Mechanical Thrombectomy in Acute Anterior Circulation Stroke

162 Pages·2017·4.31 MB·English

S Acta Universitatis Tamperensis 2303
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SARA PROTTO
Mechanical Thrombectomy
in Acute Anterior
Circulation Stroke
ACADEMIC DISSERTATION
To be presented, with the permission of
the Faculty Council of the Faculty of Medicine and Life Sciences
of the University of Tampere,
for public discussion in the auditorium F115 of the Arvo building,
Arvo Ylpön katu 34, Tampere,
on 6 October 2017, at 12 o’clock.
UNIVERSITY OF TAMPERE
SARA PROTTO
Mechanical Thrombectomy
in Acute Anterior
Circulation Stroke
Acta Universitatis Tamperensis 2303
Tampere University Press
Tampere 2017
ACADEMIC DISSERTATION
University of Tampere, Faculty of Medicine and Life Sciences
Finland
Supervised by Reviewed by
Docent Irina Rinta-Kiikka Professor Hannu Manninen
University of Tampere University of Eastern Finland
Finland Finland
D.Med.Sc. Niko Sillanpää Professor Riitta Parkkola
Tampere University Hospital University of Turku
Finland Finland
The originality of this thesis has been checked using the Turnitin OriginalityCheck service
in accordance with the quality management system of the University of Tampere.
Copyright ©2017 Tampere University Press and the author
Cover design by
Mikko Reinikka
Acta Universitatis Tamperensis 2303 Acta Electronica Universitatis Tamperensis 1807
ISBN 978-952-03-0509-3 (print) ISBN 978-952-03-0510-9 (pdf)
ISSN-L 1455-1616 ISSN 1456-954X
ISSN 1455-1616 http://tampub.uta.fi
Suomen Yliopistopaino Oy – Juvenes Print
Tampere 2017
P4a4i1n o t7u2o9te
A mio papá,
Mi hai dato tutto senza chiedere mai nulla in cambio.
Mi manchi ogni ora, ogni minuto, ogni secondo.

Contents
Abstract ........................................................................................................................................ 7
Tiivistelmä ................................................................................................................................... 9
ABBREVIATIONS ................................................................................................................. 11
LIST OF ORIGINAL COMMUNICATIONS ................................................................. 15
1 INTRODUCTION ........................................................................................................ 16
2 REVIEW OF THE LITERATURE ........................................................................... 18
2.1 ACUTE ISCHEMIC STROKE .......................................................................... 18
2.1.1 Pathophysiology and etiology ..................................................................... 18
2.1.2 Risk factors .................................................................................................... 20
2.1.3 Vascular anatomy and the brain vascular territories................................ 22
2.1.4 Functional outcome measures .................................................................... 26
2.2 DIAGNOSIS OF ISCHEMIC STROKE ......................................................... 27
2.2.1 Symptoms and signs of acute ischemic stroke ......................................... 27
2.2.2 Imaging of acute ischemic stroke ............................................................... 29
2.3 ACUTE ISCHEMIC STROKE MANAGEMENT ....................................... 41
2.3.1 Intravenous thrombolysis ............................................................................ 42
2.3.2 Intra-arterial therapy ..................................................................................... 44
3 AIMS OF THE STYDY ................................................................................................ 51
4 SUBJECTS, MATERIALS AND METHODS ......................................................... 52
4.1 Overview ................................................................................................................. 52
4.2 Subjects, study population and baseline characteristics ................................... 54
4.2.1 Mechanical thrombectomy patients (I,III) ................................................ 55
4.2.2 Mechanical thrombectomy patients treated with TREVO® or Capture
LP™ (II) 56
4.2.3 Mechanical thrombectomy patients with onset-to-imaging time less
than 3h (IV) ...................................................................................................................... 57
4.2.4 IVT Patients between January 2004 and December 2007 (IV) ............ 57
4.3 Clinical variables ..................................................................................................... 57
4.4 Imaging parameters ............................................................................................... 58
4.5 Image analysis ......................................................................................................... 59
4.6 Statistical analysis ................................................................................................... 60
5 RESULTS ......................................................................................................................... 61
5.1 Impact of the site of the occlusion on technical and clinical outcomes (I-II,
IV) 61
5.1.1 The site of the occlusion seems not to significantly affect clinical or
technical outcomes of MT (I) ....................................................................................... 61
5.1.2 The clinical benefit of MT is highest for proximal large vessel
occlusions (IV) ................................................................................................................. 64
5.1.3 The technical outcome of MT is not significantly influenced by the
selection of the stent retriever. (II) ............................................................................... 67
5.2 Low CBV-ASPECTS is a predictor of poor clinical outcome in mechanical
thrombectomy (III) ............................................................................................................. 68
6 DISCUSSION ................................................................................................................. 70
6.1 The effect of the occlusion site and the revascularization treatment type on
the outcome of stroke ......................................................................................................... 70
6.2 Influence of the device choice on technical and clinical outcomes ............... 75
6.3 Predicting the outcome of acute ischemic stroke independent of the type of
the revascularization therapy .............................................................................................. 76
6.4 Limitations .............................................................................................................. 78
7 SUMMARY AND CONCLUSIONS ......................................................................... 79
ACKNOWLEDGEMETS ..................................................................................................... 81
REFERENCES ........................................................................................................................ 83
ORIGINAL COMMUNICATIONS ................................................................................. 103
Abstract
Stroke continues to be one of the leading causes of morbidity and mortality
worldwide. Acute ischemic stroke is caused by insufficient blood flow to the brain
tissue and it most often due to occlusion of an intracranial artery by a thrombus.
There have been great advances in the treatment of this condition recently with the
development of the stentretriever-based techniques that allow rapid restoration of
perfusion to the ischemic area. The superiority of these mechanical thrombectomy
(MT) techniques over the previous pharmacological therapies (intravenous
thrombolysis, IVT) has been demonstrated in recent randomized trials. However,
the introduction of interventional techniques has amplified the need to improve
our ability to more precisely stratify risk and refine the treatment decision-making
process to select the correct treatment for patients among these diverse therapeutic
modalities.

This thesis examines in a prospectively collected, observational cohort the principal
parameters that influence the technical and clinical outcomes in patients presenting
acute anterior circulation stroke and treated via MT between January 2013 and
December 2014 in Tampere University Hospital. The 3-month modified Rankin
Scale (mRS) was used as the primary functional outcome measure and the
Thrombolysis in Cerebral Infarction scale (TICI) was used to describe the technical
outcome. The parameters studied included the location of the clot in computed
tomography angiography (CTA) and the device used to perform the intervention.
We also investigated the prognostic value of data derived from perfusion CT
studies (CTP), especially the utility of cerebral blood volume maps (CBV).
Moreover, we compared the results of patients at our institution treated with only
IVT to those treated with MT to assess the differences in clinical outcomes and to
clarify the patient subgroups for which MT outperforms IVT.
Mechanical thrombectomy was clearly superior to IVT in the treatment of
proximal large vessel occlusions whereas neither therapy outperformed the other in
distal large vessel occlusions. In our cohorts, surviving an internal carotid artery
(ICA) or a proximal M1 segment of the middle cerebral artery (MCA) occlusion
without any disability-causing neurological deficits required MT. The site of the
occlusion does not seem to have a significant effect on the technical success rates
of MT. Further, the selection of the newer generation stent retriever does not
appear to result in differences in technical or clinical outcomes. This supports the
notion that the decision of which device to use should be left to the operator based
on his/her own experience.

Cerebral blood volume mapping assessed semiquantitatively with the Alberta
Stroke Program Early CT score (ASPECTS) is an established predictor of outcome
in a variety of clinical settings. In our study, a low CBV-ASPECTS score at
admission was associated with a large infarct core in follow-up imaging and was a
significant predictor of poor clinical outcome, especially in the setting of poor
collateral circulation and/or moderate or severe stroke. The collateral score was
also a significant predictive factor. Having no visible collateral circulation in the
admission CTA was specifically related to poor clinical outcome.

Keywords: ASPECTS, mechanical thrombectomy, intravenous thrombolysis, stroke,
computed tomography perfusion, collateral score, modified Rankin scale,
Thrombolysis in Cerebral Infarction scale.