# Timing and outcome prediction of intravenous thrombolysis in posterior circulation stroke: Insights from the Austrian Stroke Unit Registry

## TL;DR

This study examines how quickly patients receive treatment affects outcomes in posterior circulation stroke, finding better results with faster treatment and highlighting gender differences.

## Contribution

The study provides novel insights into the timing and outcomes of intravenous thrombolysis in posterior circulation stroke using a large national registry.

## Key findings

- IVT improves functional outcomes in PC stroke patients compared to best medical treatment.
- The treatment benefit is strongest within the first 2 hours of stroke onset.
- Women had lower IVT rates and less favorable outcomes despite similar results when treated.

## Abstract

Posterior circulation (PC) stroke is underrepresented in most large-scale trials. While the importance of the onset-to-needle time (ONT) for intravenous thrombolysis (IVT) in anterior circulation stroke is well established, data on PC stroke are lacking. This study aimed to investigate how ONT affects functional outcome after IVT and to identify additional predictors of outcome in PC stroke.

IVT-treated PC stroke patients included in the nationwide Austrian Stroke Unit Registry between 2003 and 2024 were retrospectively analyzed. The primary outcome measure was the excellent (mRS 0–1) and non-excellent (mRS 2–6) functional outcome at 90 days. The secondary outcome measure was the occurrence of severe intracranial hemorrhage (sICH). Associations between ONT as continuous variable, clinical predictors, and functional outcomes were assessed using ordinal and binomial logistic regression models. A cut-off point for the transition from excellent to non-excellent outcome was determined by maximizing the odds ratio metric. The effect of ONT on sICH was analyzed dichotomously in time intervals of 0–150 min and 151–300 min.

Of 11,025 eligible patients with PC stroke, 1,359 (12.3%) were treated with IVT, resulting in more frequent excellent functional outcome in patients treated with IVT compared to best medical treatment (BMT) in the ordinal logistic regression (adjusted odds ratio (aOR) 1.31, 95% CI 1.16–1.47, p < 0.001). Correspondingly, binomial logistic regression showed fewer non-excellent functional outcomes in patients treated with IVT compared to BMT (aOR 0.73, 95% CI 0.63–0.85, p < 0.001). The odds of an excellent functional outcome were increased within the first 282 min, with a pronounced treatment benefit in the first 122 min. The transition cut-off point was found to be at 258 min. sICH occurred in 2.8% and was unrelated to ONT (aOR 1.28, 95% CI 0.55–2.91, p = 0.552). Overall, women had lower IVT rates (11.3% vs 13.0%, p = 0.007) and were more likely to experience a non-excellent outcome (aOR 1.31, 95% CI 1.19–1.45, p < 0.001), but had similar functional outcomes compared to men when treated with IVT (aOR 1.03, 95% CI 0.74–1.43, p = 0.883).

A treatment benefit of IVT in PC stroke was observed within 4.5 h of stroke onset, with its maximum within the first 2 h. Women should receive special attention as they may be at a prognostic disadvantage due to lower IVT rates and less favorable overall outcomes.

Graphical abstract