Abstract WP030: Association of prehospital treatment duration with the efficacy of remote ischemic conditioning in the RESIST trial

Background: Remote ischemic conditioning (RIC) initiated in the prehospital setting did not improve functional outcome at 90 days in patients with acute stroke in the RESIST trial. Trials of other neuroprotective therapies have identified the duration of treatment received prior to reperfusion (“dwell time”) as a treatment effect modifier. We examined whether the effects of RIC might be modified by the duration of prehospital treatment that patients received. Methods: In this post-hoc analysis of the RESIST randomized-controlled trial (Clinicaltrials.gov: NCT03481777), we compared outcomes in patients with prehospital stroke symptoms for less than 4 hours, assigned to RIC versus sham, and diagnosed with acute ischemic stroke (AIS) or intracerebral hemorrhage (ICH) – the modified intention-to-treat (mITT) population – stratified by time from randomization to hospital admission (i.e. prehospital treatment duration). The primary outcome was improvement in the ordinal 90-day modified Rankin Scale (mRS) score. Secondary outcomes included 90-day mRS 0-2 and neurological improvement according to the National Institutes of Health Stroke Scale (NIHSS) at 24-hours. Results: Among 902 patients in the mITT population with AIS (n=737) and ICH (n=165), the median randomization-to-admission time was 29.4 minutes (IQR 19.6-39.4 minutes). Upon examining the effect of RIC treatment by pre-hospital treatment duration, there were no significant treatment effects in either the combined mITT, ICH, or AIS groups in any of the transport time groups. Further stratifying patients with AIS based on receipt of reperfusion therapies also revealed no significant differences in RIC efficacy across time. There was no interaction between RIC and pre-hospital treatment duration in relation to 90-day mRS or early NIHSS improvement in the AIS or ICH populations. Conclusion: Longer prehospital treatment duration was not associated with efficacy of RIC in patients with AIS or ICH in the RESIST trial including among AIS patients who received reperfusion therapies, although durations were generally under an hour.