LAUSR

In Response: We would like to thank Drs Wu, Zhang, and Ji for commenting on our recently published article, which evaluated the use of intraarterial rtPA (recombinant tissue-type plasminogen activator) as rescue therapy (RT) after failed mechanical thrombectomy in the North American Solitaire Stent-Retriever Acute Stroke Registry. In the letter, the authors compare the lower rate of successful revascularization in the no intraarterial rtPA group of our study to the rates reported in the landmark randomized clinical trials of 2015. However, we respectively disagree with this comparison as our substudy focused on the RT subpopulation of North American Solitaire Stent-Retriever Acute Stroke Registry. Although not directly comparable to the randomized clinical trials, the North American Solitaire Stent-Retriever Acute Stroke Registry showed similar rates of successful revascularization (72.5% versus 71%) and 90-day good functional outcome (modified Rankin Scale score ≤2; 42% versus 46%). As our substudy focused on the RT population, we expected a decreased rate of successful revascularization as these patients failed to reperfuse after a primary stent-retriever approach. Wu et al suggests that contact aspiration may be more suitable than intraarterial thrombolysis for patients with regular M1 occlusions if stent-retrievers failed. However, the study cited (which has many limitations including small sample size) examines angiographic phenotypes in M1 occlusions and response to first-line therapy with stent-retrievers or contact aspiration. We do not feel that the author’s statement is supported by this data, as our substudy focused on a RT population. Furthermore, recent randomized clinical trials have demonstrated similar outcomes between contact aspiration and stent-retrievers; however, this has not been studied in a RT setting. The details on the type of mechanical RT were not captured in the original North American Solitaire Stent-Retriever Acute Stroke Registry and, therefore, could not be reported in the substudy. In their letter, the authors also comment that the rate of symptomatic intracranial hemorrhage should have been lower in the intraarterial rtPA cohort based on their clinical impression that intraarterial rtPA is administered as RT for patients with a potentially lower ICH risk and the shorter time from onset to groin puncture present in the intraarterial rtPA group. Previous intraarterial thrombolytic trials have reported higher rates of symptomatic intracranial hemorrhage when compared with control groups. Importantly, there is also a correlation between number of passes and increased risk of symptomatic intracranial hemorrhage. As such, we expected higher rates of symptomatic intracranial hemorrhage in our RT population with the addition of intraarterial rtPA, as this population had already failed primary mechanical thrombectomy. Given the lack of data in the literature on the use of intraarterial lytic after mechanical thrombectomy, we cannot yet predict the efficacy and safety threshold of such an approach, which underscores the importance of our substudy. Finally, as the sample size in our substudy was limited, we choose to restrict the time of onset to groin puncture to ≤8 to create a homogenous M1 subgroup, as well as to reflect the inclusion criteria of the intraarterial lytic and mechanical thrombectomy randomized clinical trials. For these reasons above, we agree that larger studies are needed to validate the findings in our study as well as to determine the role of intraarterial rtPA in the modern era of mechanical thrombectomy.