bluuebunny/crossref_metadata_2025 huggingface dataset:
Simulation of intracardiac electrograms around acute ablation lesions
Authors: Greiner Joachim , Pollnow Stefan , Schuler Steffen , Lenis Gustavo , Seemann Gunnar , Dössel Olaf
Published: December 2016

Radiofrequency ablation (RFA) is a widely used clinical treatment for many types of cardiac arrhythmias. However, nontransmural lesions and gaps between linear lesions often lead to recurrence of the arrhythmia. Intracardiac electrograms (IEGMs) provide real-time information regarding the state of the cardiac tissue surrounding the catheter tip. Nevertheless, the formation and interpretation of IEGMs during the RFA procedure is complex and yet not fully understood. In this in-silico study, we propose a computational model for acute ablation lesions. Our model consists of a necrotic scar core and a border zone, describing irreversible and reversible temperature induced electrophysiological phenomena. These phenomena are modeled by varying the intra- and extracellular conductivity of the tissue as well as a regulating zone factor. The computational model is evaluated regarding its feasibility and validity. Therefore, this model was compared to an existing one and to clinical measurements of five patients undergoing RFA. The results show that the model can indeed be used to recreate IEGMs. We computed IEGMs arising from complex ablation scars, such as scars with gaps or two overlapping ellipsoid scars. For orthogonal catheter orientation, the presence of a second necrotic core in the near-field of a punctiform acute ablation lesion had minor impact on the resulting signal morphology. The presented model can serve as a base for further research on the formation and interpretation of IEGMs.
Parametrization of activation based cardiac electrophysiology models using bidomain model simulations
Authors: Stender Birgit
Published: December 2016

Eikonal models are useful to compute approximate solutions of cardiac excitation propagation in a computationally efficient way. In this work the underlying conduction velocities for different cell types were computed solving the classical bidomain model equations for planar wavefront propagation. It was further investigated how changes in the conductivity tensors within the bidomain model analytically correspond to changes in the conduction velocity. The error in the presence of local front curvature for the derived eikonal model parametrization were analyzed. The conduction velocity simulated based on the bidomain model was overestimated by a maximum of 10%.
Resistance in a non-linear autoregressive model of pulmonary mechanics
Authors: Langdon Ruby , Docherty Paul D. , Laufer Bernhard , Möller Knut
Published: December 2016

Respiratory system modelling can enable patient-specific mechanical ventilator settings to be found, and can thus reduce the incidence of ventilator induced lung injury in the intensive care unit. The resistance of a simple first order model (FOM) of pulmonary mechanics was compared with a flow dependent term of a non-linear autoregressive (NARX) model. Model parameters were identified for consecutive non-overlapping windows of length 20 breaths. The analysis was performed over recruitment manoeuvres for 25 sedated mechanically ventilated patients. The NARX model term, b1
, consistently decreased as positive end expiratory pressure (PEEP) increased, while the FOM resistance behaviour varied. Overall the NARX b1
behaviour is more in-line with expected trends in airway resistance as PEEP increases. This work has further verified the physiologically descriptive capability of the NARX model.
Determination of regional lung function in cystic fibrosis using electrical impedance tomography
Authors: Krueger-Ziolek Sabine , Schullcke Benjamin , Zhao Zhanqi , Gong Bo , Moeller Knut
Published: December 2016

Electrical impedance tomography (EIT) can be used to monitor regional lung ventilation. Due to its relatively high temporal resolution, EIT has already been applied during lung function tests in spontaneously breathing subjects with obstructive lung diseases like chronic obstructive pulmonary disease (COPD) or cystic fibrosis (CF). In our study, ratios of the maximal volume exhaled in 1 s during forced expiration and forced vital capacity (FEV1/FVC) were calculated in predefined lung regions for five CF patients and five lung healthy subjects. The degree of FEV1/FVC homogeneity was assessed by using a slightly modified version of the global inhomogeneity index (GIFEV1

/FVC). CF patients showed a higher degree of inhomogeneity in pixel FEV1/FVC than lung healthy subjects. Since EIT is able to deliver regional information to assess airway obstruction in CF patients, it might represent a promising supplement to existing methods like spirometry providing global lung parameters.
Development of parietal bone surrogates for parietal graft lift training
Authors: Hollensteiner Marianne , Fürst David , Esterer Benjamin , Hunger Stefan , Malek Michael , Augat Peter , Schrödl Falk , Stephan Daniel , Schrempf Andreas
Published: December 2016

Currently the surgical training of parietal bone graft techniques is performed on patients or specimens. Commercially available bone models do not deliver realistic haptic feedback. Thus customized parietal skull surrogates were developed for surgical training purposes. Two human parietal bones were used as reference. Based on the measurement of insertion forces of drilling, milling and saw procedures suitable material compositions for molding cortical and cancellous calvarial layers were found. Artificial skull caps were manufactured and tested. Additionally microtomograpy images of human and artificial parietal bones were performed to analyze outer table and diploe thicknesses. Significant differences between human and artificial skulls were not detected with the mechanical procedures tested. Highly significant differences were found for the diploe thickness values. In conclusion, an artificial bone has been created, mimicking the properties of human parietal bone thus being suitable for tabula externa graft lift training.
Numerical simulation of mechanically stimulated bone remodelling
Authors: Mauck Josephine , Wieding Jan , Kluess Daniel , Bader Rainer
Published: December 2016

The numerical simulation of bone remodelling provides a great opportunity to improve the choice of therapy in particular for complex bone defects. Despite this fact, its use in clinical practice is not yet expedient because of several unresolved problems. In this paper a new bone remodelling algorithm based on standard computer tomography datasets and finite element analysis is introduced.
Conversion of engineering stresses to Cauchy stresses in tensile and compression tests of thermoplastic polymers
Authors: Schümann Kerstin , Röhr Udo , Schmitz Klaus-Peter , Grabow Niels
Published: December 2016

Thermoplastic polymers exhibit non-isochoric behaviour during tensile and compression testing as well as particular deformations like local necking (tension) or buckling (compression). A method for the determination of Cauchy stresses from tensile and compression tests is presented, that considers the actual deformations of the test specimens. The exact geometry of the specimens in the respective present configuration is determined in photographs, which are taken continuously throughout the test. The engineering stresses at several time points are converted into Cauchy stresses using newly developed formulas in consideration of the actual specimen geometry. For validation finite element analyses of the tensile and compression tests are performed using the identified stress-strain curves. The numerical results show good agreement with the experiments for the tested polymers. Thus a method for conversion of engineering to Cauchy stresses in tensile and compression tests could be established considering the non-isochoric deformation in plasticity. With this method “true” stress-strain curves as input for finite element material models can be identified for arbitrary materials.
Numerical examinations of simplified spondylodesis models concerning energy absorption in magnetic resonance imaging
Authors: Hadert Nicole , Liu Qi , Zylka Waldemar
Published: December 2016

Metallic implants in magnetic resonance imaging (MRI) are a potential safety risk since the energy absorption may increase temperature of the surrounding tissue. The temperature rise is highly dependent on implant size. Numerical examinations can be used to calculate the energy absorption in terms of the specific absorption rate (SAR) induced by MRI on orthopaedic implants. This research presents the impact of titanium osteosynthesis spine implants, called spondylodesis, deduced by numerical examinations of energy absorption in simplified spondylodesis models placed in 1.5 T and 3.0 T MRI body coils. The implants are modelled along with a spine model consisting of vertebrae and disci intervertebrales thus extending previous investigations [1], [2]. Increased SAR values are observed at the ends of long implants, while at the center SAR is significantly lower. Sufficiently short implants show increased SAR along the complete length of the implant. A careful data analysis reveals that the particular anatomy, i.e. vertebrae and disci intervertebrales, has a significant effect on SAR. On top of SAR profile due to the implant length, considerable SAR variations at small scale are observed, e.g. SAR values at vertebra are higher than at disc positions.
Influence of Siluron® insertion on model drug distribution in the simulated vitreous body
Authors: Stein Sandra , Bogdahn Malte , Weitschies Werner , Seidlitz Anne
Published: December 2016

Biorelevant in vitro test systems may be helpful to understand the in vivo behaviour of modern intravitreal dosage forms such as implants and injections. The already presented Vitreous Model (VM) in combination with the Eye Movement System (EyeMoS) was used to simulate the situation after a vitrectomy in combination with Siluron® silicone oil (SO) insertion in vitro and to investigate the distribution of the model drug fluorescein sodium (FS) within the modified VM. The state after a vitrectomy was simulated in vitro by replacing half the volume of the gelled vitreous substitute by SO. Under consideration of simulated eye movements the position of SO towards the simulated vitreous body was examined. Furthermore, the influence of two different injection techniques was studied. On the one hand, FS was injected directly into the gel and on the other hand the injection was set through the gel in order to directly reach the SO. Independent of the injection technique, it was shown that the model drug distributed almost exclusively into the gel and not into the SO. This can be explained with the backflow of FS into the gel and the lack of solubility in the SO. Using the modified VM and EyeMoS, the in vitro characterization of drug release and distribution behaviour of intravitreal injections can be performed under consideration of a simulated vitrectomy.
Minimally spaced electrode positions for multi-functional chest sensors: ECG and respiratory signal estimation
Authors: Klum Michael , Minn Tobias , Tigges Timo , Pielmus Alexandru-Gabriel , Orglmeister Reinhold
Published: December 2016

Unobtrusive medical instrumentation is a key in continuous patient monitoring. To increase compliance, multi-functional sensor concepts and measurement sites different from gold-standards are used. In this work, we aim to combine both approaches. We focus on minimally spaced electrode positions with high signal correlations to gold-standards. We present twofold experimental data from six and eleven healthy volunteers and provide chest positions with individual correlations up to 0.83 ± 0.06 for ECG and 0.73 ± 0.28 for the respiratory frequency. Using a performance index, we assess positions with correlations up to 0.77 ± 0.12 for ECG and 0.65 ± 0.35 for the respiratory frequency with 24 mm electrode distance.
Automated detection of alveolar arches for nasoalveolar molding in cleft lip and palate treatment
Authors: Bauer Franz X. , Gau Dominik , Guell Florian , Eblenkamp Markus , Loeffelbein Denys J.
Published: December 2016

Nasoalveolar moulding (NAM) has become a widely accepted and evidence-based treatment strategy for newborns with cleft lip and palate (CLP), attempting to reduce the cleft gap and to form an appropriately shaped alveolar arch by an intraoral patient-specific NAM plate and to erect the usually flattened nostrils towards a natural nose wing occurrence. The generation of such an appropriately shaped NAM plate requires, besides 3d information of the patient’s initially cleft lip and palate, an estimated target model of the maxilla. Previous studies showed the applicability of curve-based approaches to describe the maxilla during early infancy. We have developed an automated algorithm implemented with the programming language Python, describing the alveolar arch by an approximated ellipse. Therefore, the digitalized data sets of human maxillae were aligned to a global coordinate system with a total least square method and subsequently analyzed with the curvature-based algebraic point set surfaces (APSS) algorithm. The gathered information of height ratio and curvature allows the detection of points on the alveolar segments and therewith the fit of an ellipse describing the human maxilla. In 84.5% of 193 maxilla impressions of healthy newborns the fitted ellipses described the course of the maxilla within defined margins. Applying the algorithm to 38 newborns suffering from unilateral cleft lip and palate in 76.3% the fitted ellipses bridge the CLP alveolar segments, so that a harmonic alveolar arch can be deduced. Describing the alveolar arch by one or multiple ellipses allows (i) to automatically measure the dimensions of the maxilla, (ii) to derive a growth model during early infancy, (iii) to derive a healthy harmonic arch from CLP alveolar segments and (iv) to automatically generate a basic NAM device on the basis of the virtually modified maxilla.
Interactive monitoring system for visual respiratory biofeedback
Authors: Odenbach Robert , Boese Axel , Friebe Michael
Published: December 2016

In almost any medical procedure respiratory motion is an issue and may result in image degradation. Most currently available devices and systems, which are intended to reduce respiratory influences do not come into operation however in clinics due to their high cost and complex operation. In our paper we evaluated an interactive breath hold control system that helps flat breathing to subsequently reduce respiratory motion during signal acquisitions or procedure treatments. With that the human subjects are enabled to regulate their own breath by following visual feedback via a specially designed display. That display shows biofeedback information about the respiratory excursion through air pressure deviations measured inside an air bellows belt. The system was assessed quantitatively in a laboratory setup and qualitatively by applications in real clinical procedures. The obtained results are very promising and can be further improved with additional developments to provide an easy to use and relatively inexpensive solution for respiratory motion related imaging problems.
A passive beating heart setup for interventional cardiology training
Authors: Granegger Marcus , Aigner Philipp , Kitzmüller Erwin , Stoiber Martin , Moscato Francesco , Michel-Behnke Ina , Schima Heinrich
Published: December 2016

Realistic training of cardiologic interventions in a heart catheter laboratory is hardly achievable with simple tools and requires animal experiments. Therefore, first a simple mock circuit connected to a porcine heart mimicking the natural heart motion was developed. In a second step the setup was duplicated to drive both sides of the heart independently to generate motion and physiologic pressures and flows. Using this simple setup cardiologic interventions (arterial and ventricular septal defects ASD/VSD closure) were performed successfully and allowed realistic training under the C-arm, echocardiography, placement of catheters and repair of ASD/VSD. With the second setup flows of up to 4 l/min were achieved in both sides of the heart at maximum left and right ventricular pressures of 80 mm Hg and 30 mm Hg respectively. This method is inexpensive and represents a realistic alternative to training in animal experiments.
A service for monitoring the quality of intraoperative cone beam CT images
Authors: Heckel Frank , Schlamelcher Jan , Rotermund Hanna , Rockstroh Max , Zidowitz Stephan , Neumuth Thomas
Published: December 2016

In recent years, operating rooms (ORs) have transformed into integrated operating rooms, where devices are able to communicate, exchange data, or even steer and control each other. However, image data processing is commonly done by dedicated workstations for specific clinical use-cases. In this paper, we propose a concept for a dynamic service component for image data processing on the example of automatic image quality assessment (AQUA) of intraoperative cone beam computed tomography (CBCT) images. The service is build using the Open Surgical Communication Protocol (OSCP) and the standard for Digital Imaging and Communications in Medicine (DICOM). We have validated the proposed concept in an integrated demonstrator OR.
Parametric Study of Obstacle Geometry Effect on Mixing Performance in a Convergent-Divergent Micromixer with Sinusoidal Walls
Authors: Heshmatnezhad Fazlollah , Aghaei Halimeh , Solaimany Nazar Ali Reza
Published: December 2016

This study presents a numerical simulation through computational fluid dynamics on mixing and flow structures in convergent-divergent micromixer with a triangular obstacle. The main concept in this design is to enhance the interfacial area between the two fluids by creating a transverse flow and split, and recombination of fluids flow due to the presence of obstacles. The effect of triangular obstacle size, the number of units, changing the position of an obstacle in the mixing channel and operational parameter like the Reynolds number on the mixing efficiency and pressure drop are assessed. The results indicate that at inlet Reynolds numbers below 5, the molecular diffusion is the most important mechanism of mixing, and the mixing index is almost the same for all cases. By increasing the inlet Reynolds number above 5, mixing index increases dramatically, due to the secondary flows. Based on the simulation results, due to increasing the effect of dean and separation vortices as well as more recirculation of flow in the side branches and behind the triangular obstacle, the highest mixing index is obtained at the aspect ratio of 2 for the triangular obstacle and its position at the front of the mixing unit. Also the highest value of mixing index is obtained by six unit of mixing chamber. The effect of changing the position of the obstacle in the channel and changing the aspect ratio of the obstacle is evident in high Reynolds numbers. An increase in the Reynolds number in both cases (changing the aspect ratio and position of the obstacle) leads to pressure drop increases.
Metaphors and grammar teaching
Authors: Roche Jörg , Suñer Ferran
Published: December 2016

Despite the need for transparency and efficiency in explaining grammatical features to learners of a foreign language only very few systematic attempts have been undertaken to demonstrate the pedagogical added value of concept-based approaches to grammar instruction. The purpose of the paper is (1) to discuss the theoretical underpinnings of such an approach, to (2) present relevant theories of multimedia learning and (3) to summarize some empirical evidence on the efficiency of such an approach to language teaching and learning. The concept-based animated grammar, developed for German, uses a broad range of cognitive linguistic principles for foreign language learning in such areas as, for example, modal verbs or the passive voice.
The role of scaffolding in children’s questions: Implications for (preschool) language assessment from a usage-based perspective
Authors: Behrens Heike , Madlener Karin , Skoruppa Katrin
Published: December 2016

This article outlines a range of theoretical, empirical, and practical desiderata for the design of (preschool) language assessments that follow from recent insights into language development from a cognitive-linguistic and usage-based perspective. To assess children’s productive communicative abilities rather than their ability to judge the acceptability of complex sentences in isolation is a new perspective in language testing that requires theoretical motivation as well as operationalizable criteria for judging the appropriateness of children’s language productions, and for characterizing the properties of their language command. After a brief review of the basic rationale of current strands of preschool assessment in Germany (Section 2), the fundamental usage-based assumptions regarding children’s developing linguistic competence and their implications for the design of preschool language diagnostics are characterized (Section 3). In order to assess children’s language production, in particular its flexibility and productivity in context, a test environment needs to be created in which children are allowed to use a certain range of language in meaningful contexts. Section 4 thus zooms in on the central question of scaffolding. Section 5 presents corresponding corpus evidence for adult strategies of prompting children to elaborate their answers and for typical child responses. Sections 6 and 7 discuss the corpus-based findings with respect to their implications for the design of ( preschool) language assessment and point to further challenges.
Destabilisation, IL variation and restructuring in foreign language learning
Authors: Kounatidis Jannis
Published: December 2016

The article presents and analyses research data gathered in a German secondary school with early learners of English. Research on L2 development needs a clear and precise documentation of learner responses over a longer period of time. Accompanying learners in longitudinal settings helps to outline major processes in foreign language acquisition. Moreover, it provides a profound understanding of how learners’ IL systems develop. The underlying hypotheses are that (a) IL systems are constantly being restructured, (b) learner responses feature diverse variants indicating their attempts to figure out the target-like rule, and (c) the degree of variability reflects the learners’ difficulties with incorporating the target-like structures. The study’s focus was on the acquisition of three linguistic phenomena (the copula BE, negation and preterite formation) in a classroom setting. For each area, several questionnaires were developed, the responses were analysed both quantitatively and qualitatively, the IL development for the structure in question was determined and potential error sources were identified. The results of the study show what learners struggle with in the course of acquisition. Knowledge about probable difficulties does not only yield insights into the learners’ acquisition process, it can also improve current teaching materials, enable adequate interventions and provide the learners with appropriate tasks for practicing their language skills. The results of the study indicate that incorporating linguistic findings into the compilation process of textbooks proves constructive for second language teaching.
The Relationship between Trade Integration and Economic Growth: Case of ASEAN-5 Countries
Authors: Balasubramaniam Arunnan , Mansor Shazali Abu , Puah Chin‐Hong
Published: December 2016

This paper studies how regional trade among ASEAN-5 countries (Indonesia, Malaysia, the Philippines, Singapore, and Thailand) help in expanding the member countries’ output. This paper applies ARDL bound testing approach with instrumental variables to explore the relationship and finds that estimates is in range of 0.27–0.55 %. The paper concludes that trade integration should be promoted in order to stimulate economic growth within each country.
The current state of the creation and modernization of national geodetic and cartographic resources in Poland
Authors: Doskocz Adam
Published: December 2016

All official data are currently integrated and harmonized in a spatial reference system. This paper outlines a national geodetic and cartographic resources in Poland. The national geodetic and cartographic resources are an important part of the spatial information infrastructure in the European Community. They also provide reference data for other resources of Spatial Data Infrastructure (SDI), including: main and detailed geodetic control networks, base maps, land and buildings registries, geodetic registries of utilities and topographic maps. This paper presents methods of producing digital map data and technical standards for field surveys, and in addition paper also presents some aspects of building Global and Regional SDI.
Establishing Bias in an Expert Witness: The What, Why and How
Authors: Pal Sahana
Published: December 2016

An expert witness is one who is allowed to provide opinion testimony at trial based upon his or her specialized knowledge, training or experience, on matters that are relevant to the issues in the case and will help the fact finder to reach a decision. However, more often than not, these experts are found to be biased in several manners and thus render the exercise useless in the eyes of the Court. This paper discusses the various ways an expert can be considered to biased, the reasons behind such bias and the ways to establish bias in an expert witness.
A Novel Approach to the Design of Passive Filters in Electric Grids
Authors: Filho da Costa Castro José , Lima Lucas Ramalho , Belchior Fernando Nunes , Ribeiro Paulo Fernando
Published: December 2016

The design of shunt passive filters has been a topic of constant research since the 70’s. Due to the lower cost, passive shunt filters are still considered a preferred option. This paper presents a novel approach for the placement and sizing of passive filters through ranking solutions based on the minimization of the total harmonic distortion (THDV) of the supply system rather than one specific bus, without neglecting the individual harmonic distortions. The developed method was implemented using Matlab/Simulink and applied to a test system. The results shown that is possible to minimize the total voltage harmonic distortion using a system approach during the filter selection. Additionally, since the method is mainly based on a heurist approach, it avoids the complexity associated with of use of advanced mathematical tools such as artificial intelligence techniques. The analyses contemplate a sinusoidal voltage utility and also the condition with background distortion utility.
Real-Time Smart Grids Control for Preventing Cascading Failures and Blackout using Neural Networks: Experimental Approach for N-1-1 Contingency
Authors: Zarrabian Sina , Belkacemi Rabie , Babalola Adeniyi A.
Published: December 2016

In this paper, a novel intelligent control is proposed based on Artificial Neural Networks (ANN) to mitigate cascading failure (CF) and prevent blackout in smart grid systems after N-1-1 contingency condition in real-time. The fundamental contribution of this research is to deploy the machine learning concept for preventing blackout at early stages of its occurrence and to make smart grids more resilient, reliable, and robust. The proposed method provides the best action selection strategy for adaptive adjustment of generators’ output power through frequency control. This method is able to relieve congestion of transmission lines and prevent consecutive transmission line outage after N-1-1 contingency condition. The proposed ANN-based control approach is tested on an experimental 100 kW test system developed by the authors to test intelligent systems. Additionally, the proposed approach is validated on the large-scale IEEE 118-bus power system by simulation studies. Experimental results show that the ANN approach is very promising and provides accurate and robust control by preventing blackout. The technique is compared to a heuristic multi-agent system (MAS) approach based on communication interchanges. The ANN approach showed more accurate and robust response than the MAS algorithm.
The morphology of Shilluk transitive verbs
Authors: Remijsen Bert , Miller-Naudé Cynthia L. , Gilley Leoma G.
Published: December 2016

This paper offers a descriptive analysis of the morphology of transitive verbs in Shilluk. Shilluk is a language in which stem-internal changes, many of them suprasegmental in nature, play an important role in the morphology, alongside affixal markers. In particular, tone, vowel length, Advanced Tongue Root (ATR), vowel height, and the stem-final consonant are involved in the morphological marking of a range inflections, expressing tense-aspect-modality, valency changes, agreement, and focus. The paper lays out the inflectional marking of these operations, for each of seven classes that can be distinguished among transitive verbs. In this way, the study extends our understanding of stem-internal morphology and its development in West Nilotic languages.
Ultrastructural Study of the Synaptic Glomeruli in the Rat’s Cochlear Nucleus
Authors: Pencheva Svetla P. , Ivanov Emilyan A.
Published: December 2016

The granule cell domain of the cochlear nuclear complex contains interneurons, which are the targets for nonprimary auditory inputs from the superior olivary complex, inferior colliculus, auditory cortex, cuneate and trigeminal nuclei of the somatosensory system. The cellular targets of the non-primary projections are unknown due to a lack of information regarding postsynaptic profiles in the granule cell areas. In the present paper, we examined the synaptic relationships between a heterogeneous class of large synaptic terminals, called mossy fibers and their targets within subdivisions of the granule cell domain. During the late stage of postnatal development, we observed heterogenous groups of complex synaptic glomeruli. Using electron microscopy, we provide evidence for ultrastructural features of dendrites that receive input from the mossy fibers. The distinct synaptic relations between mossy fibers and dendrites of microneurons further imply fundamentally separate roles in processing of acoustic signals.
Effects of Long-Term Treatment with Atorvastatin and Rosuaastatin on Active Avoidance Test in Intact Rats
Authors: Georgieva-Kotetarova Maria T. , Kostadinova Ivanka I. , Delev Delian P.
Published: December 2016

Statins are widely used for treatment of hyperlipidemia. They have been shown to possess pleiotropic effects apart from their lipid-lowering activity - anti-inflammatory, immunomodulatory, and neuroprotective. Most studies suggest that statins can protect the brain against damage but it is not clear whether they improve cognitive function in patients without neuropathy. The aim of the present study was to investigate the effect of 3-month treatment with atorvastatin and rosuvastatin on learning and memory processes in rats without brain damage. Wistar rats were treated orally for 90 days with atorvastatin and rosuvastatin at a dose of 10 mg/kg b. w. in parallel with the vehicle-treated group. After that period, learning ability and memory retention was evaluated using an active avoidance test - automatic reflex conditioner (shuttle box). The learning session was carried out on 5 consecutive days. Memory retention test was performed on day 12. The following behavioral reactions were investigated: conditioned responses (avoidance), unconditioned responses (escapes), and intertrial crossings. We found increased number of conditioned responses in groups, treated with atorvastatin 10 mg/kg b.w., and with rosuvastatin 10 mg/kg b.w. during the learning session and on the memory retention test, as compared to the same-day control group. The atorvastatin-treated group showed an increased number of unconditioned responses on days 1 and 2, as compared to the control group. In the group treated with Rosuvastatin there was an increased number of escapes on days 1,2 and 4, as compared to the vehicle-treated group. Atorvastatin and rosuvastatin at a dose of 10 mg/kg b.w. improved processes of learning and memory retention after the 3-month treatment.
Late Prosthetic Vascular Graft Infections after Reconstructions on Aortoiliac Segment: An Eleven Years Experience
Authors: Beshev Lyubomir Ts. , Edreva-Besheva Valentina E. , Sredkova Mariya P. , Nguen Dobromir D.
Published: December 2016

The purpose of the study was to evaluate the frequency and etiology of late prosthetic vascular graft infections after reconstructions on aortoiliac segment. From 2001 to 2011,545 primary reconstructions were performed on 545 consecutive patients. We had 18 cases of late intracavitary graft infections in 14 of them. A total of 58 clinical specimens collected from patients before, during and after reoperation were analyzed. Pathogens were isolated using conventional methods for aerobic and anaerobic bacteria. The isolates were identified down to species level by conventional biochemical methods, VITEK 2 and mini API Systems (bioMereux, France). During an 11-year period after prosthetic grafting of the abdominal aorta and aortoiliac segment the incidence of late (more than 4 months after implantation) infection was 3.11%. The mean interval between the initial operation and development of infection was 39.2 months (range 4 to 84). Positive microbial cultures were found in 46 clinical specimens. A total of 66 microbial isolates were cultured, comprising 27 clinical strains. Gram-positive bacteria were predominant - 15 (55.55%) strains, followed by Gram-negative bacteria - 9 (3 3.33%), Candida albicans - 2 (7.4%) and Bacteroides fragilis - 1 (3.7%). In 7 cases, the infection was monobacterial, caused predominantly by Staphylococcus species. In the rest of the cases, the infections were polymicrobial, caused by association between two microbial species. Mortality rate was 35.71% (5 cases) - in 4 of them the infection was caused by association between two species of Gram-negative bacteria or between Gram-negative bacteria and Candida albicans. The incidence of late intracavitary vascular graft infection was low. The average period for development of this complication was about 3 years after reconstruction. Among the causative agents, Gram-positive microorganisms had a predominant role but infections caused by Gram-negative bacteria, especially when they were in association, had a worse outcome.
Predisposition to Thrombophilia and Hypofibrinolysis in Pulmonary Embolism: Analysis of Inherited Factors
Authors: Komsa-Penkova Regina , Tonchev Pencho T. , Kovacheva Katya S. , Georgieva Galya B. , Ivanov Yavor Y. , Ivanov Petar D. , Golemanov Georgi M. , Iliev Sergey D.
Published: December 2016

Pulmonary embolism (PE) is a relatively common cardiovascular emergency, though its exact incidence is difficult to assess. Accurate diagnosis is critical because of the high 30-day mortality in patients in whom the diagnosis is missed on admission. Doubt for PE is often raised by the presence of risk factors for venous thromboembolism (VTE), which are categorized into inherited and acquired. Among these, the importance of inherited/genetic thrombophilic factors is increasingly recognized. The most frequent markers of inherited thrombophilia are Factor V Leiden (FVL) and G2021OA prothrombin gene mutation. Among the inherited factors causal to thrombophilia, the C677T variant in methylentetrahydrofolate reductase (MTHFR) gene as well as factors like P1A1/P1A2 polymorphism in platelet glycoprotein Ilb/IIIa (P1A2) and hypofibrinolytic polymorphism 4G/4G in PAI-1 gene are discussed with controversial results. In our study, thrombophilic and hypofibrinolytic genetic variants were identified in 54.2% of 115 patients with PE. The most common significant genetic defects were FVL- 16.5% in patients versus 6.2% in controls (OR=3.102; p=0.05), G20210A PT 5.7% versus 2.1% (OR=2.983; p>0.05). P1A2 was found in 27.3% patients versus 19.9% in controls (OR= 1.523, p>0.05) and PAM 27.8% versus 22.6% (OR =1.501 p>0.05). MTHFR C677T carriage was inverse: 6.7% in patients versus 13.4% in controls. (OR=0.461 p=0.05). Of all the patients studied, 15.65% had a history of recurrent embolic incidents. The risk of recurrence was higher for the carriers of FVL and G20210A prothrombin gene mutation. The association between carriage of thrombophilic genetic factor and the early onset of the first embolic episode was found in the patients with PE. The awareness of risk factors and risk stratification is a critical issue in treatment and prevention policy. Preventive measures should be taken in particular medical conditions.
Abnormal Levels of Inflammatory and Oxidative Stress Markers in Patients with Arterial Hypertension and Diabetes Mellitus
Authors: Danovska Maya P. , Alexandrova Margarita L. , Gencheva Irena I.
Published: December 2016

Individuals with hypertension and diabetes mellitus are at high risk of cerebrovascular and cardiovascular morbidity and mortality. Recent advances in the multifactorial pathophysiology of atherogenesis provide important information about the complex interrelations between traditional risk factors, inflammation and oxidative stress in mediating all stages of atherosclerosis. The objective of the study was to determine if some inflammatory and oxidative stress markers in patients with arterial hypertension and diabetes mellitus differ from those in healthy age-matched controls. Our results revealed a significant difference in blood pro/antioxidant activities in hypertensive diabetics and the controls. The investigation of inflammatory and oxidative stress markers along with traditional risk factors proves useful in complex assessment of vascular risk and primary prophylaxis of cerebrovascular and cardiovascular events.
Popliteal Aneurysms as a Cause for Arterial Insufficiency
Authors: Beshev Lyubomir Ts. , Marinov Angel P. , Andreev Tihomir V. , Totzev Nachko I. , Velikov Valentin Ch. , Georgiev Tsvetomir G. , Grigorov Angel S. , Tsankov Boris D. , Ignatov Borislav A.
Published: December 2016

Clinical manifestations, possibilities for accurate diagnosis of popliteal aneurysms, and operative approaches applied depending on their location are presented, as well as results from treatment over a four-year period. Popliteal artery aneurysms accounted for 5.63% of all 266 cases of acute arterial insufficiency. The mean age of the patients was 68.8 years, and the male:female ratio – 4:1. In five patients (33.33%), the localization of aneurysm was unilateral. In 80% of the cases with bilateral popliteal aneurysms, the aneurysms were combined with aneurysms of other locations. The surgical technique applied was posterior approach with resection of the aneurysm and interposition of a polytetrafluoroethylene (PTFE) prosthesis. The early patency rate of the reconstructed segment was 100%. Late patency rate of the reconstructed segment was 90.9%. Despite the better late results in femoropopliteal reconstruction, we think that a posterior approach with prosthesis implantation is better because it saves the great saphenous vein. The presence of multiple aneurysms in the patients studied (80%) determined the low survival at 5 and 10 years, which makes it comparable to the results from applying the two surgical methods.
Study of the Carrier State for Five BRCA1/BRCA2 Deleterious Mutations in Bulgarian Women with Breast Cancer
Authors: Kovacheva Katia S. , Kamburova Zornica B. , Popovska Savelina L. , Ivanov Ivan N. , Simeonova Maria N. , Angelova Petia N.
Published: December 2016

Genetic testing for BRCA 1/2 mutation is a well recognized medical management tool. Identification of healthy carriers of such mutations allows effective risk reduction procedures to be performed. There is no data reported on the founder mutations in the Bulgarian population. To evaluate the contribution of genetic factors to breast cancer (BC), we investigated the carrier state of Bulgarian women with BC for five common (according to BIC database) deleterious BRCA1/2 mutations. The list of patients diagnosed with BC between January 2011 and April 2012 was obtained from the Cancer Registry of University Hospital, Pleven. Eighty-two women with BC were interviewed and a pedigree was constructed of each of them. The patients were classified into seven categories, according to personal, disease and family history. Based on the preliminary prepared selection criteria and the personal family history, we defined a target group of 33 Bulgarian women with BC. They were screened for five deleterious mutations: 5382insC in BRCA1 and 6174delT, 6079del4, 8138del5, 5946delCT in BRCA2, by DNA sequencing. The genetic analysis detected none of the tested mutations. Two polymorphic variants were found in BRCA2 gene: c.5744C>T (rs4987117, SNP database) in exonl 1E in one patient and c.7806-14T>C (rs9534262, SNP database) in exonl7 in 22 patients. In conclusion, without basic information on the founder mutations in the population, the genetic screening for the specific mutations in a small group of tested patients is ineffective.
Challenges and Variables Affecting the Success of Sentinel Lymph Node Biospy in Malignant Melanoma a 4-Year Analysis of Clinical Results
Authors: Dimitrov Dobromir D. , Kirov Veselin I. , Ignatov Borislav A. , Tsankov Boris D. , Feradova Hyuliya E. , Vutova Vasya , Hristova Silviya P. , Nanev Vasil D. , Valcheva Genoveva B. , Deliyski Tashko S.
Published: December 2016

In the last 15 years, sentinel lymph node biopsy (SLNB) for patients with malignant melanoma (MM) has been introduced into the clinical practice. Our aim was to make a retrospective analysis of clinical results in order to assess the success ratio of SLNB and the variables affecting it in MM patients, treated in the Oncology Center at the University Hospital “Dr George Stranski” - Pleven, Bulgaria for a 4-year period. A research index card was used to process the oncologic files of 82 out of 102 patients with MM, treated and monitored at the Oncology centre between 01.01.2008 and 31.12.2011. TNM-stages, Breslow and Clark levels, location, characteristics of the skin lesion, diagnostic excision, type of lymph node dissection, number of SLN, localization of SLN, etc. were registered in the index card. SLNB staging was carried out in 28 patients. Sentinel lymph nodes were found in 22 of them. The success ratio of the method was 78.6%. Histologically, metastatic SLN were found in 4 cases. The Patent Blue Dye method was used in 22 of the cases (78%). A combined radiocolloid and dye method was used in 5 cases (18%). A radiocolloid method was used in 1 case (4%) only. Our research showed that more therapeutic lymph node dissections were performed in cases of locally advanced MM, which in turn worsened the clinical results. According to our research, the SLNB success ratio depends on the precision of diagnostic excision (p=0.019), lesion location (p=0.015), Clark level (p=0.0229), mapping method (p=0.08) and the type of melanoma (p=0.088).
Evaluation of Recovery of Activities of Daily Living in Patients with Sequelae from Cerebral Vascular Disease
Authors: Vacheva Danelina E. , Simeonova Verjinia K. , Stamenov Boyko St.
Published: December 2016

Bulgaria ranks first in the world in incidence, morbidity and death associated with cerebrovascular disease. The aim of the study was to investigate, follow-up and register recovery of activities of daily living (using the toilet and maintaining personal hygiene) in patients with sequelae from cerebrovascular disease in a subacute stage, who underwent physiotherapy and rehabilitation. Sixty-one patients were included and followed up. They were given tailored physiotherapy and rehabilitation. This included kinesitherapy, occupational therapy and electrotherapy. All the patients filled in self-assessment questionnaires before and after the rehabilitation course. Major parameters were assessed, irrespective of the limb affected -dominant or non-dominant. Results were analyzed using the Wilcoxon rank test. At the end of the rehabilitation course, the Wilcoxon curves were driven to the right, confirming improvement concerning independence, irrespective of involvement of dominant or non-dominant limb.
A Rare Case of Subtentorial Arterio-Venous Malformation Case Report
Authors: Totsev Nachko I. , Andreev Tihomir V. , Danovska Maya P. , Ovcharov Mladen E.
Published: December 2016

The majority - over 80%, of arteriovenous malformations (AVMs) are supratentorial. The infratentorial AVM are uncommon and different from other intracranial AVMs in terms of history, diagnosis, treatment, prognosis, and follow up. The authors present a case of an intracranial hemorrhage, caused by rupture of an AVM in the posterior cranial fossa. Native (unenhanced) CT and computed tomography angiography (CTA) images of this rare location of AVM are presented.
Internal Incarceration of Left Paraduodenal Hernia with Necrosis of Proximal Jejunum and Atypical Reconstruction of the Passage: A Case Report
Authors: Tonchev Pentcho T. , Iliev Sergei D. , Presolski Ivailo M.
Published: December 2016

Internal hernias are rare and most of them are diagnosed intraoperatively. We present a case of a 53-year-old man with proximal intestinal obstruction, caused by incarcerated internal hernia. During the operation, a proximal portion of 40 cm of the jejunum was found herniated and strangulated in the lesser sac through an opening of the transverse mesocolon. The jejunum was necrotic and local purulent peritonitis was present. After resection of the proximal 40 cm of the jejunum, the passage was restored using an unconventional approach. The distal duodenum was closed and, to protect the stump, the duodenum was ligated between its second and third parts. A latero-lateral anastomosis was made between the first part of duodenum and the jejunum. Anatomical, clinical and radiological findings, diagnosis and treatment of paraduodenal hernias are discussed in brief.
Preliminary Data from a Study on Polymorphism RS4244285 of P4502c19 Cytochrome Gene in Patients with Acute Coronary Syndrome, Undergoing Treatment with Dual Antiplatelet Therapy With Clopidogrel and Aspirin
Authors: Kovacheva Katya S. , Nikolova Petya A. , Hristov Valentin V. , Pendicheva Diana I. , Marchev Sotir T. , Rashev Tihomir R. , Golemanov Georgi M. , Kamburova Zornica B. , Simeonova Maria N. , Marev Rusi G.
Published: December 2016

Administration of antiplatelet therapy Aspirin and Clopidogrel (CLP) is a corner stone inpatients with Acute Coronary Syndrome (ACS) undergoing Percutaneous Coronary Intervention (PCI) with/without stent implantation. The CYP2C19*2 allele is the most important genetic variant determining response to CLP. We aim to investigate frequency of CYP2C19*2 polymorphism in patients with ACS and significance for the individual response to CLP therapy. The preliminary data of a study including a total of 120 patients with ACS undergoing PCI with stent placement and treated with dual antiplatelet therapy (CLP and Aspirin) are presented. So far 18 patients (41-81 year age) are tested for CYP2C19*l/*2 polymorphisms. The genotype CYP2C19*1/*1; CYP2C19*l/*2 and CYP2C19*2/*2 is demonstrated in 50%, 33%, 17% respectively, of the patients. The established frequency of CYP2C 19*2 allele (33%) is significantly higher (x2=5.220; p=0.022) than in healthy Bulgarian individuals (16%). In-stent thrombosis have developed 3 (17%) of patients: 2 are C YP2C19* l/*2 carriers, and 1 - homozygous CYP2C19*2/*2. The preliminary data demonstrate high prevalence of CYP2C19*2 polymorphism in patients with ACS and point to significance of the variant for CLP therapy. Further extension of the study with larger samples and monitoring of the patients are required to determine the effects of the polymorphism on the prognosis for major adverse cardiovascular events.