Hemorrhagic transformation is related to the duration of occlusion and treatment with tissue plasminogen activator in a nonembolic stroke model

Association between basal ganglia infarction and hemorrhagic transformation after mechanical thrombectomy in acute ischemic stroke: insights from the DIRECT-MT trial

BACKGROUND

Acute ischemic stroke (AIS) often leads to significant morbidity and mortality. Mechanical thrombectomy (MT) is an effective intervention for large vessel occlusion strokes. However, hemorrhagic transformation (HT) remains a critical post-procedural complication. This study investigates the relationship between basal ganglia infarction (BGI) and the risk of HT, particularly focusing on hemorrhagic infarction (HI) and parenchymal hematoma (PH).

METHODS

Data from the DIRECT-MT trial were analyzed. Patients were categorized based on the presence of BGI identified on initial non-contrast CT. HT was classified into HI and PH following the Heidelberg criteria. Multivariate logistic regression, propensity score matching (PSM), and inverse probability of treatment weighting (IPTW) were used to assess the association between BGI and HT.

RESULTS

Among 607 patients, 273 had BGI. BGI was associated with a higher risk of HT, specifically PH. The incidence of PH in the BGI group was 20% compared with 11% in the non-BGI group. Adjusted analyses, including PSM and IPTW, confirmed the significant association between BGI and PH with an adjusted odds ratio (aOR) of 2.51 (95% CI 1.49 to 4.22, P<0.001). However, no significant association was found between BGI and HI.

CONCLUSIONS

BGI significantly increases the risk of PH following MT for AIS, underscoring the need for tailored therapeutic strategies in managing these patients. No significant correlation was observed between BGI and HI. Future research should explore the underlying mechanisms and validate these findings across diverse populations to improve patient outcomes.

Impact of Decompressive Craniectomy on Hemorrhagic Transformation in Malignant Ischemic Stroke in Mice

BACKGROUND

Endovascular thrombectomy has changed the management of ischemic stroke. The reperfusion can however lead to a hemorrhagic transformation (HT). Decompressive craniectomy (DC) is a surgical procedure used for malignant ischemic stroke. However, its efficacy was demonstrated before the era of endovascular thrombectomy trials. Here, we hypothesized that DC for ischemic stroke after thrombectomy could lead to a higher risk of HT. We thus evaluated this hypothesis in a mouse model of stroke induced by occlusion of the middle cerebral artery (MCAO) with or without mechanical reperfusion.

METHODS

Ninety mice subjected to MCAO were divided into 6 groups: permanent MCAO with or without DC; MCAO followed by a mechanical reperfusion with or without DC and MCAO with a mechanical reperfusion followed by r-tPA (recombinant tissue-type plasminogen activator)-induced reperfusion with or without DC. Mice were evaluated by magnetic resonance imaging 24 hours after the MCAO to assess ischemic lesion volumes, and the rate, type, and volume of HTs.

RESULTS

The ischemic volume was higher in the 2 groups without reperfusion than in the 4 groups with reperfusion independently of r-tPA treatment and DC. The distribution of HT types was different between the 6 groups. The HT volumes and HT scores was smaller in the 2 groups without reperfusion and in the reperfusion group without r-tPA and without DC. In mice having reperfusion, the mean HT score was higher in mice who had DC without r-tPA (HT score 5; P=0.048) or with r-tPA (HT score 8; P=0.02), than in mice without DC (HT score 1).

CONCLUSIONS

DC for a malignant stroke, after reperfusion, corresponding to an endovascular thrombectomy failure, increases the risk of severe hemorrhagic transformations in a model of ischemic stroke in mice. This result support the need of clinical studies to evaluate the added value of DC at the era of endovascular thrombectomy.

Hemorrhagic Transformation After Tissue Plasminogen Activator Treatment in Acute Ischemic Stroke

Hemorrhagic transformation (HT) is a common complication after thrombolysis with recombinant tissue-type plasminogen activator (rt-PA) in ischemic stroke. In this article, recent research progress of HT in vivo and in vitro studies was reviewed. We have discussed new potential mechanisms and possible experimental models of HT development, as well as possible biomarkers and treatment methods. Meanwhile, we compared and analyzed rodent models, large animal models and in vitro BBB models of HT, and the limitations of these models were discussed. The molecular mechanism of HT was investigated in terms of BBB disruption, rt-PA neurotoxicity and the effect of neuroinflammation, matrix metalloproteinases, reactive oxygen species. The clinical features to predict HT were represented including blood biomarkers and clinical factors. Recent progress in neuroprotective strategies to improve HT after stroke treated with rt-PA is outlined. Further efforts need to be made to reduce the risk of HT after rt-PA therapy and improve the clinical prognosis of patients with ischemic stroke.

Intravenous thrombolysis with 0.9 mg/kg alteplase for acute ischaemic stroke: a network meta-analysis of treatment delay

OBJECTIVES

The aim of this study was to evaluate the effect of alteplase in intravenous thrombolysis of acute ischaemic stroke (AIS) regarding the different time windows of treatment (<3 hours, 3-4.5 hours, >4.5 hours).

METHODS

A systematic literature search was conducted from PubMed, Cochrane Library and Embase. 12 clinical randomised controlled trials with 3402 patients with AIS met the inclusion criteria. The primary, secondary and tertiary outcomes were modified Rankin Scale (mRS) scores 0-1, mortality at 90th day after treatment and symptomatic intracerebral haemorrhage within 36 hours, respectively. Network meta-analysis and conventional meta-analysis were carried out for calculating odds ratio (OR), the surface under cumulative ranking curve (SUCRA) and the probabilities of being the best.

RESULTS

For mRS, alteplase regardless of time delay was significantly more effective than placebo (OR 1.33-2.17). However, alteplase used within 3 hours after AIS occurrence (SUCRA=98.3%) was significantly more effective (OR=1.64) than that at 3-4.5 hours (SUCRA=43%) and showed the trend of priority (OR=1.47) compared with that beyond 4.5 hours (SUCRA=58%). For the mortality, compared with placebo (SUCRA=64.7%), alteplase within 3 hours was similar to that of 3-4.5 hours whereas alteplase beyond 4.5 hours (SUCRA=7.3%) showed the trend of significantly increasing 85% mortality. For the tertiary outcome, alteplase within 3 hours (SUCRA=19.0%) was comparable with placebo (SUCRA=99.9%) whereas alteplase beyond 3 hours significantly increased (OR 5.89-6.67) the symptomatic intracerebral haemorrhage.

CONCLUSIONS

Alteplase within 3 hours should be recommended as the best treatment delay for its best efficacy among all the intervention and equivalent safety compared with placebo. Alteplase beyond 3 hours was less effective compared with that within 3 hours and increased the risk of mortality on 3 months as well as symptomatic intracerebral haemorrhage at 36 hours. More head-to-head clinical trials are needed to confirm those findings.

T Cells Prevent Hemorrhagic Transformation in Ischemic Stroke by P-Selectin Binding

Objective- Hemorrhagic transformation is a serious complication of ischemic stroke after recanalization therapies. This study aims to identify mechanisms underlying hemorrhagic transformation after cerebral ischemia/reperfusion. Approach and Results- We used wild-type mice and Selplg^-/- and Fut7^-/- mice defective in P-selectin binding and lymphopenic Rag2^-/- mice. We induced 30-minute or 45-minute ischemia by intraluminal occlusion of the middle cerebral artery and assessed hemorrhagic transformation at 48 hours with a hemorrhage grading score, histological means, brain hemoglobin content, or magnetic resonance imaging. We depleted platelets and adoptively transferred T cells of the different genotypes to lymphopenic mice. Interactions of T cells with platelets in blood were studied by flow cytometry and image stream technology. We show that platelet depletion increased the bleeding risk only after large infarcts. Lymphopenia predisposed to hemorrhagic transformation after severe stroke, and adoptive transfer of T cells prevented hemorrhagic transformation in lymphopenic mice. CD4⁺ memory T cells were the subset of T cells binding P-selectin and platelets through functional P-selectin glycoprotein ligand-1. Mice defective in P-selectin binding had a higher hemorrhagic score than wild-type mice. Adoptive transfer of T cells defective in P-selectin binding into lymphopenic mice did not prevent hemorrhagic transformation. Conclusions- The study identifies lymphopenia as a previously unrecognized risk factor for secondary hemorrhagic transformation in mice after severe ischemic stroke. T cells prevent hemorrhagic transformation by their capacity to bind platelets through P-selectin. The results highlight the role of T cells in bridging immunity and hemostasis in ischemic stroke.

Timely Visualization of the Collaterals Formed during Acute Ischemic Stroke with Fe3 O4 Nanoparticle-based MR Imaging Probe

Ischemic stroke is one of the major leading causes for long-term disability and mortality. Collateral vessels provide an alternative pathway to protect the brain against ischemic injury after arterial occlusion. Aiming at visualizing the collaterals occurring during acute ischemic stroke, an integrin α_v β₃ -specific Fe₃ O₄ -Arg-Gly-Asp (RGD) nanoprobe is prepared for magnetic resonance imaging (MRI) of the collaterals. Rat models are constructed by occluding the middle cerebral artery for imaging studies of cerebral ischemia and ischemia-reperfusion on 7.0 Tesla MRI using susceptibility-weighted imaging sequence. To show the binding specificity to the collaterals, the imaging results acquired with the Fe₃ O₄ -RGD nanoprobe and the Fe₃ O₄ mother nanoparticles, respectively, are carefully compared. In addition, an RGD blocking experiment is also carried out to support the excellent binding specificity of the Fe₃ O₄ -RGD nanoprobe. Following the above experiments, cerebral ischemia-reperfusion studies show the collateral dynamics upon reperfusion, which is very important for the prognosis of various revascularization therapies in the clinic. The current study has, for the first time, enabled the direct observation of collaterals in a quasi-real time fashion and further disclosed that the antegrade flow upon reperfusion dominates the blood supply of primary ischemic tissue during the early stage of infarction, which is significantly meaningful for clinical treatment of stroke.

Compound 21 is pro-angiogenic in the brain and results in sustained recovery after ischemic stroke

INTRODUCTION

Angiotensin II type 2 receptor (AT2R) stimulation is neuroprotective after experimental stroke. However, the therapeutic utility of AT2R stimulation has been hampered by the lack of a specific agonist with favourable bioavailability. Compound 21 (C21) - the first non-peptide AT2R agonist - offers a potential option to enhance stroke recovery. This study aimed to investigate the effect of C21 administration on early and late stroke outcomes, and the molecular mediators involved.

METHODS

Rats were subjected to 3 h or 90 min of middle cerebral artery occlusion (MCAO) and randomized to intraperitoneal C21 (0.03 mg/kg) or saline at reperfusion. Animals were sacrificed at 24 h or 7 days and brains were collected for molecular analysis and immunostaining, respectively. Functional outcome at days 1, 4 and 7 was assessed blindly. C21 angiogenic potential was assessed in vitro.

RESULTS

After 3 h of MCAO, C21 treatment reduced infarct size and improved behavioural outcome at 24 h without affecting blood pressure. Co-administration of the AT2R antagonist (PD123319) blocked these effects. On the molecular level, C21 decreased brain haemoglobin content, down-regulated apoptotic and oxidative markers, and increased pro-survival molecules in the brain. After 90 min of MCAO, C21 treatment resulted in sustained functional improvement at 7 days, together with increased vascular density in the ischemic penumbra. In vitro, C21 showed a pro-angiogenic effect that was blocked with brain-derived neurotrophic factor neutralization.

CONCLUSION

These findings demonstrate that a single dose of C21 is neurovascular-protective and improves stroke outcome possibly through increasing neurotrophin activity, mitigating brain inflammation, and promoting antioxidant and pro-angiogenic effects.

Successful recanalization post endovascular therapy is associated with a decreased risk of intracranial haemorrhage: a retrospective study

Background

The risks of intracranial haemorrhage (ICH) post intra-arterial therapy (IAT) for stroke are not well understood. We aimed to study the influence of recanalization status post IAT for anterior circulation stroke and posterior circulation stroke on ICH development.

Methods

Retrospective analysis of 193 patients in a prospectively collected database of IAT stroke patients was performed. Successful recanalization was defined as a Thrombolysis in Cerebral Infarction Score of 2b or 3 and symptomatic ICH (SICH) as parenchymal hematoma type 2 (PH2) with neurological deterioration. The association between the recanalization status and ICH/SICH was investigated using logistic regression models adjusted for baseline characteristics selected by univariate analyses.

Results

One hundred and thirty-six patients had successful recanalization post procedure, 41 patients developed ICH and 10 patients SICH. There was a statistically significant baseline imbalance between the groups with and without successful recanalization on gender, baseline National Institute of Health Stroke Scale (NIHSS) score, the use of intravenous tPA and intra-arterial urokinase (p <0.05). Logistic regression analysis adjusted for the above variables and the time to digital subtraction angiography demonstrated a statistically significant association between successful recanalization and ICH (odds ratio 0.42; 95 % CI 0.19, 0.95; p = 0.04).

Conclusion

Successful recanalization post endovascular therapy is statistically significantly and negatively associated with ICH.

Peroxynitrite Decomposition Catalyst Reduces Delayed Thrombolysis-induced Hemorrhagic Transformation in Ischemia-reperfused Rat Brains

AIM

Hemorrhagic transformation (HT) is a major complication of delayed tissue plasminogen activator (t-PA) treatment in ischemic stroke. We aimed to explore whether peroxynitrite decomposition catalyst (PDC) could prevent such complication.

METHODS

Male Sprague-Dawley (SD) rats were subjected to middle cerebral artery occlusion (MCAO) with t-PA (10 mg/kg) or t-PA plus FeTMPyP (3 mg/kg, a representative PDC) at MCAO for 2 or 5 h and reperfusion for 22 or 19 h, respectively. HT was assessed with hemoglobin assay. Neurological deficit was evaluated with Modified Neurological Severity Score (mNSS). Peroxynitrite formation was examined by detecting 3-nitrotyrosine (3-NT) formation. The expression and activity of MMP-9/MMP-2 were assessed by Western blotting and gelatin zymography.

RESULTS

t-PA treatment at 2 h of MCAO did not induce HT but attenuated neurological deficit, whereas treatment at 5 h significantly induced HT and worsened the neurological outcome. Such complications were prevented by FeTMPyP cotreatment. Early t-PA treatment inhibited 3-NT and MMP-9/MMP-2 expression, whereas delayed treatment induced 3-NT and MMP-9/MMP-2 expression and activity. FeTMPyP cotreatment downregulated 3-NT and inhibited MMP-9/MMP-2 in both time points.

CONCLUSION

Peroxynitrite decomposition catalyst could prevent hemorrhagic transformation and improve neurological outcome ischemic rat brains with delayed t-PA treatment via inhibiting peroxynitrite-mediated MMP activation.

Recommendations for preclinical research in hemorrhagic transformation

Hemorrhagic transformation (HT) is an important complication of ischemic stroke and is responsible for most of the mortality associated with acute reperfusion therapy. Although many important publications address the preclinical models of ischemic stroke, there are no current recommendations on the conduct of research aimed at understanding the mechanisms and consequences of HT. The purpose of this review is to present the various models used in HT research, the clinical correlates, and the experimental variables known to influence the quantitation of HT in preclinical investigation. Lastly, recommendations for the conduct of preclinical research in HT are provided.

Hemorrhagic transformation after ischemic stroke in animals and humans

Hemorrhagic transformation (HT) is a common complication of ischemic stroke that is exacerbated by thrombolytic therapy. Methods to better prevent, predict, and treat HT are needed. In this review, we summarize studies of HT in both animals and humans. We propose that early HT (<18 to 24 hours after stroke onset) relates to leukocyte-derived matrix metalloproteinase-9 (MMP-9) and brain-derived MMP-2 that damage the neurovascular unit and promote blood-brain barrier (BBB) disruption. This contrasts to delayed HT (>18 to 24 hours after stroke) that relates to ischemia activation of brain proteases (MMP-2, MMP-3, MMP-9, and endogenous tissue plasminogen activator), neuroinflammation, and factors that promote vascular remodeling (vascular endothelial growth factor and high-moblity-group-box-1). Processes that mediate BBB repair and reduce HT risk are discussed, including transforming growth factor beta signaling in monocytes, Src kinase signaling, MMP inhibitors, and inhibitors of reactive oxygen species. Finally, clinical features associated with HT in patients with stroke are reviewed, including approaches to predict HT by clinical factors, brain imaging, and blood biomarkers. Though remarkable advances in our understanding of HT have been made, additional efforts are needed to translate these discoveries to the clinic and reduce the impact of HT on patients with ischemic stroke.

Glibenclamide-10-h Treatment Window in a Clinically Relevant Model of Stroke

Glibenclamide improves outcomes in rat models of stroke, with treatment as late as 6 h after onset of ischemia shown to be beneficial. Because the molecular target of glibenclamide, the sulfonylurea receptor 1 (Sur1)-regulated NC(Ca-ATP) channel, is upregulated de novo by a complex transcriptional mechanism, and the principal pathophysiological target, brain swelling, requires hours to develop, we hypothesized that the treatment window would exceed 6 h. We studied a clinically relevant rat model of stroke in which middle cerebral artery occlusion (75% < reduction in LDF signal ≤90%) was produced using an intra-arterial occluder. Recanalization was obtained 4.5 h later by removing the occluder. At that time, we administered recombinant tissue plasminogen activator (rtPA; 0.9 mg/kg IV over 30 min). Immunolabeling showed modest expression of Sur1 5 h after onset of ischemia, with expression increasing 7- to 11-fold (P < 0.01) by 24 h. Rats were administered either vehicle or glibenclamide (10 μg/kg IP loading dose plus 200 ng/h by constant subcutaneous infusion) beginning 4.5 or 10 h after onset of ischemia. In rats treated at 4.5 or 10 h, glibenclamide significantly reduced hemispheric swelling at 24 h from (mean ± SEM) 14.7 ± 1.5% to 8.1 ± 1.6% or 8.8 ± 1.1% (both P < 0.01), respectively, and significantly reduced 48-h mortality from 53% to 17% or 12% (both P < 0.01), and improved Garcia scores at 48 h from 3.8 ± 0.62 to 7.6 ± 0.70 or 8.4 ± 0.74 (both P < 0.01). We conclude that, in a clinically relevant model of stroke, the treatment window for glibenclamide extends to 10 h after onset of ischemia.

Combined systemic thrombolysis with alteplase and early hyperbaric oxygen therapy in experimental embolic stroke in rats: relationship to functional outcome and reduction of structural damage

INTRODUCTION

The only causal therapy in ischemic stroke is thrombolysis with recombinant tissue plasminogen activator (rtPA), but it is feasible only for few patients, and new therapies are needed. This study investigates the effects of systemic thrombolysis with rtPA combined with hyperbaric oxygen therapy (HBOT) in embolic stroke in rats.

METHODS

In 22 male Wistar rats, an embolic ischemic stroke was induced. The animals were randomized to one of four groups: control, thrombolysis alone, HBOT sequential or HBOT parallel with thrombolysis. HBOT (2.4 ATA, 1 h) started 45 min (sequential) or 120 min (parallel) after stroke. rtPA was given intravenously 120 min after stroke onset. Functional tests were performed after stroke induction and after treatment. After 6 h infarct volume and intracerebral hemorrhagic complications were assessed.

RESULTS

Compared to the control group only the combination of HBOT and thrombolysis significantly improved the functional outcome (p=0.03) and reduced the infarct volume (p=0.01), whereas thrombolysis alone did not show a significant benefit. In all treatment groups there was a trend towards fewer hemorrhagic transformations.

CONCLUSION

Hyperbaric oxygen in combination with thrombolysis shows neuroprotection in acute ischemic stroke in rats by reducing infarct volume and improving functional outcome in the early poststroke period.

Inhibition of VEGF signaling pathway attenuates hemorrhage after tPA treatment

An angiogenic factor, vascular endothelial growth factor (VEGF), might be associated with the blood-brain barrier (BBB) disruption after focal cerebral ischemia; however, it remains unknown whether hemorrhagic transformation (HT) after tissue plasminogen activator (tPA) treatment is related to the activation of VEGF signaling pathway in BBB. Here, we hypothesized that inhibition of VEGF signaling pathway can attenuate HT after tPA treatment. Rats subjected to thromboembolic focal cerebral ischemia were assigned to a permanent ischemia group and groups treated with tPA at 1 or 4 hours after ischemia. Anti-VEGF neutralizing antibody or control antibody was administered simultaneously with tPA. At 24 hours after ischemia, we evaluated the effects of the antibody on the VEGF expression, matrix metalloproteinase-9 (MMP-9) activation, degradation of BBB components, and HT. Delayed tPA treatment at 4 hours after ischemia promoted expression of VEGF in BBB, MMP-9 activation, degradation of BBB components, and HT. Compared with tPA and control antibody, combination treatment with tPA and the anti-VEGF neutralizing antibody significantly attenuated VEGF expression in BBB, MMP-9 activation, degradation of BBB components, and HT. It also improved motor outcome and mortality. Inhibition of VEGF signaling pathway may be a promising therapeutic strategy for attenuating HT after tPA treatment.

MRI and quantitative autoradiographic studies following bolus injections of unlabeled and (14)C-labeled gadolinium-diethylenetriaminepentaacetic acid in a rat model of stroke yield similar distribution volumes and blood-to-brain influx rate constants

In previous studies on a rat model of transient cerebral ischemia, the blood and brain concentrations of gadolinium-diethylenetriaminepentaacetic acid (Gd-DTPA) following intravenous bolus injection were repeatedly assessed by dynamic contrast-enhanced (DCE)-MRI, and blood-to-brain influx rate constants (K(i)) were calculated from Patlak plots of the data in areas with blood-brain barrier (BBB) opening. For concurrent validation of these findings, after completing the DCE-MRI study, radiolabeled sucrose or α-aminoisobutyric acid was injected intravenously, and the brain disposition and K(i) values were calculated by quantitative autoradiography (QAR) assay employing the single-time equation. To overcome two of the shortcomings of this comparison, the present experiments were carried out with a radiotracer virtually identical to Gd-DTPA, Gd-[(14)C]DTPA, and K(i) was calculated from both sets of data by the single-time equation. The protocol included 3 h of middle cerebral artery occlusion and 2.5 h of reperfusion in male Wistar rats (n = 15) preceding the DCE-MRI Gd-DTPA and QAR Gd-[(14)C]DTPA measurements. In addition to K(i) , the tissue-to-blood concentration ratios, or volumes of distribution (V(R) ), were calculated. The regions of BBB opening were similar on the MRI maps and autoradiograms. Within them, V(R) was nearly identical for Gd-DTPA and Gd-[(14)C]DTPA, and K(i) was slightly, but not significantly, higher for Gd-DTPA than for Gd-[(14)C]DTPA. The K(i) values were well correlated (r = 0.67; p = 0.001). When the arterial concentration-time curve of Gd-DTPA was adjusted to match that of Gd-[(14)C]DTPA, the two sets of K(i) values were equal and statistically comparable with those obtained previously by Patlak plots (the preferred, less model-dependent, approach) of the same data (p = 0.2-0.5). These findings demonstrate that this DCE-MRI technique accurately measures the Gd-DTPA concentration in blood and brain, and that K(i) estimates based on such data are good quantitative indicators of BBB injury.

Multiparametric magnetic resonance imaging and repeated measurements of blood-brain barrier permeability to contrast agents

Breakdown of the blood-brain barrier (BBB) is present in several neurological disorders such as stroke, brain tumors, and multiple sclerosis. Noninvasive evaluation of BBB breakdown is important for monitoring disease progression and evaluating therapeutic efficacy in such disorders. One of the few techniques available for noninvasively and repeatedly localizing and quantifying BBB damage is magnetic resonance imaging (MRI). This usually involves the intravenous administration of a gadolinium-containing MR contrast agent (MRCA) such as Gadolinium-diethylenetriaminepentaacetic acid (Gd-DTPA), followed by dynamic contrast-enhanced MR imaging (DCE-MRI) of brain and blood, and analysis of the resultant data to derive indices of blood-to-brain transfer. There are two advantages to this approach. First, measurements can be made repeatedly in the same animal; for instance, they can be made before drug treatment and then again after treatment to assess efficacy. Secondly, MRI studies can be multiparametric. That is, MRI can be used to assess not only a blood-to-brain transfer or influx rate constant (Ki or K1) by DCE-MRI but also complementary parameters such as: (1) cerebral blood flow (CBF), done in our hands by arterial spin-tagging (AST) methods; (2) magnetization transfer (MT) parameters, most notably T1sat, which appear to reflect brain water-protein interactions plus BBB and tissue dysfunction; (3) the apparent diffusion coefficient of water (ADCw) and/or diffusion tensor, which is a function of the size and tortuosity of the extracellular space; and (4) the transverse relaxation time by T2-weighted imaging, which demarcates areas of tissue abnormality in many cases. The accuracy and reliability of two of these multiparametric MRI measures, CBF by AST and DCE-MRI determined influx of Gd-DTPA, have been established by nearly congruent quantitative autoradiographic (QAR) studies with appropriate radiotracers. In addition, some of their linkages to local pathology have been shown via corresponding light microscopy and fluorescence imaging. This chapter describes: (1) multiparametric MRI techniques with emphasis on DCE-MRI and AST-MRI; (2) the measurement of the blood-to-brain influx rate constant and CBF; and (3) the role of each in determining BBB permeability.

The MRI-measured arterial input function resulting from a bolus injection of Gd-DTPA in a rat model of stroke slightly underestimates that of Gd-[14C]DTPA and marginally overestimates the blood-to-brain influx rate constant determined by Patlak plots

The hypothesis that the arterial input function (AIF) of gadolinium-diethylenetriaminepentaacetic acid injected by intravenous bolus and measured by the change in the T(1)-relaxation rate (Delta R(1); R(1) = 1/T(1)) of superior sagittal sinus blood (AIF-I) approximates the AIF of (14)C-labeled gadolinium-diethylenetriaminepentaacetic acid measured in arterial blood (reference AIF) was tested in a rat stroke model (n = 13). Contrary to the hypothesis, the initial part of the Delta R(1)-time curve was underestimated, and the area under the normalized curve for AIF-I was about 15% lower than that for the reference AIF. Hypothetical AIFs for gadolinium-diethylenetriaminepentaacetic acid were derived from the reference AIF values and averaged to obtain a cohort-averaged AIF. Influx rate constants (K(i)) and proton distribution volumes at zero time (V(p) + V(o)) were estimated with Patlak plots of AIF-I, hypothetical AIFs, and cohort-averaged AIFs and tissue Delta R(1) data. For the regions of interest, the K(i)s estimated with AIF-I were slightly but not significantly higher than those obtained with hypothetical AIFs and cohort-averaged AIF. In contrast, V(p) + V(o) was significantly higher when calculated with AIF-I. Similar estimates of K(i) and V(p) + V(o) were obtained with hypothetical AIFs and cohort-averaged AIF. In summary, AIF-I underestimated the reference AIF; this shortcoming had little effect on the K(i) calculated by Patlak plot but produced a significant overestimation of V(p) + V(o).

Estimating blood and brain concentrations and blood-to-brain influx by magnetic resonance imaging with step-down infusion of Gd-DTPA in focal transient cerebral ischemia and confirmation by quantitative autoradiography with Gd-[(14)C]DTPA

An intravenous step-down infusion procedure that maintained a constant gadolinium-diethylenetriaminepentaacetic acid (Gd-DTPA) blood concentration and magnetic resonance imaging (MRI) were used to localize and quantify the blood-brain barrier (BBB) opening in a rat model of transient cerebral ischemia (n=7). Blood-to-brain influx rate constant (K(i)) values of Gd-DTPA from such regions were estimated using MRI-Patlak plots and compared with the K(i) values of Gd-[(14)C]DTPA, determined minutes later in the same rats with an identical step-down infusion, quantitative autoradiography (QAR), and single-time equation. The normalized plasma concentration-time integrals were identical for Gd-DTPA and Gd-[(14)C]DTPA, indicating that the MRI protocol yielded reliable estimates of plasma Gd-DTPA levels. In six rats with a BBB opening, 14 spatially similar regions of extravascular Gd-DTPA enhancement and Gd-[(14)C]DTPA leakage, including one very small area, were observed. The terminal tissue-plasma ratios of Gd-[(14)C]DTPA tended to be slightly higher than those of Gd-DTPA in these regions, but the differences were not significant. The MRI-derived K(i) values for Gd-DTPA closely agreed and correlated well with those obtained for Gd-[(14)C]DTPA. In summary, MRI estimates of Gd-DTPA concentration in the plasma and brain and the influx rate are quantitatively and spatially accurate with step-down infusions.

Mechanical reperfusion is associated with post-ischemic hemorrhage in rat brain

A major complication of recanalization therapy after an acute arterial occlusion in brain is hemorrhagic transformation (HT). Although it is known that prolonged ischemia is important in the development of HT, the role of reperfusion in ischemia-reperfusion induced HT is less well studied. To address the effect of reperfusion on HT, we assessed the incidence and severity of hemorrhage in rats after 5 h of middle cerebral artery occlusion (MCAO) followed by 19-hour reperfusion compared to rats with permanent occlusion (PMCAO) at the same 24-hour time point. The incidence and amount of hemorrhage, neurological function, and mortality rates were measured. MCAO (5 h) with 19-hour reperfusion was associated with a significantly higher incidence of cortical hemorrhage compared to PMCAO (81.8% vs 18.2%, p<0.05). Hemorrhage scores were higher in the 5-hour MCAO/reperfusion group compared to PMCAO rats (17.6+/-11.5 vs 2.4+/-5.3 in cortex, 20.4+/-4.6 vs 9.7+/-4.5 in striatum, p<0.01). Neurological function was worse in the ischemia-reperfusion group compared to PMCAO (p<0.05) and mortality rates were insignificantly higher in the 5-hour MCAO/reperfusion group vs PMCAO group (54.5% vs 18.1%; p<0.08). The results suggest that reperfusion after prolonged ischemia is associated with increased hemorrhagic transformation and neurological deterioration as compared to permanent ischemia. Whether pharmacological treatments prior to reperfusion attenuate post-ischemic HT requires further study.

Endogenous tissue plasminogen activator increases hemorrhagic transformation induced by heparin after ischemia reperfusion in rat brains

OBJECTIVE

Tissue plasminogen activator (tPA) as a main thrombolytic drug for acute ischemic stroke remains complicated by risk of hemorrhagic transformation. However, whether endogenous tPA is also involved in hemorrhagic transformation is yet unclear.

METHODS

We randomly assigned male Sprague-Dawley rats into three groups: the heparin group, the control group and the sham operated group. The ischemic rat models were induced by middle cerebral artery occlusion through intraluminal thread technique for 2 hours, followed by 24 hours of reperfusion. Heparin or saline was intermittent peritoneally injected after reperfusion. The extent of cerebral hemorrhage, the infarct volume, as well as the content and activity of endogenous tPA were evaluated. The matrix metalloproteinase 9 (MMP-9) expression and activity were also measured.

RESULTS

All rats receiving heparin after reperfusion were subjected to hemorrhagic transformation. Hemorrhage volume in the heparin group was remarkably present. There was significant difference between the two groups (p<0.01). In the heparin group, the expressions of endogenous tPA and MMP-9 obviously increased, while their content and activity had significant differences compared with that of the control group (p<0.01).

CONCLUSION

Endogenous tPA, through enhancement of MMP-9 expression and proteolytic activation, plays an important role in the pathogenesis of hemorrhagic transformation after cerebral reperfusion induced by heparin.

Reperfusion activates metalloproteinases that contribute to neurovascular injury

In this study, we examine the effects of reperfusion on the activation of matrix metalloproteinase (MMP) and assess the relationship between MMP activation during reperfusion and neurovascular injury. Ischemia was produced using suture-induced middle cerebral artery occlusion in rats. The MMP activation was examined with in situ and gel zymography. Injury to cerebral endothelial cells and basal lamina was assessed using endothelial barrier antigen (EBA) and collagen IV immunohistochemistry. Injury to neurons and glial cells was assessed using Cresyl violet staining. These were examined at 3 h after reperfusion (8 h after initiation of ischemia) and compared with permanent ischemia at the same time points to assess the effects of reperfusion. A broad-spectrum MMP inhibitor, AHA (p-aminobenzoyl-Gly-Pro-D-Leu-D-Ala-hydroxamate, 50 mg/kg intravenously) was administered 30 min before reperfusion to assess the roles of MMPs in activating gelatinolytic enzymes and in reperfusion-induced injury. We found that reperfusion accelerated and potentiated MMP-9 and MMP-2 activation and injury to EBA and collagen IV immunopositive microvasculature and to neurons and glial cells in ischemic cortex and striatum relative to permanent ischemia. Administering AHA 30 min before reperfusion decreased MMP-9 activation and neurovascular injury in ischemic cerebral cortex.

Nitrite does not provide additional protection to thrombolysis in a rat model of stroke with delayed reperfusion

An adjuvant therapy to prolong the therapeutic window for stroke patients is urgently needed. This randomized, blinded, placebo-controlled study investigated adjuvant intravenous sodium nitrite with recombinant tissue plasminogen activator (rtPA) in middle cerebral artery occlusion (MCAO) with 6 and 2 h of ischemia followed by reperfusion in Sprague-Dawley rats (n=59). Quantitative diffusion, T(1)-, T(2)-weighted, and semiquantitative perfusion imaging were performed before and after reperfusion and at 48 h after ischemia to determine the spatiotemporal evolution of stroke. After 48 h animals were killed and examined to evaluate infarct size and evidence of hemorrhagic transformation. Factor VIII immunostaining was performed to assess vessel morphology. Nitrite treatment (6 h group: 37.5 micromol for more than 90 mins; 2 h group: 26.25 and 1.75 micromol for more than 60 mins) did not reduce infarct volume 48 h after MCAO compared with saline-treated placebo groups after 6 or 2 h of MCAO. Stroke progression from baseline to 48 h, based on the apparent diffusion coefficient and relative cerebral blood flow deficits before and after reperfusion and T(2)-weighted hyperintensity at 48 h, did not differ between treated and control animals. These results suggest that nitrite is not a protective adjuvant therapy to delayed rtPA administration after ischemic stroke in rats.

Identification of Variations in Blood-Brain Barrier Opening After Cerebral Ischemia by Dual Contrast-Enhanced Magnetic Resonance Imaging and T 1sat Measurements

Background and Purpose— Variations in blood-brain barrier (BBB) opening after ischemia have been suggested by some tracer and magnetization transfer studies, although direct in vivo proof is still lacking. Contrast-enhanced magnetic resonance imaging (MRI) is also often used to visualize BBB damage in stroke. We hypothesized that MR contrast agents of different sizes enhance differently when BBB openings vary in size and that magnetization transfer alterations, measured by T 1 in the presence of off-resonance radiofrequency saturation (T 1sat ), in these regions reflect such differences.

Methods— Male Wistar rats (≈300 g, n=7) were subjected to 3 hours of suture occlusion of the middle cerebral artery followed by reperfusion. Status of the BBB at 24 hours after the ictus was assessed first by Gd-DTPA (554 Da) MRI and then by Gd–bovine serum albumin linked to Evans blue (Gd-BSA-EB; ≈68 kDa) MRI for contrast enhancement; T 1sat changes, cerebral blood flow, and blood-to-brain transfer constants ( K i s) for the 2 contrast agents were measured. After MRI, rats were injected with fluorescent dextran and brains were studied by fluorescence microscopy.

Results— The Gd-BSA-EB–enhancing areas were always smaller (147±80 pixels) than those for Gd-DTPA (308±204 pixels) and were contained within the latter. The difference between the 2 areas was significant ( P =0.024). Changes in T 1sat were larger in Gd-BSA-EB–enhancing areas (ipsilateral to contralateral [I/C]=1.53±0.20) than in Gd-DTPA–enhancing areas (I/C=1.40±0.24, P =0.005). The differences in cerebral blood flow values between the 2 regions were not significant ( P =0.62), but those for the K i values of the 2 tracers were different ( P =0.01 to 0.02). Excellent agreement between regions of Gd-BSA-EB enhancement and EB fluorescence was also observed.

Conclusions— These results substantiate earlier reports of regional differences in BBB opening after stroke and provide the first in vivo evidence for this phenomenon. They also support the possible use of T 1sat in quantifying stroke-induced graded BBB damage in the absence of contrast-enhanced MRI.

Increased hemorrhagic transformation and altered infarct size and localization after experimental stroke in a rat model type 2 diabetes

BACKGROUND

Interruption of flow through of cerebral blood vessels results in acute ischemic stroke. Subsequent breakdown of the blood brain barrier increases cerebral injury by the development of vasogenic edema and secondary hemorrhage known as hemorrhagic transformation (HT). Diabetes is a risk factor for stroke as well as poor outcome of stroke. The current study tested the hypothesis that diabetes-induced changes in the cerebral vasculature increase the risk of HT and augment ischemic injury.

METHODS

Diabetic Goto-Kakizaki (GK) or control rats underwent 3 hours of middle cerebral artery occlusion and 21 h reperfusion followed by evaluation of infarct size, hemorrhage and neurological outcome.

RESULTS

Infarct size was significantly smaller in GK rats (10 +/- 2 vs 30 +/- 4%, p < 0.001). There was significantly more frequent hematoma formation in the ischemic hemisphere in GK rats as opposed to controls. Cerebrovascular tortuosity index was increased in the GK model (1.13 +/- 0.01 vs 1.34 +/- 0.06, P < 0.001) indicative of changes in vessel architecture.

CONCLUSION

These findings provide evidence that there is cerebrovascular remodeling in diabetes. While diabetes-induced remodeling appears to prevent infarct expansion, these changes in blood vessels increase the risk for HT possibly exacerbating neurovascular damage due to cerebral ischemia/reperfusion in diabetes.

Relative distribution of plasma flow markers and red blood cells across BBB openings in acute cerebral ischemia

Acute blood-brain barrier (BBB) opening in cerebral ischemia is an often observed but seldom studied phenomenon. Increased permeability has been implicated with several consequences including exacerbating ischemic injury, leading to hemorrhagic transformation (HT) and also predictive of chronic damage and a way of delivering therapeutics to the diseased parts of brain. Very few studies have investigated the 'size' of such acute openings. Herein the blood-brain distribution of fluorescent isothiocyanate (FITC)- labeled red blood cells (RBCs; approximately 5 tm in diameter) and two different sized plasma flow markers in cerebral microvessels was studied by laser scanning confocal microscopy (LSCM) 6 and 24 hours after the onset of a 3 hour period of focal ischemia. At hour 6, Evans blue-tagged albumin [EB-Alb; molecular weight (MW)= 68 kDa, Stokes-Einstein radius=37 A], a marker of both plasma flow and BBB opening, was seen both inside and around microvessels whereas the RBCs were only intravascular. FITC-labeled dextran (FITC-dextran; MW=2000 kDa, Stokes-Einstein radius = approximately 150 A), another plasma flow tracer, had not leaked across the BBB into the tissue at this time. At hour 24, both RBCs and FITC-dextran were found extravascularly along with EB-Alb. We postulate that smaller sized openings in BBB at hour 6 limited the leaking of the two large tracers (RBCs and FITC-dextran) and that such size-dependency was lost by 24 hours with the progression of the ischemic injury.

Acute cerebral vascular injury after subarachnoid hemorrhage and its prevention by administration of a nitric oxide donor

Object

Structural changes in brain parenchymal vessels occur within minutes after subarachnoid hemorrhage (SAH). These changes include platelet aggregation, activation of vascular collagenases, and destruction of perivascular collagen IV. Because collagen IV is an important component of the basal lamina, the authors attempted to further define changes in vascular structure (length and luminal diameter) and their relationship to vascular permeability immediately after SAH. In addition, the authors explored whether such alterations were attenuated by administration of a nitric oxide (NO) donor.

Methods

Endovascular perforation was used to induce SAH in rats. Two sets of experiments were performed. The first established changes in vascular structure and permeability (collagen IV and endothelial barrier antigen [EBA] dual immunofluorescence) during the first 24 hours after SAH. In the second, the investigators examined the effects of an NO donor on vascular structure, permeability, and collagenase activity (in situ zymography). In this second study, animals received intravenous infusion of the NO donor S-nitrosoglutathione (GSNO, 1 μM/8 μl/min) 15 minutes after induction of SAH and were killed 3 hours after SAH onset. Controls were naive unoperated animals for the first study and saline-infused SAH animals for the second.

The authors found a time-dependent decrease in area fraction, length, and luminal diameter of collagen IV– and EBA-immunofluorescent vessels after SAH. The greatest change occurred at 3 hours after onset of SAH. Administration of GSNO was associated with striking preservation of collagen IV and EBA immunofluorescence compared with saline treatment. Zymography indicated decreased collagenase activity in GSNO-treated SAH animals compared with saline-treated SAH animals.

Conclusions

These results demonstrate changes in the structure and permeability of brain parenchymal microvessels after SAH and their reversal by treatment with an NO donor.

Acute blood-brain barrier opening in experimentally induced focal cerebral ischemia is preferentially identified by quantitative magnetization transfer imaging

Pathologic changes in brain tissue during and after stroke may lead to injury of the blood-brain barrier (BBB) and subsequent hemorrhagic transformation (HT). In a rat model of HT, the apparent diffusion coefficient of water, cerebral blood flow, relaxation times, T(1) and T(2), and magnetization transfer (MT) related parameters (T(1sat), K(for) and the MT ratio) were repetitively measured during 3 h of focal ischemia and 2 h of reperfusion (n = 8). Areas of BBB opening were identified by sequential assay of the transcapillary influx of Gd-diethylenetriaminepentaacetic acid (Gd-DTPA) by MRI and (14)C-alpha-aminoisobutyric acid (AIB) by quantitative autoradiography. Ischemia-injured regions of interest were identified from the MRI data and divided into those with and without BBB opening. Of the several MRI parameters measured, the T(1sat) in the caudate-putamen and preoptic area during ischemia and the first 2 h of reperfusion correlated best with the regional pattern of BBB opening observed thereafter. These data suggest that an ipsilateral/contralateral T(1sat) ratio > 1.6 demarcates leakage of small molecules such as Gd-DTPA and AIB across the BBB. As to clinical relevance, the quantitation of MT parameters in acute stroke may enable the early detection of areas of BBB opening and potential HT.

Effect of neutrophil depletion on gelatinase expression, edema formation and hemorrhagic transformation after focal ischemic stroke

Background

While gelatinase (MMP-2 and -9) activity is increased after focal ischemia/reperfusion injury in the brain, the relative contribution of neutrophils to the MMP activity and to the development of hemorrhagic transformation remains unknown.

Results

Anti-PMN treatment caused successful depletion of neutrophils in treated animals. There was no difference in either infarct volume or hemorrhage between control and PMN depleted animals. While there were significant increases in gelatinase (MMP-2 and MMP-9) expression and activity and edema formation associated with ischemia, neutrophil depletion failed to cause any change.

Conclusion

The main finding of this study is that, in the absence of circulating neutrophils, MMP-2 and MMP-9 expression and activity are still up-regulated following focal cerebral ischemia. Additionally, neutrophil depletion had no influence on indicators of ischemic brain damage including edema, hemorrhage, and infarct size. These findings indicate that, at least acutely, neutrophils are not a significant contributor of gelatinase activity associated with acute neurovascular damage after stroke.

Mechanisms of hyperbaric oxygen-induced neuroprotection in a rat model of subarachnoid hemorrhage

Acute cerebral ischemia occurs after subarachnoid hemorrhage (SAH) because of increased intracranial pressure (ICP) and decreased cerebral perfusion pressure (CPP). The effect of hyperbaric oxygen (HBO) on physiological and clinical outcomes after SAH, as well as the expressions of hypoxia-inducible factor-1alpha (HIF-1alpha) and its target genes, such as BNIP3 and VEGF was evaluated. Eighty-five male SD rats (300 to 350 g) were randomly assigned to sham, SAH, and SAH+HBO groups. Subarachnoid hemorrhage was induced by endovascular perforation. Cortical cerebral blood flow (CBF), ICP, brain water content, brain swelling, neurologic function, and mortality were assessed. HBO (100% O2, 2.8 ATA for 2 h) was initiated at 1 h after SAH. Rats were sacrificed at 24 h to harvest tissues for Western blot or for histology. Apoptotic morphology accompanied by strong immunostaining of HIF-1alpha, VEGF, and BNIP3 were observed in the hippocampus and the cortex after SAH. Increased expressions of HIF-1alpha, VEGF, and BNIP3 were quantified by Western blot. HBO reduced the expressions of HIF-1alpha, VEGF, and BNIP3, diminished neuronal damage and improved CBF and neurologic function. HBO reduced early brain injury after SAH, probably by inhibition of HIF-1alpha and its target genes, which led to the decrease of apoptosis and preservation of the blood-brain barrier function.

Quantitation and localization of blood-to-brain influx by magnetic resonance imaging and quantitative autoradiography in a model of transient focal ischemia

The ability of gadolinium-diethylenetriaminepentaacetic acid (Gd-DTPA) enhanced MRI to localize and quantitate blood-brain barrier (BBB) opening was evaluated against quantitative autoradiographic (QAR) imaging of (14)C-alpha-aminoisobutyric acid (AIB) distribution. The blood-to-brain transfer constant (K(i)) for Gd-DTPA was determined by MRI in rats after 3 h of focal cerebral ischemia plus 2.5 h of reperfusion (n = 9), and that of AIB was determined by QAR shortly thereafter. Tissue regions of interest (ROIs) for Gd-DTPA leakage were identified by ISODATA segmentation of pre- and post-Gd-DTPA Look-Locker (L-L) T(1) maps. Patlak plots were constructed using time course of blood and tissue T(1) changes induced by Gd for estimating K(i). Among the nine rats, 14 sizable regions of AIB uptake were found; 13 were also identified by ISODATA segmentation. Although the 13 MRI-ROIs spatially approximated those of AIB uptake, the segmentation sometimes missed small areas of lesser AIB uptake that did not extend through more than 60% of the 2.0-mm-thick slice. Mean K(i)'s of AIB were highly correlated with those of Gd-DTPA across the 13 regions; the group means (+/-SD) were similar for the two tracers (7.1 +/- 3.3 x 10(-3) and 6.8 +/- 3.5 x 10(-3) ml.g(-1) . min(-1), respectively). In most instances, Gd-DTPA MRI accurately localized areas of BBB opening.

Combining Insulin-Like Growth Factor Derivatives Plus Caffeinol Produces Robust Neuroprotection After Stroke in Rats

Background and Purpose— Insulin-like growth factor-1 (IGF-1) and caffeinol are both neuroprotective and probably have different mechanisms of action; therefore, they may be more effective in combination.

Methods— We tested the N-terminal tripeptide of IGF-1, Gly-Pro-Glu (GPE), and its analogue, G2MePE, alone and with caffeinol in a rat middle cerebral artery (MCA) suture occlusion model. We randomly assigned rats to 6 groups of 8 to 12 animals: (1) control; (2) GPE, 3 mg/kg per hour; (3) G2MePE, 0.3 mg/kg per hour; (4) caffeinol, a mixture of caffeine (10 mg/kg) with ethanol (0.32 g/kg); (5) GPE with caffeinol (combination of group 2 with 4); and (6) G2MePE with caffeinol (combination of group 3 with 4). Drugs were started 75 minutes after suture occlusion, at the start of reperfusion. Three days after MCA occlusion, neurological deficit (Neurological Deficit Score [NDS]) and lesion volume were measured.

Results— GPE and caffeinol improved NDS by 34% and 36%, respectively ( P <0.01), and also decreased cortical but not striatal lesion volume compared with control (GPE cortex, 121 mm 3 ; caffeinol cortex, 134 mm 3 ; and control, 221 mm 3 ; P <0.01). GPE plus caffeinol did not have more efficacy than either GPE or caffeinol alone. G2MePE slightly improved NDS (19.7%, P =0.05) but not lesion volume. However, G2MePE plus caffeinol very significantly improved NDS (64%) and lesion volume in both cortex (combination 95 mm 3 versus control 221 mm 3 ) and striatum (combination 74 mm 3 versus control 110 mm 3 ) ( P <0.001), and was significantly more effective than either caffeinol or G2MePE alone.

Conclusion— Both GPE and caffeinol significantly protect cortex after MCA occlusion. At the doses used in this study, the GPE analogue G2MePE by itself had minimal protective effects, but when combined with caffeinol, it demonstrated robust beneficial effects on cortical and subcortical lesion size and behavioral deficit. Further study of this combination appears justified.

Admission Fibrinolytic Profile Is Associated With Symptomatic Hemorrhagic Transformation in Stroke Patients Treated With Tissue Plasminogen Activator

Background and Purpose— Symptomatic intracranial hemorrhage (SICH) is the most feared complication after tissue plasminogen activator (tPA) stroke treatment. Endogenous fibrinolysis inhibitors play an essential role in the coagulation/fibrinolysis balance and may be involved in the bleeding process. We aim to determine the predictive value of pretreatment levels of fibrinolysis inhibitors (PAI-1, lipoprotein(a), TAFI, and homocysteine) on SICH.

Methods— Consecutive tPA-treated stroke patients with middle cerebral artery occlusion were studied. Baseline blood samples were obtained just before tPA administration and fibrinolysis inhibitors were determined. A second computed tomography (CT) scan was obtained at 24 hours or when a neurological worsening occurred to rule out SICH.

Results— Seventy-seven patients (40% women, age 75 years) were studied. Median admission National Institutes of Health Stroke Scale was 17 (range, 7 to 22) and mean time to treatment was 160 minutes. Six patients (7.9%) presented with a SICH. In analyses based on clinical and CT variables, no relation could be found with SICH. When laboratory data were analyzed, patients who experienced SICH showed lower baseline PAI-1 (21.7±3.5 ng/mL versus 31.8±12.1 ng/mL; P <0.01) and higher TAFI (216.7±78.4% versus 162.1±54.2%; P =0.03). Homocysteine and lipoprotein(a) were not related to SICH. The only factors associated with SICH were TAFI >180% (OR, 12.9; CI, 1.41 to 118.8; P =0.02) and PAI-1 <21.4 ng/mL (OR, 12.75; CI, 1.17 to 139.2; P =0.04). The combination of admission PAI-1 <21.4 ng/mL and TAFI >180% had a sensibility of 75% and a specificity of 97.6% ( P <0.01) predicting SICH, with a positive predictive value of 75% and negative predictive value of 97.6%.

Conclusions— Baseline PAI-1 and TAFI levels predict SICH after stroke tPA therapy. In the future, these biomarkers could be used to improve thrombolysis safety.