Effect of Remote Ischemic Conditioning in Ischemic Stroke Subtypes: A Post Hoc Subgroup Analysis from the RESIST Trial

BACKGROUND: Remote ischemic conditioning (RIC) is a simple and noninvasive procedure that has proved to be safe and feasible in numerous smaller clinical trials. Mixed results have been found in recent large randomized controlled trials. This is a post hoc subgroup analysis of the RESIST trial (Remote Ischemic Conditioning in Patients With Acute Stroke), investigating the effect of RIC in different acute ischemic stroke etiologies, and whether an effect was modified by treatment adherence. METHODS: Eligible patients were adults (aged ≥18 years), independent in activities of daily living, who had prehospital stroke symptoms with a duration of less than 4 hours. They were randomized to RIC or sham. The RIC treatment protocol consisted of 5 cycles with 5 minutes of cuff inflation alternating with 5 minutes with a deflated cuff. Acceptable treatment adherence was defined as when at least 80% of planned RIC cycles were received. The analysis was performed using the entire range (shift analysis) of the modified Rankin Scale (ordinal logistic regression). RESULTS: A total of 698 had acute ischemic stroke, 253 (36%) were women, and the median (interquartile range) age was 73 (63-80) years. Median (interquartile range) overall adherence to RIC/sham was 91% (68%-100%). In patients with a stroke due to cerebral small vessel disease, who were adherent to treatment, RIC was associated with improved functional outcome, and the odds ratio for a shift to a lower score on the modified Rankin Scale was 2.54 (1.03-6.25); P=0.042. The association remained significant after adjusting for potential confounders. No significant associations were found with other stroke etiologies, and the overall test for interaction was not statistically significant (χ², 4.33, P=0.23). CONCLUSIONS: In patients with acute ischemic stroke due to cerebral small vessel disease, who maintained good treatment adherence, RIC was associated with improved functional outcomes at 90 days. These results should only serve as a hypothesis-generating for future trials. REGISTRATION: URL: https://www.clinicaltrials.gov; Unique identifier: NCT03481777.