22 research outputs found
Analysis of mRNA expression of genes related to synthesis of fatty acids in goose fatty liver
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Endocardial mapping of atrial fibrillation in the human right atrium using a non-contact catheter
Background Endocardial mapping of atrial fibrillation in humans is limited by its low resolution and by complexities in the arrhythmia and atrial anatomy. Methods and Results A catheter mounted non-contact multielectrode was deployed in the right atrium of 11 patients with atrial fibrillation and used to reconstruct 3360 electrograms, superimposed onto a computer-simulated model of the endocardium, using inverse solution mathematics. This allows construction of isopotential maps of the right atrium. Patients had either sustained atrial fibrillation (n=3) for >6 months or developed atrial fibrillation during the study (n=8). Spontaneous initiation of atrial fibrillation was recorded in one patient and was demonstrated by the non-contact system to arise from two successive atrial ectopic beats from the site of a roving contact catheter. Reconstruction of electrograms recorded during atrial fibrillation was validated by comparison with contact electrograms with cross-correlation. During established atrial fibrillation, four patients predominantly had a single right atrial wave front, two had two wave fronts and five patients had three to five wave fronts for most of the time. Periods of electrical silence were seen in the right atrium in eight patients, after which, activity emerged from consistent septal sites alone, suggesting a left atrial origin. During intravenous administration of flecainide, atrial fibrillation in two patients terminated spontaneously or following pacing manoeuvres, while in the remaining patient sinus rhythm was restored via atrial tachycardia. Conclusion Non-contact mapping of the right atrium has demonstrated modes of initiation and termination of atrial fibrillation, characterized different patterns of right atrial activation in atrial fibrillation and suggests that the left atrium may sustain atrial fibrillation in some patients. Simultaneous mapping of the right and left atrium is required to further elucidate the mechanisms of human atrial fibrillation
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Effect of body characteristics on thoracic attenuation of intra-cardiac electrical activity recorded on the surface electrocardiogram
The objective of this study was to determine the effect of body characteristics on the electrical transfer function of the human thorax. Twenty patients undergoing electrophysiologic study were enrolled. Unipolar stimuli were applied in the right ventricular apical and posterioseptal areas. XYZ surface ECGs and unipolar intra-cardiac electrograms of the pacing impulses were recorded and signal-averaged. The intracardiac-to-surface transfer functions were modeled and compared with body characteristics. Physical dimensions, respiratory measures obtained by spirometry, and age correlated with magnitude intercepts and slopes of the modeled transfer functions in all three directions. The phase transfer functions were correlated with physical dimensions in the Y and Z directions. The effect of body characteristics on the frequency dependency of attenuation and phase has implications on the use of surface ECG and body surface mappin
A Mobile ECG Monitoring System with Context Collection
Preventative health management represents a shift from the traditional approach of reactive treatment-based healthcare towards a proactive wellness-management approach where patients are encouraged to stay healthy with expert support when they need it, at any location and any time. This work represents a step along the road towards proactive, preventative healthcare for cardiac patients. It seeks to develop a smart mobile ECG monitoring system that requests and records context information about what is happening around the subject when an arrhythmia event occurs. Context information about the subject’s activities of daily living will, it is hoped, provide an enriched data set for clinicians and so improve clinical decision making. As a first step towards a mobile cardiac wellness guideline system, the authors present a system which can receive bio-signals that are wirelessly streamed across a body area network from Bluetooth enabled electrocardiographs. The system can store signals as they arrive while also responding to significant changes in Electrocardiogram activity. The authors have developed a prototype on a handheld computer that detects and responds to changes in the calculated heart rate as detected in an ECG signal. Although the general approach taken in this work could be applied to a wide range of bio-signals, the work focuses on ECG signals. The components of the system are, - A Bluetooth receiver, data collection and storage module - A real-time ECG beat detection algorithm. - An Event-Condition-Action (E-CA) rule base which decides when to request context information from the user. – A simple user interface which can request additional information from the user. A selection of real-time ECG detection algorithms were investigated for this work and one algorithm was tested in MATLAB and then implemented in Java. In order to collect ECG signals (and in principle any signals), the generalised data collection architecture has also been developed using Java and Bluetooth technology. An Event-Condition-Action (ECA) rule based expert system evaluates the changes in heart beat interval to decide when to interact with the user to request context information