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Documentos generados por los docentes e investigadores de la Universidad en su labor de investigación científica producida o editada por los departamentos y centros de la Universitat Politècnica de València.

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A clinically-oriented computer model for radiofrequency ablation of hepatic tissue with internally cooled wet electrode
(Taylor & Francis, 2019) Ewertowska, Elzbieta; Quesada-Diez, Rita; Radosevic, A.; Andaluz, Anna; Moll, Xavier; García Arnás, F.; Berjano Zanón, Enrique; Burdío Pinilla, Fernando; Trujillo Guillen, Macarena; Dpto. de Ingeniería Electrónica; Dpto. de Matemática Aplicada; Escuela Técnica Superior de Ingeniería del Diseño; Escuela Técnica Superior de Arquitectura; Biosignals And Minimally Invasive Technologies-BioMIT; Ministerio de Economía, Industria y Competitividad
[EN] Purpose: To improve the computer modelling of radiofrequency ablation (RFA) by internally cooled wet (ICW) electrodes with added clinically oriented features. Methods: An improved RFA computer model by ICW electrode included: (1) a realistic spatial distribution of the infused saline, and (2) different domains to distinguish between healthy tissue, saline-infused tumour, and non-infused tumour, under the assumption that infused saline is retained within the tumour boundary. A realistic saline spatial distribution was obtained from an in vivo pig liver study. The computer results were analysed in terms of impedance evolution and coagulation zone (CZ) size, and were compared to the results of clinical trials conducted on 17 patients with the same ICW electrode. Results: The new features added to the model provided computer results that matched well with the clinical results. No roll-offs occurred during the 4-min ablation. CZ transversal diameter (4.10 +/- 0.19 cm) was similar to the computed diameter (4.16 cm). Including the tumour and saline infusion in the model involved (1) a reduction of the initial impedance by 10 - 20 ohm, (2) a delay in roll-off of 20 s and 70 - 100 s, respectively, and (3) 18 - 31% and 22 - 36% larger CZ size, respectively. The saline spatial distribution geometry was also seen to affect roll-off delay and CZ size. Conclusions: Using a three-compartment model and a realistic saline spatial distribution notably improves the match with the outcome of the clinical trials.
A cooled intraesophageal balloon to prevent thermal injury during endocardial surgical radiofrequency ablation of the left atrium: a finite element study
(IOP Publishing, 2015-10-21) Berjano Zanón, Enrique; Hornero, Fernando; Dpto. de Ingeniería Electrónica; Escuela Técnica Superior de Ingeniería del Diseño; Biosignals And Minimally Invasive Technologies-BioMIT; Ministerio de Educación y Ciencia; Universitat Politècnica de València
[EN] Recent clinical studies on intraoperative monopolar radiofrequency ablation of atrial fibrillation have reported some cases of injury to the esophagus. The aim of this study was to perform computer simulations using three-dimensional finite element models in order to investigate the feasibility of a cooled intraesophageal balloon appropriately placed to prevent injury. The models included atrial tissue and a fragment of esophagus and lung linked by connective tissue. The lesion depth in the esophagus was assessed using a 50 degrees C isotherm and expressed as a percentage of thickness of the esophageal wall. The results are as follows: (1) chilling the esophagus by means of a cooled balloon placed in the lumen minimizes the lesion in the esophageal wall compared to the cases in which no balloon is used (a collapsed esophagus) and with a non-cooled balloon; (2) the temperature of the cooling fluid has a more significant effect on the minimization of the lesion than the rate of cooling (the thermal transfer coefficient for forced convection); and (3) pre-cooling periods previous to RF ablation do not represent a significant improvement. Finally, the results also suggest that the use of a cooled balloon could affect the transmurality of the atrial lesion, especially in the cases where the atrium is of considerable thickness.
A Deep Learning Approach for Featureless Robust Quality Assessment of Intermittent Atrial Fibrillation Recordings from Portable and Wearable Devices
(MDPI AG, 2020-07) Huerta Herraiz, Álvaro; Martínez-Rodrigo, Arturo; Bertomeu-González, Vicente; Quesada, Aurelio; Rieta Ibañez, José Joaquín; Alcaraz, Raúl; Dpto. de Ingeniería Electrónica; Escuela Politécnica Superior de Gandia; Biosignals And Minimally Invasive Technologies-BioMIT; Generalitat Valenciana; Agencia Estatal de Investigación; European Regional Development Fund; Junta de Comunidades de Castilla-La Mancha
[EN] Atrial fibrillation (AF) is the most common heart rhythm disturbance in clinical practice. It often starts with asymptomatic and very short episodes, which are extremely difficult to detect without long-term monitoring of the patient's electrocardiogram (ECG). Although recent portable and wearable devices may become very useful in this context, they often record ECG signals strongly corrupted with noise and artifacts. This impairs automatized ulterior analyses that could only be conducted reliably through a previous stage of automatic identification of high-quality ECG intervals. So far, a variety of techniques for ECG quality assessment have been proposed, but poor performances have been reported on recordings from patients with AF. This work introduces a novel deep learning-based algorithm to robustly identify high-quality ECG segments within the challenging environment of single-lead recordings alternating sinus rhythm, AF episodes and other rhythms. The method is based on the high learning capability of a convolutional neural network, which has been trained with 2-D images obtained when turning ECG signals into wavelet scalograms. For its validation, almost 100,000 ECG segments from three different databases have been analyzed during 500 learning-testing iterations, thus involving more than 320,000 ECGs analyzed in total. The obtained results have revealed a discriminant ability to detect high-quality and discard low-quality ECG excerpts of about 93%, only misclassifying around 5% of clean AF segments as noisy ones. In addition, the method has also been able to deal with raw ECG recordings, without requiring signal preprocessing or feature extraction as previous stages. Consequently, it is particularly suitable for portable and wearable devices embedding, facilitating early detection of AF as well as other automatized diagnostic facilities by reliably providing high-quality ECG excerpts to further processing stages.
A Deep Learning Solution for Automatized Interpretation of 12-Lead ECGs
(IEEE, 2020-09-16) Huerta, Alvaro; Martinez-Rodrigo, Arturo; Rieta Ibañez, José Joaquín; Alcaraz, Raúl; Dpto. de Ingeniería Electrónica; Escuela Politécnica Superior de Gandia; Biosignals And Minimally Invasive Technologies-BioMIT; European Regional Development Fund; Junta de Comunidades de Castilla-La Mancha
[EN] A broad variety of algorithms for detection and classification of rhythm and morphology abnormalities in ECG recordings have been proposed in the last years. Although some of them have reported very promising results, they have been mostly validated on short and non-public datasets, thus making their comparison extremely difficult. PhysioNet/CinC Challenge 2020 provides an interesting opportunity to compare these and other algorithms on a wide set of ECG recordings. The present model was created by ¿ELBIT¿ team. The algorithm is based on deep learning, and the segmentation of all beats in the 12-lead ECG recording, generating a new signal for each one by concatenating sequentially the information found in each lead. The resulting signal is then transformed into a 2- D image through a continuous Wavelet transform and inputted to a convolutional neural network. According to the competition guidelines, classification results were evaluated in terms of a class-weighted F-score (Fß) and a generalization of the Jaccard measure (Gß). In average for all training signals, these metrics were 0.933 and 0.811, respectively. Regarding validation on the testing set from the first phase of the challenge, mean values for both performance indices were 0.654 and 0.372, respectively
A new single-instrument technique for parenchyma division and hemostasis in liver resection: a clinical feasibility study
(Elsevier, 2010-12) Burdío, Fernando; Grande, Luis; Berjano Zanón, Enrique; Martinez-Serrano, Maria; Poves, Ignasi; Burdío, José M.; Navarro, Ana; Güemes, Antonio; Dpto. de Ingeniería Electrónica; Escuela Técnica Superior de Ingeniería del Diseño; Biosignals And Minimally Invasive Technologies-BioMIT; Ministerio de Ciencia e Innovación; Instituto de Salud Carlos III
[EN] The objective of this study was to evaluate the clinical feasibility of a new technique for liver resection based on a radiofrequency-assisted (485 kHz) device that has shown high performance in the animal setting in both transection speed and blood loss per transection area. Eight patients with colorectal hepatic metastasis underwent 11 partial hepatectomies using the proposed technique for both parenchyma division and hemostasis. Main outcome measures were blood loss per transection area and transection speed. No other instruments (including sutures or clips) were used in any of the cases; temporary vascular occlusion performed was not performed. No blood transfusions were required and no mortality or morbidity linked to the hepatic procedure were observed. The median blood loss per transection area and the median transection speed were .79 mL/cm2 (range, .05–7.37 mL/cm2) and 1.28 cm2/min (range, .49–1.87 mL/cm2), respectively. During the follow-up period (range, 4–12 mo) no late complications were detected and postoperative patients were free from hepatic recurrence. The proposed radiofrequency-assisted device was shown to achieve parenchymal division and hemostasis simultaneously, resulting in extremely reduced blood loss.
A Novel Signal Restoration Method of Noisy Photoplethysmograms for Uninterrupted Health Monitoring
(MDPI AG, 2024-01) Vraka, Aikaterini; Zangróniz, Roberto; Quesada, Aurelio; Hornero, Fernando; Alcaraz, Raúl; Rieta Ibañez, José Joaquín; Dpto. de Ingeniería Electrónica; Escuela Politécnica Superior de Gandia; Biosignals And Minimally Invasive Technologies-BioMIT; Generalitat Valenciana; Agencia Estatal de Investigación; European Regional Development Fund; Ministerio de Ciencia e Innovación; Junta de Comunidades de Castilla-La Mancha
[EN] Health-tracking from photoplethysmography (PPG) signals is significantly hindered by motion artifacts (MAs). Although many algorithms exist to detect MAs, the corrupted signal often remains unexploited. This work introduces a novel method able to reconstruct noisy PPGs and facilitate uninterrupted health monitoring. The algorithm starts with spectral-based MA detection, followed by signal reconstruction by using the morphological and heart-rate variability information from the clean segments adjacent to noise. The algorithm was tested on (a) 30 noisy PPGs of a maximum 20 s noise duration and (b) 28 originally clean PPGs, after noise addition (2-120 s) (1) with and (2) without cancellation of the corresponding clean segment. Sampling frequency was 250 Hz after resampling. Noise detection was evaluated by means of accuracy, sensitivity, and specificity. For the evaluation of signal reconstruction, the heart-rate (HR) was compared via Pearson correlation (PC) and absolute error (a) between ECGs and reconstructed PPGs and (b) between original and reconstructed PPGs. Bland-Altman (BA) analysis for the differences in HR estimation on original and reconstructed segments of (b) was also performed. Noise detection accuracy was 90.91% for (a) and 99.38-100% for (b). For the PPG reconstruction, HR showed 99.31% correlation in (a) and >90% for all noise lengths in (b). Mean absolute error was 1.59 bpm for (a) and 1.26-1.82 bpm for (b). BA analysis indicated that, in most cases, 90% or more of the recordings fall within the confidence interval, regardless of the noise length. Optimal performance is achieved even for signals of noise up to 2 min, allowing for the utilization and further analysis of recordings that would otherwise be discarded. Thereby, the algorithm can be implemented in monitoring devices, assisting in uninterrupted health-tracking.
A novel wavelet-based filtering strategy to remove powerline interference from electrocardiograms with atrial fibrillation
(IOP Publishing, 2018) García, M.; Martínez, Miguel; Ródenas, Juan; Rieta Ibañez, José Joaquín; Alcaraz, R.; Dpto. de Ingeniería Electrónica; Escuela Politécnica Superior de Gandia; Biosignals And Minimally Invasive Technologies-BioMIT; Junta de Comunidades de Castilla-La Mancha; Agencia Estatal de Investigación
[EN] Objective: The electrocardiogram (ECG) is currently the most widely used recording to diagnose cardiac disorders, including the most common supraventricular arrhythmia, such as atrial fibrillation (AF). However, different types of electrical disturbances, in which power-line interference (PLI) is a major problem, can mask and distort the original ECG morphology. This is a significant issue in the context of AF, because accurate characterization of fibrillatory waves (f-waves) is unavoidably required to improve current knowledge about its mechanisms. This work introduces a new algorithm able to reduce high levels of PLI and preserve, simultaneously, the original ECG morphology. Approach: The method is based on stationary wavelet transform shrinking and makes use of a new thresholding function designed to work successfully in a wide variety of scenarios. In fact, it has been validated in a general context with 48 ECG recordings obtained from pathological and non-pathological conditions, as well as in the particular context of AF, where 380 synthesized and 20 long-term real ECG recordings were analyzed. Main results: In both situations, the algorithm has reported a notably better performance than common methods designed for the same purpose. Moreover, its effectiveness has proven to be optimal for dealing with ECG recordings affected by AF, sincef-waves remained almost intact after removing very high levels of noise. Significance: The proposed algorithm may facilitate a reliable characterization of thef-waves, preventing them from not being masked by the PLI nor distorted by an unsuitable filtering applied to ECG recordings with AF.
A proposal to encourage intuitive learning in a senior-level analogue electronics course
(Taylor & Francis, 2011-05) Berjano Zanón, Enrique; Lozano Nieto, Albert; Dpto. de Ingeniería Electrónica; Escuela Técnica Superior de Ingeniería del Diseño; Biosignals And Minimally Invasive Technologies-BioMIT
One of the most important issues in the reorganisation of engineering education is to consider new pedagogical techniques to help students develop skills and an adaptive expertise. This expertise consists of being able to recognise the nature of a problem intuitively, and also recognising recurring patterns in different types of problems. In the particular case of analogue electronics, an additional difficulty seems to be that understanding involves both analytic skills and an intuitive grasp of circuit characteristics. This paper presents a proposal to help senior students to think intuitively in order to identify the common issue involved in a group of problems of analogue electronics and build an abstract concept based on, for example, a theory or a mathematical model in order to use it to solve future problems. The preliminary results suggest that this proposal could be useful to promote intuitive reasoning in analogue electronics courses. The experience would later be useful to graduates in analytically solving new types of problems or in designing new electronic circuits.
A Straightforward Methodology to Distinguish Complex Fractionated Atrial Electrograms of Paroxysmal from Persistent Atrial Fibrillation
(IEEE, 2020-10-30) Finotti, Emanuela; Ciaccio, Edward J.; Garan, Hasan; Bertomeu-González, Vicente; Alcaraz, Raúl; Rieta Ibañez, José Joaquín; Dpto. de Ingeniería Electrónica; Escuela Politécnica Superior de Gandia; Biosignals And Minimally Invasive Technologies-BioMIT; European Regional Development Fund; Junta de Comunidades de Castilla-La Mancha
[EN] Many indices aimed at discriminating between paroxysmal and persistent atrial fibrillation (ParAF vs. PerAF) have been previously studied and assessed via statistical tests in order to suggest optimized approaches to catheter ablation (CA) of AF. However, clinicians demand the use of simple classification methods of straightforward comprehension. The present work exploits AF cycle length (AFCL), dominant frequency (DF), sample entropy (SE) and determinism (DET) of recurrent quantification analysis, applied to AF recordings of complex fractionated atrial electrograms (CFAEs), aimed at creating straightforward models to discriminate between ParAF and PerAF. AFCL and DF were calculated on the full AF recordings, whereas SE and DET were computed on segments of 1, 2 and 4s. First, correlation matrix filters removed redundant information and Random Forests made a ranking of variables by relevance. Next, coarse tree classificators were created, combining optimally high-ranked indexes which were tested with leave-one-out cross-validation. After analyzing all the possible combinations of highly ranked features, the best classification performance provided an Accuracy (Acc) of 88.2% to discriminate ParAF from PerAF, while DET provided the highest single Acc of 82.4%. As conclusion, the careful selection of limited sets of indices feeding straightforward classificators are able to discriminate accurately between CFAEs of ParAF and PerAF.
Advances in modeling and characterization of atrial arrhythmias
(2013-12-05T14:22:26Z) Rieta Ibañez, José Joaquín; Ravelli, Flavia; Sornmo, Leif; Dpto. de Ingeniería Electrónica; Escuela Politécnica Superior de Gandia; Biosignals And Minimally Invasive Technologies-BioMIT
Atrial arrhythmias (AA) represent a common health problem in adults and may appear as a consequence of cardiac interventions as well as without any associated cardiac disease. In this respect, atrial fibrillation (AF) is the most common sustained cardiac arrhythmia and accounts for one third of the hospitalizations caused by car- diac rhythm disturbances. Atrial arrhythmias are associated with increased risk of stroke, heart failure and mortality. The mech- anisms leading to the initiation, maintenance and termination of AA have been under intensive investigation in recent years, with an important contribution of signal analysis. Nevertheless much research remains to be done on modeling, signal process- ing techniques and computational methods in order to optimize AA diagnosis and treatment.
Alteration of the P-wave non-linear dynamics near the onset of paroxysmal atrial fibrillation
(Elsevier, 2015-07) Martinez, Arturo; Abasolo, Daniel; Alcaraz, Raul; Rieta Ibañez, José Joaquín; Dpto. de Ingeniería Electrónica; Escuela Politécnica Superior de Gandia; Biosignals And Minimally Invasive Technologies-BioMIT; Ministerio de Economía y Competitividad; Junta de Comunidades de Castilla-La Mancha
The analysis of P-wave variability from the electrocardiogram (ECG) has been suggested as an early predictor of the onset of paroxysmal atrial fibrillation (PAP). Hence, a preventive treatment could be used to avoid the loss of normal sinus rhythm, thus minimising health risks and improving the patient's quality of life. In these previous studies the variability of different temporal and morphological P-wave features has been only analysed in a linear fashion. However, the electrophysiological alteration occurring in the atria before the onset of PAF has to be considered as an inherently complex, chaotic and non-stationary process. This work analyses the presence of non-linear dynamics in the P-wave progression before the onset of PAF through the application of the central tendency measure (CTM), which is a non-linear metric summarising the degree of variability in a time series. Two hour-length ECG intervals just before the arrhythmia onset belonging to 46 different PAF patients were analysed. In agreement with the invasively observed inhomogeneous atrial conduction preceding the onset of PAF, CTM for all the considered P-wave features showed higher variability when the arrhythmia was closer to its onset. A diagnostic accuracy around 80% to discern between ECG segments far from PAF and close to PAP was obtained with the CTM of the metrics considered. This result was similar to previous P-wave variability methods based on linear approaches. However, the combination of linear and non-linear methods with a decision tree improved considerably their discriminant ability up to 90%, thus suggesting that both dynamics could coexist at the same time in the fragmented depolarisation of the atria preceding the arrhythmia. (C) 2015 IPEM. Published by Elsevier Ltd. All rights reserved.
Alternative Time-Domain P-wave Analysis for Precise Information on Substrate Alteration After Pulmonary Vein Isolation for Atrial Fibrillation
(IEEE, 2021-11-19) Vraka, Aikaterini; Bertomeu-González, Vicente; Hornero, Fernando; Sörnmo, Leif; Alcaraz, Raúl; Rieta Ibañez, José Joaquín; Dpto. de Ingeniería Electrónica; Escuela Politécnica Superior de Gandia; Biosignals And Minimally Invasive Technologies-BioMIT; European Regional Development Fund; Junta de Comunidades de Castilla-La Mancha
[EN] While P-wave duration (PWD) is primarily employed to observe the atrial substrate alterations after pulmonary vein isolation (PVI) on atrial fibrillation (AF) patients, the acquired information corresponds to the entire atria. Left (LA) and right atrium (RA), though, may be differently affected by PVI, implying the need for different after-PVI handling. In order to clarify this assumption, five-minute lead II recordings from 29 paroxysmal AF patients undergoing first-ever PVI were recruited before and after PVI. PWD was analyzed integrally and in parts, with the first part (PWD1) from the onset to the peak corresponding to RA and the second part (PWD2) to LA depolarization. Time from P-wave onset or offset to the R peak were also calculated (P-on - R and P-off - R, respectively). Normalization (N) to mitigate heart-rate effect was applied. Results before and after PVI were compared with Mann-Whitney U-test (MWU). Median values and variations due to PVI were calculated for all features and compared between PWD and the remaining features via Pearson correlation. After PVI, PWD (-9.84%, p = 0.0085, N : -17.96%, p = 0.0442) and PWD2 (-22.03% p = 0.0250, N : -27.77%; p = 0.0268) were significantly decreased. PWD1 did not shorten significantly (up to -8.96%, p > 0.05 at either cases). PWD - PWD1 (rho > 74.5%; p < 0.0001) showed higher correlation than PWD - PWD2 (rho > 41.9%; p < 0.0001) in before and after PVI analysis but not for PVI-related variation (rho(PWD - PWD1) = 54.0%; p = 0.0114 and rho(PWD - PWD2) = 61.4%; p = 0.0031). While RA depolarization time is more in line with PWD analysis, the effect of PVI in PWD is more coherent with LA's findings. Additionally, PWD shortening is only observed in the LA. Therefore, LA is crucial for the assessment of the atrial substrate alteration after PVI and its analysis should be considered by future studies.
An Analytical Solution for Radiofrequency Ablation with a Cooled Cylindrical Electrode
(Hindawi Limited, 2017) Romero-Méndez, Ricardo; Berjano Zanón, Enrique; Dpto. de Ingeniería Electrónica; Escuela Técnica Superior de Ingeniería del Diseño; Biosignals And Minimally Invasive Technologies-BioMIT; Ministerio de Economía, Industria y Competitividad
[EN] We present an analytical solution to the electrothermal mathematical model of radiofrequency ablation of biological tissue using a cooled cylindrical electrode. The solution presented here makes use of the method of separation of variables to solve the problem. Green's functions are used for the handling of nonhomogeneous terms, such as effect of electrical currents circulation and the nonhomogeneous boundary condition due to cooling at the electrode surface. The transcendental equation for determination of eigenvalues of this problem is solved using Newton's method, and the integrals that appear in the solution of the problem are obtained by Simpson's rule. The solution obtained here has the possibility of handling different functional dependencies of the source term and nonhomogeneous boundary condition. The solution provides a tool to understand the physics of the problem, as it shows how the solution depends on different parameters, to provide mathematical tools for the design of surgical procedures and to validate other modeling techniques, such as the numerical methods that are frequently used to solve the problem.
An Efficient Hybrid Methodology for Local Activation Waves Detection under Complex Fractionated Atrial Electrograms of Atrial Fibrillation
(MDPI AG, 2022-07) Osorio, Diego; Vraka, Aikaterini; Quesada, Aurelio; Hornero, Fernando; Alcaraz, Raúl; Rieta Ibañez, José Joaquín; Dpto. de Ingeniería Electrónica; Escuela Politécnica Superior de Gandia; Biosignals And Minimally Invasive Technologies-BioMIT; GENERALITAT VALENCIANA; AGENCIA ESTATAL DE INVESTIGACION; Agencia Estatal de Investigación; European Regional Development Fund; Junta de Comunidades de Castilla-La Mancha
[EN] Local activation waves (LAWs) detection in complex fractionated atrial electrograms (CFAEs) during catheter ablation (CA) of atrial fibrillation (AF), the commonest cardiac arrhythmia, is a complicated task due to their extreme variability and heterogeneity in amplitude and morphology. There are few published works on reliable LAWs detectors, which are efficient for regular or low fractionated bipolar electrograms (EGMs) but lack satisfactory results when CFAEs are analyzed. The aim of the present work is the development of a novel optimized method for LAWs detection in CFAEs in order to assist cardiac mapping and catheter ablation (CA) guidance. The database consists of 119 bipolar EGMs classified by AF types according to Wells' classification. The proposed method introduces an alternative Botteron's preprocessing technique targeting the slow and small-ampitude activations. The lower band-pass filter cut-off frequency is modified to 20 Hz, and a hyperbolic tangent function is applied over CFAEs. Detection is firstly performed through an amplitude-based threshold and an escalating cycle-length (CL) analysis. Activation time is calculated at each LAW's barycenter. Analysis is applied in five-second overlapping segments. LAWs were manually annotated by two experts and compared with algorithm-annotated LAWs. AF types I and II showed 100% accuracy and sensitivity. AF type III showed 92.77% accuracy and 95.30% sensitivity. The results of this study highlight the efficiency of the developed method in precisely detecting LAWs in CFAEs. Hence, it could be implemented on real-time mapping devices and used during CA, providing robust detection results regardless of the fractionation degree of the analyzed recordings.
An Experimental Review on Obstructive Sleep Apnea Detection Based on Heart Rate Variability and Machine Learning Techniques
(IEEE, 2020-10-30) Padovano, Daniele; Martinez-Rodrigo, Arturo; Pastor, Jose M.; Rieta Ibañez, José Joaquín; Alcaraz, Raúl; Dpto. de Ingeniería Electrónica; Escuela Politécnica Superior de Gandia; Biosignals And Minimally Invasive Technologies-BioMIT; Junta de Comunidades de Castilla-La Mancha
[EN] Obstructive sleep apnea (OSA) is a respiratory syndrome of high incidence in the general population and correlated with some cardiovascular diseases. Several techniques have been proposed in the last decades to find a surrogate method to polysomnography (PSG), the gold standard for the diagnosis of OSA. The present study comprises an experimental review on the state-of-the-art methods for OSA detection through the public Apnea-ECG database, which is available at PhysioNet. Precisely, traditional time-frequency domain features were extracted from the heart rate variability (HRV) signal, together with some common complexity measures. Given their ability to deal with real-world time series, two additional entropy-based measures were also tested, i.e., Rènyi and Tsallis entropies. Moreover, univariate and multivariate classifiers were applied, including diagnostic test, support vectors machine, and k-nearest neighbors. Ultimately, two sequential feature selection (SFS) algorithms were employed to reduce the computational cost of the resulting discriminant models. The major findings reported that multivariate classifiers reached similar results to those found in the literature. Moreover, univariate classification results suggested that the frequency domain features provided the best OSA detection, although a well-known entropy index also obtained a good performance.
Análisis de la variabilidad temporal de la onda P para predecir el resultado de la ablación por catéter en fibrilación auricular paroxística
(Sociedad Española de Ingeniería Biomédica, 2020-11-27) Ruiz Moreno, A.; Arias Palomares, M.A.; Puchol Calderón, A.; Pachón Iglesias, M.I.; Rieta Ibañez, José Joaquín; Alcaraz Martínez, R.; Dpto. de Ingeniería Electrónica; Escuela Politécnica Superior de Gandia; Biosignals And Minimally Invasive Technologies-BioMIT; European Regional Development Fund; Junta de Comunidades de Castilla-La Mancha
[EN] El aislamiento de las venas pulmonares es el principal tratamiento de la fibrilacion auricular (FA) paroxistica. Sin embargo, presenta una alta tasa de recurrencia y el desarrollo de predictores no invasivos de esta cuestion, es esencial para permitir un tratamiento mas personalizado de cada paciente. Para tal proposito, se han analizado varias caracteristicas de la onda P a partir de registros de electrocardiografia (ECG), pero, aun no se ha estudiado su variabilidad a lo largo del tiempo. Por tanto, este trabajo explora la capacidad de la variabilidad temporal de la duracion y la amplitud de la onda P, para anticipar el fallo de la crioablacion. Paea este estudio antes de la ablacion, se registro un ECG de 5 minutos en 45 pacientes con FA paroxistica. Las ondas P en la derivacion II se delinearon con un algoritmo automatico y se calcularon la duracion y amplitud de todas ellas. A continuacion, se obtuvieron la media, la desviacion estandar y el coeficiente de variacion (CV) para ambos parametros y se correlacionaron con el resultado de la ablacion despues del seguimiento de 9 meses. El CV para ambas caracteristicas de las ondas P presento la capacidad predictiva mas alta de la recurrencia de la FA. Ademas, obtuvo mejoras de alrededor del 10 % en la clasificacion con respecto a la media, alcanzando valores del 70 %. Estos resultados sugieren que la variabilidad temporal de la onda puede proporcionar nueva informacion sobre la heterogeneidad de la conduccion auricular, lo cual podria ser util para mejorar la estrategia de seleccion de candidatos para ser sometidos a crioablacion.
Análisis del remodelado anatomoeléctrico auricular para la predicción del éxito de la ablación quirúrgica concomitante de la fibrilación auricular a largo plazo
(Elsevier, 2016-05) Martin, Elio; Hornero, Fernando; Rieta Ibañez, José Joaquín; Hernández Alonso, Antonio; Paredes, Federico; Mena, Armando; Gil, Oscar; Canovas, Sergio; Garcia, Rafael; Martinez Leon, Juan; Dpto. de Ingeniería Electrónica; Escuela Politécnica Superior de Gandia; Biosignals And Minimally Invasive Technologies-BioMIT
[EN] Objective: To identify preoperative parameters of anatomo-electrical atrial remodelling in order to identify the subgroup of patients more favourable to long-term sinus rhythm (SR) re-establishment after concomitant ablation of persistent-permanent atrial fibrillation (AF). Methods: The study included 50 consecutive patients undergoing concomitant surgical ablation of persistent-permanent AF with cryoablation and bipolar radiofrequency Maze IV pattern. The variables collected before the operation were: demographic variables, morbidity, AF evolution time, transthoracic echocardiographic study, and digital electrocardiogram register for f-wave signal organisation analysis (sample entropy [SampEn]). An assessment was also made of the individual and combined association of atrial remodelling parameters with SR restoration by area under ROC curve (AUC). Results: Follow-up 22.32 +/- 3.19 months. Mean AF onset time 4.00 +/- 4.28 years. Mean left atrium diameter 49.90 +/- 8.18 mm (range = 32 - 81 mm), and SR restoration of 62% at the end of follow-up. Parameters best linked to postoperative SR restoration were left atrium diameter (AUC = 0.848)and SampEn (AUC = 0.845). Cut-off points were 50 mm and 0.0857, respectively, obtaining a model with a predictive accuracy when both parameters combined with an AUC = 0.893. Conclusions: Preoperative anatomo-electrical remodelling analysis through indirect non-nvasive variables could be useful to select patients more favourable to SR restoration after concomitant ablation of AF.
Análisis multidimensional de las 12 derivaciones del ECG estándar para predecir el éxito de la cardioversión eléctrica en fibrilación auricular persistente
(Sociedad Española de Ingeniería Biomédica, 2020-11-27) Cirugeda Roldan, E.M.; Calero Núñez, S.; Plancha Burguera, E.; Enero Navajo, J.; Rieta Ibañez, José Joaquín; Alcaraz Martínez, R.; Dpto. de Ingeniería Electrónica; Escuela Politécnica Superior de Gandia; Biosignals And Minimally Invasive Technologies-BioMIT; European Regional Development Fund; Junta de Comunidades de Castilla-La Mancha
[ES] La Sociedad Europea de Cardiologia recomienda la cardioversion electrica (CVE) para el control del ritmo cardiaco en situaciones de fibrilacion auricular (FA) persistente. Aunque es capaz de restaurar inicialmente el ritmo sinusal (RS) en la mayoria de los pacientes, su tasa de exito a medio plazo es limitada, presentando la arritmia una alta probabilidad de recurrencia. En este contexto, es de gran interes poder prever el resultado de la CVE, ya que de esta forma se podria tratar individualizadamente a los pacientes. Con este objetivo, durante los ultimos a nos se han propuesto distintos indices que caracterizan la actividad auricular (AA) sobre el electrocardiograma (ECG), tales como la amplitud de las ondas fibrilatorias (f), su frecuencia dominante, o su regularidad. Aunque estos indices han presentado resultados prometedores, solo se han empleado para caracterizar las ondas f en una unica derivacion, generalmente V1, descartando asi la informacion espacial que, registrada en otras derivaciones, puede resultar de gran interes. Asi pues, este trabajo evalua si una extension multidimensional de dichos indices es capaz de incrementar la capacidad de prediccion del resultado de la CVE. En los resultados se observa que las extensiones multidimensionales de los indices propuestos incrementan la prediccion de la CVE hasta casi un 6 %, lo que sugiere que las correlaciones espaciales en la AA de las distintas derivaciones del ECG obtienen informacion predictiva relevante sobre la recurrencia de la FA.
Analytical Model Based on a Cylindrical Geometry to Study RF Ablation with Needle-Like Internally Cooled Electrode
(Hindawi Publishing Corporation, 2012) López Molina, Juan Antonio; Rivera Ortun, María José; Berjano Zanón, Enrique; Dpto. de Ingeniería Electrónica; Escuela Técnica Superior de Ingeniería del Diseño; Biosignals And Minimally Invasive Technologies-BioMIT; Ministerio de Ciencia e Innovación
Radiofrequency (RF) ablation with internally cooled needle-like electrodes is widely used in medical techniques such as tumor ablation. The device consists of a metallic electrode with an internal liquid cooling system that cools the electrode surface. Theoretical modeling is a rapid and inexpensive way of studying different aspects of the RF ablation process by the bioheat equation, and the analytical approach provides an exact solution to the thermal problem. Our aim was to solve analytically the RF ablation transient time problem with a needle-like internally cooled cylindrical electrode while considering the blood perfusion term. The results showed that the maximal tissue temperature is reached 3mm from the electrode, which confirms previous experimental findings. We also observed that the temperature distributions were similar for three coolant temperature values (5 °C, 15 °C, and 25 °C). The differences were only notable in temperature very close to the probe. Finally, considering the 50 °C line as a thermal lesion mark, we found that lesion diameter was around 2cm, which is exactly that observed experimentally in perfused hepatic tissue and slightly smaller than that observed in nonperfused (ex vivo) hepatic tissue. Copyright © 2012 Juan A. Lpez Molina et al.
Analytical Solution for Electrical Problem Forced by a Finite-Length Needle Electrode: Implications in Electrostimulation
(Hindawi Limited, 2019) Romero-Méndez, Ricardo; Pérez-Gutiérrez, Francisco G.; Oviedo-Tolentino, Francisco; Berjano Zanón, Enrique; Dpto. de Ingeniería Electrónica; Escuela Técnica Superior de Ingeniería del Diseño; Biosignals And Minimally Invasive Technologies-BioMIT; Agencia Estatal de Investigación
[EN] Needle electrodes, widely used in clinical procedures, are responsible for creating an electric field in the treated biological tissue. This is achieved by setting a constant voltage along the length of their metallic section. In accordance with Laplace's equation, the electric field is spatially non-uniform around the electrode surface. Mathematical modelling can provide useful information on the spatial distribution of electrical fields. Indeed, exact solutions for the electrical problem are indispensable for validating numerical codes. All the analytical models developed to date to solve the needle electrode electrical problem have been one-dimensional models, which assumed an electrode of infinite length. We here propose the first analytical solution based on a two-dimensional model that considers the real length of the electrode in which the Laplace equation is solved through the method of separation of variables, dealing with the nonhomogeneous source term and boundary conditions by Green's functions. On assuming a needle electrode of given length, the problem combines boundary conditions on the electrode boundary (of the first and second kind). Since this rules out using the Sturm-Liouville Theorem, the problem is decomposed into two different problems and the principle of superposition is used. The solution obtained can reproduce a reasonable electric field around the electrode, especially the edge effect characterized by an extremely high gradient around the electrode tip.

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