The findings may, in part, underpin epidemiological findings of increased risk for cardiovascular morbidity and mortality. Many factors that have an adverse impact on cardiac activity were controlled for in this study, highlighting the importance of cardiovascular risk reduction strategies. Further study is needed to examine whether, how, and when such effects contribute to morbidity and mortality.

This paper presents an original hidden Markov model (HMM) approach for online beat segmentation and classification of electrocardiograms. The HMM framework has been visited because of its ability of beat detection, segmentation and classification, highly suitable to the electrocardiogram (ECG) problem. Our approach addresses a large panel of topics some of them never studied before in other HMM related works: waveforms modeling, multichannel beat segmentation and classification, and unsupervised adaptation to the patient's ECG. The performance was evaluated on the two-channel QT database in terms of waveform segmentation precision, beat detection and classification. Our waveform segmentation results compare favorably to other systems in the literature. We also obtained high beat detection performance with sensitivity of 99.79% and a positive predictivity of 99.96%, using a test set of 59 recordings. Moreover, premature ventricular contraction beats were detected using an original classification strategy. The results obtained validate our approach for real world application.

The article describes assessments and measurements performed in the Brazilian Longitudinal Study for Adult Health (ELSA-Brasil). Some assessments including anthropometric assessment, casual blood pressure measurement, and anklebrachial index have an established clinical application while others including pulse wave velocity, heart rate variability, and carotid intima-media thickness have no established application and do not have reference values for healthy Brazilian population but may be important predictors of cardiovascular outcomes. Blood pressure measurement following postural change maneuver was included in the ELSA-Brasil because it has not been much tested in epidemiological studies. Innovative approaches were developed for assessing the ankle-brachial index using an automatic device instead of the mercury column to measure blood pressure and for assessing the anterior-posterior diameter of the right lobe of the liver by ultrasound for quantitative assessment of nonalcoholic fatty liver disease. All ELSA-Brasil subjects were younger (35 years or more) than those included in other cohorts studying subclinical atherosclerosis. The inclusion of younger individuals and a variety of assessments make the ELSA-Brasil a relevant epidemiology study nationwide and worldwide.

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Heart rate variability (HRV) is a psychophysiological phenomenon with broad implications, providing an accessible index of vagal function, underpinning psychological constructs, including the capacity for social engagement and emotion regulation, and may predict future morbidity and mortality. However, the lack of reference values for short-term HRV indices for participants of both sexes across the age spectrum is a limiting factor. This was the objective of the present study. Resting electrocardiographic records were obtained from 13,214 participants (both sexes, 35-74 years), and HRV indices in time and frequency domains (mean ± SD) were determined from 5-min records. Results were based on a subsample of 2,874 nonmedicated, healthy participants stratified by sex across 10-year age groupings. Men showed lower heart rate (HR, 64 ± 8 bpm vs. 68 ± 8 bpm, p < .05) and normalized high frequency (HF; 39.4 ± 18.0 normalized units [n.u.] vs. 50.4 ± 18.5 n.u., p < .05) than women, and higher N-N variance (2,214 ± 1,890 ms vs. 1,883 ± 1,635 ms , p < .05), standard deviation of all N-N intervals (SDNN; 43.7 ± 17.3 ms vs. 40.3 ± 15.8 ms, p < .05) and LF/HF (2.30 ± 2.68 vs. 1.33 ± 1.82, p < .05). HR and HF (n.u.) were also higher in younger than older women. LF/HF was lower in women than men. Percentile curves showed almost all HRV indices decreasing with aging. The availability of short-term, resting-state HRV reference values in a large sample of healthy and nonmedicated participants from 35-74 years will provide a valuable tool for researchers, clinicians, and those in the quantified-self community.

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0.6) were obtained in the orthostatic position. Bland-Altman plots revealed that most values were inside the agreement limits, indicating concordance between measures. Only SDNN and NNv in the supine position were not reproducible. Our results showed reproducibility of HRV parameters when recorded in the same individual with a short time between two exams. The increased sympathetic activity occurring in the orthostatic position probably facilitates reproducibility of the HRV indexes.]]>

This paper investigates the viability of using the dynamic Bayesian Network framework as a tool to classify heart beats in long term ECG records. A Decision Support System composed by two layers is considered. The first layer performs the segmentation of each heartbeat available in the ECG record, whereas the second layer classifies the heartbeat as Premature Ventricular Contraction (PVC) or Other. The use of both static and dynamic Bayesian Networks is evaluated through using the records available in the MIT-BIH database, and the results show that the Dynamic one performs better, obtaining 95% of sensitivity and 98% of positive predictivity, showing that to consider the temporal relation among events is a good strategy to increase the certainty about present events.