Abstract P27: Safety and Efficacy of Alteplase in Ischemic Stroke Patients > 80 Years of Age in the Extended Time Window

Background: While patients > 80 years of age were originally excluded from the ECASS 3 trial showing benefit in the 3 – 4.5-hour window, recent studies have shown that intravenous alteplase is safe and benefits this population. We aimed to assess safety and efficacy of intravenous thrombolysis in stroke patients above 80 presenting both in the 3 and 3 – 4.5-hour windows.

Methods: We analyzed data from 3 comprehensive stroke centers in the US of consecutive patients > 80 years of age presenting with acute ischemic stroke who received intravenous alteplase in both the 3 and 4.5-hour time windows over a 3-year period. We collected baseline demographic data, stroke severity as assessed by NIHSS scores, and use of mechanical thrombectomy (MT). Primary outcome was symptomatic intracerebral hemorrhage, as defined by ECASS 2 criteria (hemorrhagic transformation post thrombolysis with worsening of NIHSS score by ≥ 4 points). Secondary outcomes included assessment of efficacy, evaluated by good functional outcome (mRS 0 – 2) at time of discharge.

Results: We identified 418 patients with ischemic stroke above 80 years (64.8% women) who received alteplase: 344 (82.3%) within 3 hour and 74 (17.7%) in the 3 to 4.5-hour window, with similar stroke severity by NIHSS scores (median [IQR] 13 [12-32] vs. 12 [6-20], p = 0.87). In addition, 147 patients received MT, 128 (37.2%) versus 19 (25.7%), (p= 0.059) in the 3 and 3-4.5-hour groups. The overall rate of sICH was 6.1% and 4.0% (p = 0.49), in the 3 and 3-4.5-hour groups, respectively. Good functional outcome was achieved in 16.7% at time of discharge, for 17.7% in the 3-hour group and for 12.2% in the 3 – 4.5-hour group (p= 0.24).

Conclusions: In our multi-center cohort, the use of alteplase in patients above 80 was safe, with low sICH rates similar to the literature, irrespective of age. Given the rare occurrence of our primary outcome in a selected cohort of acute stroke patients, our study was not powered to detect a possible significant difference in sICH.

Abstract TP52: Endovascular Therapy in Patients Over 80 Years of Age With Acute Ischemic Stroke

Introduction: Acute ischemic stroke treatment has undergone a paradigm shift, with patients being treated in the extended time window (6-24 hours post symptom onset). The purpose of this study is to assess outcomes in stroke patients above 80 years of age undergoing endovascular treatment (EVT) in the extended time window.

Methods: Acute ischemic stroke patients presenting to Hartford Hospital between January 2017 to June 2019 were considered for the study. Stroke outcomes in patients above 80 years of age with anterior circulation ischemic strokes presenting in the extended time window (Group A, n=30) were compared to a younger cohort of patients below 80 years (Group B, n=31). Patients over 80 years treated in the traditional time window (within 6 hours of symptom onset) served as a second set of controls (Group C, n=40). Statistical analysis was performed with a significance level of 0.05

Results: For angiographic results, there were no statistically significant differences in terms of good outcomes (TICI 2b-3) among patients of Group A, when compared to Groups B or C (p>0.05). For the endovascular procedures, no significant differences were noted in the total fluoroscopy time (Median Group A 44.05, Group B 38.1, Group C 35.25 min), total intra-procedure time (Median Group A 144, Group B 143, Group C 126 min) or total radiation exposure (Median Group A 8308, Group B 8960, Group C 8318 uGy-m 2 ). For stroke outcomes, a good clinical outcome was defined as modified Rankin score of 0-2 at discharge. Significantly better outcomes were noted in the younger patients in Group B - 35.4%, when compared to 13.3% in Group A (p=0.03). Comparative outcomes differed in the elderly patients above 80 years, Group A -13.3% vs Group C - 25%, although not statistically significant (p=0.23). There was a significant difference in mortality in patients of Group A - 40% as compared to 12% in the younger cohort, Group B (p= 0.01).

Conclusions: In the extended time window, patients above 80 years of age were noted to have a higher mortality, morbidity compared to the younger cohort of patients. No significant differences were noted in the stroke outcomes in patients above 80 years of age when comparing the traditional and the extended time window for stroke treatment.

Abstract WP368: CT Perfusion and Radiation Exposure in Acute Ischemic Stroke: A Quality Improvement Study

Introduction: Treatment of acute ischemic stroke has undergone a paradigm shift after recently published trials DAWN & DEFUSE-3. Imaging techniques like CT perfusion (CTP) can identify eligible candidates who may benefit from intervention, however, this entails screening patients with CTP, resulting in higher radiation & contrast exposure.

Methods: Acute ischemic stroke patients admitted between Sept 2017 & Feb 2018, who underwent CTP screening at Hartford Hospital were considered for this study. Patients admitted between April & Sept 2017 who underwent CT Angiogram (CTA) Head alone for screening were considered for controls. A standard CTP algorithm was utilized, with image acquisition time initially set at 60 secs and later reduced to 45 secs. Imaging (CTP RAPID, CTA) related variables were analyzed. SPSS was used for statistical analysis.

Results: We assessed 50 patients who underwent CTP screening (CTP group) in the extended stroke window (6-24 hours) and 45 patients who served as controls. In the CTP group, 90% scans were of optimal quality, whereas 10% were deemed suboptimal. For CTP associated radiation exposure, the median dose length product (DLP) was 1420.3 mGy-cm (IQR 1420 to 1775.31 mGy-cm). The median DLP was 2401.89 mGy-cm in patients with 60 sec CTP acquisition time, significantly higher compared to 1420.3 mGy-cm in patients with 45 sec acquisition time (p<0.001). The median total radiation exposure (excluding endovascular intervention) during entire hospitalization for the CTP group was 5260 mGy-cm as compared to 3222.27 mGy-cm for controls, which was statistically significant (p<0.001). No radiation related adverse events were observed in the CTP group. In terms of contrast exposure, there was no significant difference in Sr creatinine obtained at day one or at discharge when compared to baseline (p=0.46). Amongst 50 patients screened with CT perfusion, 16 patients (32%) were deemed eligible for endovascular therapy.

Conclusions: Although CT perfusion screening may result in higher radiation exposure, the perfusion protocols may be optimized to reduce the amount of radiation imparted to patients without compromising on the scan quality. Despite additional contrast exposure, no significant effects were observed on the renal function.

Abstract WP120: MicroRNA Expression in Patients With Acute Ischemic Stroke

Background and Purpose: MicroRNAs (miRNAs) are a class of endogenous small non-coding ribonucleic acids that regulate gene expression and can impact cellular function by suppressing or activating downstream mRNA targets. Pre-clinical studies in animal models of stroke have demonstrated specific changes in miRNA expression profiles after ischemic stroke.

Methods: Patients admitted to Hartford Hospital from January 2011 - March 2014 were considered for this study. Blood samples were collected within 24 hours of stroke presentation. miRNA profiles from peripheral blood samples of ischemic stroke patients were compared to controls. Patients with acute middle cerebral artery (MCA) cardioembolic strokes (based on TOAST criteria) were included (n=16). Blood collected from patients with no acute neurological deficits in an outpatient setting served as controls (n=8). Individuals with a history of active cancer, neoplastic brain lesions or traumatic brain injury were excluded. Based on literature review, 173 miRNAs were selected to assess for differential expression between cases and controls. miRNA profiling was conducted at Exiqon Services, Denmark, using miRCURY LNA™ microRNA Array. Statistical analysis was performed using SAS.

Results: In patients with acute ischemic strokes, a statistically significant differential expression was observed in 14 miRNAs as compared to controls. MicroRNAs miR-1273e, miR-5187-3p were found to be downregulated in stroke patients (p=0.01). Other miRNAs showing a significant downregulation included let 7e-5p (p=0.03); miR-4709-3p, miR-4756-3p, miR-5584-3p, miR-647 (p=0.02); miR-4742-3p (p=0.03); miR-4764-5p, miR-4531 and miR-2116-5p (p=0.04). MicroRNAs miR-664a-3p (p=0.02), miR-943 (p=0.04) and miR-145-5p (p=0.03) were significantly upregulated. Differential expression in males and females was not observed.

Conclusion: Ischemic stroke patients show a differential microRNA expression profile as compared to controls. Further studies can help identify microRNA signatures as well as the downstream targets involved in the ischemic stroke molecular cascade.

Abstract TP343: Differential TNFα Expression in Patients of Acute Ischemic Stroke

Introduction: Inflammation plays a critical role in the pathophysiology of ischemia and atherosclerosis. TNFα plays a multifaceted role in stroke progression, having both protective and deleterious effects. Animal studies have shown that TNFα levels increase in cerebral tissue within the first 24 hours after experimental stroke.

Hypothesis: Expression of TNFα is related to outcomes after acute ischemic stroke. Differences in expression will be seen with respect to patient gender and other stroke characteristics.

Methods: Patients admitted to Hartford Hospital between January 2011 and March 2014 were considered for this study. Blood samples were collected within 24 hours of stroke presentation. Patients with a history of active cancer, primary or secondary neoplastic brain lesions, traumatic brain injury or intracranial hemorrhage were excluded from the study. Serum was analyzed using a multiplex human cytokine panel/Bio plex (Bio-Rad laboratories Inc.). Statistical analysis was performed using SPSS.

Results: A total of 163 ischemic stroke patients were included in the study. Outcome variables including NIH stroke scale, modified Rankin scale (mRS) at discharge, 3 months, 12 months and modified Barthel’s index (BI) were collected. Composite outcome scores were determined using the mRS and BI. A negative outcome was defined as death or BI ≤ 14 or mRS >2.There was a statistically significant difference (p=0.003) in the expression of TNFα between male - 21.74 pg/ml (15.11-30.21) and female 27.9 pg/ml (19.07-35.497) stroke patients. A significant difference (p=0.009) was observed in TNFα expression in patients with a good outcome - 22.96 pg/ml (15.69-30.85) as compared to those with a poor outcome (discharge to worse/hospice or death) - 30.78 pg/ml (22.03-35.38) post stroke.

Conclusions: Male- female sex differences are associated with changes in the post ischemic inflammatory cascade. Higher TNFα levels predict poorer outcomes post stroke. Cytokines like TNFα may serve as a potential therapeutic targets in patients with acute ischemic stroke.

Ferrous iron oxidation by foam immobilized Acidithiobacillus ferrooxidans: Experiments and modeling

Ferrous iron bio-oxidation by Acidithiobacillus ferrooxidans immobilized on polyurethane foam was investigated. Cells were immobilized on foams by placing them in a growth environment and fully bacterially activated polyurethane foams (BAPUFs) were prepared by serial subculturing in batches with partially bacterially activated foam (pBAPUFs). The dependence of foam density on cell immobilization process, the effect of pH and BAPUF loading on ferrous oxidation were studied to choose operating parameters for continuous operations. With an objective to have high cell densities both in foam and the liquid phase, pretreated foams of density 50 kg/m(3) as cell support and ferrous oxidation at pH 1.5 to moderate the ferric precipitation were preferred. A novel basket-type bioreactor for continuous ferrous iron oxidation, which features a multiple effect of stirred tank in combination with recirculation, was designed and operated. The results were compared with that of a free cell and a sheet-type foam immobilized reactors. A fivefold increase in ferric iron productivity at 33.02 g/h/L of free volume in foam was achieved using basket-type bioreactor when compared to a free cell continuous system. A mathematical model for ferrous iron oxidation by Acidithiobacillus ferrooxidans cells immobilized on polyurethane foam was developed with cell growth in foam accounted by an effectiveness factor. The basic parameters of simulation were estimated using the experimental data on free cell growth as well as from cell attachment to foam under nongrowing conditions. The model predicted the phase of both oxidation of ferrous in shake flasks by pBAPUFs as well as by fully activated BAPUFs for different cell loadings in foam. Model for stirred tank basket bioreactor predicted within 5% both transient and steady state of the experiments closely for the simulated dilution rates. Bio-oxidation at high Fe(2+) concentrations were simulated with experiments when substrate and product inhibition coefficients were factored into cell growth kinetics.

Mathematical model for evaluation of mass transfer limitations in phenol biodegradation by immobilized Pseudomonas putida

A mathematical model is proposed to analyze the mass transfer limitations in phenol biodegradation using Pseudomonas putida immobilized in calcium alginate. The model takes into account internal and external mass transfer limitations, substrate inhibition kinetics and the dependence of the effective diffusivity of phenol in alginate gel on cell concentration. The model is validated with the experimental data from batch fermentation. The effect of various operating conditions such as initial phenol concentration, initial cell loading, alginate gel loading on the biodegradation of phenol is experimentally demonstrated. Phenol degradation time is found to decrease initially and reach stationary value with increase in cell loading as well as gel loading. The model predicts these trends reasonably well and shows the presence of external mass transfer limitations. A new concept of effectiveness factor is introduced to analyze the overall performance of batch fermentation.

Surface chemical studies of Thiobacillus ferrooxidans with reference to copper tolerance

A strain of Thiobacillus ferrooxidans was adapted to grow at higher concentrations of copper by single step culturing in the presence of 20 g/L (0.314 mol/L) cupric ions added to 9K medium. Exposure to copper results in change in the surface chemistry of the microorganism. The isoelectric point of the adapted strain (pI = 4.7) was observed to be at a higher pH than that of the wild unadapted strain (pI = 2.0). Compared to the wild strain, the copper adapted strain was found to be more hydrophobic and showed enhanced attachment efficiency to the pyrite mineral. The copper adsorption ability of the adapted strain was also found to be higher than that of the wild strain. Fourier transform infrared spectroscopy of adapted cells suggested that a proteinaceous new cell surface component is synthesized by the adapted strain. Treatment of adapted cells with proteinase-K, resulted in complete loss of tolerance to copper, reduction in copper adsorption and hydrophobicity of the adopted cells. These observations strongly suggest a role played by cell surface modifications of Thiobacillus ferrooxidans in imparting the copper tolerance to the cells and bioleaching of sulphide minerals.