Reduced performance of the left ventricle to eject blood – left ventricular systolic dysfunction (LVSD) – is a common predecessor of the heart failure syndrome. With or without symptoms, LVSD is associated with a poor prognosis. However, with adequate treatment, the development or progression of symptoms, the need for hospitalisation and mortality can all be reduced. In the present work, the occurrence of LVSD was evaluated by echocardiography in a community-based sample of 75-year-old men and women (n = 433). LVSD was a common condition, with a prevalence rate of 6.8%. In nearly half the participants with LVSD, there was no clinical evidence of heart failure. Community-based screening for asymptomatic LVSD has been proposed as a strategy to reduce the incidence of heart failure. Because of the high costs and low availability, echocardiography is not a suitable screening tool. The plasma concentration of B-type natriuretic peptide (BNP) has been the most advocated screening tool. Another alternative is the standard 12-lead electrocardiogram (ECG). Both the ECG and BNP were effective in excluding LVSD in our 75-year-old community-based sample. However, compared with BNP, the ECG had considerably better specificity. In screening for LVSD, BNP had a diagnostic value in addition to the ECG, but only in individuals with abnormal ECGs. The left ventricular ejection fraction (LVEF) measured by echocardiography is a well-established index for describing left ventricular systolic function. The wall motion index (WMI) and the amplitude of mitral annulus motion (MAM) are suggested as alternative echocardiographic methods. Compared with MAM, the WMI had a more favourable agreement with the LVEF in our 75-year-old participants. Nonetheless, MAM was a strong predictor of mortality. MAM predicted the risk of all-cause and cardiac mortality independently of other risk factors. In addition, when it came to cardiac mortality, the predictive ability of MAM was independent of the LV function measured as the WMI.

Introduction. Multiple clinical methods for detecting myocardial ischemia are utilised in the hospital setting each day, but there is uncertainty about their diagnostic accuracy. In the operating room, multiple methods may be employed, while in the CCU advanced electrophysiological (ECG) techniques for myocardial ischemia detection, and in particular, ST segment analysis, are common. Vectorcardiography (VCG) is one form of ECG. Several conditions other than ischemia may cause marked ST changes, which can impair the process of diagnosis of clinical ischemia. Elevated HR is one of these factors, which is studied here. The hypotheses were about concordance of different methods to detect ischemia, and relation of ECG ST levels to HR with and without myocardial ischemia. Methods. Study I. Anesthetised vascular surgical patients with coronary artery disease were studied during the start of anesthesia and surgery: ECG, hemodynamic, mechanical, and metabolic parameters were measured and categorised as positive or negative with reference to a specific definition of myocardial ischemia. Study II. Awake patients with no ischemic heart disease were paced in graded steps, and VCG ST analyses were performed. Study III. Anesthetised pigs were studied for local metabolic and VCG ST changes related to controlled HR levels and transient coronary occlusion. Study IV. Thirty five anesthetised coronary artery disease (CAD) patients and ten non-CAD patients were paced at controlled levels, and great coronary artery vein (GCV) lactate measurement was used to determine presence or absence of myocardial ischemia. The CAD patients were paced up to HR levels where myocardial ischemia could be confirmed. The relation of HR-related VCG ST levels to presence or absence of ischemia was analysed. In Studies II,, III, and IV the ST vector magnitude (ST-VM), the change from baseline in ST-VM (STC-VM), and the vector angle change from baseline (STC-VA) were analysed for each step. Results. Study I. Poor concordance was demonstrated for positive events (presumed myocardial ischemia) between the hemodynamic, ECG, mechanical, and metabolic detection methods. Study II. STC-VM but not ST-VM levels demonstrated HR-related increases in the presumed absence of myocardial ischemia in 18 awake subjects. J point time to ST measurement did not affect the response of VCG ST to HR. Study III. STC-VM levels showed HR-related increases in the absence of ischemia (tested by local metabolic observations). VCG ST parameters responded positively to transient regional ischemia. Study IV. CAD patients, which demonstrated a clear pattern of onset and progress of ischemia during pacing, were further analysed for the relation of VCG ST level to ischemia. Sensitivity and specificity of STC-VM levels were described by ROC analysis for a range of STC-VM levels. Conclusions. Concordance of different measures for detection of onset of myocardial ischemia is difficult to assess in the absence of a very reliable reference method. The contribution of HR and ischemia to VCG ST levels were estimated in study subjects. HR-related increases in STC-VM occur in the absence of ischemia. HR levels need to be considered when interpreting STC-VM as a diagnostic test for ischemia. Further study is needed to establish criteria that take into account multiple clinical factors in order to improve the predictive value of our tests for myocardial ischemia.

Heart is a vital organ that pumps blood to whole body. Synchronous contraction of the heart muscles assures that the required blood flow is supplied to organs. But sometimes the synchrony between those muscles is distorted, which results in reduced cardiac output that might lead to severe diseases, and even death. The most common of heart diseases are myocardial infarction and arrhythmias. The contraction of heart muscles is controlled by the electrical activity of the heart, therefore determination of that electrical activity could give us the information regarding the severeness and type of the disease. In order to diagnose heart diseases, classical 12 lead electrocardiogram (ECG) is the standard clinical tool. Although many cardiac diseases could be diagnosed with the 12 lead ECG, measurements from sparse electrode locations limit the interpretations. The main objective of this thesis is to determine the cardiac electrical activity from dense body surface measurements. This problem is called the inverse problem of electrocardiography. The high resolution maps of epicardial potentials could supply the physician the information that could not be obtained with any other method. But the calculation of those epicardial potentials are not easy / the problem is severely ill-posed due to the discretization and attenuation within the thorax. To overcome this ill-posedness, the solution should be constrained using prior information on the epicardial potential distributions. In this thesis, spatial and spatio-temporal Bayesian maximum a posteriori estimation (MAP), Tikhonov regularization and Kalman filter and Kalman smoother approaches are used to overcome the ill-posedness that is associated with the inverse problem of ECG. As part of the Kalman filter approach, the state transition matrix (STM) that determines the evolution of epicardial potentials over time is also estimated, both from the true epicardial potentials and previous estimates of the epicardial potentials. An activation time based approach was developed to overcome the computational complexity of the STM estimation problem. Another objective of this thesis is to study the effects of geometric errors to the solutions, and modify the inverse solution algorithms to minimize these effects. Geometric errors are simulated by changing the size and the location of the heart in the mathematical torso model. These errors are modeled as additive Gaussian noise in the inverse problem formulation. Residual-based and expectation maximization methods are implemented to estimate the measurement and process noise variances, as well as the geometric noise.

The interpretation of heart&#039 / s electrical activity is very important in clinical medicine since contraction of cardiac muscles is initiated by the electrical activity of the heart. The electrocardiogram (ECG) is a diagnostic tool that measures and records the electrical activity of the heart. The conventional 12 lead ECG is a clinical tool that provides information about the heart status. However, it has limited information about functionality of heart due to limited number of recordings. A better alternative approach for understanding cardiac electrical activity is the incorporation of body surface potential measurements with torso geometry and the estimation of the equivalent cardiac sources. The problem of the estimating the cardiac sources from the torso potentials and the body geometry is called the inverse problem of electrocardiography. The aim of this thesis is reconstructing accurate high resolution maps of epicardial potential representing the electrical activity of the heart from the body surface measurements. However, accurate estimation of the epicardial potentials is not an easy problem due to ill-posed nature of the inverse problem. In this thesis, the linear inverse ECG problem is solved using different optimization techniques such as Conic Quadratic Programming, multiple constrained convex optimization, Linearly Constrained Tikhonov Regularization and Minimum Relative Entropy (MRE) method. The prior information used in MRE method is the lower and upper bounds of epicardial potentials and a prior expected value of epicardial potentials. The results are compared with Tikhonov Regularization and with the true potentials.

The aim of this thesis is to determine whether surface electromyography (EMG) can be used as a diagnostic tool in chiropractic practice to identify the functional status of the lumbar paraspinal muscles. There were two main studies to achieve this aim. The reliability and validity of the surface EMG signal to measure the activity of paraspinal muscles during maintenance of simple static postures was evaluated. During maintenance of static postures, the raw surface EMG signal was often contaminated by an electrocardiographic (ECG) signal. Although the ECG artefact was successfully removed using two different ECG removal techniques (manual and semi-automatic), the reliability of the surface EMG signal was not significantly improved (ICC less than 0.75) for both non-normalised and normalised data. Therefore the static postures that were used in this thesis did not provide a protocol that can be used to measure the functional status of the lumbar paraspinal muscles in clinical practice. However, when muscle contraction was at a moderate level, the reliability of EMG signal became better. Walking was considered to be a possible protocol to record a reliable surface EMG signal from paraspinal muscles. Three components of the surface EMG signal were used to characterise the pattern of muscle activity during steady state walking. The narrow window technique was used to characterise the peak activation point of the activity envelope in order to capture a stationary signal from which to calculate amplitude and frequency measures. Walking is a cyclic activity. The back muscles contract rhythmically during a single gait cycle. It is possible to identify the start and end points of the activity envelope associated with the rhythmic contraction of the muscles and define the timing of the muscle activation cycle relative to heel strike. The metronome was found to be useful to control the pace of natural walking in this study. The surface EMG signal of the first recording minute (1 ~ 2 minute) was not associated with a signal that was stable in terms of the parameters that were used in this study. It wa s found that the last recording minute (9 ~ 10 minute) can be used. This suggests that it may be necessary for subjects to walk for a defined period lasting some minutes before the commencement of recording of the surface EMG. Surface EMG may be used as a tool to measure activation patterns of the low back muscles during muscle contraction associated with the support of various static postures or during the execution of dynamic movements such as walking in the real world. The static postures used in this thesis to record the surface EMG signal from the lumbar paraspinal muscles were found not to provide the basis for a reliable and valid tool. However, a walking exercise might be an alternative activity which can be used easily in clinical practice. The components of the surface EMG signal that may be used in future studies might include measures of the amplitude, frequency and timing of the surface EMG signal.

Αρχικά εξετάζεται η φυσιολογία της καρδιάς και η λειτουργία της ως αντλίας, οι διάφορες φάσεις του καρδιακού κύκλου και τα αίτια των φαινομένων που παρατηρούνται σε αυτόν. Στη συνέχεια μελετώνται οι καρδιακοί ήχοι, η προέλευσή τους και μέθοδοι παρατήρησής τους, το ηλεκτροκαρδιογράφημα, τα χαρακτηριστικά του και οι εφαρμογές του. Ακολούθως εξετάζεται η δειγματοληψία, επεξεργασία και ανάλυση βιολογικών σημάτων. Πιο συγκεκριμένα, μελετώνται οι μέθοδοι και οι αλγόριθμοι με τους οποίους λαμβάνονται τα ηλεκτροκαρδιογραφικά και φωνοκαρδιογραφικά σήματα, απομακρύνεται ο θόρυβος που προστίθεται από διάφορες πηγές και ανιχνεύονται συγκεκριμένα χαρακτηριστικά των κυματομορφών των σημάτων και ιδιότητές τους, για να αναλυθούν και να γίνει διάγνωση δυσλειτουργιών και παθολογιών της καρδιάς. Τέλος, αναπτύσσεται κώδικας συνεχούς δειγματοληψίας τεσσάρων καναλιών και καταγραφής των δεδομένων δειγματοληψίας σε μια κάρτα μνήμης πολυμέσων, προγραμματίζοντας τον μικροεπεξεργαστή MSP430F169 της Texas Instruments. / In the first part, the physiology of the heart and its functionality as a pump are studied, considering the different phases of a heart cycle and the phenomena observed within. Furthermore, heart sounds, their origin and methods of detection are examined, alongwith the electrocardiogram, its characteristics and applications. Secondly, sampling, processing and analysing methods of biosignals are described. In particular,techniques for ECG and PCG signal acquisition, noise reduction and detection of unique properties and characteristics are studied for analysis and diagnosis of heart disorders and pathologies. Finally, a code for continuous sampling of four channels and storing the sampled data into a multimedia memory card is developed, programming the MSP430F169 microcontroller, by Texas Instruments.

Orientador: Prof. Dr. Pai Chi Nan / Dissertação (mestrado) - Universidade Federal do ABC, Programa de Pós-Graduação em Engenharia Biomédica, 2014. / A alta demanda de transplantes de coração não é suprida pela quantidade de doadores do órgão. Diferentes alternativas aos transplantes são pesquisadas, sendo uma delas a utilização de bombas de sangue centrífugas (BSC) com mancal magnético (MM), apresentando maior durabilidade do que demais bombas. Porém acredita-se que o fluxo contínuo produzido por essas bombas possa causar danos no organismo em longo prazo, havendo a necessidade da utilização de fluxo sanguíneo pulsátil. O objetivo do trabalho foi produzir fluxo sanguíneo pulsátil sincronizado com o coração do paciente com uma BSC com MM. Para a produção do fluxo pulsátil foi feita a alteração da velocidade de rotação da BSC de acordo com os sinais eletrocardiográficos (ECG) do paciente. Foram utilizadas três fontes de sinal de ECG para os testes: gerador de funções, simulador de paciente e voluntário. O algoritmo implementado no Simulink® inferiu os instantes dos batimentos cardíacos seguintes identificando regiões acima de um determinado limiar (fixo e móvel) de amplitude máxima (picos QRS), que correspondem ao início dos batimentos. Calculou-se a média (fixa e móvel) da taxa de batimentos e inferiu-se o instante de tempo aproximado do pico QRS seguinte no sinal de ECG. A velocidade de rotação da BSC foi aumentada nos instantes inferidos para os QRS e após algum tempo foi reduzida. A resposta do motor foi avaliada no ar utilizando sinais degraus e velocidades de rotação definidas pelo algoritmo como entrada. As velocidades reais do motor foram obtidas utilizando a amostra do gerador e do voluntário. A possibilidade de produção de fluxo pulsátil nas condições encontradas foi avaliada. O algoritmo permitiu a identificação dos picos dos complexos QRS, o cálculo da taxa de batimentos e a inferência dos batimentos seguintes. Os valores de erro absolutos e relativos entre os instantes inferidos e reais foram baixos para os sinais das três fontes, tendo valores máximos aproximados de 0,5s (120 a 60bpm) e 51% (60 a 90bpm) para as amostras do gerador e do simulador, e de 0,157s e 15,94% para a amostra do voluntário. A elevação da velocidade de rotação de referência para 1900rpm ocorreu nos instantes dos valores inferidos e após 0,4s a velocidade foi reduzida para 1500rpm. Os momentos de elevação da velocidade de rotação se apresentaram sincronizados com os instantes dos batimentos. O tempo de resposta do motor foi de 0,04s. A estabilização das oscilações da velocidade real ocorreu após 2s, com máximos e mínimos acima e abaixo dos valores de referência, e médias das oscilações aproximadamente de 1700rpm, de acordo com a frequência do ECG. Houve sincronização entre a velocidade de referência e a real. As amplitudes de oscilação elevadas indicaram que os parâmetros do controlador do motor deveriam ser modificados para sua utilização em uma aplicação na água, com velocidade variável de entrada, e para seu ganho variável estar em intervalos de estabilidade. Outro dispositivo é necessário para medir fluxo e pressão do sistema produzindo fluxo pulsátil. / The high demand for heart transplants is not supplied by the number of donors. Alternatives to transplants are being researched, being one of these the use of centrifugal blood pumps (CBP) with magnetic bearing (MB), which have higher durability than other types of pumps. Nevertheless it is believed that the continuous flow generated by these pumps may cause long-term damage to the body, being necessary the use of pulsatile blood flow. The objective of this work is to produce pulsatile blood flow synchronized with the heart of the patient using a CBP with MB. The synchronized pulsatile flow was done by changing the rotational speed of the pump, according to the electrocardiographic (EKG) signals of the patient. Three different sources of EKG signal were used: a function generator, a patient simulator and a volunteer. The algorithm, implemented on Simulink®, inferred the moments of the following heart beats by finding points, above a certain threshold (fixed and moving), of maximum amplitude (QRS complexes) on the EKG signal. The mean of the heart beat rate (fixed or moving) was calculated and the instant of the next QRS peaks were inferred. The rotational speed of the CBP was increased on the moments of the QRS inferred and decreased after some time. The motor response was evaluated on air, using step signals and rotational speeds defined by the algorithm as inputs. The motor rotational speeds were obtained with the generators¿ and the volunteer¿s samples. The possibility of generation of pulsatile flow was evaluated. The algorithm identified the QRS complexes peaks, calculated the mean heart rate and inferred the following heart beats. The absolute and relative errors between the inferred and the real instants of the QRS peaks were low for the signals of the three sources, with maximum approximate values of 0,5s (120 to 60bpm) and 51% (60 to 90bpm) for the function generator and the simulator samples, and of 0,157s and 15,94% for the volunteer sample. The increase of the reference rotational speed to 1900rpm was done on the instants of the inferred values of QRS complexes, with reduction to 1500rpm after 0,4s. The moments in which the rotational speed is on its maximum values are about the same as the QRS complexes of the signal. The motor response was of 0,04s. The stabilization of the oscillating speed occurred after 2s, with maximum and minimum values above and below the reference ones, and mean values around 1700rpm, according to the heart beating rate. Synchronization between the reference and real rotational speeds was observed. The high amplitudes of the oscillations pointed out that the motor driver parameters should be changed to be used with variable rotational speed input and for the variable gain to remain between the driver stability values. Another device is required to measure flow and pressure of the system producing pulsatile flow.

Orientador: Aparecido Antonio Camacho / Banca: Wagner Luís Ferreira / Banca: Ruthnéa Aparecida Lázaro Muzzi / Resumo: A cardiomiopatia chagásica está presente na história da humanidade, desde os primórdios da civilização. No continente americano, aproximadamente 200 milhões de pessoas estão afetadas por essa doença, principalmente em seu Hemisfério Sul, ocasionando importantes danos econômicos e sociais. A grande variedade de cepas e seu comportamento clínico obscuro na fase crônica indeterminada intensificam as falhas de diagnóstico e morte súbita. Sendo o cão um modelo experimental adequado para o estudo dessa doença em humanos, realizou-se este trabalho visando a caracterizar as alterações eletrocardiográficas, ecodopplercardiográficas e hematimétricas, de cães experimentalmente infectados com Trypanosoma cruzi, cepa Colombiana, em sua fase crônica indeterminada. Para tanto, 13 cães adultos, fêmeas foram infectados com o referido protozoário e submetidos a avaliações eletrocardiográfica, hematimétrica, bioquímico-sérica e ecocardiográfica durante sua fase crônica (1997 a 2004). A arritmia sinusal respiratória foi o ritmo predominante durante todo o período experimental, com baixa prevalência de bloqueio de ramo direito e crescente incidência de bloqueio atrioventricular de primeiro grau. A avaliação ecodopplercardiográfica revelou inversão das ondas E e A mitral, confirmando o distúrbio diastólico nesses animais. A avaliação bioquímica revelou atividade enzimática aumentada, confirmando a lesão cardíaca provocada pela infecção mesmo nesta fase. Desta forma, o presente ensaio contribui de forma singular para o conhecimento clínico desta afecção, trazendo mais informações acerca da tênue e obscura linha que separa a fase crônica indeterminada e a fase crônica cardíaca, na espécie canina experimentalmente infectada pela cepa Colombina do Trypanosoma cruzi. / Abstract: The Chagasic cardiomiopathy is present in the human history since the first civilization. In the American continent, 200 millions people have been affecting by this disease, mainly in south hemisphere, causing important economics and social damages. The great number of strains and obscure clinical behavior in the indeterminate phase, intensify diagnostic failure and increase sudden death. The dog is an excellent experimental model to study this disease in human, therefore this research was developed to characterize the electrocardiographic, echodopplercardiographic and haematological changes, in experimentally infected dogs with Trypanosoma cruzi, Colombian strain, in a chronic indeterminate phase. For that, thirteen infected adult dogs, female, were submitted to electrocardiographic, haematological, biochemical and echocardiographic evaluations during a chronic phase (1997 to 2004). The respiratory sinus arrhythmia was the most frequent rhythm during this research, with low prevalence of right bundle branch block and growing incidence of first degree atrioventricular block. The echocardiographic mitral waves E and A inversion, demonstrated the diastolic dysfunction on this animals. All tested serum enzymes had increased activity, confirming the cardiac lesion caused by the infection even in that phase. Therefore, this research contributed in a unique way for the clinic knowledge of this disease, bringing more information about this fine transition line between the indeterminate and cardiac phase, in experimentally Trypanosoma. cruzi, Colombian strain infection of canine species. / Mestre

Orientador: Aparecido Antonio Camacho / Banca: Aulus Cavalieri Carciofi / Banca: Glaucia Bueno Pereira Neto / Banca: José Alberto Montoya Alonso / Banca: Julio Carlos Canola / Resumo: O estudo caracterizou a influência da obesidade e do sobrepeso sobre parâmetros cardiovasculares em gatos. Foram estudados 15 gatos obesos, sete com sobrepeso e sete com escore de condição corporal ideal. Não foram evidenciadas alterações laboratoriais compatíveis com estímulo do sistema renina angiotensina-aldosterona. Verificou-se a ocorrência pressão arterial sistólica acima de 150mmHg em 73,33% dos animais obesos, com nítido aumento (p < 0,0001) da PAS no grupo obeso, comparado aos grupos sobrepeso e com ECC ideal. O aumento da PAS foi acompanhado de disfunção diastólica, havendo correlação da PAS com a relação E/A do fluxo mitral (p = 0,0008, r = -0,40), além de maiores valores de espessura da parede livre e do septo interventricular na diástole (p<0,05). À avaliação radiográfica, não foram verificadas diferenças no VHS e distância precordial, apenas maiores valores da mensuração da gordura falciforme nos animais obesos. Com relação às anormalidades eletrocardiográficas, houve maior ocorrência de arritmias ventriculares complexas ao Holter de 24 horas dos gatos obesos (p<0,05). O ritmo predominante na eletrocardiografia computadorizada foi sinusal, enquanto no Holter de 24 horas, foi arritmia sinusal em todos os grupos. Não houve diferenças entre as frequências cardíacas entre os grupos, tampouco variação circadiana. Também não se observaram diferenças entre os períodos em bradicardia ou taquicardia e entre os índices de variabilidade da frequência cardíaca no domínio do tempo. Na avaliação respiratória, animais obesos anestesiados apresentaram menores volumes correntes e VCO2 (p<0,05) além da tendência à hipoxemia. Gatos em sobrepeso também apresentaram menores valores de PaO2, porém sem alterações na ventilometria ... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: This study aimed to characterize the influence of obesity and overweight on cardiovascular parameters in cats. Twenty nine cats were evaluated (15 obese, seven overweight and seven with ideal ECC). There were no differences on parameters that reflect increase of aldosterone-angiotensin renin activity in obese cats. Systolic blood pressure was higher than 150mmHg in 73.33% of obese animals with a marked increase in systolic blood pressure (p < 0,0001) in obese group, compared to overweight or cats with ideal ECC. The increase in systolic blood pressure was accompanied by diastolic dysfunction, evidenced by the correlation (p = 0.0008, r = -0.40) with the E/A ratio of mitral flow. Moreover, obese animals had higher values of free wall thickness and interventricular septum in diastole (p<0,05). At radiographic evaluation, there were no differences in VHS, precordial distance and chest depth, only higher values of falciform fat in the obese animals. Regarding electrocardiographic abnormalities, in 24-Holter of obese cats, it was found a higher occurrence of complexes ventricular arrhythmias. The predominant rhythm in computerized ECG was sinus rhythm, while in the 24-hour Holter was sinus arrhythmia in all groups. There was no difference between heart rate throughout the day, either between the groups. Also, there were no differences in the periods of bradycardia or tachycardia and in the indexes of heart rate variability in the time domain between groups. Regarding the respiratory evaluation, anesthetized obese cats showed lower tidal volumes and VCO2 (p<0,05) and obese and overweight cats showed a tendency to hypoxemia. Therefore, obesity can cause changes on cardiorespiratory parameters, proportionally to increase of body weight and body fat / Doutor

A doença de Chagas é uma doença crônica causada pela infecção pelo protozoário Trypanosoma cruzi (T.cruzi). A sua principal consequência clínica é o desenvolvimento da cardiomiopatia chagásica crônica (CCC), que acomete 30% dos pacientes. Não foi determinado um indicador de evolução para a CCC ou permanência na forma indeterminada assintomática da doença de Chagas. Diversos trabalhos têm mostrado alterações no perfil de expressão gênica e proteômica ocorridas na fase aguda e crônica da doença de Chagas experimental e humana. Tais alterações advêm da regulação estabelecida em diversos estágios da expressão gênica e podem ser fatores relevantes no prognóstico da doença. Neste contexto, os microRNAs (miRs), podem exercer uma importante função reguladora. Sua ação se dá pela associação a um RNA mensageiro (RNAm) alvo, inibindo sua tradução ou degradando este transcrito. Assim, a hipótese deste trabalho é a de que a infecção aguda por T. cruzi modula a expressão de miRs no miocárdio de camundongos. Foi avaliado por qRT-PCR o perfil de expressão de miRs 15, 30 e 45 dias após a infecção. O perfil de expressão de miRs resultante foi suficiente para segregar os grupos de acordo com o tempo da infecção. O número de miRs diferencialmente expressos aumentou com a progressão da infecção. Além disso, seis miRs tiveram sua expressão correlacionada à piora na parasitemia e intervalo QTc dos animais: miR-142-3p miR-142-5p, miR-145, miR-146b, miR-149 e miR-21. Análises de correlação realizadas com todos os miRs avaliados ressaltaram este mesmo grupo de miRs entre os mais significativamente correlacionados, além de outros 73 correlacionados com a parasitemia, 67 com o intervalo QTc e 16 com ambos os parâmetros simultaneamente. Nas análises in silico, TNF-alfa e ciclina-D1 foram moléculas nodais recorrentes nas redes criadas com alvos dos miRs diferencialmente expressos em todos os tempos avaliados. Na única rede criada com os miRs correlacionados às alterações na parasitemia e intervalo QTc, TNF-alfa, TGF-beta, Rac1 e Src foram as moléculas nodais. Este trabalho apresenta de maneira inédita o envolvimento dos miRs durante a infecção aguda por T. cruzi, proporcionando novas perspectivas em relação a potenciais ferramentas terapêuticas e prognósticas / Chagas disease is a chronic illness caused by infection with the protozoan Trypanosoma cruzi (T. cruzi). Its main clinical outcome is the development of chronic Chagas cardiomyopathy (CCC), which affects 30% of the patients. The factors that define the progression to CCC or maintenance in the asymptomatic indeterminate form of the disease are still poorly understood. Several studies have presented changes occurred in the gene and proteomic expression profiles in both acute and chronic phases of experimental and human Chagas disease. Such changes result from regulation established at different stages of gene expression and may be relevant for the disease prognosis. In this context, microRNAs (miRs) may play an important regulatory function. miRs act by association to a target messenger RNA (mRNA), inhibiting translation or degrading the transcript. Thus, our hypothesis is that acute infection by T. cruzi modulates the expression of microRNAs in the myocardium of mice. The miR expression profile was evaluated by qRT-PCR 15, 30 or 45 days after the infection. This profile was sufficient to segregate the samples according to the time of infection. The number of differentially expressed miRs was higher as the infection progressed. Moreover, six miRs had their expression correlated with worsening of parasitaemia and QTc interval: miR-142-3p miR-142- 5p, miR-145, miR-146b, miR-149 and miR-21. Secondary unbiased correlation analyses showed this cluster of miRs among the most significant and other 73 miRs correlated with parasitaemia, 67 with QTc and 16 with both parameters simultaneously. In silico target prediction analyses showed TNF-alfa and cyclin-D1 as recurrent nodal molecules of the networks created with miRs targets from all time points. The network generated with miRs correlated to changes in parasitaemia and QTc interval showed TNF-alfa, TGF-beta, Rac1 and Src as nodal molecules. This work points out for the first time the involvement of miRs in the acute infection by T. cruzi, providing new insights about potential diagnostic and prognostic tools