Intra-arterial thrombolytic therapy for acute intracranial large artery occlusive disease in patients selected by magnetic resonance image

Dose-Response Relationship and Threshold Drug Dosage Identification for a Novel Hybrid Mechanical-Thrombolytic System with an Ultra-Low Dose Patch

Introduction

Ischemic stroke treatment has advanced in the last two decades and intravenous thrombolysis is now considered the standard of care for selected patients. Recanalization can also be achieved by mechanical endovascular treatment for patients with large vessel occlusions. Complicating treatment-related symptomatic intracerebral hemorrhage and prolonged needle-to-recanalization times have been identified as major determinants of poor three-month functional outcomes. A hybrid mechanical-thrombolytic system with a patch imbued with an ultra-low dose of thrombolytic agents loaded onto a stent-retriever has been developed.

Methods

In this study, the in situ dose-response relationship of the thrombolytic patch imbued with up to 1000 IU of urokinase plasminogen activator (uPA) was quantified using Raman spectroscopy.

Results

Thrombi of up to 400 μm thickness dissolved within 15 min when patches imbued with < 1% of the conventional thrombolysis therapy dosage were applied. The results demonstrated that low-dose thrombolytic patches can dissolve normal clots compressed in the blood vessel in a short time. 500 IU is the threshold uPA dosage in the thrombolytic patch that most effectively dissolves the clots.

Conclusion

This study suggests that a novel endovascular stent-retriever loaded with an ultra-low drug dose fibrinolytic patch may be a suitable treatment for patients who are ineligible for conventional thrombolytic therapy.

Urokinase Plasminogen Activator: A Potential Thrombolytic Agent for Ischaemic Stroke

Stroke continues to be one of the leading causes of mortality and morbidity worldwide. Restoration of cerebral blood flow by recombinant plasminogen activator (rtPA) with or without mechanical thrombectomy is considered the most effective therapy for rescuing brain tissue from ischaemic damage, but this requires advanced facilities and highly skilled professionals, entailing high costs, thus in resource-limited contexts urokinase plasminogen activator (uPA) is commonly used as an alternative. This literature review summarises the existing studies relating to the potential clinical application of uPA in ischaemic stroke patients. In translational studies of ischaemic stroke, uPA has been shown to promote nerve regeneration and reduce infarct volume and neurological deficits. Clinical trials employing uPA as a thrombolytic agent have replicated these favourable outcomes and reported consistent increases in recanalisation, functional improvement and cerebral haemorrhage rates, similar to those observed with rtPA. Single-chain zymogen pro-urokinase (pro-uPA) and rtPA appear to be complementary and synergistic in their action, suggesting that their co-administration may improve the efficacy of thrombolysis without affecting the overall risk of haemorrhage. Large clinical trials examining the efficacy of uPA or the combination of pro-uPA and rtPA are desperately required to unravel whether either therapeutic approach may be a safe first-line treatment option for patients with ischaemic stroke. In light of the existing limited data, thrombolysis with uPA appears to be a potential alternative to rtPA-mediated reperfusive treatment due to its beneficial effects on the promotion of revascularisation and nerve regeneration.

Risk factors outperform intracranial large artery stenosis predicting unfavorable outcomes in patients with stroke

Background

This study examined how intracranial large artery stenosis (ILAS), symptomatic and asymptomatic ILAS, and risk factors affect unfavorable outcome events after medical treatment in routine clinical practice.

Methods

This was a 24-month prospective observational study of consecutively recruited stroke patients. All participants underwent magnetic resonance angiography, and their clinical characteristics were assessed. Outcome events were vascular outcome, recurrent stroke, and death. Cox regression analyses were performed to identify potential factors associated with an unfavorable outcome, which included demographic and clinical characteristics, the risk factors, and stenosis status.

Results

The analysis included 686 patients; among them, 371 were assessed as ILAS negative, 231 as symptomatic ILAS, and 84 as asymptomatic ILAS. Body mass index (p < .05), hypertension (p = .01), and old infarction (p = .047) were factors relating to vascular outcomes. Hypertension was the only factor for recurrent stroke (p = .035). Poor glomerular filtration rate (< 30 mL/min/1.73 m²) (p = .011) and baseline National Institutes of Health Stroke Scale scores (p < .001) were significant predictors of death.

Conclusions

This study extended previous results from clinical trials to a community-based cohort study by concurrently looking at the presence/absence of stenosis and a symptomatic/asymptomatic stenotic artery. Substantiated risk factors rather than the stenosis status were predominant determinants of adverse outcome. Although the degree of stenosis is often an indicator for treatment, we suggest risk factors, such as hypertension and renal dysfunction, should be monitored and intensively treated.

Model development and comparison of low hemorrhage-risk endoluminal patch thrombolytic treatment for ischemic stroke

Clot dissolution drugs delivered into the systemic circulation can dissolve intracranial blood clots in 90 min with 20-50% hemorrhage rate. Immobilizing <5% of the intravenous dosage on an endoluminal patch can reduce the dissolution time to <20 min with negligible hemorrhage risk. The thrombus dissolution behavior in endoluminal patch thrombolytic treatment is modeled and compared with experimental results from a companion study. Analyses showed that the thrombus dissolution time decreases with increasing dosage, but the dissolution time reaches a dosage-independent minimum when uPA dosage on the patch is >800 IU. Model analyses showed that dissolution time in the plateau regime is controlled by diffusion. Further results showed that dissolution time could be reduced in this regime by reducing thrombus thickness. This suggests that a stented endoluminal thrombolytic >800 IU patch that compresses the thrombus to thin the clot thickness can help reduce dissolution time. This ultra-low transition dosage (i.e., 800 IU), compared to 0.6-2.4 million IU in conventional thrombolysis suggests that hemorrhage risk in endoluminal patch thrombolytic treatment is low. The low hemorrhagic-risk endoluminal patch can be considered for use in patients who are ineligible for conventional thrombolytic treatment because of high hemorrhagic treatment risk.

In vitro examination of the pressure effect on clot dissolution with thrombolytic patch

Bio-kinetic thrombus dissolution model has been developed to describe the thrombus dissolution behavior during endoluminal thrombolytic patch treatment to recanalize blocked vessel in ischemic strokes. The initial model ignored the effect of pulsatile pressure in the lumen. However, pulsatile pressure in the lumen may affect molecule diffusion and bio-chemical reaction rate and accelerate clot dissolution. The effect of pressure on the dissolution rate was examined in this study. The dissolution behaviors of 100-400 μm thick blood clot specimens subject to diastolic, systolic, and pulsatile pressure were characterized using Raman spectroscopy. The results showed that dissolution time was reduced by less than 2 mins and is negligible in comparison with total treatment time. The effect of pressure may be ignored and the developed bio-kinetic model may be used in surgical applications of endoluminal thrombolytic patch to estimate treatment time in ischemic stroke.

Pharmacological revascularization of acute ischaemic stroke: focus on challenges and novel strategies

The only currently approved treatment for acute ischaemic stroke (AIS) is alteplase, a thrombolytic agent given intravenously (IV) within 4.5 hours of symptom onset, in an attempt to reopen occluded intracerebral arteries. However, no more than 5% of all AIS patients receive IV alteplase, mainly because of too long symptom-onset-to-hospital intervals. Moreover, this strategy is effective for less than half of the patients treated within the therapeutic window. Early recanalization is the most powerful prognostic factor, and novel drugs or therapeutic strategies are primarily aimed at improving alteplase efficacy to rapidly and safely reopen the occluded arteries. Because IV alteplase-resistant thrombi are those with the largest clot burden, responsible for the most devastating brain-tissue infarctions, development of novel approved AIS therapies is an urgent priority. At present, in the absence of controlled trials, no valid recommendations can be made. However, the most promising emerging strategy is a combination of standard or low-dose IV alteplase with an intra-arterial (IA) procedure, including additional endovascular thrombolytic and/or mechanical clot retrieval. Notably, results of open trials using the IA route had relatively disappointing clinical outcomes, despite remarkable arterial recanalization rates. Controlled trials are urgently needed to evaluate strategies including an IA route. In addition, logistic and cost constraints will likely limit their routine use, even in industrialized countries. Combining of another IV drug and IV alteplase is a far less studied option, although much easier to implement. Add-on IV drugs could be an antiplatelet glycoprotein (GP) IIb/IIIa receptor antagonist, a direct thrombin inhibitor or a second thrombolytic agent, e.g. tenecteplase. However, neuroimaging to measure the clot burden and infarction size will probably be necessary to predict IV alteplase failure and the subsequent use of these eventual additional therapies.

Arterial blood gas analysis of samples directly obtained beyond cerebral arterial occlusion during endovascular procedures predicts clinical outcome

Real-time intra-procedure information about ischemic brain damage degree may help physicians in taking decisions about pursuing or not recanalization efforts.

METHODS

We studied gasometric parameters of blood samples drawn through microcatheter in 16 stroke patients who received endovascular reperfusion procedures. After crossing the clot with microcatheter, blood sample was obtained from the middle cerebral artery (MCA) segment distal to occlusion (PostOcc); another sample was obtained from carotid artery (PreOcc). An arterial blood gas (ABG) study was immediately performed. We defined clinical improvement as National Institutes of Health Stroke Scale (NIHSS) decrease of ≥4.

RESULTS

The ABG analysis showed differences between PreOcc and PostOcc blood samples in mean oxygen partial pressure (Pre-PaO2: 78.9 ± 16 .3 vs. 73.9 ± 14 .9 mmHg; P < .001). Patients who presented clinical improvement had higher Post-PaO2 (81 ± 11 .4 vs. 64.8 ± 14 .4 mmHg; P = .025). A receiver-operator characteristic (ROC) curve determined Post-PaO2 > 70 mmHg that better predicted further clinical improvement. Patients with Post-PaO2 > 70 mmHg had higher chances of clinical improvement (81.8% vs. 0%; P = .002) and lower disability (median mRS:3 vs. 6; P= .024). In the logistic regression the only independent predictor of clinical improvement was Post-PaO2 > 70 (OR: 5.21 95% CI: 1.38-67.24; P = .013).

CONCLUSION

Direct local blood sampling from ischemic brain is feasible during endovascular procedures in acute stroke patients. A gradient in oxygenation parameters was demonstrated between pre- and post-occlusion blood samples. ABG information may be used to predict clinical outcome and help in decision making in the angio-suite.

Extending the time window for endovascular procedures according to collateral pial circulation

BACKGROUND AND PURPOSE

Good collateral pial circulation (CPC) predicts a favorable outcome in patients undergoing intra-arterial procedures. We aimed to determine if CPC status may be used to decide about pursuing recanalization efforts.

METHODS

Pial collateral score (0-5) was determined on initial angiogram. We considered good CPC when pial collateral score<3, defined total time of ischemia (TTI) as onset-to-recanalization time, and clinical improvement>4-point decline in admission-discharge National Institutes of Health Stroke Scale.

RESULTS

We studied CPC in 61 patients (31 middle cerebral artery, 30 internal carotid artery). Good CPC patients (n=21 [34%]) had lower discharge National Institutes of Health Stroke Scale score (7 versus 21; P=0.02) and smaller infarcts (56 mL versus 238 mL; P<0.001). In poor CPC patients, a receiver operating characteristic curve defined a TTI cutoff point<300 minutes (sensitivity 67%, specificity 75%) that better predicted clinical improvement (TTI<300: 66.7% versus TTI>300: 25%; P=0.05). For good CPC patients, no temporal cutoff point could be defined. Although clinical improvement was similar for patients recanalizing within 300 minutes (poor CPC: 60% versus good CPC: 85.7%; P=0.35), the likelihood of clinical improvement was 3-fold higher after 300 minutes only in good CPC patients (23.1% versus 90.1%; P=0.01). Similarly, infarct volume was reduced 7-fold in good as compared with poor CPC patients only when TTI>300 minutes (TTI<300: poor CPC: 145 mL versus good CPC: 93 mL; P=0.56 and TTI>300: poor CPC: 217 mL versus good CPC: 33 mL; P<0.01). After adjusting for age and baseline National Institutes of Health Stroke Scale score, TTI<300 emerged as an independent predictor of clinical improvement in poor CPC patients (OR, 6.6; 95% CI, 1.01-44.3; P=0.05) but not in good CPC patients. In a logistic regression, good CPC independently predicted clinical improvement after adjusting for TTI, admission National Institutes of Health Stroke Scale score, and age (OR, 12.5; 95% CI, 1.6-74.8; P=0.016).

CONCLUSIONS

Good CPC predicts better clinical response to intra-arterial treatment beyond 5 hours from onset. In patients with stroke receiving endovascular treatment, identification of good CPC may help physicians when considering pursuing recanalization efforts in late time windows.