Left atrial vorticity is independently associated with embolic brain infarcts and represents a promising imaging biomarker of cardioembolism in sinus rhythm and atrial fibrillation

Background

Atrial fibrillation (AF) is associated with embolic stroke, but risk scores such as CHA2DS2-VASc perform only modestly (C statistics 0.6–0.7). Meanwhile, up to 25% of embolic strokes in patients without AF have no identifiable cause, and occult left atrial (LA) thromboembolism may be a relevant mechanism in such cases.

Purpose

We hypothesised that imaging of left atrial blood flow could improve embolic risk prediction in patients with and without AF. We used 4D flow magnetic resonance imaging (MRI) to identify a biomarker that is: (a) independently associated with embolic brain infarction by brain MRI, (b) able to stratify blood flow characteristics both during AF and in sinus rhythm (SR), and (c) reproducible.

Methods

We recruited 3 patient cohorts to respectively address each aim. Firstly, to assess the association between LA flow parameters and embolic brain infarcts, we recruited cohort A, consisting of 134 patients (41% female; age 70±9 years) with a history of ischaemic stroke (N=44) or no history of stroke but with CHA2DS2VASc score ≥1 (N=90). Next, the sensitivity of 4D flow parameters to rhythm change was assessed in cohort B: 37 patients with persistent AF studied before and after cardioversion, whose results were compared with those of 23 healthy controls in SR [CHA2DS2-VASc = 0.0 (0.0–0.0)]. Finally, scan-rescan coefficients of variation (CV) and interval-scan CV at 30 days were determined in Cohort C (86 subjects; 64 in SR, 22 in AF). Brain MRI was used to identify large non-cortical or cortical brain infarcts (LNCCI) – i.e. infarcts likely to be embolic in origin.

Results

At least one LNCCI was present in 39 of 134 patients in cohort A. Lower LA vorticity was significantly associated with higher risk of prevalent LNCCIs (Figure 1), after adjustment for AF, age, and CHA2DS2VASc score [OR=2.10 (95% CI 1.12–3.92) per SD, P=0.02]. This association remained significant after further adjustment for other cardiac parameters (all P<0.05, Figure 1). By contrast, there was no significant association between peak velocity and LNCCIs (P=0.21).

LA vorticity was sensitive to rhythm change, improving significantly in patients in cohort B in SR at ≥4 weeks after cardioversion (CV) of persistent AF (Figure 2A, paired P<0.001 vs pre-CV), but remained impaired compared to healthy controls (Figure 2B, P<0.01).

Finally, reproducibility studies in cohort C showed that LA vorticity had a same-day scan-rescan CV of 7% without significant differences between SR and AF subjects (P>0.05), and also showed no significant temporal variability on interval scanning (P>0.05).

Conclusions

LA vorticity is reproducible, sensitive to changes in heart rhythm, and independently associated with embolic brain infarcts, suggesting a promising imaging biomarker of cardioembolism in SR and AF. LA blood flow imaging could improve stroke prediction and the personalisation of decisions about anticoagulation, regardless of heart rhythm.

Funding Acknowledgement

Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Oxford BRC, BHF

Expression of TLR4-PTGE2 signaling genes in atherosclerotic carotid plaques and peripheral blood

Toll-like receptor 4 (TLR4)/prostaglandine synthetase 2 (PTGS2) signaling plays a relevant role in atherosclerotic plaque vulnerability. The purpose of this study was to check the gene expression of 6 genes participating to TLR4/PTGS2 signaling (TLR4, PTGS2, ACSL4, PTGER3, PTGER4, and EPRAP) in carotid plaques and blood samples from the same individual and to evaluate these genes as biomarker of plaque progression. We investigated differential gene expression by qRT-PCR in 62 atherosclerotic patients' carotid plaques and corresponding blood sample. A very weak or no correlation was observed in the overall population or analyzing asymptomatic patients. These analyzed genes are most likely not suitable for inclusion in the clinical routine as biomarkers of plaque instability.

Markers of bone metabolism during 14 days of bed rest in young and older men

OBJECTIVE

We aimed at comparing markers of bone metabolism during unloading in young and older men, and to assess countermeasure effectiveness.

METHODS

16 older (60±2 years) and 8 younger men (23±3 years) underwent bed rest (BR) for 14 days. A subgroup of the Older performed cognitive training during BR and supplemented protein and potassium bicarbonate afterwards. Biochemical markers of bone and calcium/phosphate metabolism were assessed.

RESULTS

At baseline urinary NTX and CTX were greater in younger than in older subjects (P<0.001), but increased during BR (P<0.001) by a similar amount (P>0.17). P1NP was greater in young than in older subjects (P<0.001) and decreased during BR in the Young (P<0.001). Sclerostin increased during BR across groups (P=0.016). No systematic effects of the countermeasure were observed.

CONCLUSION

In men, older age did not affect control of bone metabolism, but bone turnover was reduced. During BR formation markers were reduced only in younger men whereas resorption markers increased to a comparable extent. Thus, we assume that older men are not at an elevated, and possibly even at a reduced risk to lose bone when immobilized.

Cerebral haemodynamics in early puerperium: A prospective study

AIM

Prospective study on 900 consecutive puerperae to assess normal values and range of the blood flow velocity in the middle cerebral artery in both hemispheres.

MATERIAL AND METHOD

M1 and M2 segments of both middle cerebral arteries were assessed in all subjects within 96 hours of delivery. Mean flow velocity was recorded after adjusting for insonation angle. Lindegaard index (LI = middle cerebral artery-Internal Carotid Artery mean flow velocity ratio) was calculated whenever the mean flow velocity exceeded 100 cm/second. Asymmetry indexes were calculated inter hemispherically for M1 and M2 segments separately.

RESULTS

Mean flow velocities were 74 ± 17 and 72 ± 17 in right and 73 ± 17 and 72 ± 17 cm/second in the left M1 and M2, respectively. A total of 136 subjects (12.1%) exceeded the threshold of 100 cm/second, but LI was consistently <3 in all of them. Mean flow velocity was inversely and independently correlated to haemoglobin levels and to parity. Mean asymmetry indexes were 0.25 ± 23 in M1 and 0.45 ± 25 in M2.

CONCLUSION

Mean flow velocity in the middle cerebral artery of healthy subjects in early puerperium is higher than in age-matched non-puerperal women and may exceed the threshold of 100 cm/second with no evidence of intracranial spasm, because of blood loss during delivery. Mean flow velocity is independently correlated with parity. Right-to-left mean flow velocity asymmetry may reach 50% as a consequence of a transient imbalance in vascular tone regulation.

Vibrational and optical spectroscopies integrated with environmental transmission electron microscopy

Here, we present a measurement platform for collecting multiple types of spectroscopy data during high-resolution environmental transmission electron microscopy observations of dynamic processes. Such coupled measurements are made possible by a broadband, high-efficiency, free-space optical system. The critical element of the system is a parabolic mirror, inserted using an independent hollow rod and placed below the sample holder which can focus a light on the sample and/or collect the optical response. We demonstrate the versatility of this optical setup by using it to combine in situ atomic-scale electron microscopy observations with Raman spectroscopy. The Raman data is also used to measure the local temperature of the observed sample area. Other applications include, but are not limited to: cathodo- and photoluminescence spectroscopy, and use of the laser as a local, high-rate heating source.

Ultralocal modification of surface plasmons properties in silver nanocubes

The plasmonic properties of individual subwavelength-sized silver nanocubes are mapped with nanometric spatial resolution by means of electron energy-loss spectroscopy in a scanning transmission electron microscope. Three main features with different energies and spatial behavior (two peaked at the corners, one on the edges) are identified and related to previous measurements on ensemble or individual nanoparticles. The highly subwavelength mapping of the energy position and intensity of the excitations shows that the surface plasmon modes, localized at specific areas of the particles, for example, the corners or the edges, are modified by their size, the presence of a substrate, and the very local environment. Helped by discrete dipole approximation numerical simulations, we discuss how local modifications of the environment affect the global modes of the particles. In particular, we show both experimentally and theoretically that absorption resonances at different corners of the same nanocube are largely independent of each other in energy and intensity. Our findings provide a better understanding of the spatial coherence of the surface plasmons in nanoparticles but also give useful insights about their roles in the nanoparticle sensing properties.

Autonomic dysfunction in mild cognitive impairment: a transcranial Doppler study

OBJECTIVES

The contribution of early microvascular and autonomic derangements to the pathogenesis of mild cognitive impairment (MCI) is unclear. Aim of this study is to evaluate cerebrovascular reactivity (CVR) and cardiac autonomic function in patients with MCI by means of transcranial Doppler (TCD).

MATERIAL AND METHODS

Fifteen patients with MCI and 28 controls underwent carotid ultrasound and TCD evaluation, including assessment of mean flow velocity (MFV) in the middle cerebral artery at baseline, after CO(2) inhalation and after hyperpnoea. End-tidal CO(2) , mean arterial blood pressure (MAP), heart rate (HR), and respiratory rate were monitored throughout the procedure, and CVR was calculated.

RESULTS

MAP, end-tidal CO(2) , and MFV variations during hypercapnia and hyperventilation showed no between-group differences. CVR was similar in controls and MCI (2.30 vs 2,39, respectively, P = 0.767). HR significantly increased in hypercapnia (+9.4%, P < 0.0001) and hyperventilation (+18.7%, P < 0.0001) in controls, while in MCI it significantly increased in hyperventilation (+10.4%, P = 0.002), but not in hypercapnia (+1.1%, P = 0.635).

CONCLUSIONS

This study demonstrates that patients with MCI have a normal CVR, but they exhibit signs of autonomic dysfunction after CO(2) challenge. Should this finding be confirmed in larger studies, HR response to CO(2) challenge could become a marker of MCI.

Nanometer scale spectral imaging of quantum emitters in nanowires and its correlation to their atomically resolved structure

We report the spectral imaging in the UV to visible range with nanometer scale resolution of closely packed GaN/AlN quantum disks in individual nanowires using an improved custom-made cathodoluminescence system. We demonstrate the possibility to measure full spectral features of individual quantum emitters as small as 1 nm and separated from each other by only a few nanometers and the ability to correlate their optical properties to their size, measured with atomic resolution. The direct correlation between the quantum disk size and emission wavelength provides evidence of the quantum confined Stark effect leading to an emission below the bulk GaN band gap for disks thicker than 2.6 nm. With the help of simulations, we show that the internal electric field in the studied quantum disks is smaller than what is expected in the quantum well case. We show evidence of a clear dispersion of the emission wavelengths of different quantum disks of identical size but different positions along the wire. This dispersion is systematically correlated to a change of the diameter of the AlN shell coating the wire and is thus attributed to the related strain variations along the wire. The present work opens the way both to fundamental studies of quantum confinement in closely packed quantum emitters and to characterizations of optoelectronic devices presenting carrier localization on the nanometer scale.

Upregulated expression of Toll-like receptor 4 in peripheral blood of ischaemic stroke patients correlates with cyclooxygenase 2 expression

OBJECTIVES

An inflammatory process following stroke in human brains and systemic inflammatory responses after stroke in humans have been reported by numerous investigators. The aim of the study was to investigate if genes involved in the cyclooxygenase 2 (COX-2) pathway are upregulated at peripheral level in patients after transient ischaemic attack (TIA) and stroke.

DESIGN OF STUDY

Blood samples were obtained from two groups of patients undergoing carotid endarterectomy. The first group included 25 patients who presented TIA or ischaemic stroke. The second group included 35 patients who had an asymptomatic internal carotid artery stenosis. Total RNA was isolated and the expression of Toll-like Receptor 4 (TLR4), COX-2, membrane-associated Prostaglandin E synthase (mPGES-1), Prostaglandin E₂ receptors (EP3 and EP4) was analysed by real time RT-PCR.

RESULTS

Expression of COX-2 and TLR4 were significantly increased in symptomatic patients (p < 0.001). Correlation analysis showed that TLR4 expression significantly correlated with COX-2 expression (R = 0.65; p < 0.01) in ischaemic stroke patients. This correlation was not observed in TIA and asymptomatic patients.

CONCLUSIONS

Our results suggest that the peripheral mechanism of inflammatory injury after stroke may be mediated by TLR4 through a COX-2-dependent pathway.

Cerebral distribution of white matter lesions in migraine with aura patients

OBJECTIVE

The objective of the study was to compare the cerebral distribution of white matter lesions (WMLs) between migraine patients with different aura symptoms.

METHODS

Migraine with aura (MA) patients were consecutively enrolled as part of the Shunt-Associated Migraine (SAM) study. According to clinical symptoms, aura was classified as motor, aphasic, sensory, visual or vertebrobasilar. Standard and FLAIR (fluid attenuated inversion recovery) T(2)-weighted MRI sequences were inspected for WMLs by three independent raters blinded to clinical data. WMLs were assessed in the periventricular areas (PV-WMLs) with the Fazekas scale and in the deep white matter (D-WMLs) with the Schelten's scale. Interobserver agreement was good to excellent (k = 0.64 to 0.96, p < .0001).

RESULTS

One hundred and eighty-five patients (77% women) were included. Aura symptoms were classified as visual in 172 (99%) patients, sensory in 76 (42%), aphasic in 54 (30%), motor in 39 (21%) and vertebrobasilar in 17 (9%) patients. One hundred and four patients (57%) exhibited more than one type of aura. D-WMLs were mainly detected in the frontal lobes (86%). There was no association between type of aura and the presence of WMLs in any cerebral location.

CONCLUSION

Aura symptoms do not influence the cerebral distribution of WMLs associated with migraine disease.

Evaluating endothelial function of the common carotid artery: an in vivo human model

BACKGROUND AND AIMS

Flow mediated dilation (FMD) of peripheral conduit arteries is a well-established tool to evaluate endothelial function. The aims of this study are to apply the FMD model to cerebral circulation by using acetazolamide (ACZ)-induced intracranial vasodilation as a stimulus to increase common carotid artery (CCA) diameter in response to a local increase of blood flow velocity (BFV).

METHODS AND RESULTS

In 15 healthy subjects, CCA end-diastolic diameter and BFV, middle cerebral artery (MCA) BFV and mean arterial blood pressure (MBP) were measured at basal conditions, after an intravenous bolus of 1g ACZ, and after placebo (saline) sublingual administration at the 15th and 20th minute. In a separate session, the same parameters were evaluated after placebo (saline) infusion instead of ACZ and after 10 microg/m(2) bs and 300 microg of glyceryl trinitrate (GTN), administered sublingually, at the 15th and 20th minute, respectively. After ACZ bolus, there was a 35% maximal MCA mean BFV increment (14th minute), together with a 22% increase of mean CCA end-diastolic BFV and a CCA diameter increment of 3.9% at the 3rd minute (p=0.024). There were no MBP significant variations up to the 15th minute (p=0.35). After GTN administration, there was a significant increment in CCA diameter (p<0.00001).

CONCLUSIONS

ACZ causes a detectable CCA dilation in healthy individuals concomitantly with an increase in BFV. Upon demonstration that this phenomenon is endothelium dependent, this experimental model might become a valuable tool to assess endothelial function in the carotid artery.

Statins and stroke

Pharmacological studies highlighted pleiotropic effects of statins, that seem to influence atherogenesis not only by increasing atherosclerotic plaque stability but also by modulating endothelial function and inflammation and acting on platelet aggregation and thrombosis. Despite a strong association between increased levels of low-density lipoprotein cholesterol (LDL-C) and the incidence of coronary heart disease (CHD) has been well proven, it not yet established whether serum LDL-C levels are related to stroke incidence. The major aim of this paper is to perform a comprehensive up-to-date review of research papers, meta-analyses and randomized controlled clinical trials reporting the effects of statins in primary and secondary stroke prevention strategies. In addition, our work provides an overview on statin chemical structure, mechanism of action and pharmacological properties, investigating also most common adverse effects and relationship between statin therapy and haemorrhagic stroke risk, in order to assess drugs safety. Although studies are heterogeneous, our analysis shows that statins reduce the risk of stroke occurrence in high risk patients and seem also to reduce stroke recurrence. Moreover, the low incidence and reversibility of adverse effects, and the unclear association with hemorrhagic events, support the safe use of these drugs.

Cerebral autosomal dominant arteriopathy with subcortical infarcts and leucoencephalopathy and right-to-left shunt: lack of evidence for an association in a prevalence study

BACKGROUND/AIMS

Up to more than 50% of cryptogenetic stroke patients and patients with migraine with aura (MA) are found to have a right-to-left shunt (RLS), which is usually due to a patent foramen ovale. Moreover, both MA and stroke are cardinal features of cerebral autosomal dominant arteriopathy with subcortical infarcts and leucoencephalopathy (CADASIL). Notch3 mutations have been suggested to induce an abnormally high incidence of atrial septal defects in a family harbouring an Arg141Cys pathogenetic mutation. We sought to determine the prevalence of RLS in CADASIL patients with different Notch3 mutations, both with and without migraine as a clinical feature.

METHODS

Subjects with a molecular diagnosis of CADASIL were tested for the presence of an RLS by means of contrast-enhanced transcranial Doppler (TCD). The diagnosis of migraine was made according to the 2004 International Headache Classification.

RESULTS

Sixteen CADASIL patients were tested; 6 had MA. Four patients displayed an RLS on contrast-enhanced TCD examination. Three of these patients had MA. Both patients with Arg141Cys displayed a large RLS.

CONCLUSION

We conclude that RLS is not necessarily linked to CADASIL as a comorbidity factor. Nevertheless, there could be a relation between RLS and specific Notch3 mutations, such as Arg141Cys.

Hyperpyrexia-triggered relapses in an unusual case of ataxic chronic inflammatory demyelinating polyradiculoneuropathy

The ataxic form of chronic inflammatory demyelinating polyradiculoneuropathy (ataxic-CIDP) has been recently described as a subtype of chronic ataxic neuropathy, distinguished by steroid responsiveness and relative preservation of myelinated fibres at sural nerve biopsy. We report on a case of progressive, predominantly sensory, steroid-responsive neuropathy with clinical, laboratory, electrophysiological and pathological features of this uncommon form of CIDP. Moreover, the present case displays peculiar hyperpyrexia-triggered relapses leading to transitory severe tetraparesis, bilateral facial drooping, dysphonia, dysphagia and dyspnoea, which leave clinicians with some unresolved questions.

A new class of pseudopeptide antagonists of the kinin B1 receptor containing alkyl spacers

Four previously reported kinin receptor peptide antagonists, including the B1 receptor-selective peptides desArg10-HOE 140 (H-D-Arg-Arg-Pro-Hyp-Gly-Thi-Ser-D-Tic-Oic-OH) and B-9858 (H-Lys-Lys-Arg-Pro-Hyp-Gly-Igl-Ser-D-Igl-Oic-OH), have been modified by replacement of the central tetrapeptide Pro-Hyp-Gly-Xaa with linear alkyl spacers of variable length. The analogue of desArg10-HOE 140 containing the 11-aminoundecanoic acid as spacer, MEN 11575 [H-D-Arg-Arg-NH-(CH2)10-CO-Ser-D-Tic-Oic-OH], was found to be slightly more potent than the unmodified peptide (pA2 = 7.1) as a kinin B1 receptor antagonist in the rat ileum longitudinal smooth muscle assay. Moreover, MEN 11575 is devoid of residual agonist activity at the kinin B1 receptor (rat ileum) and antagonist activity at the kinin B2 receptor (guinea pig ileum longitudinal smooth muscle). Both these activities are displayed by the parent peptide desArg10-HOE 140. Therefore, despite its greatly simplified chemical structure, MEN 11575 shows an improved pharmacological profile in terms of both potency and selectivity, and it represents a good template for the development of new peptidomimetic kinin B1 receptor antagonists. We also report an attempt to investigate the conformational role of the flexible, linear spacer of MEN 11575 and to design more constrained analogues, possibly locked in the bioactive conformation, using semirigid spacers based on Calpha-tetrasubstituted alpha-amino acids of the family of 1-aminocycloalkane-1-carboxylic acids (Acnc).

A synthetic glycopeptide of human myelin oligodendrocyte glycoprotein to detect antibody responses in multiple sclerosis and other neurological diseases

Glycopeptides of hMOG(30-50) containing a glucosyl moiety on the side-chains of Asn, Ser or Hyp at position 31 were synthesised. Antibody titres to hMOG(30-50) and to its glucoderivatives were measured by ELISA in sera of patients affected by different neurological diseases. Anti-hMOG(30-50) antibodies were detected only using the glycopeptide [Asn31(N-Glc)]hMOG(30-50).