(Stroke. 2000;31:1128.)
© 2000 American Heart Association, Inc.
Original Contributions |
Transcranial Doppler Ultrasound Criteria for Recanalization After Thrombolysis for Middle Cerebral Artery Stroke
From the Stroke Treatment Team, University of Texas–Houston Medical School.
Correspondence to Dr A. Alexandrov, Department of Neurology, University of Texas–Houston Medical School, 6431 Fannin, MSB 7.044, Houston, TX 77030. E-mail avalexandrov{at}worldnet.att.net
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Abstract |
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 Top Abstract IntroductionSubjects and MethodsResultsDiscussionReferences |
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Background and Purpose—Transcranial Doppler (TCD) can demonstrate arterial occlusion and subsequent recanalization in acute ischemic stroke patients treated with intravenous tissue plasminogen activator (tPA). Limited data exist to assess the accuracy of recanalization by TCD criteria.
Methods—In patients with acute middle cerebral artery (MCA) occlusion treated with intravenous tPA, we compared posttreatment TCD with angiography (digital subtraction or magnetic resonance). On TCD, complete occlusion was defined by absent or minimal signals, partial occlusion by blunted or dampened signals, and recanalization by normal or stenotic signals. Angiography was evaluated with the Thrombolysis In Myocardial Ischemia (TIMI) grading scale.
Results—Twenty-five patients were studied (age 61±18 years, 16
men and 9 women). TCD was performed at 12±16 hours and angiography at
41±57 hours after stroke onset, with 52% of studies performed within
3 hours of each other. Recanalization on TCD had
the following accuracy parameters compared with
angiography: sensitivity 91%, specificity 93%, positive predictive
value (PPV) 91%, and negative predictive value (NPV) 93%. To predict
partial occlusion (TIMI grade II), TCD had sensitivity of 100%,
specificity of 76%, PPV of 44%, and NPV of 100%. TCD predicted the
presence of complete occlusion on angiography (TIMI grade 0 or I) with
sensitivity of 50%, specificity of 100%, PPV of 100%, and NPV of
75%. TCD flow signals correlated with angiographic patency
(
2=24.2, P<0.001).
Conclusions—Complete MCA recanalization on TCD accurately predicts angiographic findings. Although a return to normal flow dynamics on TCD was associated with complete angiographic resumption of flow, partial signal improvement on TCD corresponded with persistent occlusion on angiography.
Key Words: angiography • recanalization • thrombolysis • ultrasonography
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Introduction |
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TopAbstractIntroductionSubjects and MethodsResultsDiscussionReferences |
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The advantages of transcranial Doppler (TCD) evaluation of cerebral vessels include the fact that it is a low-cost, noninvasive bedside assessment. However, in the context of acute stroke, digital subtraction angiography (DSA), magnetic resonance angiography (MRA), and computed tomography angiography (CTA) are more commonly used. These methods are more expensive and more time consuming and do not provide continuous blood flow monitoring.
As experience with cerebral thrombolysis increases, there is mounting evidence that improved outcomes are associated with recanalization and improved brain perfusion.1 2 3 4 With intra-arterial thrombolysis,2 recanalization can be monitored by the use of concurrent angiography, but recanalization is not routinely evaluated after intravenous thrombolysis.3 5 Information about recanalization may help to determine patient prognosis and direct further management.6 TCD offers an inexpensive and continuous means of monitoring vessel patency.
TCD criteria for identifying intracranial occlusion and recanalization have been described previously.6 7 8 9 Accuracy parameters for TCD assessment of middle cerebral artery (MCA) occlusion were established previously.7 8 10 However, the accuracy of TCD in identifying recanalization after thrombolysis remains unknown. The goal of the present study was to compare TCD findings after intravenous thrombolysis with subsequent angiography to determine accuracy parameters for identifying MCA recanalization.
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Subjects and Methods |
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TopAbstractIntroductionSubjects and MethodsResultsDiscussionReferences |
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We evaluated patients who received intravenous tissue plasminogen activator (tPA) from November 1996 through July 1999 and who had baseline and follow-up TCD according to a prospective protocol designed to identify the presence of an MCA occlusion and subsequent recanalization. Data on subsequent angiography were collected as part of ongoing quality-assurance evaluation. For TCD, a single-channel 2-MHz machine was used (Multigon 500M, DWL Multi-Dop-T, Marc 500 headframe, Spencer Technologies, Inc). tPA was given intravenously within the first 3 hours after stroke onset at a standard Food and Drug Administration–approved dose of 0.9 mg/kg,5 to a maximum of 90 mg, or at a dose of 0.6 mg/kg, to a maximum dose of 60 mg, started between 3 and 6 hours, as part of an experimental treatment protocol approved by the University of Texas Committee for the Protection of Human Subjects.11
Complete occlusion was diagnosed by TCD when absent or minimal signals
(Figure 1
) were found at 1 or more MCA
depths (range 40 to 65 mm) and accompanied by flow diversion to
the anterior (ACA) or posterior (PCA) cerebral arteries (mean flow
velocity ACA>contralateral MCA or PCA>contralateral MCA). We defined
a minimal flow signal as a short peak systolic spike with no
end-diastolic flow. In this case, either terminal internal
carotid artery or PCA flow signals had to be identified from the
ipsilateral temporal window to exclude suboptimal ultrasound
penetration through the bone. Absent or minimal flow signals were
confirmed by insonation from the contralateral temporal window.
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We diagnosed partial occlusion if blunted or dampened signals (Figure 1
) were found at 
1 MCA depth (40 to 65 mm) with flow
diversion signs to the ACA or PCA. A blunted flow signal was identified
when delayed (0.2 seconds) systolic flow acceleration was
present with a pulsatility index (PI) <1.2 (PI [Gosling]=[peak
systolic velocity-end-diastolic velocity]/mean
flow velocity). This PI range indicates low-resistance flow diversion
in a branching vessel (ACA) or a residual positive
end-diastolic flow at the site of occlusion (MCA). A
dampened flow signal was identified when normal systolic flow
acceleration was present in the pulsatile MCA waveform with mean
flow velocity 
70% of the contralateral MCA and positive
end-diastolic flow with variable PI values.
Complete recanalization was diagnosed if
low-resistance stenotic or normal signals (Figure 1)
were found throughout the MCA stem (depths 40 to 65 mm) with no
other signs of persisting distal occlusion (ie, dampened distal signal
or flow diversion). In cases with residual stenosis on TCD,
low-resistance flow indicates patency and perfusion of the distal
vasculature (see criteria below).
Angiographic studies after thrombolysis included DSA,
MRA, or CTA. DSA was the standard for comparison regardless of the time
it was performed. If only MRA or CTA was obtained, the test performed
closest to treatment was used as the best available standard. MCA flow
was graded on the angiograms according to the Thrombolysis
In Myocardial Infarction (TIMI) criteria.12 The
application of these criteria to cerebral vessels has been reported
previously.2 Complete occlusion (TIMI grade 0 or I) was
defined as no or minimal perfusion with no opacification of the distal
vessels on DSA and no reconstitution of distal flow on MRA or CTA
(Figure 1). Partial occlusion (TIMI grade II) was defined as an
obstruction that resulted in a delayed opacification of the distal
vessels on DSA and appearance of distal slow-flow signals of decreased
intensity on MRA or CTA. Complete recanalization
(TIMI grade III) was defined as unimpeded perfusion of the distal
vasculature (Figure 1), regardless of whether a residual
stenosis or a focal flow gap was present (Figures 2 and 3).
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Accuracy parameters included sensitivity, specificity,
positive predictive value (PPV), and negative predictive value (NPV).
Sensitivity represents the proportion of patients with a
positive TCD who also had positive results on the test considered the
standard of accuracy, in this case angiographic TIMI grades. When the
same comparison is used, specificity is the proportion with negative
results. Predictive values indicate the probability of disease (PPV) or
absence of disease (NPV) based on the results of the test.
2 Analysis was used to correlate TCD
waveform findings with vessel patency at angiography.
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Results |
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TopAbstractIntroductionSubjects and MethodsResultsDiscussionReferences |
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Emergent TCD identified 25 patients with MCA occlusion who had the following characteristics: age 61±18 years (range 31 to 93 years); 16 men, 9 women; and 13 left MCA occlusions and 12 right MCA occlusions. Of these, 20 patients were treated with a standard tPA dose within the first 3 hours after stroke and 5 with a lower dose between 3 and 6 hours. All patients were evaluated by repeat TCD and subsequent angiography: 12 patients had DSA, 11 had MRA, and 2 had CTA. Repeat TCD was performed at 12±16 hours (range 2 to 48 hours) and angiography at 41±57 hours (range 3 to 264 hours) after stroke onset with an average delay of 29±52 hours (range 0 to 240 hours) between the studies. Fifty-two percent of angiographic studies were performed within 3 hours after TCD, 20% within 3 to 24 hours, and 28% after 24 hours.
At repeat TCD after tPA infusion, MCA occlusion was found in 5 (20%) of 25 patients, partial occlusion in 9 (36%) of 25, and complete recanalization in 11 (44%) of 25. In comparison, subsequent angiography revealed complete occlusion in 10 (40%) of 25, partial occlusion in 4 (16%) of 25, and complete recanalization in 11 (44%) of 25 patients.
Complete recanalization on TCD predicted TIMI grade
III flow on angiography with the following accuracy
parameters: sensitivity 91%, specificity 93%, PPV 91%,
and NPV 93%. To predict partial occlusion (TIMI grade II), TCD had
sensitivity of 100%, specificity of 76%, PPV of 44%, and NPV of
100%. TCD predicted complete occlusion on angiography (TIMI grade 0 or
I) with sensitivity of 50%, specificity of 100%, PPV of 100%, and
NPV of 75%. TCD criteria for partial and complete occlusion, the
inverse of recanalization, predicted persisting
occlusion at angiography (TIMI grades 0 through II) with accuracy
parameters as for TIMI grade III. The TCD waveforms
correlated with vessel patency at angiography
(2=24.2, P<0.001;
Table). Typical patterns of
complete occlusion, partial occlusion, and complete
recanalization are provided (Figures 1 through 3).
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Discussion |
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TopAbstractIntroductionSubjects and MethodsResultsDiscussionReferences |
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Our study has shown the sensitivity and specificity of TCD in predicting MCA recanalization after tPA treatment. We also showed that abnormal MCA waveforms correlate with angiographic presence of occlusion. TCD evidence for partial occlusion (blunted or dampened flow signals) should be interpreted as a predictor of a persisting MCA occlusion at angiography.
Previous studies have shown that TCD can determine the presence of MCA
occlusion and that it can be used to monitor
recanalization, but the number of angiographic
studies performed was insufficient to determine accuracy
parameters for
recanalization.6 In the present
study, complete MCA recanalization on TCD was
present if a low-resistance flow was found with 70% velocity
compared with the contralateral MCA. Although TCD may not reliably
differentiate residual stenosis or hyperemia after
reperfusion,6 our criteria allow accurate prediction of
TIMI grade III, because low-resistance flow, regardless of velocity
increase, predicts rapid opacification of distal vessels. Repeat TCD
examination may be required to differentiate hyperemia
(decreasing velocities) from residual stenosis (a persistent
focal velocity increase).
Information obtained from TCD regarding MCA recanalization has clinical importance. Recovery after intravenous tPA is associated with recanalization and resumption of flow. Previous studies13 14 showed that recanalization corresponds to clinical improvement seen in some patients during or shortly after intravenous tPA infusion. The question remains as to what to do with patients who do not experience early recovery. Whether the continued neurological deficit is due to persistent occlusion has important clinical implications. The lack of clinical recovery or worsening of neurological deficit was associated with persistent occlusion or reocclusion in 50% of patients who received intravenous tPA at our center.14 These patients would be potential candidates for intra-arterial therapy used in a bridging protocol.11 15
The Intra-Arterial Prourokinase for Acute Ischemic Stroke Trial (PROACT II)16 showed a benefit in acute ischemic stroke patients who received intra-arterial thrombolysis. However, of the 474 patients who received diagnostic angiograms, only 180 were eligible for treatment on the basis of PROACT II criteria. Bedside diagnosis of MCA flow status can minimize the number of diagnostic angiograms required to find a treatable MCA occlusion.
Our data show that TCD can accurately predict complete recanalization (PPV 91%) and complete occlusion (PPV 100%). Findings of partial occlusion on TCD were relatively sensitive but not highly specific compared with angiography, with partial occlusion representing complete angiographic occlusion in 44% of cases but rarely representing complete recanalization. Therefore, tPA nonresponders with TCD findings of complete or partial occlusion are likely to have persisting occlusion on angiography and thus may be potential candidates for further intervention. Conversely, the remaining 27% of patients treated with intravenous tPA who have persistent neurological deficit despite recanalization14 might be spared the risk and expense of an angiogram that is unlikely to reveal a treatable thrombus.
Our study has limitations. Factors that affect TCD accuracy include the absence of temporal windows, the unavailability of ultrasound contrast materials in the United States, and time delays between TCD and angiography.10 17 The influence of delay could have been evaluated if follow-up TCD had been performed immediately after subsequent angiography. However, this is not a part of a standard clinical protocol for TCD at our center. The delay may slightly overestimate the rate of recanalization, because some patients may have experienced delayed recanalization during the first 3 days. However, some patients may have also experienced reocclusion or had MCA clot propagation, thus affecting correlation for partial or complete occlusion. DSA was not performed in all patients, and a substantial portion of patients in our study had MRA. This imaging modality is inferior to DSA, particularly for visualization of slow flow or severe stenosis. Nevertheless, it is often used in clinical practice, and TCD performance is judged against MRA. Also, patients included in this study were selected on the basis of pre-tPA TCD evidence of MCA occlusion. Reports by others, as well as our previous observations, indicate good accuracy of TCD as a screening tool in this setting,6 8 10 and the accuracy parameters after tPA infusion continue to confirm the accuracy of TCD. Although the results of the present study cannot be applied to arteries other than the MCA, the predictive value of abnormal MCA waveforms suggests the need for further evaluation of waveforms throughout the circle of Willis.
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Acknowledgments |
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Drs Burgin and Felberg are supported by a National Institutes of Health fellowship training grant (No. 1-T32-NS07412-O1A1) for the Stroke Program, University of Texas–Houston Medical School. Dr I. Christou is supported by a Hellenic Ministry of Defense Visiting Clinician Grant, Athens, Greece.
Received October 20, 1999; revision received January 6, 2000; accepted January 31, 2000.
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M. Daffertshofer, A. Gass, P. Ringleb, M. Sitzer, U. Sliwka, T. Els, O. Sedlaczek, W. J. Koroshetz, and M. G. Hennerici Transcranial Low-Frequency Ultrasound-Mediated Thrombolysis in Brain Ischemia: Increased Risk of Hemorrhage With Combined Ultrasound and Tissue Plasminogen Activator: Results of a Phase II Clinical Trial Stroke, July 1, 2005; 36(7): 1441 - 1446. [Abstract] [Full Text] [PDF]
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M. Rubiera, J. Alvarez-Sabin, M. Ribo, J. Montaner, E. Santamarina, J. F. Arenillas, R. Huertas, P. Delgado, F. Purroy, and C. A. Molina Predictors of Early Arterial Reocclusion After Tissue Plasminogen Activator-Induced Recanalization in Acute Ischemic Stroke Stroke, July 1, 2005; 36(7): 1452 - 1456. [Abstract] [Full Text] [PDF]
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M. Saqqur, A. Shuaib, A. V. Alexandrov, M. D. Hill, S. Calleja, T. Tomsick, J. Broderick, and A. M. Demchuk Derivation of Transcranial Doppler Criteria for Rescue Intra-arterial Thrombolysis: Multicenter Experience From the Interventional Management of Stroke Study Stroke, April 1, 2005; 36(4): 865 - 868. [Abstract] [Full Text] [PDF]
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S. U. Kwon, Y.-J. Cho, J.-S. Koo, H.-J. Bae, Y.-S. Lee, K.-S. Hong, J. H. Lee, and J. S. Kim Cilostazol Prevents the Progression of the Symptomatic Intracranial Arterial Stenosis: The Multicenter Double-Blind Placebo-Controlled Trial of Cilostazol in Symptomatic Intracranial Arterial Stenosis Stroke, April 1, 2005; 36(4): 782 - 786. [Abstract] [Full Text] [PDF]
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J. Eggers, G. Seidel, B. Koch, and I. R. Konig Sonothrombolysis in acute ischemic stroke for patients ineligible for rt-PA Neurology, March 22, 2005; 64(6): 1052 - 1054. [Abstract] [Full Text] [PDF]
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M. Ribo, C. A. Molina, A. Rovira, M. Quintana, P. Delgado, J. Montaner, E. Grive, J. F. Arenillas, and J. Alvarez-Sabin Safety and Efficacy of Intravenous Tissue Plasminogen Activator Stroke Treatment in the 3- to 6-Hour Window Using Multimodal Transcranial Doppler/MRI Selection Protocol Stroke, March 1, 2005; 36(3): 602 - 606. [Abstract] [Full Text] [PDF]
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E. A. Noser, H. M. Shaltoni, C. E. Hall, A. V. Alexandrov, Z. Garami, E. D. Cacayorin, J. K. Song, J. C. Grotta, and M. S. Campbell III Aggressive Mechanical Clot Disruption: A Safe Adjunct to Thrombolytic Therapy in Acute Stroke? Stroke, February 1, 2005; 36(2): 292 - 296. [Abstract] [Full Text] [PDF]
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 A. V. Alexandrov, C. A. Molina, J. C. Grotta, Z. Garami, S. R. Ford, J. Alvarez-Sabin, J. Montaner, M. Saqqur, A. M. Demchuk, L. A. Moye, et al. Ultrasound-Enhanced Systemic Thrombolysis for Acute Ischemic Stroke N. Engl. J. Med., November 18, 2004; 351(21): 2170 - 2178. [Abstract] [Full Text] [PDF]
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J. Alvarez-Sabin, C. A. Molina, M. Ribo, J. F. Arenillas, J. Montaner, R. Huertas, E. Santamarina, and M. Rubiera Impact of Admission Hyperglycemia on Stroke Outcome After Thrombolysis: Risk Stratification in Relation to Time to Reperfusion Stroke, November 1, 2004; 35(11): 2493 - 2498. [Abstract] [Full Text] [PDF]
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S. Pedraza, Y. Silva, J. Mendez, L. Inaraja, J. Vera, J. Serena, and A. Davalos Comparison of Preperfusion and Postperfusion Magnetic Resonance Angiography in Acute Stroke Stroke, September 1, 2004; 35(9): 2105 - 2110. [Abstract] [Full Text] [PDF]
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D. Georgiadis, J. Oehler, S. Schwarz, V. Rousson, M. Hartmann, and S. Schwab Does acute occlusion of the carotid T invariably have a poor outcome? Neurology, July 13, 2004; 63(1): 22 - 26. [Abstract] [Full Text] [PDF]
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M. A. Sloan, A. V. Alexandrov, C. H. Tegeler, M. P. Spencer, L. R. Caplan, E. Feldmann, L. R. Wechsler, D. W. Newell, C. R. Gomez, V. L. Babikian, et al. Assessment: Transcranial Doppler ultrasonography: Report of the Therapeutics and Technology Assessment Subcommittee of the American Academy of Neurology Neurology, May 11, 2004; 62(9): 1468 - 1481. [Abstract] [Full Text] [PDF]
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C. A. Molina, J. Montaner, J. F. Arenillas, M. Ribo, M. Rubiera, and J. Alvarez-Sabin Differential Pattern of Tissue Plasminogen Activator-Induced Proximal Middle Cerebral Artery Recanalization Among Stroke Subtypes Stroke, February 1, 2004; 35(2): 486 - 490. [Abstract] [Full Text] [PDF]
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A. V. Alexandrov, C. E. Hall, L. A. Labiche, A. W. Wojner, and J. C. Grotta Ischemic Stunning of the Brain: Early Recanalization Without Immediate Clinical Improvement in Acute Ischemic Stroke Stroke, February 1, 2004; 35(2): 449 - 452. [Abstract] [Full Text] [PDF]
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C. A. Molina, A. V. Alexandrov, A. M. Demchuk, M. Saqqur, K. Uchino, and J. Alvarez-Sabin Improving the Predictive Accuracy of Recanalization on Stroke Outcome in Patients Treated With Tissue Plasminogen Activator Stroke, January 1, 2004; 35(1): 151 - 156. [Abstract] [Full Text] [PDF]
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T. Neumann-Haefelin, R. du Mesnil de Rochemont, J.B. Fiebach, A. Gass, C. Nolte, T. Kucinski, J. Rother, M. Siebler, O.C. Singer, K. Szabo, et al. Effect of Incomplete (Spontaneous and Postthrombolytic) Recanalization After Middle Cerebral Artery Occlusion: A Magnetic Resonance Imaging Study Stroke, January 1, 2004; 35(1): 109 - 114. [Abstract] [Full Text] [PDF]
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J. Alvarez-Sabin, C. A. Molina, J. Montaner, J. F. Arenillas, R. Huertas, M. Ribo, A. Codina, and M. Quintana Effects of Admission Hyperglycemia on Stroke Outcome in Reperfused Tissue Plasminogen Activator-Treated Patients Stroke, May 1, 2003; 34(5): 1235 - 1240. [Abstract] [Full Text] [PDF]
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 C Foerch, R Du Mesnil de Rochemont, O Singer, T Neumann-Haefelin, M Buchkremer, F E Zanella, H Steinmetz, and M Sitzer S100B as a surrogate marker for successful clot lysis in hyperacute middle cerebral artery occlusion J. Neurol. Neurosurg. Psychiatry, March 1, 2003; 74(3): 322 - 325. [Abstract] [Full Text] [PDF]
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L. A. Labiche, F. Al-Senani, A. W. Wojner, J. C. Grotta, M. Malkoff, and A. V. Alexandrov Is the Benefit of Early Recanalization Sustained at 3 Months?: A Prospective Cohort Study Stroke, March 1, 2003; 34(3): 695 - 698. [Abstract] [Full Text] [PDF]
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A. V. Alexandrov and J. C. Grotta Arterial reocclusion in stroke patients treated with intravenous tissue plasminogen activator Neurology, September 24, 2002; 59(6): 862 - 867. [Abstract] [Full Text] [PDF]
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J. P. Broderick and W. Hacke Treatment of Acute Ischemic Stroke: Part I: Recanalization Strategies Circulation, September 17, 2002; 106(12): 1563 - 1569. [Full Text] [PDF]
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M. Arnold, G. Schroth, K. Nedeltchev, T. Loher, L. Remonda, F. Stepper, M. Sturzenegger, and H. P. Mattle Intra-Arterial Thrombolysis in 100 Patients With Acute Stroke Due to Middle Cerebral Artery Occlusion Stroke, July 1, 2002; 33(7): 1828 - 1833. [Abstract] [Full Text] [PDF]
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C. A. Molina, J. Alvarez-Sabin, J. Montaner, S. Abilleira, J. F. Arenillas, P. Coscojuela, F. Romero, and A. Codina Thrombolysis-Related Hemorrhagic Infarction: A Marker of Early Reperfusion, Reduced Infarct Size, and Improved Outcome in Patients With Proximal Middle Cerebral Artery Occlusion Stroke, June 1, 2002; 33(6): 1551 - 1556. [Abstract] [Full Text] [PDF]
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S. Akopov and G.T. Whitman Hemodynamic Studies in Early Ischemic Stroke: Serial Transcranial Doppler and Magnetic Resonance Angiography Evaluation Stroke, May 1, 2002; 33(5): 1274 - 1279. [Abstract] [Full Text] [PDF]
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R. A. Felberg, N. J. Okon, A. El-Mitwalli, W. S. Burgin, J. C. Grotta, and A. V. Alexandrov Early Dramatic Recovery During Intravenous Tissue Plasminogen Activator Infusion: Clinical Pattern and Outcome in Acute Middle Cerebral Artery Stroke Stroke, May 1, 2002; 33(5): 1301 - 1307. [Abstract] [Full Text] [PDF]
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P. Cintas, A. P. Le Traon, and V. Larrue High Rate of Recanalization of Middle Cerebral Artery Occlusion During 2-MHz Transcranial Color-Coded Doppler Continuous Monitoring Without Thrombolytic Drug Stroke, February 1, 2002; 33(2): 626 - 628. [Abstract] [Full Text] [PDF]
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C. A. Molina, J. Montaner, S. Abilleira, J. F. Arenillas, M. Ribo, R. Huertas, F. Romero, and J. Alvarez-Sabin Time Course of Tissue Plasminogen Activator-Induced Recanalization in Acute Cardioembolic Stroke: A Case-Control Study Stroke, December 1, 2001; 32(12): 2821 - 2827. [Abstract] [Full Text] [PDF]
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D. W. Krieger, M. A. De Georgia, A. Abou-Chebl, J. C. Andrefsky, C. A. Sila, I. L. Katzan, M. R. Mayberg, and A. J. Furlan Cooling for Acute Ischemic Brain Damage (COOL AID): An Open Pilot Study of Induced Hypothermia in Acute Ischemic Stroke Stroke, August 1, 2001; 32(8): 1847 - 1854. [Abstract] [Full Text] [PDF]
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Recommendations for Clinical Trial Evaluation of Acute Stroke Therapies Stroke, July 1, 2001; 32(7): 1598 - 1606. [Abstract] [Full Text] [PDF]
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A. V. Alexandrov, W. S. Burgin, A. M. Demchuk, A. El-Mitwalli, and J. C. Grotta Speed of Intracranial Clot Lysis With Intravenous Tissue Plasminogen Activator Therapy : Sonographic Classification and Short-Term Improvement Circulation, June 19, 2001; 103(24): 2897 - 2902. [Abstract] [Full Text] [PDF]
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A. M. Demchuk, W. S. Burgin, I. Christou, R. A. Felberg, P. A. Barber, M. D. Hill, and A. V. Alexandrov Thrombolysis in Brain Ischemia (TIBI) Transcranial Doppler Flow Grades Predict Clinical Severity, Early Recovery, and Mortality in Patients Treated With Intravenous Tissue Plasminogen Activator Stroke, January 1, 2001; 32(1): 89 - 93. [Abstract] [Full Text] [PDF]
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I. Christou, A. V. Alexandrov, W. S. Burgin, A. W. Wojner, R. A. Felberg, M. Malkoff, and J. C. Grotta Timing of Recanalization After Tissue Plasminogen Activator Therapy Determined by Transcranial Doppler Correlates With Clinical Recovery From Ischemic Stroke Stroke, August 1, 2000; 31(8): 1812 - 1816. [Abstract] [Full Text] [PDF]
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