Tesi sul tema "Cardiac health measurements"

The dependence of cardiac output measurement precision on ambient temperature and cardiac output stability was assessed by concurrent continuous and bolus thermodilution methods in postoperative cardiac surgery patients. The degree of agreement between the two methods was depended on room temperature (0.1 L/min for each degree below 25 degrees C). The agreement was also closer in trials where cardiac output was stable (< 10% variation). The continuous thermodilution method shows sufficient agreement with the bolus method for use in critical care; however, improved precision of cardiac output thermodilution measurements can be achieved by use of correction factors for cardiac instability and for ambient temperature.

In this thesis, a novel graphene (GN) based electrocardiogram (ECG) sensor is designed, constructed and tested to validate the concept of coating GN, which is a highly electrically conductive material, on Ag substrates of conventional electrodes. The background theory, design, experiments and results for the proposed GN-based ECG sensor are also presented. Due to the attractive electrical and physical characteristics of graphene, a new ECG sensor was investigated by coating GN onto itself. The main focus of this project was to examine the effect of GN on ECG monitoring and to compare its performance with conventional methods. A thorough investigation into GN synthesis on Ag substrate was conducted, which was accompanied by extensive simulation and experimentation. A GN-enabled ECG electrode was characterised by Raman spectroscopy, scanning electron microscopy along with electrical resistivity and conductivity measurements. The results obtained from the GN characteristic experimentation on Raman spectroscopy, detected a 2D peak in the GN-coated electrode, which was not observed with the conventional Ag/AgCl electrode. SEM characterisation also revealed that a GN coating smooths the surface of the electrode and hence, improves the skin-to-electrode contact. Furthermore, a comparison regarding the electrical conductivity calculation was made between the proposed GN-coated electrodes and conventional Ag/AgCl ones. The resistance values obtained were 212.4 Ω and 28.3 Ω for bare and GN-coated electrodes, respectively. That indicates that the electrical conductivity of GN-based electrodes is superior and hence, it is concluded that skin-electrode contact impedance can be lowered by their usage. Additional COMSOL simulation was carried out to observe the effect of an electrical field and surface charge density using GN-coated and conventional Ag/AgCl electrodes on a simplified human skin model. The results demonstrated the effectiveness of the addition of electrical field and surface charge capabilities and hence, coating GN on Ag substrates was validated through this simulation. This novel ECG electrode was tested with various types of electrodes on ten different subjects in order to analyse the obtained ECG signals. The experimental results clearly showed that the proposed GN-based electrode exhibits the best performance in terms of ECG signal quality, detection of critical waves of ECG morphology (P-wave, QRS complex and T-wave), signal-to-noise ratio (SNR) with 27.0 dB and skin-electrode contact impedance (65.82 kΩ at 20 Hz) when compared to those obtained by conventional a Ag/AgCl electrode. Moreover, this proposed GN-based ECG sensor was integrated with core body temperature (CBT) sensor in an ear-based device, which was designed and printed using 3D technology. Subsequently, a finger clipped photoplethysmography (PPG) sensor was integrated with the two-sensors in an Arduino based data acquisition system, which was placed on the subject's arm to enable a wearable multiple physiological measurement system. The physiological information of ECG and CBT was obtained from the ear of the subject, whilst the PPG signal was acquired from the finger. Furthermore, this multiple physiological signal was wirelessly transmitted to the smartphone to achieve continuous and real-time monitoring of physiological signals (ECG, CBT and PPG) on a dedicated app developed using the Java programming language. The proposed system has plenty of room for performance improvement and future development will make it adaptabadaptable, hence being more convenient for the users to implement other applications than at present.

Physical inactivity is a significant health concern for individuals in the United States, and is especially an issue for those with a history of coronary artery disease. Increased physical activity is encouraged for those who are participants in Phase III cardiac rehabilitation to promote a healthy lifestyle after a cardiac event. The purpose of the study was to assess and characterize the physical activity levels of Phase III cardiac patients. Other objectives of this study were to compare various forms of physical activity assessment and compare the activity levels of the cardiac rehabilitation participants with other populations. Comparisons of three physical activity devices were analyzed as well as activity levels on rehab and non-rehab days. Those who participated in home exercise vs. those who did not do home exercise were compared as well as those who were retired vs. those who were employed. Subject inclusion criteria included Phase III cardiac patients who were 40-69 years of age and who attended rehab a minimum of two days per week. The subjects were required to wear a pedometer and accelerometer for at least 12 days and complete a questionnaire following the trial. The mean ± S. D. for age, height, weight and BMI of the subjects was 59.4±8.2 years, 69.1±3.1 inches, 200.9±41.8 lbs., and 29.4±4.8 kg/m2 respectively. The Lifecorder, ActiGraph and International Physical Activity Questionnaire (IPAQ) were used to measure physical activity levels of the Phase III cardiac patients. The IPAQ did not correlate well with the Lifecorder or ActiGraph in assessing physical activity in Phase III cardiac patients (R=0.251, P=0.226-ActiGraph and R=0.280, P=0.175-Lifecorder), however, the Lifecorder and the ActiGraph had a significant correlation coefficient with one another (R=0.83, P<0.001). Rehab vs. non-rehab day data as well as rehab session and non-rehab session physical activity levels were compared among the subjects. On a rehab day, subjects took 9,770±3132 steps/day, which was significantly higher than what they took on a non-rehab day, 5,404±2843 steps/day. Those who did not exercise at home accumulated on average 8,194±2912 steps/day on a rehab day, while on a non-rehab day they accumulated 3,475±1579 steps/day (P<0.001). Those who did exercise at home, took 10,883±2856 steps/day on a rehab day, while on a non rehab day they took 6,767±2768 steps/day (P<0.001). Those who were employed were more active than those who were retired. In conclusion, Phase III cardiac rehabilitation is an effective way to increase physical activity levels of those with a history of coronary artery disease. All participants in Phase III cardiac rehabilitation should be encouraged to come into the center-based facility at least 4-5 days per week or implement a home exercise program into their weekly regimen.
School of Physical Education, Sport, and Exercise Science

Introduction. Quantitative myocardial perfusion measurements using positron emission tomography (PET) can be improved by introducing diagnostic tracers at a constant rate of activity. 82Rb can be produced cost effectively by eluting a 82Sr/82Rb generator with saline; however, it exhibits an undesirable, but reproducible, activity rate variation. Previously, a threshold-comparison algorithm controlled saline flow through either generator or bypass line using an on/off valve, to simulate constant-activity elutions. Methods. In this work a mechanical system and control software is developed to control tracer infusion. The valve is cycled at 5Hz and its duty-cycle controlled by a predictive-corrective algorithm in order to reduce measurable activity rate fluctuations. Results. Precision increases (RMS error improves from >40% to ∼14%) as does the range of relative activities that can be eluted from the generator. Conclusion. The proposed method demonstrates superior precision and flexibility. However, further tests must be conducted to ensure that the precision of the system does not deteriorate over time.

Dissertação (mestrado)—Universidade de Brasília, Faculdade de Tecnologia, Departamento de Engenharia Elétrica, 2016.
Conforme o sangue flui através do corpo de um indivíduo, ele muda a forma como a luz é irradiada pela pele, pois o sangue absorve luz de forma diferente dos outros tecidos. Essa sutil variação pode ser capturada por uma câmera e ser usada para monitorar a atividade cardíaca de uma pessoa. O sinal capturado pela câmera é uma onda que representa as variações de tonalidade da pele ao longo do tempo. A frequência dessa onda é a mesma frequência na qual o coração bate. Portanto, o sinal capturado pela câmera pode ser usado para estimar a taxa cardíaca de uma pessoa. Medir o pulso cardíaco remotamente traz mais conforto pois evita o uso de eletrodos. Também permite o monitoramento de uma pessoa de forma oculta para ser empregado em um detector de mentira, por exemplo. Neste trabalho nós propomos dois algoritmos para a estimação da taxa cardíaca sem contato usando câmeras convencionais sob iluminação não controlada. O primeiro algoritmo proposto é um método simples que emprega um detector de face que identifica a face da pessoa sendo monitorada e extrai o sinal gerado pelas mudanças no tom da pele devido ao fluxo sanguíneo. Este algoritmo emprega um filtro adaptativo para aumentar a energia do sinal de interesse em relação ao ruído. Nós mostramos que este algoritmo funciona muito bem para vídeos com pouco movimento. O segundo algoritmo que propomos é uma melhora do primeiro para torná-lo mais robusto a movimentos. Nós modificamos o método usado para definir a região de interesse. Neste algoritmo é utilizado um detector de pele para eliminar pixels do plano de fundo do vídeo, os frames dos vídeos são divididos em micro-regiões que são rastreados com um algoritmo de fluxo ótico para compensar os movimentos e um algoritmo de clusterização é aplicado para selecionar automaticamente as melhores micro-regiões para efetuar a estimação da taxa cardíaca. Propomos também um esquema de filtragem temporal e espacial para reduzir o ruído introduzido pelo algoritmo de fluxo ótico. Comparamos os resultados dos nossos algoritmos com um oxímetro de dedo comercial e mostramos que eles funcionam bem para situações desafiadoras.
As the blood flows through the body of an individual, it changes the way that light is irradiated by the skin, because blood absorbs light differently than the remaining tissues. This subtle variation can be captured by a camera and be used to monitor the heart activity of a person. The signal captured by the camera is a wave that represents the changes in skin tone along time. The frequency of this wave is the same as the frequency by which the heart beats. Therefore, the signal captured by the camera could be used to estimate a person’s heart rate. This remote measurement of cardiac pulse provides more comfort as it avoids the use of electrodes or others devices attached to the body. It also allows the monitoring of a person in a canceled way to be employed in lie detectors, for example. In this work we propose two algorithms for non-contact heart rate estimation using conventional cameras under uncontrolled illumination. The first proposed algorithm is a simple approach that uses a face detector to identify the face of the person being monitored and extract the signal generated by the changes in the skin tone due to the blood flow. This algorithm employs an adaptive filter to boost the energy of the interest signal against noise. We show that this algorithm works very well for videos with little movement. The second algorithm we propose is an improvement of the first one to make it more robust to movements. We modify the approach used to define the region of interest. In this algorithm we employ a skin detector to eliminate pixels from the background, divide the frames in microregions that are tracked using an optical flow algorithm to compensate for movements and we apply a clustering algorithm to automatically select the best micro-regions to use for heart rate estimation. We also propose a temporal and spatial filtering scheme to reduce noise introduced by the optical flow algorithm. We compared the results of our algorithms to an off-the-shelf fingertip pulse oximeter and showed that they can work well under challenging situations.

Abstract Analysis of beat-to-beat heart rate variability (HRV) provides information of cardiac vagal outflow to the sinus node. Some methodological problems might, however, be involved in the analysis of cardiac vagal outflow from ambulatory Holter recordings, such as saturation, physical activity, and abrubt prolongations of R-R intervals unrelated to respiration. The purpose of this thesis was to assess the physiological basis of beat-to-beat HRV and to develop and assess new methods for the quantification of cardiac autonomic modulation from ambulatory Holter recordings. The study population consisted of 89 healthy volunteers (age 24 ± 4 years) and 590 patients with a recent acute myocardial infarction (AMI, age 61 ± 10 years). The relationship between R-R interval length and the high-frequency (HF) spectral power of the R-R intervals was assessed in 76 healthy subjects and 82 post-AMI patients. The effects of aerobic exercise training on the dynamics between R-R interval and HF power were evaluated by means of a controlled 8-week training intervention (n = 17). The effects of sympathetic activation and concomitant sympathetic and vagal outflow on beat-to-beat HR dynamics were studied in laboratory conditions (n = 13). A new method for quantifying beat-to-beat HRV from the R-R interval lengths where the relationship between HF power and R-R interval is most linear was developed to avoid the confounding effects of possible saturation, physical activity, and random R-R interval dynamics. The clinical significance of the new method was assessed in a series of 590 post-AMI patients. Saturated HF R-R interval dynamics, expressed as a lack of increase in HF power despite an increased R-R interval, was observed in 35 healthy subjects and 9 post-AMI patients. In the training study, 7 subjects out of a total of 17 had saturated HF power before the intervention. After the training period, 5 new cases of saturated HF power were observed. In laboratory conditions, co-activation of sympathetic and vagal outflow resulted in random R-R interval dynamics. In post-AMI patients, HF power analyzed exclusively from the R-R intervals where the relationship between the R-R interval and HF power was most linear (Vindex) predicted independently the occurrence of SCD among post-AMI patients, while traditionally analyzed HF power did not. In conclusion, the saturation of beat-to-beat HRV in ambulatory conditions is a common phenomenon. The prevalence of saturated HF power increases due to enhanced cardiac vagal outflow induced by aerobic training. Finally, the novel analysis of vagally mediated HRV (Vindex) provides unique information that cannot be obtained by traditional analysis of HF R-R interval dynamics.

Takotsubo cardiomyopathy (TTC) is a disease characterized by transient left ventricular (LV) dysfunction and typical wall motion abnormalities in apical parts, without obvious signs of coronary influence. Due to its elusive natural cause and the lack of clarified pathology, further studies are needed. Thirteen patients presented with an episode of TTC, and referred to Örebro University Hospital (USÖ), were prospectively included and investigated by comparisons made at onset (acute phase) against at follow-up three months later (recovery phase). Including echocardiographic measurements, focused on biventricular systolic long-axis function and conventional diastolic function (DF) variables. Systolic improvement was shown, while most DF data were unchanged, suggesting that TTC is mainly a systolic disease affecting both ventricles. Diagnosis should include multidisciplinary engagement, as TTC associates both with emotional stress and pathological markers of physiological stress. In this thesis, such approach was offered to the aforementioned patients; to see if a common denominator could be found, thus, contributing to better handling. Emotional state was assessed, along with an array of cardiac investigations in addition to echocardiography. Acutely, imbalance in the autonomic cardiac control was shown, as well as a trend toward posttraumatic stress, but specific findings allowing conclusions on differential diagnosis could not be demonstrated. By adding another 15 TTC patients (i.e. 28 in total), through collaboration with observers from USA, a retrospective echocardiographic analysis could be done to further study DF; concluding that TTC associates with impairment of conventional DF variables which tends to parallel the systolic recovery, in contrary to the initial result but in line with other causesof LV dysfunction. Magnetic resonance imaging (MRI) is another method of choice at TTC. The USÖ patients had cardiac MRI, thus, a retrospective analysis was done to investigate the effect on LV geometry, both echocardiographic and by MRI; suggesting that TTC is consistently associated with increased LV mass, due to a local impact that seems to follow the change in LVconcentric wall motion.

Dissertação de Mestrado Integrado em Medicina Veterinária
A radiografia assume-se como o mais importante meio complementar de diagnóstico disponível na clínica de animais selvagens para a avaliação das dimensões do coração. Considerando que a grande variedade de aves existente na fauna ibérica é acompanhada por uma escassez de estudos, na área clínica, que lhe digam respeito, torna-se pertinente a abordagem à interpretação da silhueta cardíaca em águia-de-Bonelli (Aquila fasciata), espécie protegida por diversos programas de conservação a nível nacional e europeu, nomeadamente o projecto LIFE Bonelli. O principal objectivo deste estudo consiste na determinação de valores de referência para a silhueta cardíaca na imagem radiográfica de águias-de-Bonelli. Para tal, foram utilizadas radiografias, em projecção ventrodorsal, de vinte exemplares da espécie clinicamente saudáveis. Nestas radiografias foram mensuradas as larguras da silhueta cardíaca, do esterno, do tórax, do coracóide e da silhueta hepática. O rácio entre a largura da silhueta cardíaca e as restantes estruturas anatómicas foi calculado. Os resultados do presente estudo evidenciam que a largura da silhueta cardíaca deve constituir entre 81 a 93% da largura esternal, entre 48 a 57% da largura torácica e entre 506 a 673% da largura do coracóide. A largura da silhueta cardíaca correlacionou-se fortemente com as larguras esternal e torácica e moderadamente com a largura do coracóide. Não se verificou correlação com a largura da silhueta hepática. A largura do esterno e a largura do tórax apresentam-se como as variáveis que deverão ser preferencialmente utilizadas para comparação com a largura da silhueta cardíaca. Considera-se válida a utilização dos valores obtidos neste estudo, enquanto referência para o normal tamanho do coração de águias-de-Bonelli em radiografias.
ABSTRACT - RADIOGRAPHIC REFERENCE VALUES FOR THE CARDIAC SILHOUETTE IN BONELLI’S EAGLE (Aquila fasciata) - Radiographs are the most important diagnostic tools available in wildlife practice hospitals to evaluate the size of the avian heart. Despite of the great variability of birds in Iberian wildlife, there is a lack of clinical studies addressing these species. This is the reason why is so relevant the approach to the cardiac silhouette interpretation in Bonelli’s eagle (Aquila fasciata), a species that is protect by national and European conservation programs, including LIFE Bonelli. The main purpose of this study was to establish reference values for cardiac size in Bonelli’s eagle. Radiographs in ventrodorsal projection of twenty healthy birds were included in this study and width of the cardiac silhouette, sternum, thorax, coracoid and hepatic silhouette were measured. The ratio between cardiac width and other mentioned indices was calculated. The results show that cardiac silhouette width should occupy 81 to 93% of sternal width, 48 to 57% of thoracic width and 506 to 673% of coracoid width. Width of cardiac silhouette was strongly correlated with sternal and thoracic widths. There was a moderate correlation between width of the heart and width of the coracoid. There was no significant correlation between cardiac silhouette width and hepatic silhouette width. It is possible to conclude that sternal and thoracic width should be preferentially used when evaluating the width of the cardiac silhouette. The values obtained in this study can be used as a reference of normal cardiac size of Bonelli’s eagle in radiology.

Cardiovascular drift can occur during prolonged exercise and is characterized by a gradual decrease in stroke volume (SV) and a corresponding increase in heart rate (HR) over time, despite the maintenance of a constant level of work; cardiac output (CO) usually is unchanged. A number of factors may cause cardiovascular drift to occur, including increases in peripheral blood flow, decreases in plasma volume, increases in circulating catecholamines, and metabolic acidosis. These physiological events may be influenced by the relationship of the exercise intensity to ventilatory threshold (VT). Therefore, the purpose of this study was to examine the cardiovascular responses during prolonged exercise in boys and men at an intensity set relative to VT. Eight boys (10-13 yrs.) and 10 men (18-25 yrs.) completed an orientation trial, a graded maximal exercise test, and a 40 minute submaximal exercise bout at an intensity equal to the V02 at VT. During the 40 minute exercise bout, V02 increased significantly over time (P_<0.05),although the magnitude of change was similar in boys and men (P>0.05). Heart rate was higher and SV was lower in the boys compared to the men (P<_0.05), and the changes in HR and SV were significant over time. Although there was a trend for the HR increase and SV decrease to be greater in the men, the group-by-time interaction was not significant. Cardiac output and arteriovenous oxygen difference were higher in the men compared to the boys (P<0.05), but remained constant over time. Mean arterial blood pressure (MABP) was higher in the men than the boys (P<_0.05). In the men, MABP decreased significantly from 10 to 40 minutes, while in the boys, MABP decreased (P<_0.05) from 10 to 30 minutes and then increased to a value similar to that at 10 minutes. This differential response in MABP over time resulted in a significant groupby-time interaction. Total peripheral resistance was significantly higher in the boys than the men, but remained constant over time (P>0.05). Men exhibited a greater decrease in plasma volume from 0 to 40 minutes. There was no group difference in perceived exertion (RPE) between the boys and the men, although the boys exhibited a greater increase in RPE over time than the men (P<0.05). In conclusion, the cardiovascular responses during prolonged exercise are similar in boys and men, although there is a tendency for the magnitude of cardiovascular drift to be greater in the men. In addition, due to the fact that these results are similar to previous studies not accounting for individual differences in VT, it would seem that these differences in VT should not be of concern when studying the cardiovascular responses during prolonged exercise.
School of Physical Education

Heart failure is a common disorder and a major cause of illness and death in the population, creating an enormous health-care burden. It is a complex condition, representing the end-point of many cardiovascular diseases. In general heart failure progresses slowly over time and once it is diagnosed it has a poor prognosis which is comparable with that of many types of cancer. The heart has an ability to adapt in response to long lasting increases in hemodynamic demand; the heart conforms its shape and size in order to maintain adequate cardiac output. This process is called remodeling and can be triggered by pathologies such as hypertension or valvular disease. When the myocardial remodeling is maintained chronically it becomes maladaptive and is associated with an increased risk of heart failure. In many cases, heart failure is associated with left bundle branch block (LBBB). This electrical disturbance leads to dyssynchronous left ventricular (LV) contraction and relaxation which may contribute to cardiac dysfunction and ultimately heart failure. Mechanical dyssynchrony can be treated with cardiac resynchronization therapy (CRT). However, many heart failure patients do not demonstrate clinical improvement despite CRT. Blood flow plays an important role in the normal development of the fetal heart. However, flow-induced forces may also induce changes in the heart cells that could lead to pathological remodeling in the adult heart. Until recently, measurement tools have been inadequate in describing the complex three-dimensional and time-varying characteristics of blood flow within the beating heart. 4D (3D + time) flow cardiovascular magnetic resonance (CMR) enables acquisition of three-dimensional, three-directional, time-resolved velocity data from which visualization and quantification of the blood flow patterns over a complete cardiac cycle can be performed. In this thesis, novel 4D Flow CMR based methods are used to study the intraventricular blood flow in healthy subjects and heart failure patients with and without ventricular dyssynchrony in order to gain new knowledge of the ventricular function. Different flow components were assessed in normal heart ventricles. It was found that inflowing blood that passes directly to outflow during the same heartbeat (the Direct Flow component) was larger and possessed more kinetic energy (KE) than other flow components. Diastolic flow through the normal heart appears to create favorable conditions for effective systolic ejection. This organized blood flow pattern within the normal LV is altered in heart failure patients and is associated with decreased preservation of KE which might be unfavorable for efficient LV ejection. Inefficient flow of blood through the heart may influence diastolic wall stress, and thus contribute to pathological myocardial remodeling. In dyssynchronous LVs of heart failure patients with LBBB, Direct Flow showed even more reduced preservation of KE compared to similarly remodeled LVs without LBBB. Furthermore, in LBBB patients, LV filling hemodynamic forces, acting on the myocardium, were more orthogonal to the main flow direction compared to patients without LBBB. Deviation of LV flow forces and reduction of KE preservation and may reflect impairment of LV diastolic function and less efficient ensuing ejection related to dyssynchrony in these failing ventricles. Blood flow patterns were also studied with respect to fluctuations of the velocity of the flow (turbulent flow) in normal and failing LVs. In failing hearts, turbulent kinetic energy (TKE) was higher during diastole than in healthy subjects. TKE is a cause of energy loss and can thus be seen as a measure of flow inefficiency. Elucidating the transit of multidimensional blood flow through the heart chambers is fundamental in understanding the physiology of the heart and to detect abnormalities in cardiac function. The 4D Flow CMR parameters presented in this thesis can be utilized to detect altered intracardiac blood flow and may be used as markers of deteriorating cardiac function, pathological remodeling and mechanical dyssynchrony in heart failure.

O presente estudo, teve como objetivo desenvolver um equipamento para medir os intervalos R-R, que tivesse alta correlação com os valores do aparelho padrão ouro de eletrocardiógrafo (ECG), pelos índices de domínio do tempo e domínio da frequência. Para tanto, foi realizado um estudo com 18 alunos de Jiu-Jitsu, do sexo masculino com 35,5±8,6 anos, no mínimo uma frequência semanal de 3 vezes e 1 ano de treinamento. O local foi na academia Barra Gracie de Curitiba PR. Foram submetidos a uma análise em repouso por um período de 7 minutos e posteriormente seus resultados foram convertidos em variabilidade da frequência cardíaca (VFC) e analisados pelos índices no domínio do tempo e domínio da frequência. Os resultados foram comparados estatisticamente por meio do teste de Pearson e a correlação intraclasse (ICC) e de acordo com eles mostra-se viável o desenvolvimento deste equipamento, que apresenta alta correlação e excelente replicabilidade para medir os intervalos R-R.
This study aimed to develop a device to measure RR intervals, which have high correlation with the values of the gold standard device of electrocardiograph (ECG), by the time domain and frequency domain indices. To this end, a study was conducted with 18 students of Jiu-Jitsu, males with 35.5 ± 8.6 years, at least a weekly frequency of 3 times and one year training. The location was at the academy Gracie Barra de Curitiba PR. They underwent an examination at rest for a period of 7 minutes and then the results were converted into heart rate variability (HRV) and analyzed by the indexes in the time domain and the frequency domain. The results were compared statistically using the Pearson test and intraclass correlation (ICC) and according to them proves to be viable the development of this equipment, which is highly correlated and excellent reproducibility for measuring the RR intervals.

Considerando que o diagnóstico e os tratamentos de certas doenças do coração, entre as que provocam arritmias cardíacas, se dão por uso de equipamentos eletromédicos como eletrocardiógrafos, monitores cardíacos, holter, marcapassos externos e desfibriladores/cardioversores, torna-se de vital importância que esses tipos de produtos sejam avaliados tecnicamente e certificados como forma de verificar seu desempenho, suas limitações e capacidade de cumprir suas funções para garantir a segurança contra riscos elétricos e erros de comandos, além de assegurar que estão sendo fabricados em conformidade com as prescrições de Normas Técnicas vigentes. O registro de tais produtos na Anvisa é compulsório no Brasil, exigindo uma certificação junto ao INMETRO para que estes produtos possam ser comercializados. De acordo com a regulamentação brasileira vigente devem estar de acordo com as exigências da Série de Normas Técnicas ABNT NBR IEC 60601/ 80601 que estabelecem as prescrições de segurança e desempenho essencial que esses produtos são obrigados a atender. Portanto, a pesquisa apresenta os métodos de ensaios, processos de ensaios e a forma de como se deve mensurar os parâmetros dos equipamentos destinados à área cardíaca, além de fornecer todos os instrumentos de medição, as necessidades para efetuar tal tarefa e as gigas de ensaios. Também são apresentados os resultados finais dos ensaios indicando que alguns parâmetros dos equipamentos ensaiados não estão em conformidade com as Normas vigentes no país. Por fim, são mencionadas conclusões finais e os trabalhos futuros a serem desenvolvidos para contribuir com o aperfeiçoamento e com a busca de melhoria contínua. Esta pesquisa deve contribuir como referência para os Laboratórios de Ensaios congêneres que tenham interesse em obter capacitação técnica, além de ser uma orientação para as empresas que produzem equipamentos dedicados à área cardíaca de acordo com os requisitos e prescrições das Normas vigentes no país.
Whereas the diagnosis and treatment of certain heart diseases, including the ones that cause cardiac arrhythmia, depend on the usage of electromedical equipment such as electrocardiographs, cardiac monitors, holters, pacemakers and defibrillators / cardioverters, it is vital that such products be technically evaluated and certified as a way to check their performance, limitations, and ability to fulfill their functions, in order to ensure safety against electrical hazards and command errors, as well as to ensure that they are manufactured in accordance with the Technical Standards in force. The registration and certification of these products is compulsory in Brazil, and, in order to be marketed, they must comply with the requirements of the series ABNT NBR IEC 60601/ 80601of Technical Standards, which establish the essential safety and performance requirements that these products must meet. This paper describes testing methods, testing procedures, and the way cardiac equipment parameters have to be measured and evaluated providing all the measuring instruments and requirements for test performing and metrology. It also shows are the final results of tests indicating that some important parameters of the evaluated equipament are not in accordance with the standards adopted in Brazil. Finally, the findings and conclusions are presented, with incitements for future works, in order to contribute to pursuit of continuous improvement. This research intends to contribute as a benchmark for Testing Laboratories with similar interest in obtaining testing technical capacity, and is also an orientation to for companies that produce heart medical equipment in accordance with the requirements of the standards adopted in Brazil.

O monitoramento de sinais vitais em pacientes tem o intuito de obter rapidamente dados relevantes para decisões médicas. No entanto, tal mensuração é pouco eficiente, difícil, quando não impossível, em determinados casos, como por exemplo em pacientes vítimas de queimaduras, em função da impossibilidade de colocar o eletrodo diretamente na pele, ou em recém-nascidos, devido à fragilidade da pele. Este estudo trata do desenvolvimento de um sistema para aquisição contínua de sinais fotopletismográficos para a telemetria da frequência cardíaca em tempo real, em uma plataforma de baixo custo, utilizando a biblioteca OpenCV e o método desenvolvido pelo MIT chamado de Magnificação de Vídeo Euleriana, que revela variações que são imperceptíveis a olho nu. Para desenvolver o sistema foi utilizada a plataforma de hardware Raspberry Pi Versão B com processador ARM11 de 700MHz e 512MB de memória RAM. Os dados da frequência cardíaca coletados dos experimentos foram comparados com os dados coletados por um oxímetro de dedo More Fitness modelo MF-425. Esse foi escolhido por utilizar o mesmo princípio "Fotopletismografia"para efetuar a medição. Após a coleta de dados foi estimado o intervalo de confiança para aferir a precisão do sistema, que correspondeu a 96,5% em relação ao oxímetro utilizado. Ficou evidente que o meio utilizado para medir a frequência cardíaca via método de magnificação de vídeo Euleriana em tempo real é uma tecnologia de baixo custo (aproximadamente R$300,00) quando comparado aos monitores multiparamétricos utilizados para o monitoramento de pacientes críticos, cujo custo varia entre R$ 8.000,00 e R$ 34.000,00. Sendo assim, também contribui com a redução de custos no tratamento ao doente que necessita de monitorização constante, possibilitando que, com a economia gerada pela aquisição e implantação desta tecnologia, viabilize um maior investimento em outras áreas dos hospitais.
Monitoring vital signs in patients is used to obtain relevant data for medical decisions in a fast way. However, this measurement is both inefficient and difficult, if not impossible in certain cases, such as in burnt victims, due to the impossibility of placing the electrodes directly on the skin or in infants, because of the fragility of skin. This study aims to develop of a system for continuous acquisition of photopletismografics (PPG) signals for the telemetry of heart rate in real time in a low cost platform using the OpenCV library and the method developed by MIT called the Eulerian Video Magnification, amplifying variations that are imperceptible to the naked eye. To develop the system were used the hardware platform Raspberry Pi version B with ARM11 700MHz processor and 512MB RAM. The heart rate data collected from the experi- ments were compared with data collected by a finger oximeter model More Fitness MF-425 it was chosen, by using the same working principle "PPG"to effect the measurement. After data collection was estimated the confidence interval to measure system accuracy, which corresponded to 96,5% compared to the oximeter used. It became clear that the developed system used to measure heart rate via magnification method of Eulerian live video is a low-cost technology (approximately R$ 300.00) compared to the multiparameter monitors used for monitoring critically patients, ranging in cost from R$ 8,000.00 to R$ 34,000.00. So also, it contributes to cost reduction in the treatment to the patient in need of constant monitoring, enabling with the savings generated by the acquisition and deployment of this technology makes possible greater investment in other areas of hospitals.
5000

Sports vision gained attention in the late 90’s and has since been the focus of many research studies. Thus far sports vision research has effectively succeeded in determining the importance of visual skills and also discovering the ability to improve visual skills through training. It is this ability to enhance visual skill performance that has led to the development of vision training programmes. However, the effectiveness of these training programmes is far from unanimous with many studies yielding inconclusive results. Possible reasons for this are the lack of scientific measures implored, testing and training of skills that are not specific to the subjects and training programmes that are unrealistic. Another major area that is missing from sports vision research is the accountability of external variables like; lifestyle, anthropometric and cardiac measurements. Aspects such as; stress, nutrition and hypo/hypertension are proposed to either have an enhancing or declining effect on visual skills. These relationships have not been scientifically tested and remain undefined. It is also important to note that research has thus far been limited to athletes. This study therefore aimed to determine the effect of two different training programmes on the visual skill performance of university students. Furthermore, external variables are determined to certify that visual skill training alone would improve visual skills and to determine and define if any relationships exist between visual skills and external variables. In order to meet the aims of this study, volunteer university students underwent pre testing of specific visual skills together with lifestyle evaluations, body composition and cardiac health testing. Thereafter the total participants (n=600) were divided into three groups. Group 1 (n=169) acted as a control group with no visual training taking place in a six week period, group 2 (n=225) underwent lab-based training with a simple repetition of testing methods used as training methods and group 3 (n=205) underwent training via an internet- based training method. Thereafter all variables were tested again and statistical analysis of the data was performed. Results showed the lab-based training group having the most improvement in visual skills with all skills improving besides vergence. The Eyedrills training group also showed significant improvements in focusing, tracking and eye- hand coordination. The control group showed the least improvement in visual skills thereby ruling out the notion of improvements occurring only due to test familiarity. Significant changes occurred in a variety of the external variables across the three groups. Due to the varied results with regards to external variables, correlations between these variables and visual skill performance is still unclear and remains undefined. There is enough evidence from this study to conclude that visual skills are improved due to visual skill training. The change from the typical subject type (i.e. athletes) is important in the expansion of visual skill testing and training to other fields besides the sports one. The effect of external variables on visual skills still remains unanswered and therefore more precise research in this regard is warranted.
Dissertation (MSc)--University of Pretoria, 2014.
gm2014
Physiology
unrestricted

The dissertation studies the estimation of the degree of self-similarity and entropy of Shannon of several real electrocardiography (ECG) signals for healthy and non-healthy humans. The goal of the dissertation is to create a starting point algorithm which allows distinguishing between healthy and non-healthy subjects and can be used as a basis for further study of a diagnosis algorithm, necessarily more complex. We used a novel Hurst parameter estimation algorithm based on the Embedded Branching Process, termed modified Embedded Branching Process algorithm. The algorithm for estimation of entropy was based on Shannon‟s entropy. Both algorithms were applied on the spatial distribution of ECG signals in a windowed manner. The studied signals were retrieved from the Physionet website, where they are diagnosed as normal or as having certain pathologies. The results presented for the Hurst parameter estimation allow us to confirm the results already published on the temporal self-similarity of ECG signals, this time for its spatial distribution. We also conclude that the non-self similar signals belong to non-healthy subjects. The results obtained for entropy estimation on the spatial distribution of ECG signals also allowed a comparison between healthy and non-healthy systems. We obtained high entropy estimates both for healthy and non-healthy subjects; nevertheless, non-healthy subjects show higher variability of Shannon‟s entropy than healthy ones.

Access to abstract permanently restricted to Ball State community only
Access to thesis permanently restricted to Ball State community only
School of Physical Education, Sport, and Exercise Science

碩士
國立中興大學
獸醫學系暨研究所
106
Many biomarkers presented good prognostic value for cardiac diseases in both veterinary medicine and human medicine, such as N-terminal pro-B-type natriuretic peptide (NT-pro BNP) and cardiac troponin-I (cTnI). Recently, serial monitor of these biomarkers was considered better than one-time-point analysis for predicting prognosis. Therefore, we want to evaluate the prognostic value of serial change of cTnI concentration in the dogs with heart failure secondary to canine myxomatous mitral valve disease (MMVD) in this study. Seventy-six dogs were enrolled in this study at admission and also recruited from staffs and students for age-matched healthy control. They were classified by the American College of Veterinary Internal Medicine (ACVIM) guideline and also allocated into different groups according to the stage of cardiac remodeling and heart failure. Twenty-three of the enrolled dogs with heart failure underwent serial measurement of serum cTnI levels and their survival time was recorded. Cardiac troponin I was significantly different among the ACVIM group (P＜0.001). Moreover. the serum concentration of cTnI was significantly higher in dogs with heart failure (P=.008) compare to those without heart failure and complete cardiac remodeling (P=.011) compare to those without complete cardiac remodeling. Moreover, serum cTnI level presented significantly positive correlation with clinical score, heart rate, vertebral heart score (VHS), the intensity of heart murmur (Murmur), radiographic score (RS) and other selective echocardiographic measurements. In the serial analysis, Kaplan-Meier analysis also showed a significant difference in survival time when the cut-off points were 0.018 ng/mL and 15.56% for absolute change and relative change of baseline to third visit cTnI (cTnI1-3) respectively (P=.016 and P=.002 respectively). The hazard ratio (HRa) was 3.629 (95% confidence interval: 1.192-11.044) and 5.257 (95% confidence interval: 1.683-16.427) for absolute change cTnI 1-3 > 0.018 ng/mL and relative change cTnI1-3 > 15.56% respectively. In multiple COX regression, only relative change cTnI1-3 and the ratio of early transmitral inflow velocity and early-diastolic myocardium velocity (E/E’), which were considered indicating the diastolic dysfunction, showed significantly associated with cardiac death during follow-up 360 days.

1. An explicit mathematical description of PEP in terms of DBP was proposed, which in the first time quantitatively clarified the ventricular and arterial effects on PEP timing.
2. A nonlinear pressure-volume relationship which reflected the natural arterial wall properties was introduced into the asymmetric T-tube arterial model, which effectively and quantitatively described the effect of pulsatile BP on arterial parameters, e.g., compliance, PTT etc.
3. A mathematical relationship between PAT and BP was firstly proposed as a result of the heart-arterial interaction, which simulated a significantly strong and negative relationship between PAT and SBP and between PAT and MBP but a much weaker negative relationship between PAT and DBP during exercise. The hypothesis was supported by the experiment data. To our knowledge, it is the first study describing the quantitative relation of PAT and BP by both model-based study and experimental data.
4. A novel wearable measurable CO parameter, PTRR, was proposed and it successfully showed a significantly high and positive correlation with CO during exercise both in model simulation and in the experiments.
5. Linear prediction models using PAT to estimate MBP and using PTRR to estimate CO were proposed and evaluated in two exercise experiments conducted on 84 subjects with different ages and cardiovascular diseases. Results showed the proposed method could achieve the accuracy required for medical diagnosis.
6. Taken the findings in 3, 4 and 5 together, this study in the first time provided both the theoretical basis and experimental verifications of developing a wearable and direct measurement technique of CPO in dynamic exercise using multiple physiological signals measured on body surface.
Cardiac power output (CPO) is defmed as the product of mean arterial blood pressure (MBP) and cardiac output (CO), and CPO measured during peak dynamic exercise (i.e. peak CPO) has been shown as a powerful predictor of death for heart failure patients. However, so far there has been no existing device which directly measures CPO, and CPO is acquired from simultaneous measurement of MBP and CO. Further, simultaneous MBP and CO measurement during dynamic exercise is a challenge for current BP and CO methods. Therefore, there is an urgent need to develop new devices which are fully wearable and unobtrusive for monitoring of CPO during dynamic exercise. Since the core problem in most wearable devices is how to estimate the target cardiovascular parameter, e.g. CPO in this study, through physiological signals measured from body surface, this thesis focus on developing a direct measurement technique of CPO in dynamic exercise using multiple physiological signals measured on body surface, specifically, electrocardiogram (ECG) and photoplehtysmogram (PPG).
Finally, based on the theoretical and experimental verifications, linear prediction models were proposed to estimate MBP from PAT and estimate CO from PTRR. The results showed that PAT can estimate MBP with a standard deviation of 7.42 mmHg, indicating PAT model has the potential to achieve the accuracy required by AMMI standard (mean error within +/- 5 mmHg and SD less than 8 mmHg). The results also showed that PTRR can estimate CO with a percent error of 22.57%, showing an accuracy which was considered as clinically acceptable (percent error less than 30%).
Heart failure is the end stage of many cardiovascular diseases, such as hypertension, coronary heart disease, diabetes mellitus, etc. Around 5.8 million people in the United States have heart failure and about 670,000 people are diagnosed with it each year. In 2010, heart failure will cost the United States $30.2 billion, and the cost of healthcare services is a major component of this total. With the resultant burden on health care resources it is imperative that heart failure patients with different risk stages are identified, ideally with objective indicators of cardiac dysfunction, in order that appropriate and effective treatment can be instituted.
In order to verify the theoretical findings, two experiments were carried out. One was incremental supine bicycle exercise conducted on 19 young healthy subjects and the other was incremental to maximum supine bicycle exercise conducted on 65 subjects, including heart failure patients, cardiovascular patients and healthy elderly. PAT showed significantly high and negative correlation with SBP and MBP, but lower correlation with DBP. PTRR showed significantly high and positive correlation with CO.
In this thesis, a model based study is conducted to address the above problem. Firstly, we deduced the mathematical expression of PEP as a function of DBP by introducing the arbitrary heart rate into the exponential mathematical description of a pressure-source model. Secondly, an asymmetric T-tube model was modified by introducing a nonlinear pressure-volume relationship where PTT was expressed as a dependent variant of BP. Thirdly, we proposed the mathematical equation between PAT and BP by coupling the modified ventricular and arterial models. Then, the relationships between PAT with systolic blood pressure (SBP), MBP and DBP were simulated under changing heart contractility, preload, heart rate, peripheral resistance, arterial stiffness and a mimic exercise condition. The simulation results indicated significantly high and negative correlations between PAT and SBP and between PAT and MBP whereas the correlation between DBP and PAT was low.
Next, we developed a novel CO index, namely pulse time reflection ratio (PTRR), expressed in terms of MBP and mean aortic reflection coefficient (Gamma(0)), from the modified asymmetric T-tube model. PTRR was further expressed in terms of PAT and inflection point area (IPA), a surrogate of Gamma(0) from the shape feature of PPG. The simulation results suggested significantly and positive relationship between PTRR and CO and between IPA and Gamma(0) during dynamic exercise.
Recently, a wearable measurable parameter, pulse arrival time or PAT, has been developed for BP measurement. PAT is the time delay from the R peak of ECG to the systolic foot of PPG. PAT consists of two timing components, the pre-ejection period (PEP) of the heart and pulse transit time (PTT). PTT is related to BP by an arterial elastic model and thus can be used to estimate beat-to-beat BP. However, PTT is difficult to be measured through a wearable device, and thus PAT is usually used as a surrogate of PTT for BP estimation, under the assumption of a constant PEP. However, PEP is not a constant but changing with physiological conditions, which may alter the PAT-BP relationship. Thus, it is important to clarify the PAT-BP relationship and address the feasibility of MBP estimation using PAT during dynamic exercise.
To summarize, the original contributions of this thesis are:
Wang, Ling.
Adviser: Y.T. Zhang.
Source: Dissertation Abstracts International, Volume: 73-03, Section: B, page: .
Thesis (Ph.D.)--Chinese University of Hong Kong, 2010.
Includes bibliographical references.
Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web.
Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [201-] System requirements: Adobe Acrobat Reader. Available via World Wide Web.
Abstract also in Chinese.

Tese de mestrado integrado em Engenharia Biomédica e Biofísica, apresentada à Universidade de Lisboa, através da Faculdade de Ciências, 2017
De acordo com os dados de 2017 da Organização Mundial da Saúde, as doenças cardiovasculares são a principal causa de morte a nível mundial. Se estes tipos de doenças não forem diagnosticadas e tratadas atempadamente, podem levar a insuficiências cardíacas ou outras complicações irreversíveis. As duas doenças cardiovasculares congénitas estudadas neste trabalho são a coarctação aórtica (CoA), caracterizada por uma estenose, habitualmente, na zona do arco da artéria aorta, e a doença da válvula aórtica (AvD), uma malformação ao nível da válvula aórtica. Estas doenças são responsáveis por cerca de 50,000 intervenções por ano. Deste modo, a melhoria métodos de diagnóstico e de intervenção adequados e eficientes é uma prioridade e pode levar ao decréscimo no número das intervenções, bem como reduzir a morbilidade e a mortalidade. A área de imagiologia médica de diagnóstico tem tido uma evolução significativa ao longo dos anos e é de extrema importância nas tentativas de substituição de métodos de diagnóstico invasivos. As imagens médicas são adquiridas e posteriormente processadas e analisadas, com recurso a programas adequados. Atualmente, é possível obter os valores de gradientes de pressão relativa a partir de Ecocardiografia Doppler e Ressonância Magnética. Contudo, os gradientes de pressão medidos no cateterismo cardíaco, o método gold standard para o diagnóstico de CoA e AvD, são gradientes de pressão absoluta. Nesta dissertação desenvolveu-se um método de diagnóstico de CoA e AvD, a partir dos mapas de pressão relativa no estreitamento da aorta e na válvula aórtica, respectivamente. O método matemático desenvolvido tem por base as equações de Poisson, resolvida com a condição de fronteira de Neumann utilizando os métodos de elementos finitos, e a de Navier Stokes para a conservação do momento. O método desenvolvido também tem em conta a informação proveniente da função de Windkessel da artéria aorta, uma artéria distensível. Esta função dá-nos o comportamento da propagação do pulso de pressão com uma velocidade de pulso de propagação. Deste modo, é observado um desfasamento temporal entre as curvas de fluxo da pressão e da velocidade, entre as duas regiões de interesse escolhidas. Deste modo, o método, denominado de Time-shift Corrected Pressure Maps (TCPM, sigla em inglês), permite obter os mapas de pressão absoluta, isto é, mapas de pressão que têm em conta o intervalo de tempo entre os picos de pressão na aorta descendente e ascendente, no caso do primeiro estudo, e antes e depois da válvula aórtica, no caso do segundo estudo. Os pacientes de ambos os estudos tinham indicação clínica para cateterismo cardíaco e foram submetidos a ressonância magnética cardiovascular de contraste de fase em tempo real (4D PC MRI, em inglês), para recolher as imagens ao nível da aorta e da válvula aórtica e os respectivos campos de velocidade da corrente sanguínea. O primeiro estudo tem como objetivo a aplicação do método TCPM a 27 pacientes de CoA (n=16 masculinos, n=11 femininos, faixa etária de 4 a 52 anos, idade média de 20±15 anos). Após aquisição das imagens, estas foram processadas usando programas específicos. Em primeiro lugar foi necessário segmentar a aorta, seguiu-se a seleção das regiões de interesse e, finalmente, a obtenção dos campos de velocidade e dos mapas de pressão relativa entre as duas regiões de interesse selecionadas. Após aplicação do método TCPM, foram aplicados testes estatísticos (correlação, teste t e Bland-Altman) para comparar os valores obtidos a partir de TCPM com os valores obtidos no cateterismo cardíaco. Após processamento das imagens dos 27 pacientes, 6 pacientes foram retirados do estudo. N=3 pacientes foram retirados porque a percentagem de fluxo que passa pelo estreitamento é insuficiente para calcular o gradiente de pressão a partir de TCPM e N=3 pacientes foram retirados porque a aorta não estava inserida por completo no FOV. As medições obtidas a partir de TPCM e cateterismo cardíaco têm uma correlação linear significante (R²=0,90; p<0,001). A partir dos gráficos Bland-Altman é possível verificar uma boa concordância entre as medições de ambos os métodos, com bias de -2,69 mmHg e os limites de concordância de ±4,74 mmHg. O teste de equivalência mostrou uma relação significante entre os métodos (p=0,007). O segundo estudo tem como objetivo a aplicação do método TPCM e o método da Área de Gorlin a 4 pacientes de AvD (n=4 masculinos, faixa etária 17 a 36 anos, idade média 27±7 anos). O método da Área de Gorlin permite obter o gradiente de pressão absoluta a partir da área geométrica da válvula e do fluxo total que passa nessa área. Após a aquisição das imagens, foi feito o processamento das mesmas. Numa primeira fase, as imagens foram segmentadas na região da válvula aórtica. Depois, as imagens segmentadas foram analisadas em dois programas distintos. O primeiro foi utilizado de forma a obter os campos de velocidade e os mapas de pressão relativa entre dois pontos antes e depois da válvula aórtica. O segundo permitiu definir a região da válvula como região de interesse e exportar os valores de velocidade, área, pressão relativa e fluxo absoluto nessa região. Os resultados mostram uma correlação linear significativa entre os valores de cateterismo cardíaco e de TCPM (R²=0,99; p<0,001). Os gráficos de Bland-Altman mostram uma boa concordância entre os valores de TCPM (24,75±22,50 mmHg) e de cateterismo (20,88±19,51 mmHg), com um bias de -3,87 mmHg e limites de concordância de ±3,64 mmHg. Os resultados também sugeriram uma ligeira subestimação dos valores do cateterismo cardíaco a partir do método da Área de Gorlin (14,47±13,00 mmHg), com um bias de 6,41 mmHg e limites de concordância de ±7,15 mmHg. Este estudo foi feito com uma amostra diminuta de 4 pacientes, o que não é suficiente para retirar conclusões com significância. Contudo, foi uma primeira abordagem positiva, que mostra a potencialidade que este método pode vir a apresentar. O método TCPM proposto neste projeto permite a medição não invasiva de gradientes de pressão absoluta a partir de mapas de pressão relativa em pacientes de CoA e AvD. Vários aspectos têm que ser tidos em conta de forma a garantir a eficácia deste método. Por exemplo, as regiões de interesse escolhidas têm que se cuidadosamente selecionadas de forma a serem perpendicular à direção do fluxo naquele local. Só desta maneira é possível obter o fluxo, os campos de velocidade e as pressões relativas corretas. Também, se o raio da estenose for menor que 2 voxéis, a relação sinal-ruído aumenta substancialmente, e a resolução especial da aquisição é insuficiente. Contudo, a aplicação do método TPCM a casos de grande estreitamento não é necessária visto que estes casos já são tipicamente identificados em imagens anatómicas de ressonância magnética e que o paciente segue automaticamente para intervenção quando a área do estreitamente representa cerca de 50% do valor de área típico da aorta. O método não invasivo TCPM apresenta uma boa concordância com o cateterismo cardíaco em termos da medição dos gradientes de pressão em CoA e AvD. Os bias e os limites de concordância entre cateterismo e TCPM foram substancialmente mais pequenos que os bias e os limites de concordância entre cateterismo e ecocardiografia Doppler e entre o cateterismo e o método da Área de Gorlin. Com os resultados apresentados já é possível ver o potencial desta técnica no processo de diagnóstico e decisão de intervenção em casos de CoA e AvD. Contudo, estudos com populações maiores será extremamente benéfico para validar clinicamente este método.
This dissertation aims to validate MRI-based time-shift corrected pressure mapping (TCPM) against cardiac catheterization in CoA and AvD patients. Also, in AvD patients, catheterization will be compared against Gorlin Area method. This project is divided in two independent studies: the first one for CoA patients and the second one for AvD patients, all with clinical indication for cardiac catheterization. In both CoA and AvD, clinical guidelines recommend treatment in the presence of a relevant pressure gradient. While reliable non-invasive measurement approaches would be crucial, the accuracy of currently available methods has been limited. In both studies, 4D PC-MRI was performed to compute relative pressure maps via Pressure-Poisson equation. To consider the patient-specific peak pressure time-shift from the ascending to the descending aorta and before and after the aortic valve, relative pressure gradient maps were corrected by the inertial term. Comparison between TCPM and invasive peak-to-peak measurements was performed using correlation, Bland-Altman plots and mean-equivalence t-test. In the first study, with a cohort of 21 patients with CoA, TCPM and catheter measurements showed significant linear correlation (R²=0.90; p<0.001). Bland-Altman plots demonstrated good agreement between TCPM and catheter derived pressure gradients with mean differences of -2.69 mmHg and 95% limits of agreement between -6.38 and 1.00 mmHg between methods. The mean-equivalence test was significant (p=0.007). In the second study, with a cohort of 4 patients with AvD, the catheterization measurements were compared against TPCM measurements. The results showed significant linear correlation (R²=0.99; p<0.001). Bland Altman plots showed a good agreement between TCPM (24.75±22.50 mmHg) and catheter derived peak-to-peak pressure gradients (20.88±19.51 mmHg), and suggested slight underestimation of the pressure gradients by the Gorlin Area method (14.47±13.00 mmHg). Non-invasive TCPM showed equivalence to pressure gradients from invasive heart catheterization in patients with CoA and AvD. However, in the AvD study, they were obtained for a very small cohort of patients and do not have sufficient statistical significance to validate the method for AvD patients.

Dissertação de Mestrado em Investigação Biomédica apresentada à Faculdade de Medicina
A insuficiência cardíaca com fração de ejeção preservada (ICFEP) constitui um frequente problema clínico, mas até hoje, nenhuma intervenção terapêutica parece modular o seu desfecho clínico. Alguns doentes com ICFEP possuem alterações no eixo hormonal da tiroide e é já conhecido o impacto da influência destas hormonas sobre o sistema cardiovascular. Neste projeto, testamos a hipótese de que administração oral preventiva com triiodotironina (T3) pode prevenir o desenvolvimento de ICFEP. Iniciou-se às 14 semanas de idade a administração oral de T3 (0.04 - 0.06 µg/mL) ou veículo em ratos ZSF1 obesos (ICFEP), utilizando ratos ZSF1 magros (CT) como controlo. A função tiroideia foi avaliada através de medições dos níveis plasmáticos de T3, T4 e TSH a cada 2 semanas e a dose de T3 administrada ajustada. No final do protocolo (24 semanas), foi realizada a avaliação ecocardiográfica, hemodinâmica e morfométrica dos animais. Os corações foram recolhidos e perfundidos enzimaticamente para isolamento de cardiomiócitos de forma a medir a contractilidade e a cinética dos transientes de Ca2+, usando a sonda fluorescente FURA-2. Cardiomiócitos isolados de ratos ICFEP apresentaram disfunção inotrópica e lusitrópica relativamente ao CT tal como observado pela diminuição na amplitude de contração, aumento no tempo até ao pico de contração e de relaxamento. A suplementação com T3 mostrou-se efetiva a normalizar a função. A maiores frequências de estimulação, a concentração de Ca2+ citoplasmático aumentou significativamente, mas o tratamento com T3 provou prevenir essa subida. Estes resultados constituem uma base de evidência promissora para os benefícios que a suplementação de T3 tem num subtipo particular de doentes com ICFEP com evidência de hipotiroidismo.
Heart failure with preserved ejection fraction (HFpEF) constitutes a major clinical problem, but to this day no therapy has effectively changed the course of the disease. Some HFpEF patients have alterations in the thyroid hormonal axis, and these hormones are known to influence cardiac function. In this project, we tested the hypothesis that preemptive triiodothyronine (T3) oral administration can prevent HFpEF development. Beginning at 14 weeks of age, ZSF1 obese rats (HFpEF) were orally administered with T3 (0.04 - 0.06 µg/mL) or vehicle, using ZSF1 lean rats (CT) as a control. Thyroid function was assessed through T3, T4 and TSH serum levels every two weeks and the dose was adjusted accordingly. At the end of the protocol (24 weeks), animals were evaluation by echocardiography, hemodynamics and morphometrics. The hearts were removed and enzymatically perfused to isolate cardiomyocytes for contractility and Ca2+ transient kinetics measurements using the FURA-2 fluorescent probe. Cardiomyocytes isolated from HFpEF rats shown inotropic and lusitropic impairments, as assessed by decreased contractile amplitude, increased time to peak contraction and relaxation, when compared to CT. T3 supplementation was found to be effective at normalizing these parameters. Higher stimulation frequencies led to cytoplasmic Ca2+ accumulation in HFpEF rat cardiomyocytes, while T3 treatment prevented this. These results constitute promising findings supporting the benefits of T3 supplementation in a certain subtype of HFpEF patients with evidence of hypothyroidism.