National Repository of Grey Literature 13 records found  1 - 10next  jump to record: Search took 0.00 seconds. 
Arrhythmias in Pulmonary Hypertension
Dusík, Milan ; Havránek, Štěpán (advisor) ; Petrák, Ondřej (referee) ; Honěk, Jakub (referee)
Pulmonary hypertension (PH) is defined by the elevation of the mean pulmonary artery pressure above 20 mmHg. PH affects about 1% of population. Based on the similar pathophysiological mechanisms, clinical and hemodynamic characteristics, and therapeutic possibilities, PH is classified into 5 groups. Right heart catheterization is a crucial assessment to establish the diagnosis. Supraventricular tachycardias (SVTs), including atrial fibrillation (AF) and other atrial tachycardias (AT), are frequently found in patients with PH with a reported cumulative incidence of 10-36 %. The presence of an SVT in a PH patient leads to further deterioration and worsens the prognosis. This thesis is based on four distinct analyses focused on the SVTs in PH. The first analysis described the arrhythmias in patients with chronic thromboembolic pulmonary hypertension. The prevalence of AF/AT reached 29% and their presence was associated with reduced functional capacity. Despite the improved hemodynamics, the incidence of arrhythmias rose significantly after the pulmonary endarterectomy. The second analysis retrospectively studied the SVT prevalence and its association with PAWP values in patients with pre-capillary PH. Patients with PAWP above 11mmHg had higher arrhythmia prevalence, possibly because of the involvement...
Catheter-based left atrial appendage closure
Hozman, Marek ; Osmančík, Pavel (advisor) ; Bulava, Alan (referee) ; Havránek, Štěpán (referee)
Transseptal puncture in left atrial appendage closure guided by 3D printing and multiplanar CT reconstruction Abstract Introduction: The presented study investigates the application of bi-atrial 3D printed models to guide transseptal puncture (TSP) in left atrial appendage occlusion (LAAC). The objectives are to (1) test the feasibility of 3D printing (3DP) for TSP guidance, (2) analyse the distribution of the optimal TSP locations, and (3) define a CT-derived 2D parameter suitable for predicting the optimal TSP locations. Methods: Pre-procedural planning included multiplanar CT reconstruction, 3D segmentation, and 3DP. TSP was pre-procedurally simulated in vitro at six defined sites. Based on the position of the sheath, TSP sites were classified as optimal, sub-optimal, or non-optimal. The aim was to target the TSP in the recommended position during the procedure. Procedure progress was assessed post hoc by the operator. Results: Of 68 screened patients, 60 patients in five centres (mean age of 74.68 ± 7.64 years, 71.66% males) were prospectively analysed (3DP failed in one case, and seven patients did not finally undergo the procedure). In 55 patients (91.66%), TSP was performed in the optimal location as recommended by the 3DP. The optimal locations for TSP were postero-inferior in 45.3%, mid-inferior in...
The effect of nutritional intervention in patients with obesity and atrial fibrillation
Buzická, Julie ; Souza Lopes, Kristýna (advisor) ; Havránek, Štěpán (referee)
Introduction: Due to its high and increasing prevalence, obesity is among the most prevalent and one of the most serious risk factors for cardiovascular diseases. It is well established that there is an epidemiological link between obesity and atrial fibrillation and the risk of atrial fibrillation increases with increasing BMI. Studies show that weight reduction combined with antiarrhythmic drug therapy has a good effect in the treatment of atrial fibrillation in some patients. Nutritional intervention is an important part of the treatment of obesity and for this reason this paper focuses on its effect. Objectives: The aim of this theses is to evaluate the effect of individual nutritional intervention using telemedicine in obese patients with atrial fibrillation on the intake of total energy, individual major nutrients and fibre. In addition, the development of body weight and adipose tissue mass over a 6 month period should be evaluated. A secondary objective is to evaluate the exercise intervention based on the number of steps per day. Methods: Data were collected on III. Department of Internal Medicine, Department of Endocrinology and Metabolism, 1st Faculty of Medicine, Charles University and General University Hospital in Prague, in the outpatient clinic of dietitians. The study included...
Genetic Algorithms driven by MCTS
Havránek, Štěpán ; Hric, Jan (advisor) ; Moudřík, Josef (referee)
Evolutionary and genetic algorithms are problem-solving methods designed according to a nature inspiration. They are used for solving hard problems that we cannot solve by any efficient specialized algorithm. The Monte Carlo method and its derivation the Monte Carlo Tree Search (MCTS) are based on sampling and are also commonly used for too complex problems, where we are dealing with enormous memory consumption and it is impossible to perform a complete searching. The goal of this thesis is to design a general problem solving method that is built from these two completely different approaches. We explain and implement the new method on one example problem: the Traveling salesman problem (TSP). Second part of this thesis contains various tests and experiments. We compare different settings and parametrizations of our method. The best performing variant is then compared with the classical evolutionary TSP solution or, for example, with greedy algorithms. Our method shows competitive results. The best results were achieved with the cooperation of our method and the classical evolutionary TSP solution. This union shows better results than any of its parts separately, which we find as a great success.
Financial stability and the impact of instability on the real economy
Havránek, Štěpán ; Hlaváček, Michal (advisor) ; Mertlík, Pavel (referee)
This thesis focuses on the problematic of financial stability - its maintenance and the detection of possible sources of instability. In the first theoretical part, a summary of the role of financial stability for properly working financial system is followed by identification of threats to stability and historical examples of instability. The thesis continues with an analysis of the recent subprime crisis. In the second empirical part, vector autoregression is used to estimate interconnections between financial instability indicators. This is followed by impulse response analysis. Although some assumed relationships are affirmed, their scop does not answer the fundamental question: why do values of these indicators change so vigorously during the time of distress.
Pathophysiological consequences of different cardiac support regimens in cardiorespiratory insufficiency
Lacko, Stanislav ; Kittnar, Otomar (advisor) ; Havránek, Štěpán (referee) ; Rohn, Vilém (referee)
Introduction: Veno-arterial extracorporeal membrane oxygenation (VA ECMO) is a rapidly applicable type of mechanical circulatory support that overcomes acute hemodynamic breakdowns, whether in acute or chronic heart failure or cardiac arrest. In recent years, the method has seen a very significant increase in use. VA ECMO can fully replace the function of the heart and lungs, delivering about 5 l / min of fully saturated blood. However, the method is burdened with a number of risks. Currently much-discussed issue is the effect of circulatory support on left ventricular residual function as VA ECMO increases its work and the risk of developing left ventricular distension and subsequent pulmonary edema. A detailed analysis of these pathophysiological mechanisms is a key objective of this work. Methods: The focus of the work is three series of experiments on a large biomodel (domestic pig). First, we developed a new model of acute hypoxic-ischemic heart failure by proximal occlusion of one of the main branches of the left coronary artery with a balloon catheter with a lumen for controlled perfusion of deoxygenated venous blood behind the balloon. Furthermore, we monitored the hemodynamic response and energy parameters in detail in the porcine biomodel of acute and chronic heart failure with a gradual...
Hemodynamic adaptation mechanisms of heart failure to percutaneous venoarterial extracorporeal circulatory support
Hála, Pavel ; Kittnar, Otomar (advisor) ; Szárszoi, Ondrej (referee) ; Havránek, Štěpán (referee)
Introduction: Venoarterial extracorporeal membrane oxygenation (VA ECMO) is widely used in the treatment of circulatory failure, but repeatedly, its negative effects on the left ventricle (LV) have been observed. The purpose of this study is to assess the influence of ex- tracorporeal blood flow (EBF) on systemic hemodynamic changes and LV performance parameters during VA ECMO therapy of decompensated heart failure. Methods: Porcine models of low-output chronic and acute heart failure were developed by long-term fast cardiac pacing and coronary hypoxemia, respectively. Profound signs of circulatory decompensation were defined by reduced cardiac output and tissue hypoperfusion. Sub- sequently, under total anesthesia and artificial ventilation, VA ECMO was introduced. LV performance and organ specific parameters were recorded at different levels of EBF using an LV pressure-volume loop analysis, arterial flow probes on carotid and subclavian arteries, and transcutaneous probes positioned to measure cerebral and forelimb regional tissue oxygen saturations. Results: Conditions of severely decompensated heart failure led to systemic hypotension, low tissue and mixed venous oxygen saturations, and increase in LV end-diastolic pressure. By increasing the EBF from minimal flow to 5 L/min, we observed a...
Using of non-invasive cardiac imaging for precise evaluation of atrium size and prediction of atrial wall fibrosis in patients with atrial fibrillation
Fingrová, Zdeňka ; Havránek, Štěpán (advisor) ; Kittnar, Otomar (referee) ; Skála, Tomáš (referee)
Atrial fibrillation is the most prevalent arrhythmia worldwide and remains one of the major causes of morbidity and mortality. Atrial fibrillation is an arrhythmia that has a various etiology and takes number of clinical forms. Due to the heterogenity of atrial fibrillation, it is necessary to individualize the optimal treatment strategy, ie conservative pharmacological therapy or interventional therapy as catheter ablation. Inncorrect indication of catheter ablation of atrial fibrillation leads to low success rate of the procedure and increases the risk of the procedure. The success rate of catheter ablation of atrial fibrillation depends on many clinical parameters, including the size and volume of the left atrium and the presence of pathological tissue in the atrial myocardium. In everyday practice, echocardiography (2D-echocardiography) is the most dominant method in estimation of the left atrial parameters, for it's simplicity, non- invasiveness, financial costs and the absence of ionizing radiation. Different methods for assesment of left atrial parameters are cardiac CT, cardiac magnetic resonance imaging and methods of 3-D echocardiography or 3-D angiography. The results of the present studies show that in patients with non-valvular atrial fibrillation who are indicated for catheter...
Genetic Algorithms driven by MCTS
Havránek, Štěpán ; Hric, Jan (advisor) ; Moudřík, Josef (referee)
Evolutionary and genetic algorithms are problem-solving methods designed according to a nature inspiration. They are used for solving hard problems that we cannot solve by any efficient specialized algorithm. The Monte Carlo method and its derivation the Monte Carlo Tree Search (MCTS) are based on sampling and are also commonly used for too complex problems, where we are dealing with enormous memory consumption and it is impossible to perform a complete searching. The goal of this thesis is to design a general problem solving method that is built from these two completely different approaches. We explain and implement the new method on one example problem: the Traveling salesman problem (TSP). Second part of this thesis contains various tests and experiments. We compare different settings and parametrizations of our method. The best performing variant is then compared with the classical evolutionary TSP solution or, for example, with greedy algorithms. Our method shows competitive results. The best results were achieved with the cooperation of our method and the classical evolutionary TSP solution. This union shows better results than any of its parts separately, which we find as a great success.
3D akční hra v podivném městě
Havránek, Štěpán ; Balyo, Tomáš (advisor) ; Hauzar, David (referee)
This thesis deals with a conception and implementation of a real-time 3D action game. This game is placed in a bizzare surrounding that is not a subset of an ordinary real three- dimensional linear space. The work presents the whole game implementation process. It goes through various sets of techniques, algorithms and data structures used or considered during the development. It also describes different ways of solving specified problems and the choices between them. Moreover there are artificial beings situated in the town inside the surrounding. The player's goal is to capture the whole city. There is also an opponent, who systematically plans his tasks and tries to possess the city as well.

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