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Thrombectomy Complications in Large Vessel Occlusions: Incidence, Predictors, and Clinical Impact in the ETIS Registry

and on behalf of the ETIS Registry Investigators†
Originally published 2021;52:e764–e768


Background and Purpose:

Procedural complications in thrombectomy for large vessel occlusions of the anterior circulation are not well described. We investigated the incidence, risk factors, and clinical implications of thrombectomy complications in daily clinical practice.


We used data from the ongoing prospective multicenter observational Endovascular Treatment in Ischemic Stroke Registry in France. The present study is a retrospective analysis of 4029 stroke patients with anterior large vessel occlusions treated with thrombectomy between January 2015 and May 2020 in 18 centers. We systematically collected procedural data, incidence of embolic complications, perforations and dissections, clinical outcome at 90 days, and hemorrhagic complications.


Procedural complications occurred in 7.99% (95% CI, 7.17%–8.87%), and embolus to a new territory (ENT) was the most frequent (5.2%). Predictors of ENTs were terminal carotid/tandem occlusion (odds ratio [OR], 5 [95% CI, 2.03–12.31]; P<0.001) and an increased total number of passes (OR, 1.22 [95% CI, 1.05–1.41]; P=0.006). ENTs were associated to worse clinical outcomes (90-day modified Rankin Scale score, 0–2; adjusted OR, 0.4 [95% CI, 0.25–0.63]; P<0.001), increased mortality (adjusted OR, 1.74 [95% CI, 1.2–2.53]; P<0.001), and symptomatic intracerebral hemorrhage (adjusted OR, 1.87 [95% CI, 1.15–3.03]; P=0.011). Perforations occurred in 1.69% (95% CI, 1.31%–2.13%). Predictors of perforations were terminal carotid/tandem occlusions (39.7% versus 27.6%; P=0.028). 40.7% of patients died at 90 days, and the overall rate of poor outcome was 74.6% in case of perforation. Dissections occurred in 1.46% (95% CI, 1.11%–1.88%) and were more common in younger patients (median age, 64.2 versus 70.2 years; P=0.002). Dissections did not affect the clinical outcome at 90 days. Besides dissection, complications were independent of the thrombectomy technique.


Thrombectomy complication rate is not negligible, and ENTs were the most frequent. ENTs and perforations were associated with disability and mortality, and terminal carotid/tandem occlusions were a risk factor.


URL:; Unique identifier: NCT03776877.

Thrombectomy is a highly effective treatment for anterior circulation acute ischemic stroke due to large vessel occlusion, with an increasing number of eligible patients.1 Despite its high efficiency, thrombectomy may be hampered by several procedural complications that may be associated with worse clinical outcomes. Knowledge of the rate, predictors, and clinical impact may allow optimization of thrombectomy procedures. Relatively few studies have described procedural complications for anterior circulation endovascular stroke treatment.2–4 Therefore, we aimed to report the individual complication rate, clinical characteristics, risk factors, and outcomes of thrombectomy in current clinical practice.


The data that support the findings of this study are available from the corresponding author upon reasonable request.


We used data from the Endovascular Treatment in Ischemic Stroke Registry (; unique identifier: NCT03776877)—an ongoing, prospective, observational study in 18 comprehensive stroke centers in France performing thrombectomy for large vessel occlusions between January 1, 2015, and May 31, 2020. The local institutional review boards approved data collection and analyses. All data of the Endovascular Treatment in Ischemic Stroke registry were collected, stored, and accessed locally according to the recommendations of the Comité consultatif sur le traitement de l’information en matière de recherche dans le Domaine de santé. All patients who underwent thrombectomy for acute ischemic stroke in the anterior or posterior circulation in these centers get recorded in the Endovascular Treatment in Ischemic Stroke Registry. For the present analysis, inclusion criteria were as follows: (1) anterior large vessel occlusions (intracranial internal carotid artery [ICA], tandem, M1, and M2 segments) confirmed on angiogram; (2) thrombectomy using stent retrievers or large-bore aspiration catheters as the primary treatment or as an add-on to intravenous thrombolysis with alteplase (0.9 mg/kg) if eligible according to the guidelines.


Procedure-related complications were defined and recorded by the attending neurointerventionist as follows: emboli to a new territory (ENT) on the final intracranial angiographic run, vessel perforation as contrast extravasation during the procedure, and arterial dissection as a new intimal flap. Further details on collected procedural data are available in the Supplemental Material. Early neurological improvement represented complete recovery or a decrease by ≥4 points on the National Institutes of Health Stroke Scale at baseline and at 24 hours. Favorable and excellent clinical outcomes were defined as modified Rankin Scale (mRS) score of 0 to 2 and mRS score of 0 to 1 at 90 days. Ninety days after the acute event, functional outcome was assessed by board-certified vascular neurologists during a routinely scheduled clinical visit or by a study nurse certified in administering the mRS during a standardized telephone interview if the patient was unable to attend.

Statistical Analysis

Continuous variables are expressed as means±SD or medians (interquartile range) and categorical variables as numbers (percentage). Normality of distribution was assessed using histograms and the Shapiro-Wilk test. Bivariate comparisons for baseline, treatment characteristics, and outcomes between the study groups were made using the χ2 test for categorical variables and the Mann-Whitney U test for nongaussian continuous and ordinal categorical variables.

We assessed independent predictors only for embolic complications because of the low incidence of the other complications. To determine the independent predictors of ENTs, all baseline and treatment characteristics with P<0.10 in the bivariate analyses were entered into a forward stepwise multivariable logistic model using an entrance criterion of P<0.10; adjusted odds ratios (ORs) were derived from these models as effect sizes using the absence of ENTs as the reference group. The difference in ordinal outcome (overall distribution in 90-day mRS) is expressed as the common OR for 1-point improvement calculated using a mixed ordinal logistic regression model (shift analysis). Finally, we assessed the impact of individual complication types on clinical efficacy and safety outcome (favorable and excellent outcomes, early neurological improvement, mortality, and parenchymal hematoma) using univariate mixed models with center as random effect. For ENTs, effect sizes were further adjusted for age, initial National Institutes of Health Stroke Scale, Alberta Stroke Program Early CT Scale, use of prior intravenous thrombolysis, occlusion site, total number of passes, and time from onset to puncture. Statistical testing was done at the 2-tailed α-level of 0.05 with no Bonferroni correction. Data were analyzed using STATA, software v 16.1.


Flowchart of the study is presented in Figure I in the Supplemental Material. Among the 4029 patients, 322 (7.99%) presented a procedural complication: 203 (5.2%) ENTs, 68 (1.69%) perforations, and 59 (1.46%) dissections.

At univariate analysis, a younger age (mean, 68.2 versus 70.2 years; P=0.048), higher initial National Institutes of Health Stroke Scale (median, 18 versus 16; P<0.001), lower proportion of M1 or M2 occlusions (46.8% versus 73.5%; P<0.001), lower clot burden score (mean, 5.6 versus 6.1; P=0.039), higher likelihood to have an Alberta Stroke Program Early CT Scale score <7 (32.3% versus 47.6%; P<0.001), and lower likelihood to have a stroke of cardioembolic etiology (42.2% versus 50%; P=0.038) were associated with ENTs (Table I in the Supplemental Material). Terminal ICA/tandem occlusion (OR, 5 [95% CI, 2.03–12.31]; P=0.001) and the total number of passes (OR, 1.22 [95% CI, 1.05–1.41]; P=0.006) were predictors of ENTs at multivariate analysis. ENTs were associated with a lower rate of good reperfusion (modified Thrombolysis in Cerebral Infarction 2b-3, 75% versus 86%; P<0.001). Patients with ENT had worse clinical outcomes with an adjusted OR of 0.40 ([95% CI, 0.25–0.63] P<0.001) for 90-day mRS score of 0 to 2 and 1.74 ([95% CI, 1.2–2.53] P=0.003) for mortality (Table 1). ENT patients had an increased likelihood of developing symptomatic intracranial hemorrhage (adjusted OR, 1.87 [95% CI, 1.5–3.03]; P=0.011). The worse clinical outcomes associated with ENTs are also observed in the distribution of mRS at 90 days (adjusted OR, 0.61 [95% CI, 0.42–0.87]; P=0.007; Figure).

Table 1. Clinical Impact of Embolic Complications

no ENT (n=3826)ENT (n=203)Unadjusted OR* (95% CI)P valueAdjusted OR (95% CI)P value
Early neurological improvement1922 (50.2)62 (30.5)0.45 (0.33–0.62)<0.0010.46 (0.32–0.67)<0.001
mRS 0–2 at 90 d1421 (43.5)42 (22.5)0.35 (0.24–0.49)<0.0010.40 (0.25–0.63)<0.001
mRS 0–1 at 90 d924 (28.3)26 (13.9)0.38 (0.25–0.58)<0.0010.39 (0.22–0.7)0.002
mRS 6 at 90 d709 (21.7)69 (36.9)2.16 (1.58–2.95)<0.0011.74 (1.2–2.53)0.003
PH390 (13.1)35 (19.9)1.69 (1.14–2.5)0.0091.31 (0.84–2.06)0.229
sICH239 (7.9)28 (15.6)2.11 (1.37–3.24)0.0011.87 (1.15–3.03)0.011

Values are expressed as n/total n (%) unless otherwise indicated. ASPECTS indicates Alberta Stroke Program Early CT Scale; ENT, emboli to new territory; mRS, modified Rankin Scale; mTICI, modified Thrombolysis in Cerebral Infarction; NIHSS, National Institutes of Health Stroke Scale; OR, odds ratio; PH, parenchymal hemorrhage; and sICH, symptomatic intracranial hemorrhage.

* Calculated with a mixed model with center as random effect.

† Calculated with a mixed model with center as random effect and good recanalization (mTICI 2b-3), age, initial NIHSS, ASPECTS, occlusion site.

‡ Significant at the 2-tailed a=0.05.


Figure. Distribution of modified Rankin Scale (mRS) at 90 d for the different types of intraprocedural complications. ENT indicates emboli to new territory. *Calculated using the no-complication group as a reference using a mixed model with center as random effect and good recanalization (modified Thrombolysis in Cerebral Infarction 2b-3), age, initial National Institutes of Health Stroke Scale, Alberta Stroke Program Early CT Scale, occlusion site, total number of passes, and time from onset to puncture. **Calculated using the no-complication group as a reference using a mixed model with center as random effect.

Univariate analysis for perforations is reported on Table II in the Supplemental Material. Perforations resulted in a worse mRS at 90 days (OR, 0.38 [95% CI, 0.24–0.61]; P=0.011), a higher mortality (OR, 2.36 [95% CI, 1.39–4.02]; P=0.001), and were associated with a higher incidence of symptomatic intracranial hemorrhage (OR, 4.73 [95% CI, 2.55–8.79]; P<0.001; Table 2; Figure).

Table 2. Outcomes for Perforations and Dissections

Unadjusted OR* (95% CI)P valueUnadjusted OR* (95% CI)P value
Early neurological improvement0.53 (0.32–0.89)0.0160.52 (0.3–0.91)0.023
mRS 0–2 at 90 d0.46 (0.25–0.83)0.0110.84 (0.49–1.45)0.555
mRS 0–1 at 90 d0.28 (0.12–0.66)<0.0010.69 (0.36–1.31)0.259
mRS 6 at 90 d2.36 (1.39–4.02)0.0011.23 (0.68–2.24)0.484
PH1.9 (0.96–3.76)0.0650.53 (0.18–1.48)0.228
sICH4.73 (2.55–8.79)<0.0011.38 (0.58–3.28)0.458

mRS indicates modified Rankin Scale; OR, odds ratio; PH, parenchymal hemorrhage; and sICH, symptomatic intracranial hemorrhage.

* Adjusted with a mixed model with center as random effect.

† Significant at the 2-tailed a=0.05.

Univariate analysis for dissections is reported on Table III in the Supplemental Material. Though dissections were associated with an inferior rate of successful reperfusion (modified Thrombolysis in Cerebral Infarction 2b-3, 55.4% versus 85.9%; P<0.001), they did not result in a worse clinical outcome except a diminished rate of early neurological improvement (OR, 0.52; 95% CI, 0.3–0.91]; P=0.023; Table 2; Figure).

Complications type according to the occlusion location is reported in Table IV in the Supplemental Material.


The main findings of the present study are as follows: (1) procedural complications were not so rare, occurring in around 8%, and the most frequent are ENTs; (2) ENTs and perforations were mainly related to the occlusion location (ICA/tandem occlusions) and an increased number of passes for ENTs but not to the thrombectomy technique itself; (3) though dissections did not affect clinical outcome, ENT and perforations had a substantial adverse effect increasing disability and mortality.

Our findings confirm that ENTs are the most frequent complication of thrombectomy and negatively impact clinical outcome. ENT prevalence was 5.2% as identified on angiogram. Recent studies based on diffusion-weighted imaging post-thrombectomy demonstrated that emboli to the same or new territory may occur in up to one-third of patients.5 Therefore, a minority of embolic complications is angiographically detectable, and their clinical relevance seems related to the size of the ischemic lesion.5 Because of its higher sensitivity, diffusion-weighted imaging appears as a potentially more sensitive technical safety end point than angiographically observed emboli, which, however, may be challenging to implement in everyday clinical practice. In the present study, only ICA/tandem occlusion and the total number of passes were predictors of ENTs at multivariate analysis. A plausible explanation is that ICA/tandem occlusions are caused by larger clots and are technically more challenging, while the total number of passes may reflect the technical difficulty of a case. More passes could equally increase the likelihood of thrombus fragmentation. Interestingly, we did not find a protective effect of prior intravenous thrombolysis or the use of balloon guide catheters and found no association with the thrombectomy technique as demonstrated in the ASTER trial (The Contact Aspiration vs Stent Retriever for Successful Revascularization).6

Vessel perforation occurred in 1.7% of patients. The only predictor of perforation was ICA/tandem occlusions. Thrombectomy in this location may be more technically demanding and may entail blind navigation in partially overlapping anatomies, as also highlighted for ENTs. In agreement with the ASTER trial results, perforation was not dependent on the thrombectomy technique.6 Though distal aspiration does not require traversing the occlusion, thus theoretically reducing the risk of vessel perforation, we did not find an excess of perforations with the use of stentrievers. Perforations were associated with a reduced rate of modified Thrombolysis in Cerebral Infarction 2b-3, probably related to no further attempts to pursue recanalization efforts once a perforation occurs. We found a poor prognosis related to perforation: at 90 days, 40.7% of patients died, and the overall rate of poor outcome was 74.6%.

Dissections occurred in 1.5%, in line with a previous study.4 Dissections occurred more frequently in younger patients without cardiovascular risk factors. This could suggest an increased vascular vulnerability in this patient group. We failed to find an association between dissection and smoking or terminal carotid/tandem occlusions, as suggested by other authors.7 Though recanalization results were inferior in the dissection group, patients had only lower odds of early neurological improvement with similar rates of good clinical outcome at 90 days and hemorrhagic complications, a finding corroborated by other series.7

The present study has several limitations inherent to retrospective registries with no data quality control and no central adjudication of imaging and clinical parameters and include data from only one country (France). However, imaging outcomes were evaluated by experienced neuroradiologists (>10 years), and clinical outcomes were evaluated independently by phone by a clinical nurse. In addition, our data represent real-world, everyday clinical practice in a large number of medium- to high-volume French centers. Differences between centers experience may have impact on our results. However, in 2019, we found no difference between centers performing ≤150 cases versus >150 cases yearly (OR, 1.64 [95% CI, 0.81–3.31]; P=0.163).


Whereas dissection did not affect clinical outcome, ENTs and perforations have a substantial negative clinical effect. ENTs and perforations were related to terminal carotid/tandem occlusions and an increased number of passes for ENTs, but the thrombectomy technique had no impact on procedural complications.

Article Information

Supplemental Materials

Expanded Materials and Methods

Supplemental Tables I–IV

Nonstandard Abbreviations and Acronyms


embolus to a new territory


internal carotid artery


modified Rankin Scale


odds ratio


List of Endovascular Treatment in Ischemic Stroke (ETIS) Investigators: Rothschild Foundation: Michel Piotin, Raphael Blanc, Hocine Redjem, Simon Escalard, Jean-Philippe Dessilles, François Delvoye, Stanislas Smajda, Benjamin Maier, Hebert Solène, Mikael Mazighi, Mikael Obadia, Candice Sabben, Pierre Seners, Igor Raynouard, Ovide Corabianu, Thomas de Broucker, Eric Manchon, Guillaume Taylor, Malek Ben Maacha, Laurie-Anne Thion, Augustin Lecler, Julien Savatovsjy. Foch Hospital: Adrien Wang, Serge Evrard, Maya Tchikviladze, Nadia Ajili, Bertrand Lapergue, David WeisenburgerLile, Lucas Gorza, Géraldine Buard, Oguzhan Coskun, Arturo Consoli, Federico Di Maria, Georges Rodesh, Sergio Zimatore, Morgan Leguen, Julie Gratieux, Fernando Pico, Haja Rakotoharinandrasana, Philippe Tassan, Roxanna Poll, Sylvie Marinier. CHU Bordeaux: Gaultier Marnat, Florent Gariel, Xavier Barreau, Jérôme Berge, Patrice Menegon, Igor Sibon, Ludovic Lucas, Stéphane Olindo, Pauline Renou, Sharmila Sagnier, Mathilde Poli, Sabrina Debruxelles, François Rouanet, Thomas Tourdias, Jean- Sebastien Liegey, Pierre Briau, Nicolas Pangon. CHU Nantes: Romain Bourcier, Lili Detraz, Benjamin Daumas-Duport, Pierre-Louis Alexandre, Monica Roy, Cédric Lenoble, Hubert Desal, Benoît Guillon, Solène de Gaalon, Cécile Preterre. CHRU-Nancy: Benjamin Gory, Serge Bracard, René Anxionnat, Marc Braun, Anne-Laure Derelle, Tonnelet Romain, Liang Liao, François Zhu, Emmanuelle Schmitt, Sophie Planel, Sébastien Richard, Lisa Humbertjean, Gioia Mione, Jean-Christophe Lacour, Nolwenn Riou-Comte, Gérard Audibert, Marcela Voicu, Lionel Alb, Marie Reitter, Madalina Brezeanu, Agnès Masson, Adriana Tabarna, Iona Podar, Sarah Guy, Fatiha Bechiri, Pauline Bourst. CHU Limoges: Francisco Macian-Montoro, Suzanna Saleme, Charbel Mounayer, Aymeric Rouchaud, Laetitia Gimenez, Alexandre Cosnard. CHRU Gui de Chauliac: Vincent Costalat, Caroline Arquizan, Cyril Dargazanli, Grégory Gascou, Pierre-Henri Lefèvre, Imad Derraz, Carlos Riquelme, Nicolas Gaillard, Isabelle Mourand, Lucas Corti, Federico Cagnazzo, Adrien ter Schiphorst. CHU Rennes: Francois Eugene, Stéphane Vannier, Jean-Christophe Ferre, Hélène Raoult, Thomas Ronziere, Maria Lassale, Christophe Paya, Jean-Yves Gauvrit, Clément Tracol, Sophie Langnier-Lemercier, Axelle Maurice, Sabrina Cochennec, Mélanie Pinault. CHU Pitié-Salpétrière: Eimad Shotar, Nader Sourour, Stéphanie Lenck, Kévin Premat, Yves Samson Anne Léger, Sophie Crozier, Flore Baronnet, Sonia Alamowitch, Laure Bottin, Mathon Yger, Vincent Degos. CHU Kremlin-Bicêtre: Laurent Spelle, Christian Denier, Olivier Chassin, Vanessa Chalumeau, Jildaz Caroff, Olivier Chassin, Laura Venditti, Mariana Sarov, Nicolas Legris. Hôpital Saint-Anne: Olivier Naggara, Wagih Ben Hassen, Grégoire Boulouis, Christine Rodriguez-Régent, Denis Trystram, Basile Kerleroux, Guillaume Turc, Pierre Seners, Valérie Domigo, Catherine Lamy, Julia Birchenall, Clothilde Isabel, François Lun. CHU Toulouse: Alain Viguier, Christophe Cognard, Anne Christine Januel, Jean-Marc Olivot, Louis Fontaine, Nicolas Raposo, Fabrice Bonneville, Jean François Albucher, Lionel Calviere, Jean Darcourt, Guillaume Bellanger, Philippe Tall. CHU Caen: Emmanuel Touzé, Charlotte Barbier, Romain Schneckenburger, Marion Boulanger, Julien Cogez, Sophie Guettier, Maxime Gauberti. CHU Brest: Serge Timsit, Jean-Christophe Gentric, Julien Ognard, Francois Mathias Merrien. CHU Rouen: Ozlem Ozku Wermester, Evelyne Massardier, Chrysanthi Papagiannaki, Aude Triquenot, Margeaux Lefebvre. CH Bayonne: Frédéric Bourdain, Patricia Bernady, Laurent Lagoarde-Segot, Hélène Cailliez, Louis Veunac, David Higue. CHU Strasbourg: Valérie Wolff, Veronique Quenardelle, Valerie Lauer, Roxana Gheoca, Irene Pierre-Paul, Raoul Pop, Remy Beaujeux, Dan Mihoc, Monica Manisor, Julien Pottecher, Alain Meyer, Thiên-Nga Chamaraux-Tran. CH Vannes: Anthony Le Bras, Sarah Evain, Arnaud Le Guen.


*E.H. Ngankou, B. Gory, and S. Finitsis contributed equally.

†A list of the ETIS Investigators is given in the Appendix.

Supplemental Material is available with this article at

For Sources of Funding and Disclosures, see page e768.

Correspondence to: Benjamin Gory, MD, PhD, Department of Diagnostic and Therapeutic Neuroradiology, CHRU Nancy, Hôpital Central, 29 Ave du Maréchal de Lattre de Tassigny, 54035 Nancy, France. Email


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