Response to the letter to the editor regarding “Minor stroke in large vessel occlusion: A matched analysis of patients from the German Stroke Registry–Endovascular Treatment (GSR‐ET) and patients from the Safe Implementation of Treatments in Stroke–International Stroke Thrombolysis Register (SITS‐ISTR)”
2022-10-18

We sincerely thank Dr Malhotra and colleagues for their interest in our article, “Minor stroke in large vessel occlusion: A matched analysis of patients from the German Stroke Registry–Endovascular Treatment (GSR-ET) and patients from the Safe Implementation of Treatments in Stroke–International Stroke Thrombolysis Register (SITS-ISTR)” [1]. We appreciate the discussion of bias and highlighting of several key aspects when dealing with observational data, which we believe applies both to our article and broadly to similar observational studies. As observed in the recent meta-analysis by Wu et al. 2] that many observational studies involving endovascular treatment (EVT) for patients presenting with minor stroke symptoms allocated treatment based on local clinician's decisions. This was also the case for the EVT-treated GSR-ET patients, which reflects the current real-world practice, as there are no evidence-based guidelines to use. Patients from the GSR-ET reflect the reality of daily life care for EVT patients; thus, we do not have more structured information regarding patient selection for EVT. However, as per GSR-ET recommendations, all participating centers are to record all consecutive EVT-treated patients in the GSR-ET database, and only data from centers that include >90% of their ET patients in the GSR-ET database will be analyzed further. Both the European Stroke Organization and the American Heart Association/American Stroke Association guidelines regarding EVT treatment for minor stroke patients acknowledge the lack of high-quality data within this patient subgroup [3, 4]. These guidelines present only weak recommendations suggesting that treatment could be beneficial, but that patients should be enrolled in randomized controlled trials, of which several are ongoing (ENDOLOW, https://clinicaltrials.gov/ct2/show/NCT04167527; MOSTE, https://clinicaltrials.gov/ct2/show/NCT03796468). Awaiting the results of these trials, we believe that our data from a real-world setting of EVT centers provides valuable results for the ongoing discussion among stroke physicians, as our results suggest there is a similar effectiveness of IVT alone compared to EVT with or without IVT in minor stroke patients. We included all patients from the Safe Implementation of Thrombolysis in Stroke (SITS) database to improve our chances of good matches to the GSR-ET patients. The SITS database provides summarized radiological data for all patients treated with IVT, including data from Computer Tomography Angiography or Magnetic Resonance Angiography, which was present for all SITS patients who were included in the Propensity score matchin, as they were matched for occlusion site. For perfusion imaging and collateral scores, we were unable to compare this between the treatment groups, as the intravenous thrombolysis (IVT)-treated SITS patients were not routinely screened with perfusion imaging and therefore lacked these data. We agree that the impact of time may affect the outcomes after EVT and IVT treatment. Our longer onset to door/IVT times could therefore have skewed the results of the EVT-treated patients more negatively. However, our analysis of EVT- and IVT-treated patients compared to IVT only-treated patients did not show a significant effect for EVT treatment, despite all patients in that analysis being eligible for IVT within the current guideline time window. We agree that site of occlusion is an important factor to consider when analyzing outcomes after EVT treatment. We have summarized the occlusion site data for our outcome of modified Rankin Scale score of 0–2 at 3-month follow-up (Table 1). Katharina Feil received funding for research from Boehringer Ingelheim and speaker honoraria from Pfizer outside of this study. Niaz Ahmed is the Chairman of SITS International, which receives unrestricted sponsorship from Boehringer Ingelheim, and has received speaker honoraria from Boehringer Ingelheim. Lars Kellert has received funding for travel or speaker honoraria from Bayer Vital, Boehringer Ingelheim, Bristol Meyer Squibb, Daiichi Sankyo, and Pfizer outside of this study, and funding for research from Boehringer Ingelheim. Marius Matusevicius reports no disclosures. The data that support the findings of this study are available from the corresponding author upon reasonable request.