Deep Neural Networks for ECG-Based Pulse Detection during Out-of-Hospital Cardiac Arrest

The automatic detection of pulse during out-of-hospital cardiac arrest (OHCA) is necessary for the early recognition of the arrest and the detection of return of spontaneous circulation (end of the arrest). The only signal available in every single defibrillator and valid for the detection of pulse is the electrocardiogram (ECG). In this study we propose two deep neural network (DNN) architectures to detect pulse using short ECG segments (5 s), i.e., to classify the rhythm into pulseless electrical activity (PEA) or pulse-generating rhythm (PR). A total of 3914 5-s ECG segments, 2372 PR and 1542 PEA, were extracted from 279 OHCA episodes. Data were partitioned patient-wise into training (80%) and test (20%) sets. The first DNN architecture was a fully convolutional neural network, and the second architecture added a recurrent layer to learn temporal dependencies. Both DNN architectures were tuned using Bayesian optimization, and the results for the test set were compared to state-of-the art PR/PEA discrimination algorithms based on machine learning and hand crafted features. The PR/PEA classifiers were evaluated in terms of sensitivity (Se) for PR, specificity (Sp) for PEA, and the balanced accuracy (BAC), the average of Se and Sp. The Se/Sp/BAC of the DNN architectures were 94.1%/92.9%/93.5% for the first one, and 95.5%/91.6%/93.5% for the second one. Both architectures improved the performance of state of the art methods by more than 1.5 points in BAC.This work was supported by: The Spanish Ministerio de Economía y Competitividad, TEC2015-64678-R, jointly with the Fondo Europeo de Desarrollo Regional (FEDER), UPV/EHU via GIU17/031 and the Basque Government through the grant PRE_2018_2_0260

Diagnóstico del ritmo cardíaco durante la resucitación cardiopulmonar mediante técnicas de aprendizaje profundo

Las compresiones torácicas inducen artefactos en el electrocardiograma (ECG) que dificultan el diagnóstico fiable del ritmo durante la reanimación cardiopulmonar (RCP). Esto obliga al rescatador a detener la terapia durante el análisis del ritmo comprometiendo la circulación y, por lo tanto, reduciendo la probabilidad de supervivencia del paciente. Este estudio propone un nuevo enfoque para la discriminación de ritmos desfibrilables y no desfibrilables durante compresiones torácicas. El método se basa en técnicas de aprendizaje profundo que han demostrado ser más precisas en múltiples problemas de clasificación en el ámbito de la ingeniería biomédica. Se usó una base de datos compuesta por 506 ritmos desfibrilables y 1697 no-desfibrilables adquiridos de pacientes en parada cardiorrespiratoria extrahospitalaria. El modelo fue entrenado y testeado mediante un esquema de validación cruzada de 10 iteraciones (10-fold CV). Este proceso se repitió 10 veces para caracterizar estadísticamente los resultados en términos de sensibilidad (SE), especificidad (SP) y precisión balanceada (BAC). Los resultados se compararon con los obtenidos utilizando técnicas de aprendizaje automático tradicionales. El método de aprendizaje profundo proporcionó un rendimiento similar al obtenido mediante el algoritmo tradicional con una SE, SP y BAC de 95.0 %, 96.1 % y 95.5%, respectivamente.Este trabajo ha recibido ayuda financiera del Ministerio de Ciencia, Innovación y Universidades, proyecto RTI2018-101475-BI00, junto con el Fondo Europeo de Desarrollo Regional (FEDER). Ha recibido también financiación del Gobierno Vasco mediante la beca PRE- 2019-2-0066 y la subvención a grupos IT-1229-19

Modelo predictivo del retorno de circulación espontánea en la parada cardiorrespiratoria utilizando el ECG y la impedancia torácica

El análisis de los diferentes tipos de ritmo cardíaco durante la parada cardiorrespiratoria y la predicción de su evolución permitiría ajustar la terapia de resucitación a cada paciente. El ritmo con actividad eléctrica sin pulso (AESP) es el ritmo inicial predominante durante la parada cardiorrespiratoria extrahospitalaria, y es de gran interés disponer de modelos que predigan el retorno espontáneo de circulación (RCE). En este trabajo se propone un método automático que discrimina los casos de AESP que evolucionan a RCE de los que no recuperan el pulso. El modelo combina parámetros de las señales de electrocardiograma (ECG) e impedancia torácica (IT) adquiridas con los parches del desfibrilador. La base de datos consiste en 185 pacientes (73 con RCE) de los que se extrajeron 1600 segmentos (432 con RCE). Aplicando una validación cruzada de 10 particiones y un clasificador de máquinas de vectores de soporte (SVM), se demuestra que la IT añade valor discriminativo al modelo basado en ECG. Para un clasificador SVM con un núcleo polinómico de orden 2 se obtuvo una sensibilidad del 79.8%, una especificidad del 85.5% y un área bajo la curva ROC de 0.91.Este trabajo ha sido parcialmente financiado por el Ministerio de Ciencia, Innovación y Universidades a través del proyecto RTI2018-101475-BI00, en conjunto con el Fondo Europeo de Desarrollo Regional (FEDER), y en parte por el Gobierno Vasco por medio del proyecto IT- 1229-19

Autofluorescence image reconstruction and virtual staining for in-vivo optical biopsying

Modern photonic technologies are emerging, allowing the acquisition of in-vivo endoscopic tissue imaging at a microscopic scale, with characteristics comparable to traditional histological slides, and with a label-free modality. This raises the possibility of an ‘optical biopsy’ to aid clinical decision making. This approach faces barriers for being incorporated into clinical practice, including the lack of existing images for training, unfamiliarity of clinicians with the novel image domains and the uncertainty of trusting ‘black-box’ machine learned image analysis, where the decision making remains inscrutable. In this paper, we propose a new method to transform images from novel photonics techniques (e.g. autofluorescence microscopy) into already established domains such as Hematoxilyn-Eosin (H-E) microscopy through virtual reconstruction and staining. We introduce three main innovations: 1) we propose a transformation method based on a Siamese structure that simultaneously learns the direct and inverse transformation ensuring domain back-transformation quality of the transformed data. 2) We also introduced an embedding loss term that ensures similarity not only at pixel level, but also at the image embedding description level. This drastically reduces the perception distortion trade-off problem existing in common domain transfer based on generative adversarial networks. These virtually stained images can serve as reference standard images for comparison with the already known H-E images. 3) We also incorporate an uncertainty margin concept that allows the network to measure its own confidence, and demonstrate that these reconstructed and virtually stained images can be used on previously-studied classification models of H-E images that have been computationally degraded and de-stained. The three proposed methods can be seamlessly incorporated on any existing architectures. We obtained balanced accuracies of 0.95 and negative predictive values of 1.00 over the reconstructed and virtually stained image-set on the detection of color-rectal tumoral tissue. This is of great importance as we reduce the need for extensive labeled datasets for training, which are normally not available on the early studies of a new imaging technology.The authors would like to thank all pathologists that generated the BIOPOOL dataset (FP7-ICT-296162) that has been used for this work and specially to M. Saiz, A. Gaafar, S. Fernandez, A. Saiz, E. de Miguel, B. Catón, J. J. Aguirre, R. Ruiz, Ma A. Viguri, and R. Rezola

Mixed convolutional and long short-term memory network for the detection of lethal ventricular arrhythmia

Early defibrillation by an automated external defibrillator (AED) is key for the survival of out-of-hospital cardiac arrest (OHCA) patients. ECG feature extraction and machine learning have been successfully used to detect ventricular fibrillation (VF) in AED shock decision algorithms. Recently, deep learning architectures based on 1D Convolutional Neural Networks (CNN) have been proposed for this task. This study introduces a deep learning architecture based on 1D-CNN layers and a Long Short-Term Memory (LSTM) network for the detection of VF. Two datasets were used, one from public repositories of Holter recordings captured at the onset of the arrhythmia, and a second from OHCA patients obtained minutes after the onset of the arrest. Data was partitioned patient-wise into training (80%) to design the classifiers, and test (20%) to report the results. The proposed architecture was compared to 1D-CNN only deep learners, and to a classical approach based on VF-detection features and a support vector machine (SVM) classifier. The algorithms were evaluated in terms of balanced accuracy (BAC), the unweighted mean of the sensitivity (Se) and specificity (Sp). The BAC, Se, and Sp of the architecture for 4-s ECG segments was 99.3%, 99.7%, and 98.9% for the public data, and 98.0%, 99.2%, and 96.7% for OHCA data. The proposed architecture outperformed all other classifiers by at least 0.3-points in BAC in the public data, and by 2.2-points in the OHCA data. The architecture met the 95% Sp and 90% Se requirements of the American Heart Association in both datasets for segment lengths as short as 3-s. This is, to the best of our knowledge, the most accurate VF detection algorithm to date, especially on OHCA data, and it would enable an accurate shock no shock diagnosis in a very short time.This study was supported by the Ministerio de Economía, Industria y Competitividad, Gobierno de España (ES) (TEC-2015-64678-R) to UI and EA and by Euskal Herriko Unibertsitatea (ES) (GIU17/031) to UI and EA. The funders, Tecnalia Research and Innovation and Banco Bilbao Vizcaya Argentaria (BBVA), provided support in the form of salaries for authors AP, AA, FAA, CF, EG, but did not have any additional role in the study design, data collection and analysis, decision to publish, or preparation of the manuscript. The specific roles of these authors are articulated in the author contributions section

Aprendizaje automático para la anotación de ritmos en parada cardiorrespiratoria

Resumen (castellano) Las paradas cardiorrespiratorias extrahospitalarias (PCREH) se posicionan como una de las principales causas de defunción en los países desarrollados. Ante dicho evento, existen ciertos factores determinantes para la supervivencia del sujeto, incluyendo la reanimación cardio pulmonar, una pronta desfibrilación y la calidad del tratamiento ofrecido por el Servicio de Emergencias Médicas. El corazón del paciente puede presentar hasta cinco tipos de ritmos distintos. Puesto que cada estado clínico precisa un tratamiento diferente, es de vital importancia para el personal médico, la pronta y correcta identificación del ritmo/estado del paciente. Por consiguiente, existen numerosos estudios dedicados al entendimiento de dichas patologías, los cuales emplean grabaciones de la señal electrocardiograma (ECG) durante episodios PCREH. Dichas grabaciones deben ser anotadas manualmente por un grupo de expertos clínicos. Por lo tanto, resulta una tarea dispendiosa, lo cual ocasiona escasez de bases de datos debidamente caracterizadas y anotadas. Con el objetivo de facilitar el acceso a colecciones de datos correctamente anotadas, existen algoritmos de anotación semiautomáticos. Estos algoritmos permiten identificar con elevada certeza, las patologías presentes en distintos intervalos temporales de la señal ECG. De esta forma, los expertos clínicos se focalizan en repasar las decisiones del algoritmo, ahorrando tiempo y coste. Por todo ello, los algoritmos de anotación facilitan los estudios de enfermedades cardiacas, mejorando la calidad del tratamiento realizado y, de esta forma, la probabilidad de supervivencia del paciente. En este trabajo se presentan cuatro clasificadores de ritmos de pacientes en PCREH. Para su desarrollo, primero se prepara una colección de episodios PCREH con los que entrenar los algoritmos. El primer clasificador extrae información únicamente de la señal ECG. El segundo añade la información presente en la impedancia transtorácica del paciente. Después, se desarrolla un tercer clasificador mediante técnicas de Deep Learning, puesto que recientemente ha demostrado su potencial en este campo. El cuarto clasificador lo conforma una versión optimizada del anterior modelo. Finalmente, se analizan los resultados y se compara el rendimiento de las distintas soluciones propuestas.Summary (English) Out-of-hospital cardiac arrest (OHCA) is one of the leading causes of death in developed countries. There are several key factors to survive an OHCA event, including cardiopulmonary resuscitation, early defibrillation and the overall quality of treatment given by the Emergency Medical System. The patient's heart can present up to five different types of rhythms. Since each clinical condition requires a different treatment, a fast and precise identification of the patient's rhythm/status is crucial for the medical staff. Therefore, there are numerous studies that focus on the understanding of these pathologies, using electrocardiogram signals (ECG) recorded during OHCA events. These recordings must be manually annotated by a group of clinical experts. Because the high costs associated to manual annotation, there is a lack of properly characterized and annotated databases. In order to facilitate access to correctly annotated data collections, there are semiautomatic annotation algorithms. These algorithms identify with high accuracy the pathologies present in different time intervals of the ECG signal. In this way, clinical experts would focus on reviewing the algorithm's decisions, saving time and money. All these considerations make annotation algorithms a key factor to develop studies on OHCA, improving the quality of the treatment performed and the probability of patient survival. In this work, four classifiers of OHCA rhythms are presented. For their development, first a collection of OHCA episodes is prepared, in order to train the algorithms. The first classifier extracts information only from the ECG signal. The second one, adds the information present in the patient's transthoracic impedance. Then, a third classifier is developed using Deep Learning techniques, since it has recently demonstrated its potential in this field. After that, a fourth classifier is made optimizing the previous model. Lastly, the results are analysed and the performance of the different proposed solutions is compared.Laburpena (Euskara) Hospitalez kanpoko bihotz geldiketa (HKBG) mundo garatuko heriotza kausa handienetariko bat dira. Geldiketa bat ematen denean zenbait gertakari gako dira pazientearen biziraupenerako, adibidez bihotz biriketako masajea, desfibrilazio goiztiarra edota emergentzia zerbitzuek emandako tratamendua. Pazientearen bihotzak bost erritmo desberdin aurkez ditzazke HKGB batean. Egoera kliniko bakoitzak tratamendu desberdina behar duenez, pazientearen erritmoa/egoera goiz eta zehatz detektatzea oso garrantzitsua da. Ondorioz, lan asko egin dira patologia horiek ulertzeko eta identifikatzeko, orokorrean pazientearen grabatutako elektrokardiograma (EKG) erabiliz. Grabaketa horietan aditu klinikoek erritmoa identifikatu eta anotatu behar dute. Azken hau kostu handiko lana da, eta ondorioz oso HKBG datubase gutxi dago erritmo anotazio egokiekin. Erritmo anotazioak dituzten HKGB datubaseak sortzeko badira erritmoa modu erdiautomatikoan anotatzeko algoritmoak. Algoritmo hauek modu nahiko zehatzean identifika dezaketa HKGB pazientearen erritmo/egoera, horretarako grabatutako EKG erabiliz. Horrela aditu klinikoek emandako diagnostikoa baino ez dute berrikusi behar, denbora eta kostuak aurreztuz. Horregatik anotaziorako algoritmoek HKGBaren inguruko ikerkuntza errazteu eta hobetuko lituzkete, emandako tratamendua hobetuz, eta pazienteen biziraupen aukerak handituz. Lan honetan lau algoritmo garatu dira HKGB erritmoak modu automatikoan sailkatzeko. Algoritmoak garatzeko lehendabizi HKGB kasuen datubase bat prestatu da, algoritmoak entrenatzeko. Lehen sailkatzailea EKG-tik soilik lortzen du informazioa. Bigarrenak bular inpedantziako informazioa ere erabiltzen du. Gero, ikasketa sakonean oinarritutako sailkatzailea garatu da, esparru honetan teknika hauek oso emaitza onak eman izan baitituzte. Azkenik laugarren sailkatzailea aurrekoaren bertsio hobetua da. Bukatzeko, emaitzak aztertu eta sailkatzaileen errendimenduak alderatu dira