High-energy acceleration phenomena in extreme-radiation-plasma interactions

We simulate, using a particle-in-cell code, the chain of acceleration processes at work during the Compton-based interaction of a dilute electron-ion plasma with an extreme-intensity, incoherent γ-ray flux with a photon density several orders of magnitude above the particle density. The plasma electrons are initially accelerated in the radiative flux direction through Compton scattering. In turn, the charge-separation field from the induced current drives forward the plasma ions to near-relativistic speed and accelerates backwards the nonscattered electrons to energies easily exceeding those of the driving photons. The dynamics of those energized electrons is determined by the interplay of electrostatic acceleration, bulk plasma motion, inverse Compton scattering and deflections off the mobile magnetic fluctuations generated by a Weibel-type instability. The latter Fermi-like effect notably gives rise to a forward-directed suprathermal electron tail. We provide simple analytical descriptions for most of those phenomena and examine numerically their sensitivity to the parameters of the problem.

Development of a 3D-printed bioabsorbable composite scaffold with mechanical properties suitable for treating large, load-bearingarticular cartilage defects

Extracellular matrix (ECM) biomaterials have shown promise for treating small artucular-joint defetcs. However, ECM-based biomaterials generally lack appropriate mechanical properties to support physiological loads and are prone to delamination in larger cartilage defects. To overcome these common mechanical limitations, a collagen hyaluronic-acid (CHyA) matrix, with proven regenerative potential, was reinforced with a bioabsorbable 3D-printed framework to support physiological loads. Polycaprolactone (PCL) was 3D-printed in two configurations, rectilinear and gyroid designs, that were extensively mechanically characterised. Both scaffold designs increased the compressive modulus of the CHyA matrices by three orders of magnitude, mimicking the physiological range (0.5-2.0 MPa) of healthy cartilage. The gyroid scaffold proved to be more flexible compared to the rectilinear scaffold, thus better contouring to the curvature of a femoral condyle. Additionally, PCL reinforcement of the CHyA matrix increased the tensile modulus and allowed for suture fixation of the scaffold to the subchondral bone, thus addressing the major challenge of biomaterial fixation to articular joint surfaces in shallow defects. In vitro evaluation confirmed successful infiltration of human mesenchymal stromal cells (MSCs) within the PCL-CHyA scaffolds, which resulted in increased production of sulphated glycosaminoglycans (sGAG/DNA; p = 0.0308) compared to non-reinforced CHyA matrices. Histological staining using alcian blue confirmed these results, while also indicating greater spatial distribution of sGAG throughout the PCL-CHyA scaffold. These findings have a great clinical importance as they provide evidence that reinforced PCL-CHyA scaffolds, with their increased chondroinductive potential and compatibility with joint fixation techniques, could be used to repair large-area chondral defects that currently lack effective treatment options.

Pulsed field ablation for atrial fibrillation: acute procedural efficacy and safety of an initial German multicenter experience

Background

Pulsed field ablation (PFA) is a novel non-thermal energy source to conduct catheter ablation of atrial fibrillation (AF). However, real-world multi-center data regarding acute procedural efficacy and safety is sparse.

Purpose

To study acute procedural success and safety in patients undergoing PFA for catheter ablation of AF in a multicenter registry.

Methods

Consecutive paroxysmal and persistent AF patients undergoing PFA-based catheter ablation using a multispline catheter were enrolled. The cohort included first and repeat ablation procedures. Procedural parameters, acute success and in-hospital safety were evaluated. A follow-up of all patients was conducted.

Results

Five German centers enrolled a total of 154 patients undergoing PFA in this study. Mean age was 68±12 years, median CHA2DS2-VASc Score was 3 (Q1-Q3: 2–4).

Patients suffered from paroxysmal AF (n=55; 36%), persistent AF (n=93; 60%) and consecutive atrial tachycardias (AT) due to previous CA (n=6; 4%).

The median left atrial (LA) PFA and total procedure times were 33 (Q1-Q3: 24–53) and 90 (Q1-Q3: 73–116) minutes, respectively. Mean LA PFA fluoroscopy and total fluoroscopy times were 12.1±5.5 and 20.2±8.7 minutes. Of all 154 procedures, 130 (84%) were index ablation procedures with isolation of pulmonary veins (PVI) only and 24 (16%) were repeat procedures (including re-PVI and ablation of consecutive AT).

Acute PV reconnection following primary PVI and the initial set of PFA-applications was found in 20/130 (15%) patients, necessitating additional PFA ablation. Finally, successful PFA-guided PVI was achieved in all patients.

Additional PFA lesion sets (including LA posterior wall isolation, anterior ablation, mitral isthmus ablation) were applied in 17/154 (11%) patients.

Complications occurred in a total of 6/154 (3.8%) patients (including three groin site complications, two pericardial tamponades, one transient coronary spasm without sequela). The follow up data is still being assessed and will be provided by the time of the ESC 2022 meeting.

Conclusion

PFA performed in patients with atrial fibrillation demonstrates high acute procedural success rates and a favorable safety profile in this first real-world multicenter registry.

Funding Acknowledgement

Type of funding sources: None.

Comparison of left atrial lesion size and troponin release of two novel single shot devices for pulmonary vein isolation: pulsed field ablation vs. multi-electrode radiofrequency balloon

Funding Acknowledgements

Type of funding sources: None.

Introduction

Pulsed-field ablation (PFA) and the multi-electrode radiofrequency balloon (RFB) are two novel ablation technologies to perform pulmonary vein isolation (PVI). It is currently unknown whether these technologies differ in lesion formation and lesion extent.

Purpose

We compared the acute lesion extent after PVI induced by PFA and RFB by measuring low-voltage area in high-density maps and the release of biomolecules reflecting cardiac injury.

Methods

PVI was performed with a pentaspline catheter (FARAPULSE) applying PFA or with the compliant multi-electrode radiofrequency balloon (HELIOSTAR). Before and after PVI high-density mapping with CARTO3 was performed. In addition, blood samples were taken before transseptal puncture and after post-PVI remapping. Serum concentrations of high-sensitive Troponin I (hsTropI) were quantified by Immunoassay.

Results

50 patients undergoing PVI by PFA (n=26, age 71±10 y, 58% males, 58% persistent AF) or RFB (n=24; age 64±13 y, 54% males, 25% persistent AF) were evaluated. Acute PVI was achieved in all patients in both groups. Mean number of PFA pulses were n=34±5 and mean number RFB applications were n=8±3. Total posterior ablation area was bigger in PFA (19.0±6.2 cm²) than in RFB (9.0±2.2 cm²; p<0.001). The posterior distance between septal and lateral lesions was shorter in PFA (23.7±10.5 mm) than in RFB (30.0±7.3 mm; p=0.021). In a total of 38 patients increase of hsTropI was higher after PFA (625±138 pg/ml, n=28) vs. RFB (148±36 pg/ml; n=10; p=0.049) supporting the evidence of larger lesion extent by PFA.

Conclusion

Pulse-field ablation delivers larger acute lesion areas and higher troponin release upon successful pulmonary vein isolation than multi-electrode array balloon-based pulmonary vein isolation in this single-center series.

Pulmonary vein isolation by pulsed-field ablation induces smaller neurocardiac damage than cryoballoon ablation

Funding Acknowledgements

Type of funding sources: Private company. Main funding source(s): FARAPULSE, Inc.

Introduction

Thermal energy sources damage the entire atrial tissue during pulmonary vein isolation (PVI) including cardiac nerves and ganglia. This induces a postinterventional increase in heart rate. Pulsed-field ablation (PFA), a new non-thermal energy source for PVI, primarily damages cardiomyocytes by electroporation. Whether use of PFA reduces damage to cardiac nerves and ganglia and influences postinterventional increase of heart rate is not known.

Purpose

We compared the acute effects of PFA with a pentaspline catheter and cryoballoon ablation (CBA) on secretion of circulating biomolecules reflecting cardiomyocyte and neuronal injury and postinterventional increase in heart rate to estimate damage to the cardiac autonomic nervous system and autonomic dysfunction after PVI.

Methods

Blood samples were taken before and after PVI in consecutive patients undergoing PFA and CBA. All patients participated in the TRUST registry. Serum concentrations of high-sensitive Troponin I (hsTropI, Immunoassay) and S100b (ELISA), a surrogate marker for neuronal injury, were quantified in blood samples taken prior to PVI and directly after PVI. Pre- and postinterventional heart rates were measured in ECGs and Holter-ECGs.

Results

Fifty-six patients underwent PVI, either by PFA (n=28, age 63 [54; 75] y, 64% males, 57% persistent AF) or CBA (n=28, age 71 [62; 78] y, 61% males, 54% persistent AF). All 112 blood samples were analyzable. Acute success of PVI was 100% in both groups without major complications, especially, no TIA and no stroke. After CBA, one patient suffered from phrenic palsy, which reversed after 3 months. HsTropI increased 3.3-fold more after PFA compared to CBA (625±138 vs. 185±42 pg/ml; p=0.004) suggesting more damage to cardiomyocytyes. S100b increased 2.9-fold less after PFA compared to CBA (21.1±3.7 vs. 61.2±8.1 pg/ml; p<0.001). The ratio of ∆S100b/∆hsTropI was five-fold smaller after PFA compared to CBA (0.19±0.1 vs. 0.98±0.3; p=0.007), suggesting a lower neurocardiac injury in comparison to lesion size. Concomitantly, increase in heart rate at the postinterventional day was smaller in PFA (-0.2±3.0 bpm; n=45) than in CBA (+6.1±2.7 bpm, n=15; p=0.024).

Conclusion

This study in patients validates the experimental concept that PFA-based AF ablation leads to more specific damage to cardiomyocytes than to cardiac nerves and ganglia, reflected by lower S100B concentrations and no post-interventional heart rate increase compared to CBA.

Catheter ablation of the mitral isthmus line using the novel DiamondTemp ablation system: first experience using two different ablation protocols

Funding Acknowledgements

Type of funding sources: None.

Background

Mitral ishmus ablation is an established approach to treat perimitral reentrant tachycardia, and is often performed as substrat modification in patients with persistent atrial fibrillation (AF). Bidirectional block of the mitral isthmus line (MIL) is still a great challenge using conventional ablation catheters, but is essential to prevent recurrence of atrial arrhythmia.

Recently, the novel DiamondTempTM (DT) ablation system was introduced and allows for high-power, short-duration ablation in a temperature-controlled mode. Its use during pulmonary vein isolation (PVI) using a recommended ablation setting with a catheter-tip temperature limit of 60°C, a temperature-controlled power of 50 W and an application duration of 10 sec has shown to be effective and safe. However, data on DT ablation settings for substrate modification, i.e., creation of linear lesions are lacking.

Aim

The aim of the present study was to evaluate acute efficacy and safety of the novel DT ablation system for bidirectional block of the MIL using two different protocols.

Methods

The study population comprised 14 patients [67±8 years, 10/14 male (71%)] suffering from persistent AF and/or atrial tachycardia who underwent catheter re-ablation with creation of a MIL using the DT ablation system. Ablation settings were a catheter-tip temperature limit of 60°C, a temperature-controlled power of 50 W with an application duration of either 10 sec (group A, n=7) or 20 sec (group B, n=7). Additional epicardial ablation from within the coronary sinus with a temperature limit of 60°C, a temperature-controlled power of 20 W and an application duration of 20 sec was performed, if bidirectional block could not be achieved with endocardial ablation only.

Results

Mean procedure and fluoroscopy time, and dose area product for group A and group B were 103±24 vs. 119±38 min, 12±5 vs. 13±4 min, and 572±270 vs. 537±202 cGycm, respectively. Bidirectional block of the MIL was achieved in 7/7 (100%) patients in group A and in 6/7 (86%) patients in group B. Additional epicardial ablation was required in 6/7 patients (86%) in group A and in 4/7 (57%) patients in group B. In group B, bidirectional block of the MIL required fewer endocardial (31±11 vs. 26±10 applications) as well as epicardial RF-applications (10±6 vs. 7±3 applications). Pericardial effusion without hemodynamic relevance occurred in 1/7 (14%) patients of group B. No further complications occurred.

Conclusion

Catheter ablation of the MIL using the novel DT ablation system is safe and associated with high acute efficacy. A lower number of RF-applications and a less frequent need for additional epicardial ablation was observed when applying longer RF-applications of 20 sec. Further analyses are warranted to confirm these findings.

Optimizing catheter ablation of atrial fibrillation by a novel wide-band dielectric imaging system: first experience on real-time wall thickness measurement

Funding Acknowledgements

Type of funding sources: None.

Background

Conventional mapping systems do not provide wall-thickness data, which is, however, known to be a determinant of radiofrequency ablation lesion transmurality. KODEX-EPD is a novel open-platform system, which uses dielectric tissue properties to provide real-time, high-resolution cardiac images, tissue characteristics and wall-thickness measurement to guide ablation procedures.

Aim

The aim of this case series was to report on our first experiences with KODEX-EPD regarding estimation of myocardial wall-thickness during catheter ablation of atrial fibrillation (AF).

Methods

We retrospectively analyzed consecutive patients undergoing radiofrequency AF-ablation in combination with KODEX-EPD. A high-resolution image from the left atrium (LA) and the pulmonary veins (PV) was obtained prior to ablation using a spiral mapping catheter in conjunction with KODEX-EPD. Wall-viewer points were collected within the LA, the PVs and the left atrial appendage (LAA) using a standard radiofrequency non-contact force ablation catheter and analyzed for wall-thickness applying the latest KODEX-EPD software version (1.5.0, not yet commercially released). Wall-viewer points were divided into a total of 10 segments (PV ostia, anterior wall, posterior wall, LA roof, LA floor, LAA and PV carina, details see Figure 1) in order to characterize wall-thickness in respective areas.

Results

A total of 570 wall-viewer points in 5 patients were analyzed. Most of the wall-viewer points were collected at the PV ostia as well as along the posterior and anterior wall (449/570, 79%). Actual myocardial atrial thickness ranged from 1.6 to 3.9 mm. Thickest myocardial LA-tissue was measured at the anterior wall (median 3.1 mm) and thinnest at the LA-roof (median 2.2 mm). Figure 2 gives a detailed distribution of wall-thickness measurements at different sites in the LA and PVs.

Conclusion

Atrial wall thickness can be estimated in patients during AF ablation procedures using dielectric tissue properties. Further evaluation and validation of the method are needed to study its reliability and utility for clinical practice.

Accuracy and acute efficacy of a novel occlusion tool to guide cryoballoon-based pulmonary vein isolation

Background

Cryoballoon (CB)-based pulmonary vein isolation (PVI) currently requires to verify occlusion of each pulmonary vein (PV) using fluoroscopy and dye injection.

Objective

The current study evaluated whether the novel CB-occlusion tool integrated into the wide-band dielectric imaging system KODEX-EPD reliably verifies occlusion of PV according to a novel dye-injection based algorithm.

Methods

Consecutive patients suffering from symptomatic atrial fibrillation (AF) underwent CB-based PVI using the KODEX-EPD and the novel occlusion-tool (group I). To confirm accurate display of the PVs, selective PV-angiography was performed in the first half of the patients of group I (group Ia) in addition to a three-dimensional left atrial (LA) map using a spiral mapping catheter (Achieve, SMC1, Medtronic, MN, USA). PV-angiographies were waived for the following patients (group Ib). Procedural duration and radiation exposure were compared to a control group of patients undergoing conventional CB-based PVI.

Results

CB-based PVI was successful in 50/50 patients of group I (mean age 63±11 years, 18 paroxysmal (36%)) and 25/25 patients of group II (66±10 years, 9 paroxysmal (60%)). Concordance of PV-occlusion as assessed by either PV-occlusion-angiography or KODEX-EPD, was documented in 237/272 (87%) occlusion-analyses among 198 PVs (95% for left superior PV, 93% for left inferior PV, 86% for right inferior PV and 77% for right superior PV).

In the final evaluation phase (group Ib) LA fluoroscopy times and dose area products were comparable to the conventional CB-ablation group (10.5±5 vs 8.8±4 minutes (p=0.23) and 403±425 vs 321±202 cGycm2 (p=0.44), whereas the amount of dye could be significantly reduced (group Ib: 31±10 ml vs group II: 70±20 ml, p<0.0001).

Conclusion

The novel KODEX-EPD PV-occlusion tool allows for accurate PV-occlusion assessment in the majority of PVs and a high acute success rate. The system has the potential to reduce dye and radiation exposure. This should be evaluated in controlled clinical trials.

Funding Acknowledgement

Type of funding sources: None.

Maternal and personal information mediates the use of social cues about predation risk

Organisms can gain information about predation risks from their parents, their own personal experience, and their conspecifics and adjust their behavior to alleviate these risks. These different sources of information can, however, provide conflicting information due to spatial and temporal variation of the environment. This raises the question of how these cues are integrated to produce adaptive antipredator behavior. We investigated how common lizards (Zootoca vivipara) adjust the use of conspecific cues about predation risk depending on whether the information is maternally or personally acquired. We experimentally manipulated the presence of predator scent in gestating mothers and their offspring in a full-crossed design. We then tested the consequences for social information use by monitoring offspring social response to conspecifics previously exposed to predator cues or not. Lizards were more attracted to the scent of conspecifics having experienced predation cues when they had themselves no personal information about predation risk. In contrast, they were more repulsed by conspecific scent when they had personally obtained information about predation risk. However, the addition of maternal information about predation risk canceled out this interactive effect between personal and social information: lizards were slightly more attracted to conspecific scent when these two sources of information about predation risk were in agreement. A chemical analysis of lizard scent revealed that exposure to predator cues modified the chemical composition of lizard scents, a change that might underlie lizards’ use of social information. Our results highlight the importance of considering multiple sources of information while studying antipredator defenses.

Does case management provides support for staff facing frequent users of emergency departments?

Background

Frequent users of emergency departments (FUED; 5 ED visits during the preceding 12 months) account for a disproportionate part of ED visits, causing a wide range of work difficulties to ED staff potentially leading to FUED discrimination. Whereas case management (CM) tailored to FUED leads to a reduction in ED visits, CM impact on ED staff has not been explored yet. This study aimed to compare ED staff perceptions of FUED with and without dedicated CM support.

Methods

Participants (N = 253) were ED staff (81 physicians; 172 nurses/assistant nurses) of two Swiss university hospitals, one with CM and one without CM support. Perceptions regarding FUED (i.e., knowledge and awareness of the issue extent; related work difficulties; FUEDs’ legitimate use of ED resources) were measured with a 25-item online survey (4 to 10-level Likert scales). Multivariable regression analyses were conducted to 1) explore the associations between CM implementation and FUED perceptions, and 2) test the moderating effect of profession (physician or nurse/nurse assistant) on these associations. All analyses were adjusted by gender and years of practical experience.

Results

Physicians with CM considered FUED as a less important problem (=.375, R2=.11, p <.05) and rated their knowledge of FUED issue higher (=.245, R2=.077, p <.05) compared to those without CM. In contrast, nurses without CM perceived fewer FUED-related work difficulties (i.e., feeling of failure and helplessness) than nurses with CM. (=-1.01, R2=.06, p <.05) No significant difference was found regarding ED staff’s perceptions of FUEDs’ legitimate use of ED resources and frequentation, nor on nurses’ knowledge of the issue.

Conclusions

These results suggest that CM intervention for FUED is a potential source of support for ED physicians working with FUED. Further qualitative research is needed to explore why nurses without CM support reported feeling less failure and helplessness regarding FUED.

Key messages

By highlighting a different impact of CM on nurses’ perception, this study illustrates where CM intervention might be improved. This study supports CM as a promising intervention for FUED by potentially having a positive impact on ED physicians’ perception besides the one previously proved on FUEDs’ number of visits and QOL.

Healthcare providers’ perceptions of difficulties related to frequent users of emergency departments

Background

Frequent users of emergency department (FUEDs; ≥ 5 ED visits/ year) are often vulnerable individuals cumulating medical, social and substance use problems. FUEDs often require complex and sustained care coordination generally unavailable in ED and are commonly considered contributing to ED crowding. In view of supporting ED health-care providers through specific training and interventions tailored to FUEDs, this study aimed to explore ED healthcare providers’ perceptions of difficulties related to FUEDs.

Methods

Participants (N = 208) were ED healthcare providers (i.e., nurses, physicians) from 75 university and community hospitals in Switzerland (71% of all EDs) who answered a questionnaire on FUEDs. They were asked to indicate the extent to which FUEDs represent a problem in their ED. Perceived difficulties related to FUEDs were elicited by an open-ended question. Conventional content analysis was used to extract common categories and themes.

Results

Among the 208 participants, 134 (64%) reported that FUEDs represent a problem. Of those, 132 provided 1 to 5 answers to the open-ended question. Twenty-eight categories were identified and organized in 4 themes. First, participants reported difficulties related to FUEDs’ characteristics themselves (e.g., problem’s chronicity; behavioural difficulties) leading to healthcare complexity. Second, participants perceived negative consequences related to the presence of FUEDs in the ED (e.g., work overload, staff helplessness and fatigue). Third, ED healthcare offer was considered inappropriate and inefficient to respond to FUEDs needs and fourth collaborating with FUEDs’ existing healthcare network was perceived as difficult.

Conclusions

ED healthcare providers experience a wide range of difficulties related to the management of FUEDs. Providing training and implementing a case management intervention tailored to FUEDs might support ED health-care providers and contribute to address FUEDs’ complex needs.

Key messages

ED healthcare providers perceive FUEDs to represent a problem. Perceived difficulties might decrease through training and case management support might contribute to better address FUEDs complex needs.

P3778Long-term outcome of non-pharmacologial treatment of atrial fibrillation in hypertrophic cardiomyopathy: a large single-centre experience

Introduction

Atrial fibrillation (AF) is common in hypertrophic cardiomyopathy (HCM) and is generally associated with a significant deterioration of clinical status. Non-pharmacological treatment such as surgical and catheter ablation has become an established therapy for symptomatic AF but in patients with HCM often having a chronically increased left atrial pressure and extensive atrial cardiomyopathy the long-term outcome is uncertain.

Purpose

The present study aimed to analyse the long-term outcome of AF ablation in HCM and the mechanism of recurrent atrial arrhythmias using high-density mapping systems.

Methods

A total of 65 patients (age 64.5±9.9 years, 42 (64.6%) male) with HCM undergoing AF ablation for symptomatic AF were included in our study. The ablation strategy for catheter ablation included pulmonary vein isolation in all patients and biatrial ablation of complex fractionated electrograms with additional ablation lines if appropriate. In patients with suspected atrial tachycardia (AT) high-density activation and substrate mapping were performed. A surgical ablation at the time of an operative myectomy for left ventricular outflow tract obstruction was performed in 8 (12.3%) patients. The outcome was analysed using clinical assessment, Holter ECG and continuous rhythm monitoring of cardiac implantable electric devices.

Results

Paroxysmal AF was present in 27 (41.6%), persistent AF in 37 (56.9%) and primary AT in 1 (1.5%) patients. The mean left atrial diameter was 54.1±12.5 ml. In 11 (16.9%) patients with AT high-density mapping was used to characterize the mechanism of the ongoing tachycardia. After 1.9±1.2 ablation procedures and a follow-up of 48.5±37.2 months, ablation success was demonstrated in 58.9% of patients. The success rate for paroxysmal and persistent AF was 70.0% and 55.8%, respectively (p=0.023). Of those patients with AT high-density mapping guided ablation was successful in 44.4% of patients. The LA diameter of patients with a successful ablation was smaller (52.2 vs. 58.1 mm; p=0.003).

Conclusion

Non-pharmacological treatment of AF in HCM is effective during long-term follow-up. Paroxysmal AF and a smaller LA diameter are favourable for successful ablation. In patients with complex AT the use of high-density mapping can guide ablation resulting in further ablation success in a reasonable number of patients.

Implementation of an in-house quantitative real-time polymerase chain reaction method for Hepatitis B virus quantification in West African countries

Hepatitis B virus (HBV) is a major cause of chronic liver disease worldwide. HBV infection is diagnosed by serological tests, while real-time polymerase chain reaction (qRT-PCR) assays are used to quantify viral load, which is a crucial parameter to determine viral replication and to monitor antiviral treatments. However, measuring viral load in resource-limited countries remains nonsystematic, due to the high cost of commercial kits. Here, we describe the development, validation and implementation of a low-cost, in-house qRT-PCR assay to monitor HBV viral load in chronic carriers enrolled in the PROLIFICA programme in the Gambia and Senegal. Over 1500 HBsAg-positive patients, including 210 chronically infected HBV patients, who were given antiviral treatment (tenofovir), were monitored by qRT-PCR using the SYBR Green- and HBV-specific primers. Twenty-four tenofovir-treated patients were followed up and their viral load was tested every 3 months over the 12-month experimental time course. Compared to commercial assays, our in-house assay was shown to be (i) highly reliable, with good intra- and interassay reproducibility over a wide range (45-4.5 × 108 copies mL-1 ), (ii) very similar in the viral loads detected (R2  = .90), (iii) highly sensitive, as it detected loads as low as 30 copies mL-1 (~5 IU mL-1 ), (iv) cheaper (2- to 3-fold), (v) easier to implement and (vi) more rapid. Based on our experience, we recommend this assay as a reliable alternative to commercial assays, for monitoring HBV viraemia in resource-limited, highly endemic countries to reduce the cost and technical obstacles associated with commercial kits.

The microphysics of collisionless shock waves

Collisionless shocks, that is shocks mediated by electromagnetic processes, are customary in space physics and in astrophysics. They are to be found in a great variety of objects and environments: magnetospheric and heliospheric shocks, supernova remnants, pulsar winds and their nebulæ, active galactic nuclei, gamma-ray bursts and clusters of galaxies shock waves. Collisionless shock microphysics enters at different stages of shock formation, shock dynamics and particle energization and/or acceleration. It turns out that the shock phenomenon is a multi-scale non-linear problem in time and space. It is complexified by the impact due to high-energy cosmic rays in astrophysical environments. This review adresses the physics of shock formation, shock dynamics and particle acceleration based on a close examination of available multi-wavelength or in situ observations, analytical and numerical developments. A particular emphasis is made on the different instabilities triggered during the shock formation and in association with particle acceleration processes with regards to the properties of the background upstream medium. It appears that among the most important parameters the background magnetic field through the magnetization and its obliquity is the dominant one. The shock velocity that can reach relativistic speeds has also a strong impact over the development of the micro-instabilities and the fate of particle acceleration. Recent developments of laboratory shock experiments has started to bring some new insights in the physics of space plasma and astrophysical shock waves. A special section is dedicated to new laser plasma experiments probing shock physics.

Hepatitis E virus infection and acute-on-chronic liver failure in West Africa: a case-control study from The Gambia

BACKGROUND

In sub-Saharan Africa, it is unknown whether hepatitis E virus (HEV) infection is a common precipitating event of acute-on-chronic liver failure (ACLF).

AIMS

To estimate the prevalence of HEV infection in general population and assess whether HEV is a common trigger of ACLF in cirrhotic patients in The Gambia, West Africa.

METHODS

We first conducted an HEV sero-survey in healthy volunteers. We then tested cirrhotic patients with ACLF (cases) and compensated cirrhosis (controls) for anti-HEV IgG as a marker of exposure to HEV, and anti-HEV IgA and HEV RNA as a marker of recent infection. We also described the characteristics and survival of the ACLF cases and controls.

RESULTS

In the healthy volunteers (n = 204), 13.7% (95% CI: 9.6-19.2) were positive for anti-HEV IgG, and none had positive HEV viraemia. After adjusting for age and sex, the following were associated with positive anti-HEV IgG: being a Christian, a farmer, drinking water from wells, handling pigs and eating pork. In 40 cases (median age: 45 years, 72.5% male) and 71 controls (39 years, 74.6% male), ≥70% were infected with hepatitis B virus. Although hepatitis B flare and sepsis were important precipitating events of ACLF, none had marker of acute HEV. ACLF cases had high (70.0%) 28-day mortality.

CONCLUSIONS

Hepatitis E virus infection is endemic in The Gambia, where both faecal-oral route (contaminated water) and zoonotic transmission (pigs/pork meat) may be important. However, acute HEV was not a common cause of acute-on-chronic liver failure in The Gambia.

Immune Reconstitution Inflammatory Syndrome Secondary to Mycobacterium kansasii Infection in a Kidney Transplant Recipient

Nontuberculous mycobacteria (NTM) infection is a challenging diagnosis for clinicians in solid organ transplantation. Immune reconstitution inflammatory syndrome (IRIS) is so far unreported in this context. We report here the case of a renal transplant recipient who developed Mycobacterium kansasii-associated lymphadenitis complicated by IRIS while undergoing reduction of his immunosuppressive therapy. For IRIS, the patient required low-dose steroids and an increase in global immunosuppression, in association with NTM antibiotherapy.

Ultrafast Synchrotron-Enhanced Thermalization of Laser-Driven Colliding Pair Plasmas

We report on the first self-consistent numerical study of the feasibility of laser-driven relativistic pair shocks of prime interest for high-energy astrophysics. Using a QED-particle-in-cell code, we simulate the collective interaction between two counterstreaming electron-positron jets driven from solid foils by short-pulse (~60 fs), high-energy (~100 kJ) lasers. We show that the dissipation caused by self-induced, ultrastrong (>10^{6} T) electromagnetic fluctuations is amplified by intense synchrotron emission, which enhances the magnetic confinement and compression of the colliding jets.

Association between IL28B polymorphism, TNFα and biomarkers of insulin resistance in chronic hepatitis C-related insulin resistance

TNFα has been shown to play a role in hepatitis C virus (HCV)-induced insulin resistance (IR). Polymorphism of the IL28B gene that encodes IFN-lambda 3 may be associated with IR through modulation of TNFα. The aim of this study was to investigate the relationship between IL28B rs12979860 genotype, the level of TNFα activation and the degree of IR in patients with chronic hepatitis C. One hundred and thirty-three nondiabetic genotype 1 HCV-infected patients with biopsy proven noncirrhotic hepatitis C were investigated for IR (using HOMA index), IL28B rs12979860 genotype and fasting circulating levels of soluble receptor 1 of TNFα (sTNFR1) and adipokines: leptin, adiponectin and IL-6. The HOMA-IR was positively correlated with serum levels of leptin (r = 0.35, P < 0.0001) and sTNFR1 (r = 0.35, P < 0.0001) but not with IL-6 or adiponectin. IL28B rs12979860 CC genotype was observed in 35% patients. Genotype CC and nongenotype CC patients were similar in terms of HOMA-IR (means 1.6 ± 0.9 vs 1.7 ± 1.4) and had similar circulating levels of sTNFR1 and adipokines. Independent factors associated with IR were ferritin (OR = 1.002, P = 0.02), leptin (OR = 1.06, P = 0.02) and sTNFR1 (OR = 7.9, P = 0.04). This study suggests that in nondiabetic, noncirrhotic, HCV genotype 1-infected patients, there is no relationship between IL28B rs12979860 genotype and HOMA-IR or sTNFR1 level. HCV-related IR may be mediated through TNFα independent of IL28B genotype.

Characterization of harbor sediments from the English Channel: assessment of heavy metal enrichment, biological effect and mobility

For a full assessment of the environmental risk posed by dredged sediments not only the anthropogenic enrichment of contaminants, but also their mobility and biological impact should be considered. This study reports on the enrichment factor (EF), mobility, and Adverse Effect Index (AEI) of metals and metalloids in nine dredged sediments. Significant enrichment of As, Cd, Pb and Zn with respect to background values is detected, and calculated AEI values for these elements suggest that it is possible that a corresponding biological effect may be observed. Correlation coefficients also reveal a link between mobility in HCl and enrichment for Cd, Cr, Ni, Pb and Zn, however As and Cu do not display such a link, possibly suggesting that the source of contamination for these elements is less recent. Mobility and enrichment are two parameters which are often studied separately; however this paper shows that in some cases strong correlations occur.

Contemporary ecotypic divergence during a recent range expansion was facilitated by adaptive introgression

Although rapid phenotypic evolution during range expansion associated with colonization of contrasting habitats has been documented in several taxa, the evolutionary mechanisms that underlie such phenotypic divergence have less often been investigated. A strong candidate for rapid ecotype formation within an invaded range is the three-spine stickleback in the Lake Geneva region of central Europe. Since its introduction only about 140 years ago, it has undergone a significant expansion of its range and its niche, now forming phenotypically differentiated parapatric ecotypes that occupy either the pelagic zone of the large lake or small inlet streams, respectively. By comparing museum collections from different times with contemporary population samples, we here reconstruct the evolution of parapatric phenotypic divergence through time. Using genetic data from modern samples, we infer the underlying invasion history. We find that parapatric habitat-dependent phenotypic divergence between the lake and stream was already present in the first half of the twentieth century, but the magnitude of differentiation increased through time, particularly in antipredator defence traits. This suggests that divergent selection between the habitats occurred and was stable through much of the time since colonization. Recently, increased phenotypic differentiation in antipredator defence traits likely results from habitat-dependent selection on alleles that arrived through introgression from a distantly related lineage from outside the Lake Geneva region. This illustrates how hybridization can quickly promote phenotypic divergence in a system where adaptation from standing genetic variation was constrained.

Prevention of materno-foetal transmission of hepatitis B in sub-Saharan Africa: the evidence, current practice and future challenges

Hepatitis B (HBV) infection is highly endemic in sub-Saharan Africa (SSA), where more than 8% of the population remain chronic HBV carriers. SSA has one of the highest HBV-related liver cancer rates in the world (CA Cancer J Clin, 55, 2005, 74) and HBV-related liver cancer is the most common cause of premature death in West Africa (Lancet Oncol, 9, 2008, 683; Hepatology, 39, 2004, 211). As such, HBV represents a significant global threat to health in the African continent. Most SSA countries have elected to vaccinate all children against HBV through the WHO-sponsored Expanded Program of Immunization and the current recommendation from WHO-AFRO is for birth-dose HBV vaccination to prevent maternal/child transmission (MFT) and early horizontal transmission of HBV. However, in Africa, HBV vaccine coverage remains low and HBV birth-dose vaccination has not been implemented. HBV transmission from mother to child in the early perinatal period therefore remains a significant contributor to the burden of HBV-related disease in SSA. This review explores the evidence for materno-foetal transmission of HBV in SSA, outlining current practice for HBV MFT prevention and identifying the significant challenges to implementation of HBV prevention in SSA.

Food intake increases liver stiffness measurements and hampers reliable values in patients with chronic hepatitis B and healthy controls: the PROLIFICA experience in The Gambia

BACKGROUND

By increasing the hepatic blood circulation, food intake has been suggested to increase liver stiffness measurement (LSM) values in HCV-infected patients.

AIM

To investigate prospectively the effects of food intake on LSM in hepatitis B virus (HBV)-infected patients and healthy controls.

METHODS

In The Gambia, patients included in the PROLIFICA project are screened for HBV at the community level and then invited for fasting assessment including LSM. Between April 2012 and October 2012, each day, the first five participants were invited to participate in this study. After the initial examination, a standardised 850 Kcal breakfast was provided. Effect of food intake was assessed by examining mean difference of LSM, IQR and IQR/LSM at T0 (fasting LSM1), T30min (LSM2) and T120min (LSM3) respectively.

RESULTS

A total of 209 subjects were enrolled in this study (133 were HBV positive, 76 healthy controls). Unreliable measurements occurred more frequently after food intake (5%, 24% and 18% at T0, T30min and T120min respectively). In both groups, median LSM2 was significantly higher than LSM1 [6.2 (IQR: 5.4, 7.9)] vs. 4.9 (4.2, 6.2), P < 0.0001. LSM3 was still higher than the baseline, but lower than LSM2. In multivariable analysis, no factor modified the effect of breakfast on LSM. In a subgroup of patients having liver biopsies, we confirmed that food intake can overestimate liver fibrosis.

CONCLUSIONS

Food intake significantly increases liver stiffness measurement and its IQR values in patients with chronic hepatitis B as well as healthy individuals; and also the number of unreliable liver stiffness measurement values.

Influence of host profitability and microenvironmental conditions on parasite specialization on a main and an alternative hosts

Parasite success depends on both host profitability and the microenvironment provided by the host, which together define host-parasite compatibility and can differ between hosts. We experimentally disentangled the effects of host profitability and microenvironmental conditions provided by nest material on the reproduction of a nest-based ectoparasite when exploiting its main and an alternative avian host species. Parasite reproductive performance was similar on both hosts when breeding in nests of their own species, suggesting no difference in host-parasite compatibility between hosts. The apparent parasite specialization could therefore result from differences in host-parasite encounter processes. However, when hosts were successful, the main host produced more young in infested nests, whereas the alternative host produced less; furthermore, host reproductive performance was higher in nests of the main host species, suggesting that this nest material alleviates parasitism cost. Therefore, our results suggest different evolutionary responses to parasites of the main and alternative hosts, with either higher tolerance or higher resistance, modulated by nest material.

Definition and natural history of metabolic steatosis: clinical aspects of NAFLD, NASH and cirrhosis

Metabolic steatosis or non-alcoholic fatty liver (NAFLD) is the most common cause of chronic liver injury in Western countries. Histological signs of necroinflammation, indicating the presence of non-alcoholic steatohepatitis (NASH), are present in 20-30% of cases. While steatosis on its own has a benign course, NASH may be associated with fibrosis and may progress to cirrhosis, terminal liver failure and hepatocellular carcinoma. NAFLD is closely associated with the metabolic syndrome, its prevalence reaching 50-90% in obese patients. The clinical impact of NAFLD has been demonstrated in large cohort studies by the overprevalence of cirrhosis and hepatocellular carcinoma in obese and diabetic patients. In terms of survival, liver disease is the third most common cause of mortality in patients with NAFLD. When associated with other causes of liver disease such as alcohol consumption or hepatitis C infection, metabolic steatosis may be a major risk factor for disease progression.

Liver stiffness measurement as a predictive tool of clinically significant portal hypertension in patients with compensated hepatitis C virus or alcohol-related cirrhosis

BACKGROUND

Hepatic venous pressure gradient (HVPG) is the gold standard for assessing the presence and the severity of portal hypertension (PHT). Liver stiffness measurement (LSM) is a non-invasive method for liver fibrosis assessment.

AIMS

To assess the relationship between LSM and HVPG in patients with compensated cirrhosis related to hepatitis C virus (HCV) or alcohol and to define the performance and the best cut-off of LSM for the diagnosis of PHT in these patients.

METHODS

Between January 2004 and September 2006, we studied all the consecutive patients with compensated HCV or alcohol-related-cirrhosis referred for transjugular liver biopsy with HVPG measurement and LSM performed the same day.

RESULTS

Ninety-two patients were eligible, 44 had HCV related-cirrhosis and 48 alcoholic cirrhosis. LSM was positively correlated to HVPG in both groups. The area under the receiver operating characteristic curve for the diagnosis of significant PHT was 0.76 +/- 0.07 in HCV patients (best cut-off at 20.5 kPa) and 0.94 +/- 0.03 (best cut-off at 34.9 kPa) in alcoholic patients.

CONCLUSIONS

Liver stiffness measurement and HVPG were significantly correlated in patients with compensated cirrhosis because of HCV infection or alcohol. LSM could predict significant PHT in both these groups of patients with a higher cut-off and a better performance in alcoholic patients.

A reappraisal of the factors involved in in vitro initiation of the acrosome reaction in chicken spermatozoa

Chicken spermatozoa may remain in the female oviduct for a prolonged period before induction of the acrosome reaction on contact with the inner perivitelline layer (IPVL). By contrast, the acrosome reaction may be induced very rapidlyin vitroin the presence of IPVL and Ca2+. In the present study, we examined the extent to which the chicken acrosome reaction can be induced in media of various compositions in the presence or absence of IPVL and/or Ca2+and other factors known to be efficient in mammals. We also compared the efficacy of perivitelline layer (PL) taken at various states of oocyte maturation in initiating the reaction. The acrosome reaction was induced in less than 5 min in the presence of Ca2+and IPVL. Incubation of spermatozoa in different saline media (Beltsville poultry semen extender (BPSE); Dulbecco's modified eagle medium; NaCl-TES buffer) without IPVL showed a significant induction of acrosome reaction in BPSE supplemented with 5 mM Ca2+and in the three media after supplementation with Ca2+and Ca2+ionophore A23187. By contrast, the acrosome reaction was never induced without Ca2+. BSA, NaHCO3, and progesterone did not stimulate the acrosome reaction. Ca2+plus PL taken at various physiological states (follicle IPVL, ovulated IPVL, oviposited IPVL, and/or outer perivitelline layer) strongly stimulated the acrosome reaction, the latest states being the most efficient. Although PL induced the acrosome reaction in the presence of extracellular Ca2+, it was not possible to induce hyperactivation in chicken spermatozoa. Taken together, these results emphasize the central role of Ca2+in thein vitroinitiation of the acrosome reaction in chickens and show specific features of this induction in birds.

A new population of very high energy gamma-ray sources in the Milky Way

Very high energy gamma-rays probe the long-standing mystery of the origin of cosmic rays. Produced in the interactions of accelerated particles in astrophysical objects, they can be used to image cosmic particle accelerators. A first sensitive survey of the inner part of the Milky Way with the High Energy Stereoscopic System (HESS) reveals a population of eight previously unknown firmly detected sources of very high energy gamma-rays. At least two have no known radio or x-ray counterpart and may be representative of a new class of "dark" nucleonic cosmic ray sources.