Evolutionary algorithms and decision trees for predicting poor outcome after endovascular treatment for acute ischemic stroke

Despite the large overall beneficial effects of endovascular treatment in patients with acute ischemic stroke, severe disability or death still occurs in almost one-third of patients. These patients, who might not benefit from treatment, have been previously identified with traditional logistic regression models, which may oversimplify relations between characteristics and outcome, or machine learning techniques, which may be difficult to interpret. We developed and evaluated a novel evolutionary algorithm for fuzzy decision trees to accurately identify patients with poor outcome after endovascular treatment, which was defined as having a modified Rankin Scale score (mRS) higher or equal to 5. The created decision trees have the benefit of being comprehensible, easily interpretable models, making its predictions easy to explain to patients and practitioners. Insights in the reason for the predicted outcome can encourage acceptance and adaptation in practice and help manage expectations after treatment. We compared our proposed method to CART, the benchmark decision tree algorithm, on classification accuracy and interpretability. The fuzzy decision tree significantly outperformed CART: using 5-fold cross-validation with on average 1090 patients in the training set and 273 patients in the test set, the fuzzy decision tree misclassified on average 77 (standard deviation of 7) patients compared to 83 (+/- 7) using CART. The mean number of nodes (decision and leaf nodes) in the fuzzy decision tree was 11 (+/- 2) compared to 26 (+/- 1) for CART decision trees. With an average accuracy of 72% and much fewer nodes than CART, the developed evolutionary algorithm for fuzzy decision trees might be used to gain insights into the predictive value of patient characteristics and can contribute to the development of more accurate medical outcome prediction methods with improved clarity for practitioners and patients.Neuro Imaging Researc

Added Prognostic Value of Hemorrhagic Transformation Quantification in Patients With Acute Ischemic Stroke

Introduction and Aim: Hemorrhagic transformation (HT) frequently occurs after acute ischemic stroke and negatively influences the functional outcome. Usually, HT is classified by its radiological appearance. Discriminating between the subtypes can be complicated, and interobserver variation is considerable. Therefore, we aim to quantify rather than classify hemorrhage volumes and determine the association of hemorrhage volume with functional outcome in comparison with the European Cooperative Acute Stroke Study II classification. Patients and Methods: We included patients from the MR CLEAN trial with follow-up imaging. Hemorrhage volume was estimated by manual delineation of the lesion, and HT was classified according to the European Cooperative Acute Stroke Study II classification [petechial hemorrhagic infarction types 1 (HI1) and 2 (HI2) and parenchymal hematoma types 1 (PH1) and 2 (PH2)] on follow-up CT 24 h to 2 weeks after treatment. We assessed functional outcome using the modified Rankin Scale 90 days after stroke onset. Ordinal logistic regression with and without adjustment for potential confounders was used to describe the association of hemorrhage volume with functional outcome. We created regression models including and excluding total lesion volume as a confounder. Results: We included 478 patients. Of these patients, 222 had HT. Median hemorrhage volume was 3.37 ml (0.80–12.6) and per HT subgroup; HI1: 0.2 (0.0–1.7), HI2: 3.2 (1.7–6.1), PH1: 6.3 (4.2–13), and PH2: 47 (19–101). Hemorrhage volume was associated with functional outcome [adjusted common odds ratio (acOR): 0.83, 95% CI: 0.73–0.95] but not anymore after adjustment for total lesion volume (acOR: 0.99, 95% CI: 0.86–1.15, per 10 ml). Hemorrhage volume in patients with PH2 was significantly associated with functional outcome after adjusting total lesion volume (acOR: 0.70, 95% CI: 0.50–0.98). Conclusion: HT volume is associated with functional outcomes in patients with acute ischemic stroke but not independent of total lesion volume. The extent of a PH2 was associated with outcome, suggesting that measuring hemorrhage volume only provides an additional benefit in the prediction of the outcome when a PH2 is present

Hemorrhagic transformation in acute ischemic stroke

Hemorrhagic transformation of an ischemic stroke can occur as stroke progresses or as a complication of stroke treatment. Hemorrhagic transformation varies in severity and is divided into four subtypes. Small petechial bleedings along the margins of the infarct constitute hemorrhagic infarction (HI) type 1, with more confluent petechial bleeding constituting HI type 2. Parenchymal hematomas (PH) are frank hematomas that are categorized in hemorrhages that consist of less than 30% of the infarct area without substantial mass effect (PH type 1) or consist of more than 30% of the infarct area with a space occupying effect (PH type 2). Some large hematomas result in acute neurological deterioration with high mortality rates; these hemorrhages causing acute neurological deterioration are classified as symptomatic intracranial hemorrhage (sICH). In most of these cases PH2 is the underlying hemorrhagic transformation subtype. Smaller hemorrhages have no or less apparent clinical consequences than large hemorrhages and their precise impact on outcome remains unclear. Additionally, it is unclear which patients are at increased risk for hemorrhagic transformation and whether that risk is modifiable. In this thesis, we showed that hemorrhagic transformation is associated with a poor functional outcomes. Several markers of large final infarcts such as poor collateral score and high NIHSS were associated with HI while clinical markers such as blood pressure and atrial fibrillation were associated with PH and sICH. Hemorrhagic transformation classified on NCCT and B0 EPI are not readily comparable. Last, patients treated within 4.5 hours after stroke onset do not have an increased risk for hemorrhagic transformation after treatment with IVT compared with EVT without IVT. Patients without successful reperfusion and IVT were more prone to developing subarachnoid hemorrhage

Hemorrhagic transformation in acute ischemic stroke

Hemorrhagic transformation of an ischemic stroke can occur as stroke progresses or as a complication of stroke treatment. Hemorrhagic transformation varies in severity and is divided into four subtypes. Small petechial bleedings along the margins of the infarct constitute hemorrhagic infarction (HI) type 1, with more confluent petechial bleeding constituting HI type 2. Parenchymal hematomas (PH) are frank hematomas that are categorized in hemorrhages that consist of less than 30% of the infarct area without substantial mass effect (PH type 1) or consist of more than 30% of the infarct area with a space occupying effect (PH type 2). Some large hematomas result in acute neurological deterioration with high mortality rates; these hemorrhages causing acute neurological deterioration are classified as symptomatic intracranial hemorrhage (sICH). In most of these cases PH2 is the underlying hemorrhagic transformation subtype. Smaller hemorrhages have no or less apparent clinical consequences than large hemorrhages and their precise impact on outcome remains unclear. Additionally, it is unclear which patients are at increased risk for hemorrhagic transformation and whether that risk is modifiable. In this thesis, we showed that hemorrhagic transformation is associated with a poor functional outcomes. Several markers of large final infarcts such as poor collateral score and high NIHSS were associated with HI while clinical markers such as blood pressure and atrial fibrillation were associated with PH and sICH. Hemorrhagic transformation classified on NCCT and B0 EPI are not readily comparable. Last, patients treated within 4.5 hours after stroke onset do not have an increased risk for hemorrhagic transformation after treatment with IVT compared with EVT without IVT. Patients without successful reperfusion and IVT were more prone to developing subarachnoid hemorrhage

Timing of symptomatic intracranial hemorrhage after endovascular stroke treatment

Introduction: Little is known about the timing of occurrence of symptomatic intracranial hemorrhage (sICH) after endovascular therapy (EVT) for acute ischemic stroke. A better understanding could optimize in-hospital surveillance time points and duration. The aim of this study was to delineate the probability of sICH over time and to identify factors associated with its timing. Patients and methods: We retrospectively analyzed data from the Dutch MR CLEAN trial and MR CLEAN Registry. We included adult patients who underwent EVT for an anterior circulation large vessel occlusion within 6.5 h of stroke onset. In patients with sICH (defined as ICH causing an increase of > 4 points on the National Institutes of Health Stroke Scale [NIHSS]), univariable and multivariable linear regression analysis was used to identify factors associated with the timing of sICH. This was defined as the time between end of EVT and the time of first CT-scan on which ICH was seen as a proxy. Results: SICH occurred in 205 (6%) of 3391 included patients. Median time from end of EVT procedure to sICH detection on NCCT was 9.0 [IQR 2.9-22.5] hours, with a rapidly decreasing incidence after 24 h. None of the analyzed factors, including baseline NIHSS, intravenous alteplase treatment, and poor reperfusion at the end of the procedure were associated with the timing of sICH. Conclusion: SICHs primarily occur in the first hours after EVT, and less frequently beyond 24 h. Guidelines that recommend to perform frequent neurological assessments for at least 24 h after intravenous alteplase treatment can be applied to ischemic stroke patients treated with EVT