1/ Study design and data collection
Data from these patients were collected within a regional emergency stroke network registry (RESUVAL), approved by the local ethics committee (Comité de Protection des Personnes Sud-Est II, registration E-2012-069). This observational study was carried out in accordance with the ethical standards of the Declaration of Helsinki. No patient expressed opposition to the research. The Lyon Stroke Center (tertiary university hospital) serving the greater Lyon metropolitan area (population: 2.3 million), treats ∼1,700 ischemic stroke patients each year and is only comprehensive stroke center (CSC, i.e. thrombectomy-capable) within our regional stroke network (5 primary stroke centers, population: 3 million) (Fig. 2).
The analyzed period ranged from the entry into level-2 of the pandemic in France (February 29th) and the lifting of lockdown on May 10th. The same period in 2019 served as control. To take into account the local trend (i.e. yearly increase in case volumes), we also provided data about the total number of reperfusion procedures from January 1st to May 10th of the previous five years.
2/ Study population
All consecutive patients with AIS treated with IVT and/or MT in the Lyon Stroke Center, France, were included during the COVID-19 period and the control periods.
Baseline data on demographic characteristics, risk factors and medical history were systematically collected at admission as well as times from stroke onset to hospital admission (to our CSC or to primary stroke center or to emergency department as appropriate), door to imaging, door to needle and door to groin puncture. When the time of symptoms onset was unknown, the time when patients woke up or were identified was considered as the time of symptom onset. Neurological status was assessed by board certified neurologists using National Institute of Health Stroke Scale (NIHSS) score at admission.
Data about the daily number of calls to EMD were obtained from the hospital administrative database.
The first-line imaging method in our CSC is magnetic resonance imaging (MRI), including diffusion-weighted imaging (DWI), T2∗-weighted imaging, Fluid-Attenuated-Inversion-Recovery (FLAIR), 3D-Time-of-Flight MR-angiography (MRA), perfusion-weighted imaging and cervical-vessels angiography were optional. If MRI was unavailable or contra-indicated, non-enhanced computed tomography (CT) followed by CT-angiography were performed; CT- perfusion was optional. Lesion side and baseline ischemic core size were assessed on DWI or CT using the Alberta Stroke Program Early CT Score (ASPECTS) for patients with stroke in the middle cerebral artery territory . Baseline arterial occlusion site was evaluated with MRA or CT-angiography. A follow-up CT performed at 24 hours classified any hemorrhagic transformation according to the European Co-operative Acute Stroke Study (ECASS II) classification .
4/ Statistical analysis
Continuous variables are expressed as means (standard deviation [SD]) or medians (interquartile range [IQR]), and categorical variables as percentages. The Mann-Whitney U-test and Fisher's exact test were used to compare continuous and categorical variables, respectively. A p-value <0.05 was considered significant. Data were analyzed with Stata Version 15™ (STATACORP, COLLEGE STATION, TEXAS 77845 USA).