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Search Results: 1 - 10 of 698 matches for " Tamas Szili-Torok "
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Dynamic three-dimensional echocardiography combined with semi-automated border detection offers advantages for assessment of resynchronization therapy
Tamas Szili-Torok, Boudewijn J Krenning, Marco M Voormolen, Jos RTC Roelandt
Cardiovascular Ultrasound , 2003, DOI: 10.1186/1476-7120-1-14
Abstract: Simultaneous electrical stimulation of both ventricles in patients with interventricular conduction disturbance and advanced heart failure improves hemodynamics and results in increased exercise tolerance, quality of life [1-3]. Reduction in morbidity and mortality was recently reported.We have developed a novel technique for the assessment and optimization of resynchronization therapy. Our approach is based on transthoracic dynamic three-dimensional (3D) echocardiography and allows determination of the most delayed contraction site of the left ventricle (LV) together with global LV function data. We use a self-developed fast rotating transducer, which is connected to a commercially available ultrasound system (GE Vingmed Vivid FiVe, Horton, Norway). The 64-element phased-array transducer has a center frequency of 3 MHz, second harmonic capabilities and continuously rotates inside the transducer assembly at 8-revolutions/ sec. During resynchronization device implantation, images are obtained with the patient in the left lateral decubitus position with the transducer in the apical position and the image plane rotating around the LV long axis. Images are acquired in sinus rhythm and in two different pacing modes: during right ventricular apical pacing and biventricular pacing. With a self-developed software, using MatLab (The MathWorks, Inc, Natick, MA, USA), the original 2D images are post-processed by placing them in their correct spatial and temporal (ECG reference) position using multi beat data fusion. All the cross-sectional images re-sampled from each dataset are subsequently imported into the TomTec? 4D LV-analysis software (TomTec? Imaging Systems GmbH, Germany) for automated endocardial border detection.Subsequently, the program performs a dynamic surface rendered endocardial reconstruction of the LV in sinus rhythm and in the different pacing modes. For each pacing mode, a time volume curve (TVC) is plotted from which global end-diastolic (LVEDV), end-systo
Mid-term echocardiographic follow up of left ventricular function with permanent right ventricular pacing in pediatric patients with and without structural heart disease
Tchavdar Shalganov, Dora Paprika, Radu Vatasescu, Attila Kardos, Attila Mihalcz, Laszlo Kornyei, Andras Szatmari, Tamas Szili-Torok
Cardiovascular Ultrasound , 2007, DOI: 10.1186/1476-7120-5-13
Abstract: A group of 99 pediatric patients with previously implanted pacemaker was studied retrospectively. Forty-three patients (21 males) had isolated congenital complete or advanced atrioventricular block. The remaining 56 patients (34 males) had pacing indication in the presence of structural heart disease. Thirty-two of them (21 males) had isolated structural heart disease and the remaining 24 (13 males) had complex congenital heart disease. Patients were followed up for an average of 53 ± 41.4 months with 12-lead electrocardiogram and transthoracic echocardiography. Left ventricular shortening fraction was used as a marker of ventricular function. QRS duration was assessed using leads V5 or II on standard 12-lead electrocardiogram.Left ventricular shortening fraction did not change significantly after pacemaker implantation compared to preimplant values overall and in subgroups. In patients with complex congenital heart malformations shortening fraction decreased significantly during the follow up period. (0.45 ± 0.07 vs 0.35 ± 0.06, p = 0.015). The correlation between the change in left ventricular shortening fraction and the mean increase of paced QRS duration was not significant. Six patients developed dilated cardiomyopathy, which was diagnosed 2 months to 9 years after pacemaker implantation.Chronic right ventricular pacing in pediatric patients with or without structural heart disease does not necessarily result in decline of left ventricular function. In patients with complex congenital heart malformations left ventricular shortening fraction shows significant decrease.Chronic right ventricular (RV) apical pacing alters unfavorably left ventricular (LV) electrical activation, mechanical contraction, cardiac output, myocardial perfusion and histology. Permanent RV pacing may have detrimental effect on LV function and may promote to heart failure in adult patients with LV dysfunction [1-10]. The effect of chronic RV apical pacing on LV performance in pediatric pati
Ablation lesions in Koch's triangle assessed by three-dimensional myocardial contrast echocardiography
Tamas Szili-Torok, Geert-Jan Kimman, Marcoen Scholten, Andrew Thornton, Folkert Cate, Jos Roelandt, Luc Jordaens
Cardiovascular Ultrasound , 2004, DOI: 10.1186/1476-7120-2-27
Abstract: 18 patients underwent catheter ablation of a supraventricular tachycardia and were included in this prospective single-blind study. Twelve patients were ablated inside Koch's triangle and 6, who served as controls, outside this area. Three-dimensional echocardiography of Koch's triangle was performed before and after the ablation procedure in all patients, using respiration and ECG gated pullback of a 9 MHz ICE transducer, with and without continuous intravenous echocontrast infusion (SonoVue, Bracco). Two independent observers analyzed the data off-line.MCE identified ablation lesions as a low contrast area within the normal atrial myocardial tissue. Craters on the endocardial surface were seen in 10 (83%) patients after ablation. Lesions were identified in 11 out of 12 patients (92%). None of the control patients were recognized as having been ablated. The confidence score of the independent echo reviewer tended to be higher when the number of applications increased.1. MCE allows direct visualization of ablation lesions in the human atrial myocardium. 2. Both RF and cryo energy lesions can be identified using MCE.Catheter ablation is a curative treatment for most patients with arrhythmias. In some patients, the results are still suboptimal[1] because of inadequate lesion formation during ablation. Therefore, in these patients direct visualization of ablation lesions may have significant impact on the outcome of the ablation procedures. Direct visualization can also provide additional information for both the development and testing of new dedicated ablation tools. Intracardiac echocardiography (ICE) has been extensively investigated for this purpose [2-6], but the reported results are disappointing[5,7]. Recently, myocardial contrast echocardiography (MCE) has been tested for visualization of ablation lesions in animals in the left ventricle during continuous intracoronary echocontrast infusion[8]. The aim of the present study was to assess the potential use of MC
The Effects Of Right Ventricular Apical Pacing On Left Ventricular Function: Stimulation Of The Right Ventricular Apex: Should It Still Be The Gold Standard?
T Szili-Torok,Thornton A
Indian Pacing and Electrophysiology Journal , 2003,
Abstract: Current pacing practice is undergoing continuous and substantial changes. Initially pacing had an exclusively palliative role, since it was reserved for patients developing complete heart block or severe symptomatic bradycardia. With the appearance of novel pacing indications such as pacing for heart failure and atrial fibrillation, the effect of pacing site on cardiac function has become a critically important issue and a subject for consideration. It seems that the classical pacing site in the right ventricular apex is no longer the gold standard because of possible disadvantageous effects on cardiac function. The aim of this review article is to discuss the effect of right ventricular apical pacing on cardiac function including cellular and hemodynamic changes. We also aim to discuss the role of alternative pacing sites in the light of cardiac function.
Visualization of elusive structures using intracardiac echocardiography: Insights from electrophysiology
T Szili-Torok, EP McFadden, LJ Jordaens, JRTC Roelandt
Cardiovascular Ultrasound , 2004, DOI: 10.1186/1476-7120-2-6
Abstract: During the last two decades revolutionary diagnostic and therapeutic changes were implemented in the management of patients with arrhythmias. The development of transcatheter ablation provided a curative treatment of most supraventricular tachyarrhythmias including atrioventricular (AV) and AV nodal reentry tachycardias and more recently atrial flutters. Life threatening ventricular arrhythmias are effectively palliated by implantable anti-tachycardia devices and conduction disorders treated by pacemakers, with instantaneous improvement. New challenges are the effective treatment of patients with atrial fibrillation, which is the most frequent and often disabling arrhythmia and the curative treatment of patients with life threatening arrhythmias. The development of novel ablative procedures are currently being investigated but the success rate still remains suboptimal. Since the arrhythmia substrate is frequently associated with certain anatomical structures or morphological variants, improved imaging has increasing role in the improvement of these treatments. Furthermore, novel catheter ablation approaches require catheter placement to sites, which may be associated with increased complication risk. Therefore imaging has a crucial role both in guiding and improving safety of electrophysiology (EP) procedures. Also, thromboembolic risk stratification, fine-tuning of the implanted sophisticated devices require advanced and effective imaging techniques as does their follow-up.Electrophysiological mapping and ablation techniques are increasingly used to diagnose and treat many types of supraventricular and ventricular tachycardias. These procedures require an intimate knowledge of intracardiac anatomy and their use has led to a renewed interest in visualization of specific structures [1-3]. This has required collaborative efforts from imaging as well as electrophysiology experts. Classical imaging techniques may be unable to visualize structures involved in arrhythmia
Orientational order and alignment of elongated particles induced by shear
Tamas Borzsonyi,Balazs Szabo,Gabor Toros,Sandra Wegner,Janos Torok,Ellak Somfai,Tomasz Bien,Ralf Stannarius
Physics , 2012,
Abstract: Shear induced alignment of elongated particles is studied experimentally and numerically. We show that shear alignment of ensembles of macroscopic particles is comparable even on a quantitative level to simple molecular systems, despite the completely different types of particle interactions. We demonstrate that for dry elongated grains the preferred orientation forms a small angle with the streamlines, independent of shear rate across three decades. For a given particle shape, this angle decreases with increasing aspect ratio of the particles. The shear-induced alignment results in a considerable reduction of the effective friction of the granular material.
Shear induced alignment and dynamics of elongated granular particles
Tamas Borzsonyi,Balazs Szabo,Sandra Wegner,Kirsten Harth,Janos Torok,Ellak Somfai,Tomasz Bien,Ralf Stannarius
Physics , 2012,
Abstract: The alignment, ordering and rotation of elongated granular particles was studied in shear flow. The time evolution of the orientation of a large number of particles was monitored in laboratory experiments by particle tracking using optical imaging and x-ray computed tomography. The experiments were complemented by discrete element simulations. The particles develop an orientational order. In the steady state the time and ensemble averaged direction of the main axis of the particles encloses a small angle with the streamlines. This shear alignment angle is independent of the applied shear rate, and it decreases with increasing grain aspect ratio. At the grain level the steady state is characterized by a net rotation of the particles, as dictated by the shear flow. The distribution of particle rotational velocities was measured both in the steady state and also during the initial transients. The average rotation speed of particles with their long axis perpendicular to the shear alignment angle is larger, while shear aligned particles rotate slower. The ratio of this fast/slow rotation increases with particle aspect ratio. During the initial transient starting from an unaligned initial condition, particles having an orientation just beyond the shear alignment angle rotate opposite to the direction dictated by the shear flow.
Interactions between Bacillus anthracis and Plants May Promote Anthrax Transmission
Holly H. Ganz ,Wendy C. Turner,Eoin L. Brodie,Martina Kusters,Ying Shi,Heniritha Sibanda,Tamas Torok,Wayne M. Getz
PLOS Neglected Tropical Diseases , 2014, DOI: 10.1371/journal.pntd.0002903
Abstract: Environmental reservoirs are essential in the maintenance and transmission of anthrax but are poorly characterized. The anthrax agent, Bacillus anthracis was long considered an obligate pathogen that is dormant and passively transmitted in the environment. However, a growing number of laboratory studies indicate that, like some of its close relatives, B. anthracis has some activity outside of its vertebrate hosts. Here we show in the field that B. anthracis has significant interactions with a grass that could promote anthrax spore transmission to grazing hosts. Using a local, virulent strain of B. anthracis, we performed a field experiment in an enclosure within a grassland savanna. We found that B. anthracis increased the rate of establishment of a native grass (Enneapogon desvauxii) by 50% and that grass seeds exposed to blood reached heights that were 45% taller than controls. Further we detected significant effects of E. desvauxii, B. anthracis, and their interaction on soil bacterial taxa richness and community composition. We did not find any evidence for multiplication or increased longevity of B. anthracis in bulk soil associated with grass compared to controls. Instead interactions between B. anthracis and plants may result in increased host grazing and subsequently increased transmission to hosts.
Evolution of shear zones in granular materials
Balazs Szabo,Janos Torok,Ellak Somfai,Sandra Wegner,Ralf Stannarius,Axel Bose,Georg Rose,Frank Angenstein,Tamas Borzsonyi
Physics , 2014, DOI: 10.1103/PhysRevE.90.032205
Abstract: The evolution of wide shear zones (or shear bands) was investigated experimentally and numerically for quasistatic dry granular flows in split bottom shear cells. We compare the behavior of materials consisting of beads, irregular grains (e.g. sand) and elongated particles. Shearing an initially random sample, the zone width was found to significantly decrease in the first stage of the process. The characteristic shear strain associated with this decrease is about unity and it is systematically increasing with shape anisotropy, i.e. when the grain shape changes from spherical to irregular (e.g. sand) and becomes elongated (pegs). The strongly decreasing tendency of the zone width is followed by a slight increase which is more pronounced for rod like particles than for grains with smaller shape anisotropy (beads or irregular particles). The evolution of the zone width is connected to shear induced density change and for nonspherical particles it also involves grain reorientation effects. The final zone width is significantly smaller for irregular grains than for spherical beads.
Developing an explanatory model for the process of online radicalisation and terrorism
Robyn Torok
Security Informatics , 2013, DOI: 10.1186/2190-8532-2-6
Abstract: While the use of the internet and social media as a tool for extremists and terrorists has been well documented, understanding the mechanisms at work has been much more elusive. This paper begins with a grounded theory approach guided by a new theoretical approach to power that utilizes both terrorism cases and extremist social media groups to develop an explanatory model of radicalization. Preliminary hypotheses are developed, explored and refined in order to develop a comprehensive model which is then presented. This model utilizes and applies concepts from social theorist Michel Foucault, including the use of discourse and networked power relations in order to normalize and modify thoughts and behaviors. The internet is conceptualized as a type of institution in which this framework of power operates and seeks to recruit and radicalize. Overall, findings suggest that the explanatory model presented is a well suited, yet still incomplete in explaining the process of online radicalization.
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