Revisiting nonlinearity of heart rate variability in healthy aging.

Aging is commonly regarded as a physiological process in which the dynamic complexity of physiological time series and organ systems is gradually lost. This notion is derived from the identification of a decline of nonlinear measures with the advance of aging. However, additional research on cardiovascular control studied through heart rate variability (HRV), i.e., the instantaneous changes in heart rate, shows that despite the constriction of its statistical distribution, the nonlinear organization remains present in advanced age. Here, we used surrogate data testing to investigate the presence of nonlinear information in HRV time series from a publicly available database of 1121 healthy human subjects from 18 to 92 years old. We also studied the influence of basic clinical features, such as sex, body mass index (BMI), and mean heart rate (HR), on such nonlinear information. We found that the percentage of nonlinear time series after 30 years of age diminishes significantly (p < 0.01). Furthermore, larger BMI and HR are associated with the presence of more linear information in HRV, while the female sex is associated with the manifestation of nonlinear information. This work provides a common background for the contextualized interpretation of nonlinear testing and shows that the nonlinear content of HRV time series diminishes through aging.

Recurrence Quantitative Analysis of Wavelet-Based Surrogate Data for Nonlinearity Testing in Heart Rate Variability.

Exploring the presence of nonlinearity through surrogate data testing provides insights into the nature of physical and biological systems like those obtained from heart rate variability (HRV). Short-term HRV time series are of great clinical interest to study autonomic impairments manifested in chronic diseases such as the end stage renal disease (ESRD) and the response of patients to treatment with hemodialysis (HD). In contrast to Iterative Amplitude Adjusted Fourier Transform (IAAFT), the Pinned Wavelet Iterative Amplitude Adjusted Fourier Transform (PWIAAFT) surrogates preserve nonstationary behavior in time series, a common characteristic of HRV. We aimed to test synthetic data and HRV time series for the existence of nonlinearity. Recurrence Quantitative Analysis (RQA) indices were used as discriminative statistics in IAAFT and PWIAAFT surrogates of linear stationary and nonstationary processes. HRV time series of healthy subjects and 29 ESRD patients before and after HD were tested in this setting during an active standing test. Contrary to PWIAAFT, linear nonstationary time series may be erroneously regarded as nonlinear according to the IAAFT surrogates. Here, a lower proportion of HRV time series was classified as nonlinear with PWIAAFT, compared to IAAFT, confirming that the nonstationarity condition influences the testing of nonlinear behavior in HRV. A contribution of nonlinearity was found in the HRV data of healthy individuals. A lower proportion of nonlinear time series was also found in ESRD patients, but statistical significance was not found. Although this proportion tends to be lower in ESRD patients, as much as 60% of time series proved to be nonlinear in healthy subjects. Given the important contribution of nonlinearity in HRV data, a nonlinear point of view is required to achieve a broader understanding of cardiovascular physiology.

Cardiac Autonomic Response to Active Standing in Calcific Aortic Valve Stenosis.

Aortic stenosis is a progressive heart valve disorder characterized by calcification of the leaflets. Heart rate variability (HRV) analysis has been proposed for assessing the heart response to autonomic activity, which is documented to be altered in different cardiac diseases. The objective of the study was to evaluate changes of HRV in patients with aortic stenosis by an active standing challenge. Twenty-two volunteers without alterations in the aortic valve (NAV) and twenty-five patients diagnosed with moderate and severe calcific aortic valve stenosis (AVS) participated in this cross-sectional study. Ten minute electrocardiograms were performed in a supine position and in active standing positions afterwards, to obtain temporal, spectral, and scaling HRV indices: mean value of all NN intervals (meanNN), low-frequency (LF) and high-frequency (HF) bands spectral power, and the short-term scaling indices (α1 and αsign1). The AVS group showed higher values of LF, LF/HF and αsign1 compared with the NAV group at supine position. These patients also expressed smaller changes in meanNN, LF, HF, LF/HF, α1, and αsign1 between positions. In conclusion, we confirmed from short-term recordings that patients with moderate and severe calcific AVS have a decreased cardiac parasympathetic supine response and that the dynamic of heart rate fluctuations is modified compared to NAV subjects, but we also evidenced that they manifest reduced autonomic adjustments caused by the active standing challenge.

Association between Mean Heart Rate and Recurrence Quantification Analysis of Heart Rate Variability in End-Stage Renal Disease.

Linear heart rate variability (HRV) indices are dependent on the mean heart rate, which has been demonstrated in different models (from sinoatrial cells to humans). The association between nonlinear HRV indices, including those provided by recurrence plot quantitative analysis (RQA), and the mean heart rate (or the mean cardiac period, also called meanNN) has been scarcely studied. For this purpose, we analyzed RQA indices of five minute-long HRV time series obtained in the supine position and during active standing from 30 healthy subjects and 29 end-stage renal disease (ESRD) patients (before and after hemodialysis). In the supine position, ESRD patients showed shorter meanNN (i.e., faster heart rate) and decreased variability compared to healthy subjects. The healthy subjects responded to active standing by shortening the meanNN and decreasing HRV indices to reach similar values of ESRD patients. Bivariate correlations between all RQA indices and meanNN were significant in healthy subjects and ESRD after hemodialysis and for most RQA indices in ESRD patients before hemodialysis. Multiple linear regression analyses showed that RQA indices were also dependent on the position and the ESRD condition. Then, future studies should consider the association among RQA indices, meanNN, and these other factors for a correct interpretation of HRV.

Ten years of experience of the Mexican Academy of Surgery in the promotion of the next generations of researchers.

OBJECTIVE: To describe the productivity of the research works presented in the Interuniversity and resident doctors Competition of the Mexican Academy of Surgery since its origin in 2010. METHOD: Observational cross-sectional descriptive study in which the variables are considered: category of participation (university/resident) type of work (research, clinical case, etc.), university and institution of origin, type of presentation [poster/oral]) Descriptive statistics was used. RESULTS: Since 2010, 9 interuniversity competitions and 8 resident doctors have been developed. A total of 974 papers were presented, predominantly residents (65.29%), oral presentations (54.51%) and original works (58.11%). 8.9% of the published works. CONCLUSIONS: The Contest is a good forum to disseminate research in the new generations of doctors.

OBJETIVO: Describir los primeros 10 años del Concurso Interuniversitario y de Médicos Residentes de la Academia Mexicana de Cirugía. MÉTODO: Estudio observacional de tipo transversal descriptivo en el que se consideran las variables categoría de participación (universitario/residente), tipo de trabajo (investigación, caso clínico, etc.), universidad e institución de procedencia, y tipo de presentación (cartel/oral). Se empleó estadística descriptiva. RESULTADOS: Desde 2010 se han desarrollado nueve concursos interuniversitarios y ocho de médicos residentes. En total se han presentado 974 trabajos, predominando los de residentes (65.29%), las presentaciones orales (54.51%) y los trabajos originales (58.11%). El 8.9% de los trabajos han sido publicados. CONCLUSIONES: El Concurso es un buen foro para difundir la investigación de las nuevas generaciones de médicos.

Academic-assistance activities registered by the graduates of the specialty of Emergency of the Regional Hospital No. 25 of the Instituto Mexicano del Seguro Social (1991-2018).

OBJECTIVE: To describe the academic-assistance activities of the graduates of the specialty of emergencies in the Regional General Hospital 25 of the Mexican Institute of Social Security. METHOD: Observational descriptive type study in which the 25 generations graduated from the specialty will be analyzed. The scientific, teaching and care productivity of its graduates was analyzed, as well as the subsequent training and the managerial positions held. RESULTS: From 1991 to 2018 238 residents entered, of which 88.65% concluded the specialty. 57.34% are male. 78.67% of the graduates work exclusively in the IMSS and 68.72% do it in more than one institution. 72% of them have certification. They published 112 scientific articles and 4 books. 12.32% of the graduates attended a second specialty, being the predecessor of patient care in the critical state (84.61%). Among the main achievements of the headquarters are in the first emergency room of the country in the Quality Postgraduate Program of Consejo Nacional de Ciencia y Tecnología. 53% of these specialists work or perform in management positions. CONCLUSIONS: This office is considered a reference in the specialty of emergencies in Latin America.

OBJETIVO: Describir las actividades académico-asistenciales de los egresados de la especialidad de urgencias en el Hospital General Regional 25 del Instituto Mexicano del Seguro Social (IMSS). MÉTODO: Estudio observacional de tipo descriptivo en el que se analizaron las 25 generaciones egresadas de la especialidad. Se analizó la productividad científica, docente y asistencial de sus egresados, así como la formación posterior y los puestos directivos desempeñados. RESULTADOS: De 1991 a 2018 ingresaron 238 residentes, de los cuales el 88.65% concluyó la especialidad. El 57.34% son de sexo masculino. El 78.67% de los egresados laboran exclusivamente en el IMSS y el 68.72% lo hacen en más de una institución. El 72% cuentan con certificación. Publicaron 112 artículos científicos y 4 libros. El 12.32% de los egresados cursaron una segunda especialidad, siendo la predominante la de Atención del Paciente en Estado Crítico (84.61%). Entre los logros principales de la sede están el de ser la primera sede de urgencias del país en ser incluida en el Programa de Posgrados de Calidad del Consejo Nacional de Ciencia y Tecnología. El 53% de estos especialistas se desempeñan o han desempeñado en puestos directivos. CONCLUSIONES: Esta sede se constituye como un referente dentro de la especialidad de urgencias en Latinoamérica.

The Severity of Neurological Dysfunction in Preschool Children, Secondary to Damage Generated During the Perinatal Period, is Associated With a Pro-Inflammatory Pattern of Serum Molecules.

Disorders in the child's neurological development caused by perinatal risks can lead to long-term altered neurological signs that begin at an early age and involve persistent functional disorders. Recent data suggest that tissue dysfunction, not just acute damage, may initiate or perpetuate an inflammatory response. The aim of this study was to find out if any neurological dysfunction in preschool children secondary to damage generated during the perinatal period is associated with the magnitude of perinatal risks and long-term modifications in the serum concentrations of inflammatory molecules. The participants, aged 1-4 years, were on neurodevelopmental follow-up and rehabilitation therapy from the first three months of life and had no acute disease data. We classified the children into three groups according to the importance of their perinatal risks: low, medium, and high. The results show that 1) the magnitude of perinatal risks correlated with the severity of neurological dysfunction; 2) the greatest changes in the concentrations of the molecules of the inflammatory process were associated with the most altered neurological signs. This suggests that persistent nervous system dysfunction keeps inflammatory responses active even in the absence of an acute process of infection or damage.

Symbolic analysis of heart rate fluctuations identifies cardiac autonomic modifications during LPS-induced endotoxemia.

The present study aimed to compare linear and symbolic dynamics (SD) indices for detecting the autonomic cardiac changes produced by endotoxemia in freely-moving rats. In this context, we analyzed ECG-derived R-R time series in freely moving Dark Agouti rats, which received lipopolysaccharide (LPS, n = 9), or vehicle (V, n = 7). Five minutes R-R time series were assessed every hour up to +12 h and + 24 h post-LPS injection. We found that SD indices showed significant differences at +7 h between V vs. LPS groups and at +9 h between basal levels of LPS (-3 h) and post-LPS injection (pre-LPS vs. post-LPS). In general, SD seems more appropriate than linear indices to evaluate the autonomic changes of endotoxemic rats. Overall, the symbolic parameters detected decreased R-R variability and complexity, which indicate a modification of the autonomic regulation during LPS-induced endotoxemia. This modification is probably related to a reduced activity of the cholinergic anti-inflammatory pathway at the long term.

Concurso interuniversitario y de médicos residentes, la apuesta de la Academia Mexicana de Cirugía por las próximas generaciones de académicos / No disponible

No disponible

Multifractal Analysis Reveals Decreased Non-linearity and Stronger Anticorrelations in Heart Period Fluctuations of Fibromyalgia Patients.

Objective: To characterize the multifractal behavior of the beat to beat heart-period or RR fluctuations in fibromyalgia patients (FM) in comparison with healthy-matched subjects. Methods: Multifractral detrended fluctuation analysis (MDFA) was used to study multifractality in heartbeat times-series from 30 female healthy subjects and 30 female patients with fibromyalgia during day and night periods.The multifractal changes as derived from the magnitude and sign analysis of these RR fluctuations were also assessed. Results: The RR fluctuations dynamics of healthy subjects showed a broad multifractal spectrum. By contrast, a noticeable decrease in multifractality and non-linearity was observed for patients with fibromyalgia. In addition, the spectra corresponding to FM subjects were located on the average to the right of the spectra of healthy individuals, indicating that the local scaling exponents reflect a smoother behavior compared to healthy dynamics. Moreover, the multifractal analysis as applied to the magnitude and sign heartbeat series confirmed that, in addition to a decreased nonlinearity, fibromyalgia patients presented stronger anticorrelation in directionality, which did not remain invariant for small or rather larger fluctuations as it occurred in healthy subjects. Conclusion: When compared to healthy controls, fibromyalgia patients display decreased nonlinearity and stronger anticorrelations in heart period fluctuations. These findings reinforce the hypothesis of the potential role of the dysfunctional autonomic nervous system in the pathogenesis of fibromyalgia.

[Tecnologías de la información en la formación de evaluadores del Programa Hospital Seguro en México]. / Information technologies in the training of evaluators of the Safe Hospital Program in Mexico.

OBJETIVO: Describir el proceso para la formación de evaluadores del Programa Hospital Seguro centrado en el uso de las tecnologías de la información. MÉTODO: Estudio observacional descriptivo en el que se analiza la participación dentro del nuevo curso de evaluadores del Programa Hospital Seguro. RESULTADOS: Se inscribieron 1323 participantes, de los cuales aprobaron 298 (18%); la calificación media fue de 8.85. CONCLUSIONES: La plataforma educativa tipo Moodle fue de utilidad para la capacitación del Programa Hospital Seguro. Se tendrían que mejorar los criterios de participación de los alumnos a fin de incrementar la eficiencia terminal. OBJECTIVE: To describe the process for the training of evaluators of the safe hospital program in the use of ICT. METHOD: Descriptive observational study in which the participation in the new course of appraisers of the safe hospital program is analyzed. RESULTS: 1323 participants registered of which 298 (18%) passed; the average grade was 8.85. CONCLUSIONS: The Moodle type educational platform was useful for the training of the Safe Hospital Program. The criteria for student participation would have to be improved in order to increase terminal efficiency.

Sign and magnitude scaling properties of heart rate variability in patients with end-stage renal failure: Are these properties useful to identify pathophysiological adaptations?

The scaling properties of heart rate variability data are reliable dynamical features to predict mortality and for the assessment of cardiovascular risk. The aim of this manuscript was to determine if the scaling properties, as provided by the sign and magnitude analysis, can be used to differentiate between pathological changes and those adaptations basically introduced by modifications of the mean heart rate in distinct manoeuvres (active standing or hemodialysis treatment, HD), as well as clinical conditions (end stage renal disease, ESRD). We found that in response to active standing, the short-term scaling index (α1) increased in healthy subjects and in ESRD patients only after HD. The sign short-term scaling exponent (α1sign) increased in healthy subjects and ESRD patients, showing a less anticorrelated behavior in active standing. Both α1 and α1sign did show covariance with the mean heart rate in healthy subjects, while in ESRD patients, this covariance was observed only after HD. A reliable estimation of the magnitude short-term scaling exponent (α1magn) required the analysis of time series with a large number of samples (>3000 data points). This exponent was similar for both groups and conditions and did not show covariance with the mean heart rate. A surrogate analysis confirmed the presence of multifractal properties (α1magn > 0.5) in the time series of healthy subjects and ESDR patients. In conclusion, α1 and α1sign provided insights into the physiological adaptations during active standing, which revealed a transitory impairment before HD in ESRD patients. The presence of multifractal properties indicated that a reduced short-term variability does not necessarily imply a declined regulatory complexity in these patients.

Effects of Orthostatism and Hemodialysis on Mean Heart Period and Fractal Heart Rate Properties of Chronic Renal Failure Patients.

The aim of this work was to evaluate the short-term fractal index (α1 ) of heart rate variability (HRV) in chronic renal failure (CRF) patients by identifying the effects of orthostatism and hemodialysis (HD), and by evaluating the correlation between α1 and the mean RR interval from sinus beats (meanNN). HRV time series were derived from ECG data of 19 CRF patients and 20 age-matched healthy subjects obtained at supine and orthostatic positions (lasting 5 min each). Data from CRF patients were collected before and after HD. α1 was calculated from each time series and compared by analysis of variance. Pearson's correlations between meanNN and α1 were calculated using the data from both positions by considering three groups: healthy subjects, CRF before HD and CRF after HD. At supine position, α1 of CRF patients after HD (1.17 ± 0.30) was larger (P < 0.05) than in healthy subjects (0.89 ± 0.28) but not before HD (1.10 ± 0.34). α1 increased (P < 0.05) in response to orthostatism in healthy subjects (1.29 ± 0.26) and CRF patients after HD (1.34 ± 0.31), but not before HD (1.25 ± 0.37). Whereas α1 was correlated (P < 0.05) with the meanNN of healthy subjects (r = -0.562) and CRF patients after HD (r = -0.388), no significance in CRF patients before HD was identified (r = 0.003). Multiple regression analysis confirmed that α1 was mainly predicted by the orthostatic position (in all groups) and meanNN (healthy subjects and patients after HD), showing no association with the renal disease condition in itself. In conclusion, as in healthy subjects, α1 of CRF patients correlates with meanNN after HD (indicating a more irregular-like HRV behavior at slower heart rates). This suggests that CRF patients with stable blood pressure preserve a regulatory adaptability despite a shifted setting point of the heart period (i.e., higher heart rate) in comparison with healthy subjects.

Evaluation of the continuous detection of mental calculation episodes as a BCI control input.

This paper presents an evaluation of the continuous detection of mental calculation episodes, which may be useful for users who strive to operate current BCI paradigms or even for augmenting degrees of freedom. The experimentation consisted in the alternated realization of basic arithmetic mental calculations and resting periods. EEG data were analyzed using sliding windows of 2s length. The experimental population was comprised of fifteen healthy subjects who participated in three sessions on different days. The features used for the classification process were the power spectral density over the beta band ([14-35] Hz) and the scaling exponent obtained via detrended fluctuation analysis. Both indices were estimated over four channels, specifically selected for each subject. The performance was evaluated using the Area Under the ROC Curve (AUC) by measuring the overall classification performance of each experimental session with a cross-validation procedure, and by transferring the model obtained from one session to the others called inter Session Validation (iSV). The best AUC values computed in each cross-validation session were: 0.87±0.067, 0.89±0.056 and 0.88±0.040 respectively; and the iSV provided a value of 0.67±0.122. These high values indicate that a mental calculation paradigm and a combination of features can efficiently control a BCI system. Notwithstanding that several days passed between sessions, the AUC mean value estimated for the iSV is similar to the performance of a motor imagery-BCI calibrated on the same day.