early recanalization during continuous
exposure to low-intensity, 2-MHz ultrasound. The findings
suggest that ultrasound may have played a role in
thrombolysis. These findings need to be confirmed in other
laboratories before a prospective, controlled study is
considered.
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High Rate of Recanalization of Middle Cerebral Artery Occlusion During 2-MHz
Transcranial Color-Coded Doppler Continuous Monitoring Without Thrombolytic Drug
Pascal Cintas, Anne Pavy Le Traon and Vincent Larrue
Stroke. 2002;33:626-628
doi: 10.1161/hs0202.103073
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