Background and Purpose: The efficiency of prehospital care chain response and the adequacy of hospital resources are challenged amid the coronavirus disease 2019 (COVID-19) outbreak, with suspected consequences for patients with ischemic stroke eligible for mechanical thrombectomy (MT). Methods: We conducted a prospective national-level data collection of patients treated with MT, ranging 45 days across epidemic containment measures instatement, and of patients treated during the same calendar period in 2019. The primary end point was the variation of patients receiving MT during the epidemic period. Secondary end points included care delays between onset, imaging, and groin puncture. To analyze the primary end point, we used a Poisson regression model. We then analyzed the correlation between the number of MTs and the number of COVID-19 cases hospitalizations, using the Pearson correlation coefficient (compared with the null value). Results: A total of 1513 patients were included at 32 centers, in all French administrative regions. There was a 21% significant decrease (0.79; [95%CI, 0.76–0.82]; P <0.001) in MT case volumes during the epidemic period, and a significant increase in delays between imaging and groin puncture, overall (mean 144.9±SD 86.8 minutes versus 126.2±70.9; P <0.001 in 2019) and in transferred patients (mean 182.6±SD 82.0 minutes versus 153.25±67; P <0.001). After the instatement of strict epidemic mitigation measures, there was a significant negative correlation between the number of hospitalizations for COVID and the number of MT cases ( R 2 −0.51; P =0.04). Patients treated during the COVID outbreak were less likely to receive intravenous thrombolysis and to have unwitnessed strokes (both P <0.05). Conclusions: Our study showed a significant decrease in patients treated with MTs during the first stages of the COVID epidemic in France and alarming indicators of lengthened care delays. These findings prompt immediate consideration of local and regional stroke networks preparedness in the varying contexts of COVID-19 pandemic evolution.
Abstract. We are interested in the multifractal analysis of a class of self-similar measures with overlaps. This class, for which we obtain explicit formulae for the L qspectrum τ (q) as well as the singularity spectrum f (α), is sufficiently large to point out new phenomena in the multifractal structure of self-similar measures. We show that, unlike the classical quasi-Bernoulli case, the L q -spectrum τ (q) of the measures studied can have an arbitrarily large number of non-differentiability points (phase transitions). These singularities occur only for the negative values of q and yield to measures that do not satisfy the usual multifractal formalism. The weak quasi-Bernoulli property is the key point of most of the arguments.
Reçu le 8 octobre 2003 ; reçu en forme révisée le 12 juillet 2004 ; accepté le 3 janvier 2005 Disponible sur Internet le 22 juin 2005 Résumé On introduit une nouvelle condition d'homogénéité (quasi-Bernoulli au sens faible) sur les mesures sous laquelle le formalisme multifractal fonctionne. Cette condition englobe le cas classique où la mesure est quasi-Bernoulli et permet donc de raffiner les résultats obtenus successivement par Michon, Brown, Peyrière et Heurteaux. On met ensuite en évidence certaines mesures autosimilaires qui ne satisfont pas les conditions classiques de séparation, non quasi-Bernoulli mais qui vérifient la condition mentionnée auparavant. Ces mesures interviennent par exemple lors de l'analyse de certains graphes autoaffines déjà étudiés par McMullen, Przytycki et Urbański, Kenyon et Peres. 2005 Elsevier SAS. Tous droits réservés. AbstractWe introduce a new homogeneity condition (weak quasi-Bernoulli) to the measures under which the multifractal formalism holds. This condition includes the well known case where the measure is quasi-Bernoulli and thus we can precise the results obtained successively by Michon, Brown, Peyrière and Heurteaux. Then, we highlight some self similar measures with overlaps which are not quasi-Bernoulli but satisfy the condition mentioned above. Moreover, we show how these measures can be used to analyse some self affine graphs studied before by McMullen, Przytycki and Urbański, Kenyon and Peres. 2005 Elsevier SAS. Tous droits réservés.
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