Plasma angiopoietin-1 is lower after ischemic stroke and associated with major disability but not stroke incidence

BACKGROUND AND PURPOSE

Studies in rodent models suggest that upregulating angiopoietin-1 (Angpt1) improves stroke outcomes. The aims of this study were to assess the association of plasma Angpt1 with stroke occurrence and outcome.

METHODS

Plasma Angpt1 was measured in 336 patients who had experienced a recent stroke and 321 healthy controls with no stroke history. Patients with stroke (n=285) were reassessed at 3 months and plasma Angpt1 concentration on admission compared between those with severe and minor disability as assessed by the modified Rankin scale. In a separate cohort of 4032 community-acquired older men prospectively followed for a minimum of 6 years, the association of plasma Angpt1 with stroke incidence was examined.

RESULTS

Median plasma Angpt1 was 3-fold lower in patients who had experienced a recent stroke (6.42, interquartile range, 4.26-9.53 compared with 17.36; interquartile range, 14.01-22.46 ng/mL; P<0.001) and remained associated with stroke after adjustment for other risk factors. Plasma Angpt1 concentrations on admission were lower in patients who had severe disability or died at 3 months (median, 5.52; interquartile range, 3.81-8.75 ng/mL for modified Rankin scale 3-6; n=91) compared with those with minor disability (median, 7.04; interquartile range, 4.75-9.92 ng/mL for modified Rankin scale 0-2; n=194), P=0.012, and remained negatively associated with severe disability or death after adjusting for other risk factors. Plasma Angpt1 was not predictive of stroke incidence in community-dwelling older men.

CONCLUSIONS

Plasma Angpt1 concentrations are low after ischemic stroke particularly in patients with poor stroke outcomes at 3 months. Interventions effective at upregulating Angpt1 could potentially improve stroke outcomes.

Abstract W P28: Precision of Tmax and CBF Lesion Volume Estimates in CT Perfusion Imaging

Objective: CT perfusion (CTP) imaging is increasingly used to select patients for acute stroke trials. Patient selection criteria are typically based on the volumes of reversibly and irreversibly injured tissue. Modern software allows for automated and quantitative assessment of these lesion volumes. There is a push towards reducing the radiation dose used in CTP protocols which may adversely affect the reproducibility of lesion volume assessments. The aim of this study was to assess the effect of radiation dose dependent image noise on the precision of lesion volume estimates.

Methods: We generated 6 synthetic noise-less datasets based on a brain atlas of gray matter, white matter and CSF and integrated co-registered perfusion lesions from 6 acute stroke patients. For each pixel, concentration time curves were simulated using standard tracer kinetic models to obtain CTP source data based on the lesions of the 6 patients. To simulate a CTP protocol with standard radiation dose, we added CT textured noise (“Standard noise”) with a SD of 10 Hounsfield Units (HU) to the dynamic datasets and to simulate a low-dose (“high noise”) CTP protocol we added noise with a SD of 14 HU. This step was repeated 50 times per noise level and for each iteration we determined, using automated perfusion software, the volumes of the ischemic core (rCBF based) and of critically hypoperfused tissue (Tmax>6s).

Results: With standard noise, mean CBF volume was 5.6 ml (SD 2.1) and mean Tmax>6s volume was 38.2 ml (SD 1.3). In the high noise condition, the Tmax>6s lesion volume was on average 13% (5 ml) larger (p<0.0001) than in the standard noise condition. The SD of the Tmax volumes increased from 1.3 mL to 1.8 mL with higher noise. Conversely, with high noise there was an average 5 mL (range 0-16 mL) absolute reduction in CBF lesion volume as compared to the low noise condition (p<0.0001). The CBF lesion became in many cases undetectable (estimated as 0 ml) in the high noise setting.

Conclusions: Noise in CTP data influences the precision of lesion volume estimates. The estimate of the infarcted core seems particularly sensitive to noise. This knowledge should be used to develop guidelines that specify the maximum amount of noise (ie minimum amount of radiation) that is acceptable in a given CTP protocol.

Defining acute ischemic stroke tissue pathophysiology with whole brain CT perfusion

BACKGROUND

This study aimed to identify and validate whole brain perfusion computed tomography (CTP) thresholds for ischemic core and salvageable penumbra in acute stroke patients and develop a probability based model to increase the accuracy of tissue pathophysiology measurements.

METHODS

One hundred and eighty-three patients underwent multimodal stroke CT using a 320-slice scanner within 6hours of acute stroke onset, followed by 24hour MRI that included diffusion weighted imaging (DWI) and dynamic susceptibility weighted perfusion imaging (PWI). Coregistered acute CTP and 24hour DWI was used to identify the optimum single perfusion parameter thresholds to define penumbra (in patients without reperfusion), and ischemic core (in patients with reperfusion), using a pixel based receiver operator curve analysis. Then, these results were used to develop a sigma curve fitted probability based model incorporating multiple perfusion parameter thresholds.

RESULTS

For single perfusion thresholds, a time to peak (TTP) of +5seconds best defined the penumbra (area under the curve, AUC 0.79 CI 0.74-0.83) while a cerebral blood flow (CBF) of < 50% best defined the acute ischemic core (AUC 0.73, CI 0.69-0.77). The probability model was more accurate at detecting the ischemic core (AUC 0.80 SD 0.75-0.83) and penumbra (0.85 SD 0.83-0.87) and was significantly closer in volume to the corresponding reference DWI (P=0.031).

CONCLUSIONS

Whole brain CTP can accurately identify penumbra and ischemic core using similar thresholds to previously validated 16 or 64 slice CTP. Additionally, a novel probability based model was closer to defining the ischemic core and penumbra than single thresholds.

Health service management study for stroke: a randomized controlled trial to evaluate two models of stroke care

BACKGROUND

The most effective and efficient model for providing organized stroke care remains uncertain. This study aimed to compare the effect of two models in a randomized controlled trial.

METHODS

Patients with acute stroke were randomized on day one of admission to combined, co-located acute/rehabilitation stroke care or traditionally separated acute/rehabilitation stroke care. Outcomes measured at baseline and 90 days postdischarge included functional independence measure, length of hospital stay, and functional independence measure efficiency (change in functional independence measure score ÷ total length of hospital stay).

RESULTS

Among 41 patients randomized, 20 were allocated co-located acute/rehabilitation stroke care and 21 traditionally separated acute/rehabilitation stroke care. Baseline measurements showed no significant difference. There was no significant difference in functional independence measure scores between the two groups at discharge and again at 90 days postdischarge (co-located acute/rehabilitation stroke care: 103.6 ± 22.2 vs. traditionally separated acute/rehabilitation stroke care: 99.5 ± 27.7; P = 0.77 at discharge; co-located acute/rehabilitation stroke care: 109.5 ± 21.7 vs. traditionally separated acute/rehabilitation stroke care: 104.4 ± 27.9; P = 0.8875 at 90 days post-discharge). Total length of hospital stay was 5.28 days less in co-located acute/rehabilitation stroke care compared with traditionally separated acute/rehabilitation stroke care (24.15 ± 3.18 vs. 29.42 ± 4.5, P = 0.35). There was significant improvement in functional independence measure efficiency score among participants assigned to co-located acute/rehabilitation stroke care compared with traditionally separated acute/rehabilitation stroke care (co-located acute/rehabilitation stroke care: median 1.60, interquartile range: 0.87-2.81; traditionally separated acute/rehabilitation stroke care: median 0.82, interquartile range: 0.27-1.57, P = 0.0393). Linear regression analysis revealed a high inverse correlation (R(2) = 0.89) between functional independence measure efficiency and time spent in the acute stroke unit.

CONCLUSION

This proof-of-concept study has shown that co-located acute/rehabilitation stroke care was just as effective as traditionally separated acute/rehabilitation stroke care as reflected in functional independence measure scores, but significantly more efficient as shown in greater functional independence measure efficiency. Co-located acute/rehabilitation stroke care has potential for significantly improved hospital bed utilization with no patient disadvantage.

Comprehensive Stroke Units: A Review of Comparative Evidence and Experience

Background

Stroke unit care offers significant benefits in survival and dependency when compared to general medical ward. Most stroke units are either acute or rehabilitation, but comprehensive (combined acute and rehabilitation) model (comprehensive stroke unit) is less common.

Aim

To examine different levels of evidence of comprehensive stroke unit compared to other organized inpatient stroke care and share local experience of comprehensive stroke units.

Methods

Cochrane Library and Medline (1980 to December 2010) review of English language articles comparing stroke units to alternative forms of stroke care delivery, different types of stroke unit models, and differences in processes of care within different stroke unit models. Different levels of comparative evidence of comprehensive stroke units to other models of stroke units are collected.

Results

There are no randomized controlled trials directly comparing comprehensive stroke units to other stroke unit models (either acute or rehabilitation). Comprehensive stroke units are associated with reduced length of stay and greatest reduction in combined death and dependency in a meta-analysis study when compared to other stroke unit models. Comprehensive stroke units also have better length of stay and functional outcome when compared to acute or rehabilitation stroke unit models in a cross-sectional study, and better length of stay in a ‘before-and-after’ comparative study. Components of stroke unit care that improve outcome are multifactorial and most probably include early mobilization. A comprehensive stroke unit model has been successfully implemented in metropolitan and rural hospital settings.

Conclusions

Comprehensive stroke units are associated with reductions in length of stay and combined death and dependency and improved functional outcomes compared to other stroke unit models. A comprehensive stroke unit model is worth considering as the preferred model of stroke unit care in the planning and delivery of metropolitan and rural stroke services.

Genome-wide association study identifies a variant in HDAC9 associated with large vessel ischemic stroke

Genetic factors have been implicated in stroke risk, but few replicated associations have been reported. We conducted a genome-wide association study (GWAS) for ischemic stroke and its subtypes in 3,548 affected individuals and 5,972 controls, all of European ancestry. Replication of potential signals was performed in 5,859 affected individuals and 6,281 controls. We replicated previous associations for cardioembolic stroke near PITX2 and ZFHX3 and for large vessel stroke at a 9p21 locus. We identified a new association for large vessel stroke within HDAC9 (encoding histone deacetylase 9) on chromosome 7p21.1 (including further replication in an additional 735 affected individuals and 28,583 controls) (rs11984041; combined P = 1.87 × 10(-11); odds ratio (OR) = 1.42, 95% confidence interval (CI) = 1.28-1.57). All four loci exhibited evidence for heterogeneity of effect across the stroke subtypes, with some and possibly all affecting risk for only one subtype. This suggests distinct genetic architectures for different stroke subtypes.

Should there be a standardised approach to the diagnostic workup of suspected adult encephalitis? A case series from Australia

BACKGROUND

The clinical diagnosis of encephalitis is often difficult and identification of a causative organism is infrequent. The encephalitis syndrome may herald the emergence of novel pathogens with outbreak potential. Individual treatment and an effective public health response rely on identifying a specific pathogen. In Australia there have been no studies to try to improve the identification rate of encephalitis pathogens. This study aims to review the diagnostic assessment of adult suspected encephalitis cases.

METHODS

A retrospective clinical audit was performed, of all adult encephalitis presentations between July 1998 and December 2007 to the three hospitals with adult neurological services in the Hunter New England area, northern New South Wales, Australia. Case notes were examined for evidence of relevant history taking, clinical features, physical examination, laboratory and neuroradiology investigations, and outcomes.

RESULTS

A total of 74 cases were included in the case series. Amongst suspected encephalitis cases, presenting symptoms and signs included fever (77.0%), headache (62.1%), altered consciousness (63.5%), lethargy (32.4%), seizures (25.7%), focal neurological deficits (31.1%) and photophobia (17.6%). The most common diagnostic laboratory test performed was cerebrospinal fluid (CSF) analysis (n = 67, 91%). Herpes virus polymerase chain reaction (n = 53, 71.6%) and cryptococcal antigen (n = 46, 62.2%) were the antigenic tests most regularly performed on CSF. Neuroradiological procedures employed were computerized tomographic brain scanning (n = 68, 91.9%) and magnetic resonance imaging of the brain (n = 35, 47.3%). Thirty-five patients (47.3%) had electroencephalograms. The treating clinicians suspected a specific causative organism in 14/74 cases (18.9%), of which nine (12.1%) were confirmed by laboratory testing.

CONCLUSIONS

The diagnostic assessment of patients with suspected encephalitis was not standardised. Appropriate assessment is necessary to exclude treatable agents and identify pathogens warranting public health interventions, such as those transmitted by mosquitoes and those that are vaccine preventable. An algorithm and guidelines for the diagnostic workup of encephalitis cases would assist in optimising laboratory testing so that clinical management can be best tailored to the pathogen, and appropriate public health measures implemented.

Time to treatment with intravenous alteplase and outcome in stroke: an updated pooled analysis of ECASS, ATLANTIS, NINDS, and EPITHET trials

BACKGROUND

Early administration of intravenous recombinant tissue plasminogen activator (rt-PA) after ischaemic stroke improves outcome. Previous analysis of combined data from individual patients suggested potential benefit beyond 3 h from stroke onset. We re-examined the effect of time to treatment with intravenous rt-PA (alteplase) on therapeutic benefit and clinical risk by adding recent trial data to the analysis.

METHODS

We added data from ECASS III (821 patients) and EPITHET (100 patients) to a pool of common data elements from six other trials of alteplase for acute stroke (2775 patients). We used multivariate logistic regression to assess the relation of stroke onset to start of treatment (OTT) with treatment on favourable 3-month outcome (defined as modified Rankin score 0-1), mortality, and occurrence and outcome of clinically relevant parenchymal haemorrhage. The presence of an arterial occlusion was inferred from the patient's symptoms and absence of haemorrhage or other causes of ischaemic stroke. Vascular imaging was not a requirement in the trials. All patients with confirmed OTT within 360 min were included in the analysis.

FINDINGS

Treatment was started within 360 min of stroke onset in 3670 patients randomly allocated to alteplase (n=1850) or to placebo (n=1820). Odds of a favourable 3-month outcome increased as OTT decreased (p=0.0269) and no benefit of alteplase treatment was seen after around 270 min. Adjusted odds of a favourable 3-month outcome were 2.55 (95% CI 1.44-4.52) for 0-90 min, 1.64 (1.12-2.40) for 91-180 min, 1.34 (1.06-1.68) for 181-270 min, and 1.22 (0.92-1.61) for 271-360 min in favour of the alteplase group. Large parenchymal haemorrhage was seen in 96 (5.2%) of 1850 patients assigned to alteplase and 18 (1.0%) of 1820 controls, with no clear relation to OTT (p=0.4140). Adjusted odds of mortality increased with OTT (p=0.0444) and were 0.78 (0.41-1.48) for 0-90 min, 1.13 (0.70-1.82) for 91-180 min, 1.22 (0.87-1.71) for 181-270 min, and 1.49 (1.00-2.21) for 271-360 min.

INTERPRETATION

Patients with ischaemic stroke selected by clinical symptoms and CT benefit from intravenous alteplase when treated up to 4.5 h. To increase benefit to a maximum, every effort should be taken to shorten delay in initiation of treatment. Beyond 4.5 h, risk might outweigh benefit.

FUNDING

None.

Baseline diabetic status and admission blood glucose were poor prognostic factors in the EPITHET trial

BACKGROUND

Previous data have suggested that diabetes and hyperglycemia predict poor outcome following stroke. We studied the prognostic impact of diabetes and admission blood glucose in the Echoplanar Imaging Thrombolytic Evaluation Trial (EPITHET).

METHODS

EPITHET was a prospective randomized placebo-controlled trial of intravenous tissue plasminogen activator (tPA) in the 3- to 6-hour time window. A preexisting diagnosis of diabetes was noted and baseline serum glucose was measured.

RESULTS

Intravenous tPA attenuated infarct growth in non-diabetics, but not in diabetics (p = 0.029). In the tPA treatment group, admission blood glucose was higher among patients with poor functional outcome (p = 0.002).

CONCLUSIONS

Diabetes and hyperglycemia attenuate the effects of tPA on infarct evolution. Future thrombolytic trials should consider randomizing patients by subgroups based on diabetic status and serum glucose levels.

Intralines of quasi-conical intersections on torsion planes: methylamine as a case study

Recently we reported on a novel feature associated with the intersection of the two lowest states (1)A' and (1)A'' of the methylamine (J. Chem. Phys. 2008, 128, 244302). We established the existence of a finite (closed) line of conical intersections (ci), namely, a finite seam, located in the HC-NHH symmetry plane, a line that is formed by moving a single hydrogen on that plane while locking the positions of the (six) other atoms. In the present article, this study is extended to the corresponding torsion planes formed by rotating the methyl group around the CN axis. The torsion planes, in contrast with the HC-NHH symmetry plane, do not satisfy the symmetry feature that enables the seam just mentioned. Nevertheless, the calculated nonadiabatic coupling terms (NACTs) resemble features similar to those encountered in the HC-NHH symmetry plane. Following a tedious numerical study supported by a theoretical model (Section III), it was verified that these NACTs may become similar to those on the symmetry plane, sometimes even to the level of almost no distinction, but lack one basic feature; namely, they are not singular and therefore do not form topological effects.