Risk of intracranial haemorrhage in patients with acute ischaemic stroke and prior antiplatelet therapy

Introduction Whether patients with acute ischaemic stroke (AIS) and prior antiplatelet therapy (APT) are at higher risk of symptomatic intracranial haemorrhage (sICH) has not been established. This study aimed to determine whether prior APT increases the risk of bleeding. Methods 41,113 patients treated for AIS in Switzerland between 2014 and 2022 were analysed. The primary outcome was sICH, and secondary outcomes were recurrent ischaemic stroke (IS), all-cause mortality, functional outcome at discharge and 90 days. Patients grouped by prior APT: no APT (nAPT), single APT (SAPT), and dual APT (DAPT) were analysed using logistic and Cox proportional hazards regression. Confounding variables, including revascularisation treatment, were accounted for using multivariable adjustment and matching, and a time-to-event analysis was performed. Results In the adjusted analysis at 90 days, patients with nAPT versus SAPT had a decreased risk of sICH (aOR 0.75 (0.62–0.90), p < 0.01), while these occurred within the first days. There was no difference in the risk of recurrent IS, all-cause mortality, or functional outcome. Patients with DAPT had no higher risk of sICH or mortality than those with SAPT, but a higher occurrence of recurrent IS (aOR 1.41 (1.12–1.77), p < 0.01) and worse functional outcome (aOR 1.18 (1.07–1.31), p < 0.01). The results were consistent after adjusting for revascularisation treatment. Conclusions Patients with nAPT had a lower risk of sICH than those with SAPT. Patients with DAPT have a higher risk of recurrent IS and worse functional outcome respectively. The majority of sICH occurred within the first days after admission.