Asymptomatic parenchymal haemorrhage following endovascular treatment: Impact on functional outcome in patients with acute ischaemic stroke

Background and purpose In patients with acute ischaemic stroke (AIS), haemorrhagic transformation (HT) following endovascular treatment (EVT) is associated with poor functional outcome. However, the impact of asymptomatic HT, not linked to neurological deterioration in the acute phase, is unknown. We aimed to investigate the impact of asymptomatic PH1 (aPH1) and PH2 (aPH2) subtypes of HT on the functional outcome of patients treated with EVT. Methods We conducted a retrospective study of patients with AIS who were consecutively admitted to our comprehensive stroke centre between January 2019 and December 2022, and who underwent EVT. We collected clinical, radiological, and procedural data. HTs were categorized according to the Heidelberg classification. The primary outcome was the shift on the modified Rankin Scale (mRS) at 3 months of follow‐up. We performed bivariate and multivariable ordinal regression analyses to test the association between aPH1/aPH2 and the primary outcome. Results We included 314 patients (mean age = 72.5 years [SD = 13.6], 171 [54.5%] women). We detected 54 (17.2%) patients with HT; 23 (7.3%) were classified as PH2 (11 asymptomatic) and 17 (5.4%) as PH1 (16 asymptomatic). The adjusted common odds ratio for aPH2 of worsening 1 point on the 3‐month mRS was 3.32 (95% confidence interval = 1.16–9.57, p = 0.026). No association was observed for aPH1. aPH2 was also independently associated with lower odds of achieving a favourable outcome (mRS = 0–2). Neither aPH1 nor aPH2 was associated with mortality. Conclusions In patients with AIS treated with EVT, aPH2 is independently associated with unfavourable functional outcome.