Although endovascular treatment has revolutionized the prognosis of stroke patients, half of them do not regain their independence. Among the different causes explaining this lack of improvement are brain hemorrhages. These may occur after an ischemic stroke treated with endovascular therapy and have traditionally been considered concerning only when they cause evident neurological deterioration. However, a study published in Neurology and led by the Institut de Recerca Sant Pau (IR Sant Pau) shows that even asymptomatic forms of hemorrhagic transformation—those that do not cause clinical worsening—also have a negative impact on patients’ functional recovery and survival.
“Until now, we only paid attention to hemorrhages detected on the follow-up CT scan when the patient showed clinical deterioration,” explains Dr. Marina Guasch-Jiménez, first author of the study, researcher at the Cerebrovascular Diseases Group of the IR Sant Pau, and neurologist at the Stroke Unit of Hospital de Sant Pau. “Our data suggest that this is not the case. Even asymptomatic hemorrhagic transformations are associated with more limited functional recovery and higher three-month mortality.”
Dr. Pol Camps, principal investigator of the study and coordinator of the Cerebrovascular Diseases Group and the Stroke Unit at Sant Pau, adds that “these results call for a reassessment of endovascular treatment safety indicators. It is not enough to monitor only symptomatic hemorrhages; any hemorrhagic transformation, even if asymptomatic, should be considered a risk marker that can influence patient outcomes.”
The study, titled “Influence of Asymptomatic Hemorrhagic Transformation After Endovascular Treatment on Stroke Outcome,” is based on the Catalonia Stroke Code (CICAT) population registry, a prospective and mandatory database that systematically collects stroke care data across the entire Catalan hospital network.
The study included 3,067 consecutive patients treated with endovascular therapy for an anterior circulation ischemic stroke between 2017 and 2023 in ten reference centers across Catalonia, including Hospital de Sant Pau. The researchers analyzed detailed clinical, radiological, and therapeutic data to determine whether asymptomatic hemorrhagic transformation, detected on control neuroimaging 24 hours after treatment, had an impact on functional recovery or medium-term mortality.
Among the more than 3,000 patients included, one in four (25.8%) experienced some form of hemorrhagic transformation, and one in five (20%) did so without associated clinical symptoms. Among the radiological categories described—hemorrhagic infarction types 1 and 2 (HI1, HI2) and parenchymal hemorrhage types 1 and 2 (PH1, PH2), in addition to remote parenchymal hemorrhage (rPH)—the milder forms (HI1 and HI2) were the most frequent, while the most severe (PH2) showed the lowest percentage of asymptomatic cases.
Multivariable analysis adjusted for known prognostic factors such as age revealed that the presence of asymptomatic hemorrhagic transformation doubled the likelihood of a worse functional outcome and was associated with a 50% higher mortality rate. Among subtypes, asymptomatic PH2 showed the highest risk of poor functional outcome.
“The value of this work lies in its representativeness: we analyzed over three thousand patients treated in real-world conditions, which allows us to draw solid conclusions applicable to daily clinical practice,” highlights Dr. Guasch-Jiménez. “Catalonia has a unique population-based stroke registry in Europe, offering the opportunity to generate high-quality clinical evidence on endovascular treatment and its complications,” adds Dr. Camps.
The study also identified several factors associated with the occurrence of asymptomatic hemorrhagic transformations, including higher glucose and systolic blood pressure levels at admission, greater initial neurological severity, lower ASPECTS score (indicator of viable brain tissue), and longer time from stroke onset to femoral puncture. It also identified more thrombectomy passes.
“Some of these factors are potentially modifiable, which opens the door to targeted clinical interventions,” notes Dr. Guasch-Jiménez. “Better control of blood glucose and blood pressure, as well as optimizing devices to reduce the number of thrombectomy passes, could help prevent this type of complication.”
According to Dr. Camps, “the results reinforce the need to include radiological monitoring of any post-treatment hemorrhage as part of safety assessments in clinical trials and routine practice. Understanding why even clinically silent hemorrhages affect prognosis may help us develop safer and more effective therapies.”
Furthermore, the authors suggest that studying the underlying mechanisms—such as toxicity due to blood extravasation or disruption of the blood-brain barrier—could improve understanding of post-stroke brain injury and guide the design of more specific neuroprotective strategies.
The researchers emphasize that asymptomatic hemorrhagic transformations, far from being a benign or anecdotal finding, should be regarded as a relevant warning sign and a new safety parameter in acute ischemic stroke endovascular treatment. Although they do not cause immediate clinical worsening, the study data consistently show that their mere presence is associated with worse functional outcomes and higher medium-term mortality.
“These findings show that any type of hemorrhage following endovascular treatment, even without symptoms, may reflect underlying tissue damage that affects brain recovery,” explains Dr. Guasch-Jiménez. “Therefore, all hemorrhagic transformations, regardless of their clinical expression, should be systematically monitored and reported to improve safety and efficacy assessment of the procedure.”
According to Dr. Camps, “hemorrhagic transformations should be included as an additional safety indicator in clinical registries and trials on new reperfusion strategies. Incorporating this measure will provide a more comprehensive view of the real impact of endovascular treatment and help develop safer, more personalized protocols for each patient.”
The authors also highlight that identifying modifiable factors—such as hyperglycemia or elevated blood pressure at admission—reinforces the importance of a comprehensive approach to stroke care that combines metabolic and hemodynamic control with increasingly precise and safe endovascular procedures.
The study was conducted in collaboration with the Consorci Codi Ictus de Catalunya (CICAT) and funded by the Instituto de Salud Carlos III (project PMP21/00165) within the RICORS-ICTUS program (RD21/0006/0006), with support from FEDER and Next Generation EU European funds.
Guasch-Jiménez M, Ezcurra Díaz G, Lambea-Gil Á, Ramos-Pachón A, Martinez-Domeño A, Prats-Sanchez L, Fernández-Vidal JM, Toscano-Prat C, Marti-Fabregas J, Martínez-González JP, Fernandez-Cadenas I, Cardona P, Rodriguez-Villatoro N, Rodríguez Vázquez A, Gomis M, Xuclà-Ferrarons T, Rodriguez-Campello A, Cánovas D, Seró L, Purroy F, Salvat-Plana M, Abilleira S, Camps-Renom P, as the Catalan Stroke Code and Reperfusion Consortium (CICAT). Influence of asymptomatic hemorrhagic transformation after endovascular treatment on stroke outcome: A population-based study. *Neurology* 2025;104:e213509. https://doi.org/10.1212/WNL.0000000000213509.
