Dimension Analysis in Atrial Fibrillation’s Spontaneous Termination

Suarez, Kleydis; Najim, Md.; Gonzalez, C.

doi:10.1007/978-3-540-74471-9_36

Cited by 2 publications

(2 citation statements)

References 5 publications

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“…Their outcomes were consistent with the 3 types of AF previously classified by Konings et al [9], whom based this classification on the spatio-temporal complexity of the atrial activation and the DFCL. In a recent approach, topological dimension of the ECG signals during atrial fibrillation, showed an increasing of the topological dimension (meaning more dynamical complexity) close to spontaneous termination of atrial fibrillation [10].…”

Section: Introductionmentioning

confidence: 99%

Nonlinear analysis of the ECG during atrial fibrillation in patients for low energy internal cardioversion

Diaz

Gonzalez

Escalona

et al. 2008

2008 30th Annual International Conference of the IEEE Engineering in Medicine and Biology Society

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The goal of this study was to investigate the usefulness of nonlinear analysis in determining the success of low energy internal cardioversion (IC) in patients with atrial fibrillation (AF). Nonlinear analysis has previously been used for characterizing AF patterns, and spontaneous termination in its paroxysmal form. However, the relationship between the probability to restore sinus rhythm by IC and quantitative nonlinear analysis based electrocardiographic (ECG) markers has not been explored before. Thirty nine patients with AF, for elective DC cardioversion at the Royal Victoria Hospital in Belfast, were included in this study. One catheter was positioned in the right atrial appendage and another in the coronary sinus, to deliver a biphasic shock waveform. A voltage step-up protocol (50-300 V) was used for patient cardioversion. Residual atrial fibrillatory signal (RAFS) was derived from 60 seconds of surface ECG from defibrillator pads, prior to shock delivery, by bandpass filtering and ventricular activity (QRST) cancellation. QRST complexes were cancelled using a recursive least squared (RLS) adaptive filter. The maximal Lyapunov exponent (lambda), correlation dimension (course grained estimation, CDcg) and approximate entropy (ApEn) were extracted from the RAFS. These variables were calculated from 10 s of the RAFS before shock delivery. 26 patients were successfully cardioverted, employing a maximum energy of 11.84 joules. A lower lambda (0.037+/-0.006 vs. 0.044+/-0.008, P=0.01) and CDcg (5.552+/-2.075 vs. 6.592+/-1.130, P=0.049) were found in successfully cardioverted patients than in those non successful ones, with an energy

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Section: Introductionmentioning

confidence: 99%

Nonlinear analysis of the ECG during atrial fibrillation in patients for low energy internal cardioversion

Diaz

Gonzalez

Escalona

et al. 2008

2008 30th Annual International Conference of the IEEE Engineering in Medicine and Biology Society

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“…Los sistemas dinámicos presentan el estudio de toda señal que evoluciona en el tiempo, según una ley física, presentando estados o fases dinámicas. Un tipo particular de dinámica lo constituyen las señales caóticas, las cuales se caracterizan por ser sensibles a las condiciones iniciales del sistema que las genera, lo que dificulta la predicción de su evolución a largo plazo (Strogatz, 1994;Suárez et al, 2007;Dumas et al, 1993).…”

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Caracterización dinámica de los cambios microestructurales en barras de aceros dúplex SAF 2205 utilizando la dimensión de información

et al. 2014

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RESUMEN:En el presente estudio se evalúa el comportamiento dinámico de las señales ultrasónicas de muestras de acero dúplex SAF 2205 (UNS31803), sometidos a tratamientos de envejecimiento a 875 y 950 °C. En el primer tratamiento se promueve la precipitación de la fase sigma y en el segundo su disolución. Los resultados obtenidos por microscopía óptica indican que la cantidad relativa de la fase sigma aumenta progresivamente con el tiempo de envejecimiento a 875 °C, observándose la transformación de la fase ferrita en fase sigma y en austenita secundaria. Por otra parte, a medida que se aumenta el tiempo de tratamiento a 950 °C, se observa una reducción del porcentaje de fase sigma y un aumento de la fase ferrítica. El estudio propone evaluar en el ámbito de sistemas dinámicos la influencia de las fases microestructurales en el comportamiento de las señales y su dependencia con las pérdidas de energía, que ocurren en el sistema por efecto de los tratamientos térmicos, utilizando la teoría del caos determinista. Para caracterizarlos se emplea la representación del espacio de fases dinámicas y el cálculo de la dimensión de información. Los resultados obtenidos muestran una mayor correlación entre la dimensión de información y el coeficiente de atenuación, en comparación con las fracciones de fase. No obstante, la eficiencia de este tipo de estudio depende de la frecuencia seleccionada durante la evaluación del material. SUMMARY: Dynamics characterization of microstructural changes in bars of duplex steels SAF 2205 using the information dimension.This study evaluates the ultrasonic signals behavior of a duplex stainless steel SAF 2205 (UNS S31803) after aging treatments at 875 and 950 °C. The first treatment promotes the precipitation of the sigma phase and the second, its dissolution. The microstructural evaluation was carried out by optical microscopy. The results showed an increase of the sigma phase fraction and the secondary austenite with the time of aging treatment at 875 °C. On the other hand, increasing the time of treatment at 950 °C promotes a reduction of the sigma phase and the corresponding increase of the ferrite phase fraction. The study proposed to evaluate in the dynamical system field the influence of microstructural phases in the signals behavior and their dependence on the energy losses occurring in system during heat treatment, by deterministic chaos theory. To accomplish characterization, algorithm employs the representation of dynamic phase space and the information dimension estimate. The results show a higher correlation between the information dimension and the attenuation coefficient in comparison with the phase fractions. However, the efficiency of this type of study will depend on the frequency selected for the evaluation of the material.

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Dimension Analysis in Atrial Fibrillation’s Spontaneous Termination

Cited by 2 publications

References 5 publications

Nonlinear analysis of the ECG during atrial fibrillation in patients for low energy internal cardioversion

Nonlinear analysis of the ECG during atrial fibrillation in patients for low energy internal cardioversion

Caracterización dinámica de los cambios microestructurales en barras de aceros dúplex SAF 2205 utilizando la dimensión de información

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