Bayesian inference and prediction in cardiac electrophysiology models with an application to representing variability

Many different techniques have been used for parameter estimation in cardiac electrophysiology models, from optimization algorithms to heuristic and frequentist statistical methods. However, the fixed parameter values obtained from such approaches cannot provide a complete description of variability within an individual or across a population. To overcome this shortcoming, in this work we adopt a Bayesian approach by applying the Hamiltonian Monte Carlo (HMC) algorithm to cardiac electrophysiology models and data for the first time through three studies. (i) Using HMC, we fit synthetic and experimental cardiac voltage data from different pacing rates and find the probability distributions of the parameters of two relatively low-dimensional models, the Mitchell-Schaeffer (MS) and Fenton-Karma (FK) models. We successfully fit synthetic and experimental voltage traces and build populations of action potentials with the posterior probability distributions of the parameters. (ii) We compare the performance of HMC with that of the main Bayesian approach used previously for similar applications, the Approximate Bayesian Computation Sequential Monte Carlo (ABC SMC) algorithm. Both techniques are able to describe the dynamics of synthetic and experimental voltage data using the MS and FK models, with HMC more consistent and ABC SMC more versatile and easier to implement. (iii) We study the variability of cardiac action potentials in space within an individual. We use HMC and a novel approach employing a Gaussian process prior for one spatially varying MS model parameter along with a hierarchical model for the remaining parameters, considered spatially invariant. Using this approach, we do inference and prediction on synthetic cardiac voltage data, exploiting the spatial correlations in cardiac tissue that arise from cellular coupling to use voltage information from a small number of sites to predict parameter value distributions and families of voltage data in other locations. Together these three studies show the potential of Bayesian inference and prediction in providing a framework to represent variability within cardiac electrophysiology modeling

Un modelo neokaleckiano con pensionados, conflicto de clases y distribución del ingreso

Este documento presenta un modelo neokaleckiano con tres grupos sociales: capitalistas, trabajadores y pensionados. Se asumen dos sistemas pensionales que coexisten: capitalización y reparto. Este tipo de modelos se contraponen a la visión ortodoxa de plena utilización de recursos y la relación de causalidad del ahorro hacia la inversión. Partiendo de la distribución funcional del ingreso entre los factores productivos: trabajo y capital, se muestra que la inclusión de los pensionados en la estructura económica tiene efectos relevantes en la determinación de la tasa de utilización de capacidad y la tasa de acumulación de capital.Abstract. This document presents a neokaleckian model with three social classes: capitalists, workers and retirees. It is assumed two pensions systems that coexist: Fully funded and PAYGO. This kind of models is opposed to the orthodox models in which there is full utilization of productive resources and the causal relationship is saving causes investment. Based on the functional distribution of income between labor and capital, it is showed that including retirees in the economic structure has relevant effects in the determination of the capacity utilization rate and the capital accumulation rate.Maestrí

Colombia: un solo país, múltiples realidades. Una mirada regional del empleo en Colombia, en el marco de una reforma de protección a la vejez

This document aims to present a descriptive analysis of the Colombian labor context, with a particular interest in the regional differences. Using the data available on the Household Surveys (GEIH) for 2007 to 2018 as the primary source, we show the comparative results based on distinct classification criteria as economic activity and occupational position. We conclude that the labor composition differs significantly along Colombian zones and regions, which implies discrepancies on pension coverage both in the productive and in the retired stage. These results suggest that the pension debate in Colombia must be extended, including new and relevant issues to the discussion; on the contrary, a significant proportion of the Colombian population will keep excluded from a protection scheme.El propósito de este documento es presentar un análisis descriptivo del contexto laboral colombiano, haciendo énfasis en las diferencias regionales que existen en el país. La información disponible en la Gran Encuesta Integrada de Hogares (GEIH) entre los años 2008 y 2017, permite obtener cifras comparativas, siguiendo distintos criterios de clasificación, como rama de actividad y posición ocupacional. Se demuestra que la estructura laboral difiere considerablemente entre zonas y regiones, lo que, a su vez, implica importantes discrepancias en las tasas de cotización y cobertura pensional. Tales diferencias hacen imperativo que el país amplíe e incluya en la discusión pensional nuevos elementos de debate, o de lo contrario una significativa proporción de la población colombiana seguirá marginada del sistema pensional

¿A quiénes y cuánto subsidia el régimen pensional de prima media en Colombia? Análisis paramétrico y lecciones de política

This paper analyses the benefits provided by Colpensiones (Colombian Average Premium with Defined Benefit Solidarity Public System Operator) to this system members. We present a set of simulation results that were ran following the existing regulation and commonly accepted actuarially assumptions from which we conclude that all pensions recognized by Colpensiones could be subsidized. We also estimate that when simulations followed the same returns that the affiliates’ savings get within the Colombian Individual Saving with Defined Benefit Private System (RAIS), the implicit subsidies for the higher pensions provided by Colpensiones disappear. In addition, we found that the same result could be achieved through some reasonable parametric adjustments. Finally, on the basis of the above we discuss on the existing policies regarding the pension systemEn este artículo se discuten los subsidios pensionales otorgados por Colpensiones (operador del Régimen de Prima Media en Colombia). Se presentan los resultados obtenidos a partir de simulaciones que parten de las reglas vigentes del sistema pensional y la aplicación de supuestos actuariales comúnmente aceptados, encontrando que bajo estos paradigmas, todas las pensiones otorgadas por Colpensiones estarían subsidiadas. Por otra parte, cuando en los ejercicios de simulación se asumen rentabilidades similares a las que el Régimen de Capitalización Individual (RAIS) otorga a sus afiliados a través de los fondos privados, desaparecen los subsidios de las pensiones más altas. Asimismo, se muestra que se pueden alcanzar iguales resultados implementando algunos ajustes paramétricos razonables, todo lo que da pie a una discusión sobre la política que regula el sistema pensiona

Employing Gaussian process priors for studying spatial variation in the parameters of a cardiac action potential model

Cardiac cells exhibit variability in the shape and duration of their action potentials in space within a single individual. To create a mathematical model of cardiac action potentials (AP) which captures this spatial variability and also allows for rigorous uncertainty quantification regarding within-tissue spatial correlation structure, we developed a novel hierarchical Bayesian model making use of a latent Gaussian process prior on the parameters of a simplified cardiac AP model which is used to map forcing behavior to observed voltage signals. This model allows for prediction of cardiac electrophysiological dynamics at new points in space and also allows for reconstruction of surface electrical dynamics with a relatively small number of spatial observation points. Furthermore, we make use of Markov chain Monte Carlo methods via the Stan modeling framework for parameter estimation. We employ a synthetic data case study oriented around the reconstruction of a sparsely-observed spatial parameter surface to highlight how this approach can be used for spatial or spatiotemporal analyses of cardiac electrophysiology

Neuroma mentoniano traumático. Reporte de caso clínico

Traumatic neuroma is not a true neoplasm but rather a reactive proliferation of neural tissue after transection or other damage to a nerve bundle. They can develop anywhere but are most common in the area of the mental foramen, tongue, and lower lip. Traumatic neuroma formation is a major cause of neuropathic pain, which remains a difficult problem for surgeons. The exact mechanism of the pain associated with the neuroma is still not fully understood and the prevention of its formation is essential to avoid it. To date the most effective treatment has been surgical removal. We report the case of a 23-year-old female patient who presented an increase in the volume of the vestibular sulcus at the level of teeth 44 and 45, as well as spontaneous burning pain with an evolution of approximately five months. It was decided to perform the surgical resection of the lesion and the histopathological result was a traumatic neuroma. At 7 days of follow-up, slight edema is observed in the oral and mental region; as well as anesthesia at the level of the skin of the chin and lower lip. A 10-month follow-up anesthesia persisted, and no recurrence data were observed.El neuroma traumático no es una verdadera neoplasia sino una proliferación reactiva del tejido neural después de la transección u otro daño de un haz de nervios. Pueden desarrollarse en cualquier lugar, pero son más comunes en el área del foramen mentoniano, la lengua y el labio inferior. La formación de neuromas traumáticos es una causa importante de dolor neuropático, que sigue siendo un problema difícil al que se enfrentan los cirujanos. El mecanismo exacto del dolor asociado al neuroma aún no se comprende completamente y la prevención de su formación es primordial para evitarlo. Hasta la fecha el tratamiento más efectivo ha sido la extirpación quirúrgica. Se reporta el caso de un paciente de sexo femenino de 23 años de edad que presenta un aumento de volumen en el fondo de surco vestibular a nivel de los dientes 44 y 45, así como dolor espontáneo de tipo ardoroso con una evolución de aproximadamente cinco meses. Se decide realizar la resección quirúrgica de la lesión y el resultado histopatológico fue de un neuroma traumático. A los 7 días de seguimiento, se observa un ligero edema en la región bucal y mentoniana; así como anestesia a nivel de la piel del mentón y labio inferior. A 10 meses de seguimiento persistió la anestesia y no se observaron datos de recidiva

Control strategy of a pseudo-stationary gait rehabilitation robot

[Resumen] La recuperación de la marcha es una prioridad para las personas con enfermedades neurológicas o lesión medular espinal. Los exoesqueletos actuales de reentrenamiento de la marcha implementan estrategias de control por seguimiento de la trayectoria o por asistencia según la necesidad, sin embargo, éstas no han mostrado aún ser superiores a la rehabilitación convencional de manera concluyente. En este artículo se presenta de forma conceptual la estrategia de control de un nuevo sistema robótico ambulatorio para la rehabilitación de la marcha basado en un exoesqueleto comercial, integrando módulos robóticos adicionales para proporcionar mayor libertad de movimiento al usuario y fomentar el control voluntario y la participación activa. De esta forma se espera que el sistema permita desarrollar de forma satisfactoria la terapia y, a futuro, favorezca la plasticidad neuronal y el aprendizaje motor.[Abstract] The restoration of gait is a priority for people with neurological disease or spinal cord injury. Current gait training exoskeletons implement path-following or assist-as-needed control strategies. However, they have not shown to be conclusively superior to conventional rehabilitation yet. This paper conceptually presents the control strategy of a new ambulatory robotic gait rehabilitation system based on a commercial exoskeleton. The system integrates additional robotic modules to provide more freedom to the user during motion and encourage voluntary control and active participation in the therapy. In this way, the system is expected to provide a successful therapy development and, in the future, to promote neural plasticity and motor learning.Ministerio de Ciencia e Innovación; PID2021-123657OB-C3

Multimorbidity Patterns and Their Association with Social Determinants, Mental and Physical Health during the COVID-19 Pandemic

Background: The challenge posed by multimorbidity makes it necessary to look at new forms of prevention, a fact that has become heightened in the context of the pandemic. We designed a questionnaire to detect multimorbidity patterns in people over 50 and to associate these patterns with mental and physical health, COVID-19, and possible social inequalities. Methods: This was an observational study conducted through a telephone interview. The sample size was 1592 individuals with multimorbidity. We use Latent Class Analysis to detect patterns and SF-12 scale to measure mental and physical quality-of-life health. We introduced the two dimensions of health and other social determinants in a multinomial regression model. Results: We obtained a model with five patterns (entropy = 0.727): ‘Relative Healthy’, ‘Cardiometabolic’, ‘Musculoskeletal’, ‘Musculoskeletal and Mental’, and ‘Complex Multimorbidity’. We found some differences in mental and physical health among patterns and COVID-19 diagnoses, and some social determinants were significant in the multinomial regression. Conclusions: We identified that prevention requires the location of certain inequalities associated with the multimorbidity patterns and how physical and mental health have been affected not only by the patterns but also by COVID-19. These findings may be critical in future interventions by health services and governments17 página