Assessing stress variations in children during the strange situation procedure: comparison of three widely used respiratory sinus arrhythmia estimation methods.

Objective.The respiratory sinus arrhythmia (RSA) is a well-known marker of vagal activity that can be exploited to measure stress changes. RSA is usually estimated from heart rate variability (HRV). This study aims to compare the RSA obtained with three widely adopted methods showing their strengths and potential pitfalls.Approach.The three methods are tested on 69 healthy preschoolers undergoing a stressful protocol, the strange situation procedure (SSP). We compare the RSA estimated by the Porges method, the univariate autoregressive (AR) spectral analysis of the HRV signal, and the bivariate AR spectral analysis of HRV and respirogram signals. We examine RSA differences detected across the SSP episodes and correlation between the estimates provided by each method.Main results.The Porges and the bivariate AR approaches both detected significant differences (i.e. stress variations) in the RSA measured across the SSP. However, the latter method showed higher sensitivity to stress changes induced by the procedure, with the mean RSA variation between baseline and first separation from the mother (the most stressful condition) being significantly different among methods: Porges, -17.5%; univariate AR, -18.3%; bivariate AR, -23.7%. Moreover, the performances of the Porges algorithm were found strictly dependent on the applied preprocessing.Significance.Our findings confirm the bivariate AR analysis of the HRV and respiratory signals as a robust stress assessment tool that does not require any population-specific preprocessing of the signals and warn about using RSA estimates that neglect breath information in more natural experiments, such as those involving children, in which respiratory frequency changes are extremely likely.

Model-Based Evaluation of Methods for Respiratory Sinus Arrhythmia Estimation.

OBJECTIVE: Respiratory sinus arrhythmia (RSA) refers to heart rate oscillations synchronous with respiration, and it is one of the major representations of cardiorespiratory coupling. Its strength has been suggested as a biomarker to monitor different conditions, and diseases. Some approaches have been proposed to quantify the RSA, but it is unclear which one performs best in specific scenarios. The main objective of this study is to compare seven state-of-the-art methods for RSA quantification using data generated with a model proposed to simulate, and control the RSA. These methods are also compared, and evaluated on a real-life application, for their ability to capture changes in cardiorespiratory coupling during sleep. METHODS: A simulation model is used to create a dataset of heart rate variability, and respiratory signals with controlled RSA, which is used to compare the RSA estimation approaches. To compare the methods objectively in real-life applications, regression models trained on the simulated data are used to map the estimates to the same measurement scale. Results, and conclusion: RSA estimates based on cross entropy, time-frequency coherence, and subspace projections showed the best performance on simulated data. In addition, these estimates captured the expected trends in the changes in cardiorespiratory coupling during sleep similarly. SIGNIFICANCE: An objective comparison of methods for RSA quantification is presented to guide future analyses. Also, the proposed simulation model can be used to compare existing, and newly proposed RSA estimates. It is freely accessible online.

Respuesta al ECG de octubre de 2019 / Response to ECG, October 2019

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Unconstrained Estimation of HRV Indices After Removing Respiratory Influences From Heart Rate.

OBJECTIVE: This paper proposes an approach to better estimate the sympathovagal balance (SB) and the respiratory sinus arrhythmia (RSA) after separating respiratory influences from the heart rate (HR). METHODS: The separation is performed using orthogonal subspace projections and the approach is first tested using simulated HR and respiratory signals with different spectral properties. Then, RSA and SB are estimated during autonomic blockade and stress using the proposed approach and the classical heart rate variability (HRV) analysis. Both real- and ECG-derived respiration (EDR) are used and the reliability of the EDR is evaluated. RESULTS: Mean absolute percentage errors lower than [Formula: see text] were obtained after removing previously known respiratory signals from simulated HR. The proposed indices were able to improve the quantification of SB during autonomic withdrawal. In the stress data, differences ( ) among relaxed and stressful phases were found with the proposed approach, using both the real respiration and the EDR, but they disappeared when using the classical HRV. CONCLUSION: A better assessment of the autonomic nervous system' response to pharmacological blockade and stress can be achieved after removing respiratory influences from HR, and this can be done using either the real respiration or the EDR. SIGNIFICANCE: This work can be used to better identify vagal withdrawal and increased sympathetic activation when the classical HRV analysis fails due to the respiratory influences on HR. Furthermore, it can be computed using only the ECG, which is an advantage when developing wearable systems with limited number of sensors.

Non-Contact, Simple Neonatal Monitoring by Photoplethysmography.

This paper presents non-contact vital sign monitoring in neonates, based on image processing, where a standard color camera captures the plethysmographic signal and the heart and breathing rates are processed and estimated online. It is important that the measurements are taken in a non-invasive manner, which is imperceptible to the patient. Currently, many methods have been proposed for non-contact measurement. However, to the best of the authors' knowledge, it has not been possible to identify methods with low computational costs and a high tolerance to artifacts. With the aim of improving contactless measurement results, the proposed method based on the computer vision technique is enhanced to overcome the mentioned drawbacks. The camera is attached to an incubator in the Neonatal Intensive Care Unit and a single area in the neonate's diaphragm is monitored. Several factors are considered in the stages of image acquisition, as well as in the plethysmographic signal formation, pre-filtering and filtering. The pre-filter step uses numerical analysis techniques to reduce the signal offset. The proposed method decouples the breath rate from the frequency of sinus arrhythmia. This separation makes it possible to analyze independently any cardiac and respiratory dysrhythmias. Nine newborns were monitored with our proposed method. A Bland-Altman analysis of the data shows a close correlation of the heart rates measured with the two approaches (correlation coefficient of 0.94 for heart rate (HR) and 0.86 for breath rate (BR)) with an uncertainty of 4.2 bpm for HR and 4.9 for BR (k = 1). The comparison of our method and another non-contact method considered as a standard independent component analysis (ICA) showed lower central processing unit (CPU) usage for our method (75% less CPU usage).

Dengue Fever Detecting System Using Peak-detection of Data from Contactless Doppler Radar.

Infectious diseases, such as dengue fever and Middle East respiratory syndrome, have become prevalent worldwide in recent times. To conduct highly accurate and effective infection screening, we are working on the development of a contactless infection screening system using Doppler radar and thermography. In our previous work, three parameters (face temperature, heartbeat rate, and respiration rate) were used to judge whether a subject was infected. However, facial temperature measurements may be vastly different from temperatures measured at the axilla owing to influence from the immediate environment. In this study, heartbeat rate (HR), respiration rate (RR), and standard deviation of heartbeat interval (SDHI) were used to quantify the infection screening system without using facial temperature as a parameter. We found that respiratory sinus arrhythmia (RSA) diminished in patients who had dengue fever. We gathered data from 47 patients with dengue fever using a 10-GHz Doppler radar system at the National Hospital of Tropical Diseases (NHTD) in Hanoi, Vietnam. To evaluate the accuracy, the data of these patients were compared to that of 23 unaffected subjects. We observed that a linear discriminant analysis (LDA) was effective at detecting the dengue fever conditions, and the detection accuracy was approximately 97.6%.

Adapting detection sensitivity based on evidence of irregular sinus arrhythmia to improve atrial fibrillation detection in insertable cardiac monitors.

Aims: Intermittent change in p-wave discernibility during periods of ectopy and sinus arrhythmia is a cause of inappropriate atrial fibrillation (AF) detection in insertable cardiac monitors (ICM). To address this, we developed and validated an enhanced AF detection algorithm. Methods and results: Atrial fibrillation detection in Reveal LINQ ICM uses patterns of incoherence in RR intervals and absence of P-wave evidence over a 2-min period. The enhanced algorithm includes P-wave evidence during RR irregularity as evidence of sinus arrhythmia or ectopy to adaptively optimize sensitivity for AF detection. The algorithm was developed and validated using Holter data from the XPECT and LINQ Usability studies which collected surface electrocardiogram (ECG) and continuous ICM ECG over a 24-48 h period. The algorithm detections were compared with Holter annotations, performed by multiple reviewers, to compute episode and duration detection performance. The validation dataset comprised of 3187 h of valid Holter and LINQ recordings from 138 patients, with true AF in 37 patients yielding 108 true AF episodes ≥2-min and 449 h of AF. The enhanced algorithm reduced inappropriately detected episodes by 49% and duration by 66% with <1% loss in true episodes or duration. The algorithm correctly identified 98.9% of total AF duration and 99.8% of total sinus or non-AF rhythm duration. The algorithm detected 97.2% (99.7% per-patient average) of all AF episodes ≥2-min, and 84.9% (95.3% per-patient average) of detected episodes involved AF. Conclusion: An enhancement that adapts sensitivity for AF detection reduced inappropriately detected episodes and duration with minimal reduction in sensitivity.

The prevalence of electrocardiogram abnormalities in professional divers.

BACKGROUND: The underwater environment presents physiological challenges for the cardiovascular, renal and pulmonary systems. Increases in external hydrostatic pressure reduce the capacity of the venous compartment and cause blood to move toward the lung. The aim of this study was to evaluate retrospectively electrocardiographic (ECG) changes in a cohort of professional divers. METHODS: Between January 2009 and January 2012, 225 randomly selected professional divers, 204 male (91%) and 21 female (9%) attended our clinic for their biannual diving medical assessment. Their ECG records were evaluated retrospectively. RESULTS: The most common ECG abnormality observed was incomplete right bundle branch block (IRBBB) in 30 divers (13.3%). Eleven divers (4.9%) showed right QRS axis deviation (seven with IRBBB). Six divers had a sinus tachycardia; in four divers there was early repolarization; three divers had ventricular extrasystoles; one diver had ST elevation in lead V3; there was one with sinus arrhythmia and another with T-wave inversion in leads V2, V3 and aVF. These ECG changes were evaluated retrospectively by a cardiologist who made various recommendations for further review including bubble contrast echocardiography for IRBBB. CONCLUSIONS: No serious ECG abnormalities were identified, but IRBBB should be further investigated because of its association with persistent (patent) foramen ovale. Rapid cardiological review of ECGs could be achieved using modern communications technology, such as telecardiography, and further clinical investigations directed by specialist recommendation arranged promptly if indicated.

Stability of pacing indices and need for pacing in cardiac transplant patients over 1 year of follow-up.

BACKGROUND: A significant minority of cardiac transplant patients require permanent pacemaker (PPM) implant, primarily for sinus node dysfunction. The stability of pacing indices has not been determined in this unique patient population, and data regarding ongoing need for pacing are limited. METHODS: Pacing indices (sensing, threshold, and impedance) as well as the percentage of time patients required pacing were recorded, from 30 cardiac transplant patients that underwent PPM implant, over 1 year of follow-up. Repeated measure ANOVA (analysis of variance) was used to compare pacing indices and the percentage of time patients required pacing in each cardiac chamber (right atrium (RA) and right ventricle (RV)) and at different time points. RESULTS: There was no difference in sensing among the follow-up time points (p = 0.9). Thresholds at 3 months were significantly higher compared to the day of implant (p = 0.005) and the day after implant (p = 0.03). Impedances at implant were significantly higher compared to day 1 (p < 0.001), 3 months (p < 0.003), and 12 months (p < 0.001) post-implant. The mean percentage of RA pacing was 85 ± 6% the day after implant, 74 ± 6% at 3 months, and 80 ± 6% at 1 year (p = 0.17). CONCLUSION: In cardiac transplant patients, pacing impedances decrease and thresholds trend up in short-term follow-up, but subsequent sensing, threshold, and impedance remain stable at 1 year. This is comparable to the pattern observed among noncardiac transplant PPM recipients. The atrial pacing percentage was stable over 1 year, suggesting continued relative sinus node dysfunction.

Serum interleukin-6: Association with circulating cytokine serum levels in patients with sinus arrhythmia and patients with coronary artery disease.

In this study, we were focused on the differences between certain circulating cytokine levels in patients with or without sinus arrhythmia, according to the median IL-6 level. All patients were stable with regards to symptoms and therapy for at least one month prior to the measurements conducted within this study.Exclusion criteria were: patients with sleep apnea, asthma, respiratory insufficiency of any genesis, active infection, allergy, inflammatory diseases, cancer, diabetes of any type and treatment with anti-inflammatory drugs. The study was approved by the Institutional Review Board. All recruited patients gave their verbal and written consent for participation in the study. The study group consisted of 74 patients divided into two groups: with (38) and without sinus arrhythmia but with diagnosed coronary artery disease (36). Sinus arrhythmia was confirmed by 24h Holter monitoring. From all test parameters only cytokines IL-2, IL-8, IL-10, IL-17 and IL-18, showed statistically significant increasing in patients with statistically higher IL-6 levels. It is possible that IL-6 may not be a marker for the selection of patients with sinus arrhythmia or coronary artery disease. The findings indicate that IL-6 represents a reliable indicator for increased expression of IL-2, IL-8, IL-10, IL-17 and IL-18 in patients with sinus arrhythmia or coronary artery disease. Further studies in a large number of patients would be necessary to confirm our observations.

ECG Of The Month: Sepsis, ARDS, and Tracheal Intubation.

A furuncle on the leg of a 23-year-old woman led to methicillin-resistant staphylococcus aureus sepsis and adult respiratory distress syndrome (ARDS) requiring tracheal intubation in the intensive care unit (ICU). Initially her electrocardiograms (ECGs) showed sinus tachycardia, but otherwise were unchanged from prior ECGs. A week into her ICU stay a different rhythm occurred.

Mean platelet volume is related with ischemic stroke in patients with sinus rhythm.

Stroke is the leading cause of disability worldwide. It is known that atrial fibrillation and left atrial enlargement contribute ischemic stroke, and mean platelet volume (MPV) increases in patients with ischemic stroke and atrial fibrillation. We aimed to determine whether higher MPV is associated with ischemic stroke in patients with sinus rhythm. We evaluated 74 patients in sinus rhythm and with ischemic stroke (Group 1) and 90 age-matched and sex-matched healthy individuals as control group (Group 2). After physical and echocardiographic examination, 24-48 h Holter monitoring and complete blood counts were studied. There were no statistically significant differences in age, sex rates, and comorbidities between groups. Left atrial diameter was higher in Group 1 than Group 2 (P = 0.001), but both were in normal range. MPV was significantly higher in Group 1 (P < 0.001) and was an independent determinant [odds ratio (OR): 1.840; P < 0.001; 95% confidence interval (CI) 1.330-2.545] of ischemic stroke with left atrial (OR: 1.138; P = 0.006; 95% CI 1.037-1.248). In conclusion, higher MPV is associated with acute ischemic stroke in patients with sinus rhythm and without heart failure or left atrial enlargement. MPV and left atrial diameter are independent predictors of ischemic stroke in this patient population.