Mapping and Removing the Ventricular Far Field Component in Unipolar Atrial Electrograms.

OBJECTIVE: Unipolar intracardiac electrograms (uEGMs) measured inside the atria during electro-anatomic mapping contain diagnostic information about cardiac excitation and tissue properties. The ventricular far field (VFF) caused by ventricular depolarization compromises these signals. Current signal processing techniques require several seconds of local uEGMs to remove the VFF component and thus prolong the clinical mapping procedure. We developed an approach to remove the VFF component using data obtained during initial anatomy acquisition. METHODS: We developed two models which can approximate the spatio-temporal distribution of the VFF component based on acquired EGM data: Polynomial fit, and dipole fit. Both were benchmarked based on simulated cardiac excitation in two models of the human heart and applied to clinical data. RESULTS: VFF data acquired in one atrium were used to estimate model parameters. Under realistic noise conditions, a dipole model approximated the VFF with a median deviation of 0.029 mV, yielding a median VFF attenuation of 142. In a different setup, only VFF data acquired at distances of more than 5 mm to the atrial endocardium were used to estimate the model parameters. The VFF component was then extrapolated for a layer of 5 mm thickness lining the endocardial tissue. A median deviation of 0.082 mV (median VFF attenuation of 49x) was achieved under realistic noise conditions. CONCLUSION: It is feasible to model the VFF component in a personalized way and effectively remove it from uEGMs. SIGNIFICANCE: Application of our novel, simple and computationally inexpensive methods allows immediate diagnostic assessment of uEGM data without prolonging data acquisition.

Automatic Identification of Reentry Mechanisms and Critical Sites During Atrial Tachycardia by Analyzing Areas of Activity.

OBJECTIVE: Atrial tachycardia (AT) still poses a major challenge in catheter ablation. Although state-of-the-art electroanatomical mapping systems allow to acquire several thousand intracardiac electrograms (EGMs), algorithms for diagnostic analysis are mainly limited to the amplitude of the signal (voltage map) and the local activation time (LAT map). We applied spatio-temporal analysis of EGM activity to generate maps indicating reentries and diastolic potentials, thus identifying and localizing the driving mechanism of AT. METHODS: First, the time course of active surface area ASA is determined during one basic cycle length (BCL). The chamber cycle length coverage cCLC reflects the relative duration within one BCL for which activity was present in each individual atrium. A local cycle length coverage lCLC is computed for circular subareas with 20 mm diameter. The simultaneous active surface area sASA is determined to indicate the spatial extent of depolarizing tissue. RESULTS: Combined analysis of these spatial scales allowed to correctly identify and localize the driving mechanism: cCLC values of 100% were indicative for atria harbouring a reentrant driver. lCLC could detect micro reentries within an area of 1.65 $\pm$ 1.28 cm $^2$ in simulated data and differentiate them against focal sources. Middiastolic potentials, being potential targets for catheter ablation, were identified as areas showing confined activity based on sASA values. CONCLUSION: The concept of spatio-temporal activity analysis proved successful and correctly indicated the tachycardia mechanism in 20 simulated AT scenarios and three clinical data sets. SIGNIFICANCE: Automatic interpretation of intracardiac mapping data could help to improve the treatment strategy in complex cases of AT.

Comparison of Baseline Wander Removal Techniques considering the Preservation of ST Changes in the Ischemic ECG: A Simulation Study.

The most important ECG marker for the diagnosis of ischemia or infarction is a change in the ST segment. Baseline wander is a typical artifact that corrupts the recorded ECG and can hinder the correct diagnosis of such diseases. For the purpose of finding the best suited filter for the removal of baseline wander, the ground truth about the ST change prior to the corrupting artifact and the subsequent filtering process is needed. In order to create the desired reference, we used a large simulation study that allowed us to represent the ischemic heart at a multiscale level from the cardiac myocyte to the surface ECG. We also created a realistic model of baseline wander to evaluate five filtering techniques commonly used in literature. In the simulation study, we included a total of 5.5 million signals coming from 765 electrophysiological setups. We found that the best performing method was the wavelet-based baseline cancellation. However, for medical applications, the Butterworth high-pass filter is the better choice because it is computationally cheap and almost as accurate. Even though all methods modify the ST segment up to some extent, they were all proved to be better than leaving baseline wander unfiltered.

Electrocardiographic features for the measurement of drivers' mental workload.

This study examines the effect of mental workload on the electrocardiogram (ECG) of participants driving the Lane Change Task (LCT). Different levels of mental workload were induced by a secondary task (n-back task) with three levels of difficulty. Subjective data showed a significant increase of the experienced workload over all three levels. An exploratory approach was chosen to extract a large number of rhythmical and morphological features from the ECG signal thereby identifying those which differentiated best between the levels of mental workload. No single rhythmical or morphological feature was able to differentiate between all three levels. A group of parameters were extracted which were at least able to discriminate between two levels. For future research, a combination of features is recommended to achieve best diagnosticity for different levels of mental workload.

P wave detection and delineation in the ECG based on the phase free stationary wavelet transform and using intracardiac atrial electrograms as reference.

Robust and exact automatic P wave detection and delineation in the electrocardiogram (ECG) is still an interesting but challenging research topic. The early prognosis of cardiac afflictions such as atrial fibrillation and the response of a patient to a given treatment is believed to improve if the P wave is carefully analyzed during sinus rhythm. Manual annotation of the signals is a tedious and subjective task. Its correctness depends on the experience of the annotator, quality of the signal, and ECG lead. In this work, we present a wavelet-based algorithm to detect and delineate P waves in individual ECG leads. We evaluated a large group of commonly used wavelets and frequency bands (wavelet levels) and introduced a special phase free wavelet transformation. The local extrema of the transformed signals are directly related to the delineating points of the P wave. First, the algorithm was studied using synthetic signals. Then, the optimal parameter configuration was found using intracardiac electrograms and surface ECGs measured simultaneously. The reverse biorthogonal wavelet 3.3 was found to be optimal for this application. In the end, the method was validated using the QT database from PhysioNet. We showed that the algorithm works more accurately and more robustly than other methods presented in literature. The validation study delivered an average delineation error of the P wave onset of -0.32±12.41 ms when compared to manual annotations. In conclusion, the algorithm is suitable for handling varying P wave shapes and low signal-to-noise ratios.

Automatic SVM classification of sudden cardiac death and pump failure death from autonomic and repolarization ECG markers.

BACKGROUND: Considering the rates of sudden cardiac death (SCD) and pump failure death (PFD) in chronic heart failure (CHF) patients and the cost-effectiveness of their preventing treatments, identification of CHF patients at risk is an important challenge. In this work, we studied the prognostic performance of the combination of an index potentially related to dispersion of repolarization restitution (Δα), an index quantifying T-wave alternans (IAA) and the slope of heart rate turbulence (TS) for classification of SCD and PFD. METHODS: Holter ECG recordings of 597 CHF patients with sinus rhythm enrolled in the MUSIC study were analyzed and Δα, IAA and TS were obtained. A strategy was implemented using support vector machines (SVM) to classify patients in three groups: SCD victims, PFD victims and other patients (the latter including survivors and victims of non-cardiac causes). Cross-validation was used to evaluate the performance of the implemented classifier. RESULTS: Δα and IAA, dichotomized at 0.035 (dimensionless) and 3.73 µV, respectively, were the ECG markers most strongly associated with SCD, while TS, dichotomized at 2.5 ms/RR, was the index most strongly related to PFD. When separating SCD victims from the rest of patients, the individual marker with best performance was Δα≥0.035, which, for a fixed specificity (Sp) of 90%, showed a sensitivity (Se) value of 10%, while the combination of Δα and IAA increased Se to 18%. For separation of PFD victims from the rest of patients, the best individual marker was TS ≤ 2.5 ms/RR, which, for Sp=90%, showed a Se of 26%, this value being lower than Se=34%, produced by the combination of Δα and TS. Furthermore, when performing SVM classification into the three reported groups, the optimal combination of risk markers led to a maximum Sp of 79% (Se=18%) for SCD and Sp of 81% (Se=14%) for PFD. CONCLUSIONS: The results shown in this work suggest that it is possible to efficiently discriminate SCD and PFD in a population of CHF patients using ECG-derived risk markers like Δα, TS and IAA.

Removing ventricular far-field signals in intracardiac electrograms during stable atrial tachycardia using the periodic component analysis.

BACKGROUND: Intracardiac electrograms are an indispensable part during diagnosis of supraventricular arrhythmias, but atrial activity (AA) can be obscured by ventricular far-fields (VFF). Concepts based on statistical independence like principal component analysis (PCA) cannot be applied for VFF removal during atrial tachycardia with stable conduction. METHODS: A database of realistic electrograms containing AA and VFF was generated. Both PCA and the new technique periodic component analysis (πCA) were implemented, benchmarked, and applied to clinical data. RESULTS: The concept of πCA was successfully verified to retain compromised AA morphology, showing high correlation (cc=0.98±0.01) for stable atrial cycle length (ACL). Performance of PCA failed during temporal coupling (cc=0.03±0.08) but improved for increasing conduction variability (cc=0.77±0.14). Stability of ACL was identified as a critical parameter for πCA application. Analysis of clinical data confirmed these findings. CONCLUSION: πCA is introduced as a powerful new technique for artifact removal in periodic signals. Its concept and performance were benchmarked against PCA using simulated data and demonstrated on measured electrograms.

Characterization of radiofrequency ablation lesion development based on simulated and measured intracardiac electrograms.

Radiofrequency ablation (RFA) therapy is the gold standard in interventional treatment of many cardiac arrhythmias. A major obstacle is nontransmural lesions, leading to recurrence of arrhythmias. Recent clinical studies have suggested intracardiac electrogram (EGM) criteria as a promising marker to evaluate lesion development. Seeking for a deeper understanding of underlying mechanisms, we established a simulation approach for acute RFA lesions. Ablation lesions were modeled by a passive necrotic core surrounded by a borderzone with properties of heated myocardium. Herein, conduction velocity and electrophysiological properties were altered. We simulated EGMs during RFA to study the relation between lesion formation and EGM changes using the bidomain model. Simulations were performed on a three-dimensional setup including a geometrically detailed representation of the catheter with highly conductive electrodes. For validation, EGMs recorded during RFA procedures in five patients were analyzed and compared to simulation results. Clinical data showed major changes in the distal unipolar EGM. During RFA, the negative peak amplitude decreased up to 104% and maximum negative deflection was up to 88% smaller at the end of the ablation sequence. These changes mainly occurred in the first 10 s after ablation onset. Simulated unipolar EGMs reproduced the clinical changes, reaching up to 83% negative peak amplitude reduction and 80% decrease in maximum negative deflection for transmural lesions. In future studies, the established model may enable the development of further EGM criteria for transmural lesions even for complex geometries in order to support clinical therapy.

Ectopic beats and their influence on the morphology of subsequent waves in the electrocardiogram.

Ventricular ectopic beats (VEBs) trigger a characteristic response of the heart called heart rate turbulence(HRT). The HRT can be used to predict sudden cardiac death in patients with a history of myocardial infarction. In this work, we present a reliable algorithm to detect and classify ectopic beats. Every electrocardiogram(ECG) is processed with innovative filtering techniques, artifact detection methods, and a robust multichannel analysis to produce accurate annotation results. For the classification task, a support vector machine was used. Furthermore, a new approach to the analysis of HRT is proposed. The HRT is interpreted as the response of a second-order system to an external perturbation. The system theoretical parameters were estimated. The influence of VEB on the morphology of subsequent T waves was also analyzed. A strong influence was detected in the study with 14 patients experiencing frequent VEB. The evolution of the morphology of the T wave with every new beat was studied, and it could be concluded that an exponential shape underlies this dynamic process and was called morphological heart rate turbulence (MHRT). Parameters were defined to quantify the MHRT. The analysis of the MHRT could help to understand the influence of an ectopic beat on the repolarization processes of the heart and more accurately stratify the risk of sudden cardiac death.

Evaluación de tres protocolos de tratamiento hormonal sobre el diámetro de ovocitos de sabaleta Brycon henni / Avaliação de tres protocolos de tratamento hormonal sob o diámetro dos ovocitos da sabaleta Brycon henni / Evaluation of three protocols hormone treatment on the size of the oocytes of sabaleta

El estudio fue realizado en el Municipio de San Carlos (Antioquia, Colombia), por la Facultad de Ciencias Agrarias de la Universidad de Antioquia, en convenio con la Corporación CORNARE, ISAGEN,durante la temporada reproductiva Mayo-Julio de 2008. 12 hembras y 24 machos de sabaleta Brycon hennide aproximadamente 100 g de peso corporal y 20 cm de longitud estándar, provenientes de un lote de 320 reproductores capturados del ambiente natural en Agosto del 2007 y antenidos en cautiverio en un estanque de tierra de 200 m², fueron seleccionados por sus características externas de madurez sexual como vientre abultado, papila genital enrojecida y expulsión de semen después de leve presión sobre la cavidadcelómica. Además como carácter de dimorfismo sexual se consideró para las hembras la presencia de aleta anal lisa o con espinaciones en máximo el 50% de su longitud, mientras que en los machos es rugosa en toda su extensión. También se tuvieron en cuenta características internas, en las hembras se realizó biopsia ovárica por aspiración de una muestra de ovocitos para observar la posición de sus núcleos y medición delde diámetro.. Las hembras fueron seleccionadas con la condición que presentaran ovocitos con diámetrossuperiores a 900 μm. Los animales fueron distribuidos para recibir uno de tres tratamientos, T1 Extracto de Hipófisis de Carpa (Argent, USA) (EHC), n=4; T2 Ovopel (Sigma Co., St Louis, Missouri), n=4; T3 Ovaprim (Syndel Laboratories Ltd, Vancouver, BC Canadá), n=4, durante cuatro fechas de muestreo y fertilizadas cada una con el semen de dos machos, inyectados previamente con EHC. 11 de las 12 hembras respondieron a los tratamientos y presentaron diámetros ovocitarios promedio de 1428.8 y 1679.8 (T1), 1531.2 y 1879.2 (T2) y de 1712.8 a 1803.3 (T3), antes y después del tratamiento hormonal, respectivamente.

The evaluation of three hormone treatments on the diameter size of ovocytes in Sabaleta wasconducted during the breeding season from May to July 2008. Twelve Brycon henni females and 24males, 100 g and a standard length of 24 cm, were selected according to their sexual maturity andexternal features such as bulging belly, red genital papilla and semen expulsion after softly pressingits coelomic cavity. The fish were selected from a 320 brood fish batch caught in the wild in August2007 and kept in captivity in a 200 m² earth pond. The presence of an anal fin with or without spines ofa maximum length of 50% was considered as sexual dimorphism in females. Internal characteristicswere also considered; e.g., an ovarian aspiration biopsy was performed in females in order to observe itsnuclei position and diameter. Ovocytes from selected females were at least 900 μm in diameter. Animalswere distributed into three treatment groups for four sampling dates: T1 carp pituitary extract (CPE)(Argent Chemical Laboratories Inc., USA), n = 4; T2 Ovopel (Sigma Co. USA), n = 4; and T3 Ovaprim(Syndel Laboratories Ltd., Canada), n = 4. Each female was fertilized with the semen of two malespreviously injected with CPE. 11 out of 12 females had a treatment response, and resulting ovocyteaverage diameters were 1428.8 and 1679.8 (T1), 1531.2 and 1879.2 (T2), and 1712.8 to 1803.3 (T3),before and after hormone treatment, respectively. Significant differences were found within T1 andT2 (p <0.05); however, this was not the case for T3. For T1, frequency distribution of the diameterof ovocytes before the hormonal treatment was bimodal. T2 had two modes before and one after thetreatment (bimodal and unimodal), and T3 had two before and two after (bimodal). Fertilization rateswere low in T1; nevertheless, T2 and T3 had high rates until 12 h eggs incubation.

O estudo foi realizado no Município de San Carlos (Antioquia, Colombia), pela Facultad de CienciasAgrarias de la Universidad de Antioquia, conjuntamente com a corporação CORNARE, ISAGEN, entreos meses de maio e julho de 2008. Foram utilizadas 12 fêmeas e 24 machos de sabaleta Brycon henni deaproximadamente 100 g de peso corporal e 20 cm de comprimento, provenientes de um lote de reprodutorescapturados em ambiente natural em agosto de 2007. Os animais receberam um dos três tratamentos: T1extrato de hipófise de Hipófise de Carpa (Argent, USA) (EHC), n=4; T2 Ovopel (Sigma Co., St Louis,Missouri), n=4; T3 Ovaprim (Syndel Laboratories Ltd, Vancouver, BC Canadá), n=4, durante quatro datasde amostragem e fertilizadas cada uma com sêmen de dois machos, injetados previamente com EHC. 11das 12 fêmeas responderam aos tratamentos e apresentaram ovócitos entre 1428.8 e 1679.8 (T1), 1531.2 e1879.2 (T2) e de 1712.8 a 1803.3 (T3) de diâmetro, antes e depois do tratamento hormonal, respectivamente.Observaram-se diferencias significativas ao interior do T1 e T2 (p<0.05), mas não para o T3. A distribuiçãode freqüências do diâmetro do ovócito apresentou no T1, duas modas antes do tratamento hormonal e doisdepois do tratamento hormonal (bimodal); T2, duas modas antes e 1 depois (bimodal e unimodal) e T3,duas antes e duas depois (bimodal). As porcentagens de fertilização foram baixas em T1, e foram altas emT2 e T3 até as 12 h de incubação dos ovos.

Reproducción inducida y producción de alevinos de Sabaleta Brycon henni: determinación del tiempo de latencia utilizando extracto de hipófi sis de carpa / Reprodução induzida e produção de alevinos da Sabaleta Brycon henni: determinação do tempo de latência utilizando Extrato de Hipófise de Carpa / Induced breeding and production of fingerlings of Sabaleta Brycon henni:Determining the time of latency using Carp Pituitary Extract

Esta investigación fue realizada en la estación piscícola de San José del Nus (Antioquia). Fue iniciadaen el año 2002 con la captura y adaptación de un lote de 100 reproductores silvestres, provenientes de tresmicrocuencas cercanas a la estación piscícola y fue continuada en el año 2003 con la captura de otros80 ejemplares, con los cuales se hicieron los primeros ensayos de inducción hormonal estimulando lamaduración final y la ovulación con dos dosis de Extracto Pituitario de Carpa (EPC) (0.5 + 5.0 mg/kg depeso corporal). Para la obtención de los gametos se utilizó extrusión en seco en los tres grupos de peces.La maduración final y la ovulación se indujo en 20 hembras y la espermiación en 20 machos. El resultadomás relevante fue la ovulación y desove de ocho hembras, de las cuales sólo dos fueron completamenteexitosas, con un tiempo de latencia de 13 y 11 h, respectivamente. De la primera hembra con un peso de136.2 g, se extrajeron 1421 huevos, los cuales fueron fertilizados, mostrando una sobrevivencia de embrióna larva de 28% y de larva a alevino de 35.7%. La segunda hembra, de 90 g de peso corporal, desovó 1348huevos mostrando un porcentaje de fertilidad de 74%, sobrevivencia larval del 40% y sobrevivencia hastaalevino comercial de 25%. En cada uno de los desoves se obtuvo un número de alevinos netos de 141 y 101,respectivamente. La temperatura de incubación fue de 24.5 °C y de 25.3 °C. Cabe destacar que el en mismoaño se encontró una hembra ya desovada que presentó nuevamente madurez gonadal tres meses más tarde.

This research was conducted in the San José del Nus fish farm, located in the Municipality of San Roque(department of Antioquia). This study began in 2002 with the capture and suitability of 100 wild breeding fishbatches coming from three sub-basins near to San José del Nus fish farm. In 2003, another 80 specimenswere captured and utilized for first hormonal induction trials by stimulating final maturation and ovulationwith two doses of Carp pituitary extract (CPE) (0.5 + 5.0 mg/kg B.W.). Dry extrusion was used in the threegroups of fish to obtain gametes. Spermiation and final maturation plus ovulation were induced in twentymales and females, respectively. The most relevant result was ovulation and spawning in 8 cases. Two ofthem were completely successful; their latency period was 13 and 11 h, respectively. From the first previouslyfertilized female (136.2 g. B.W.) 1421 eggs were extracted, with a survival of 28% from embryo to larva; and35.7% from larva to alevin. The second female (90 g B.W.) spawned 1348 eggs, resulting in a fertilization rateof 74%, larval survival of 40% and survival until alevin for commercial use of 25%. In both cases, spawningresulted in an alevin net number of 141 and 101, respectively. Water incubation temperature was 24.5 °C and25.3 °C. It is important to emphasize that in the same year a previously spawned female was found, and threemonths later this female presented gonadal maturity once again.

Esta pesquisa foi realizada na estação de piscicultura de São José del Nus (Antioquia). Foi iniciada noano 2002 com a captura e adaptação de um lote de 100 reprodutores selvagens provenientes de três córregosperto da estação piscicola e foi continuada no ano 2003 com a captura de outros 80 exemplares, com osquais foram feitos os primeiros ensaios de indução hormonal estimulando a maduração final e a ovulaçãocom duas doses de extrato de hipófise de carpa (0.5 + 5.0 mg / kg de peso corporal). Para a obtenção dosgametas se utilizo extrusão em seco para os três grupos de peixes. A maduração final e a ovulação foiinduzida em 20 fêmeas e a espermiação em 20 machos. O resultado mais relevante foi a ovulação e desovade oito fêmeas, das quais apenas duas foram completamente bem sucedidas, o período de latência foi de13 e 11 h, respectivamente.. Da primeira fêmea, com 136.2 g de peso corporal, obtiveram-se 1421, os quaisforam fertilizados, com uma sobrevivência desde embrião a larva de 28% e de larva até alevin de 35.7%. Asegunda fêmea de 90 g de peso corporal, desovou 1348 ovos mostrando uma percentagem de fertilidade de74%, sobrevivência larval de 40% e sobrevivência desde larva a alevin comercial de 25%. Em cada uma dasdesovas foram obtidos 141 e 101 alevines, respectivamente. A temperatura da água de incubação foi de 24.5°C e 25.3 °C, respectivamente. Outra observação importante foi que, durante o mesmo período encontrouseuma fêmea desovada que apresentou de novo maturação gonadal 3 meses mais tarde.

Espermiación inducida y crioconservación de semen de Cachama Blanca (Piaractus brachypomus) / Induced spermiation and semen cryopreservation in White Cachama (Piaractus brachypomus)

La Cachama Blanca (Piaractus brachypomus), carácido originario de las cuencas de los ríos Orinoco y Amazonas fue introducida en la cuenca del Magdalena Medio. Especie rústica de rápido crecimiento, carne de gran aceptación y excelentes condiciones para la piscicultura. No se reproduce en cautiverio, siendo necesaria la administración exógena de hormonas para inducir la ovulación y la espermiación. El objetivo de esta investigación fue evaluar el efecto del tratamiento hormonal sobre el espermograma de reproductores de cachama blanca y determinar el porcentaje de fertilización y eclosión de huevos utilizando semen crioconservado. Se evaluaron 26 reproductores provenientes de la estación piscícola de San José del Nus de la Universidad de Antioquia. A doce machos se les indujo la espermiación mediante la administración IM de 2.5 mg/kg de extracto de hipófisis de carpa, y 14 sirvieron como control. Posterior a la evaluación seminal se diluyó en DMSO o en Metanol y se congeló. Una pajilla de semen (80por ciento de viabilidad) de cada uno de los grupos, se descongeló a temperatura ambiente (28°C) se activó con 3 ml de bicarbonato de sodio 3 M y se depositó sobre 1 gr de huevos. La fertilidad fue evaluada a las seis horas, determinando la proporción entre huevos en estado de botón y huevos degenerados (blancos). El semen fresco de los dos tratamientos difiere en el volumen del eyaculado (mayor en los animales inducidos) y en el pH que disminuye ligeramente en los animales inducidos. Los valores de motilidad y tiempo de activación entre los dos crioprotectores fue similar con cualquiera de los dos crioprotectores. El porcentaje de fertilización y eclosión de larvas fue diferente dependiendo de la hembra utilizada. Las diferencias entre los porcentajes de fertilización comparando los dos crioprotectores o los machos inducidos o no inducidos no fue estadísticamente significativa. Se concluye que la criopreservación de semen es una forma fácil de mantenerlo para inseminar....