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Accurate mapping of cardiac fibrillation activity: an experimental contribution


Atrial Fibrillation (AF) is the sustained cardiac arrhythmia most common in clinical practice, affecting between 1 and 2% of the world population. This disorder has high morbidity and mortality and has become a chronic non-infectious cardiovascular epidemic that poses a serious threat to human health, becoming an important problem of public health and with a high burden of the National Health Service budget. In the last decades, basic and clinical research has made great progress in improving the diagnosis and treatment of AF, and its mechanism has been gradually elucidated, but not fully understood. During AF, the interpretations of the signals and maps provided by commercial electrical mapping systems is in many cases complex and uncertain, making it difficult to correctly characterize and locate arrhythmogenic sources for ablation. Correct identification of the type of mechanism and its location in the atria is the current challenge for electrophysiologists. Considering the complexity of this arrhythmia and the high sensitivity to errors in current commercial systems, it is important that proposed methods validations are carefully done through controlled conditions experiments mimicking clinical situations. The main objective of this project is to develop an experimental model of induced AF by electrical stimulation and record simultaneously epicardial and non-invasive electrical activity for customization of traditional research maps generated to study and treat AF. The experiments will be conducted in rabbit hearts under Langendorff preparation. AF induction will be performed by a standard train of pulses with a pacing restitution protocol (S1-S1) in the left atrium. The acquisition of biopotentials in the epicardium will be performed by simultaneous unipolar contact electrodes and panoramic optical mapping system. The acquisition of non-invasive electrical activity will be by 64 electrodes distributed between the faces of a translucent acrylic hexagonal tank which is in contact with a heated (37°C) Krebs-Henseleit or Tyrode solution. Thus, the heart is submerged in a tank with a nutrient solution inside, conducting its electrical activity to the electrodes of the tank. From the non-contact signals, the epicardial electrograms will be estimated by the non-invasive electrocardiographic imaging (iECG) method, where a discretization of the epicardial and tank 3D surfaces in triangular elements is performed followed by the Tikhonov regularization method. Signal analysis and generation of electrophysiological and electrocardiographic maps will be done by Matlab Version 9.7 (R2019) software (Mathworks, Inc.). Time and frequency domain metrics and maps will be calculated from the epicardial and non-invasive optical and electrical signals. Through a pipeline of pre-processing and postprocessing techniques to be applied to the signals used by electrical mapping, it is expected to develop more realistic maps related to the AF pathophysiology. This research project is inspired by interdisciplinary areas (engineering and cardiology) where important concepts about biological signal processing, hardware and animal experimentation will be necessary, with a possibility of in the future implement the validate techniques in medical equipment. The refinement and development of new techniques to be implemented as current health technologies represent an innovation to contribute to medical diagnosis and prognosis within medical environments. (AU)

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