Agreement between three commercially available instruments for measuring short-term heart rate variability

The effects of a 3-day mountain bike cycling race on the autonomic nervous system (ANS) and heart rate variability in amateur cyclists: a prospective quantitative research design

BACKGROUND

The acute and chronic adaptation of endurance athletes' hearts shows that increased volume of endurance exercise might cause an acute reduction in cardiac function, causing a physiological cascade that leads to the release of cardiac biomarkers specific to cardiomyocyte stress. Heart rate variability (HRV) is a valuable tool used as a physiological measurement to evaluate the autonomic nervous system (ANS). It is frequently used to assess cardiac autonomic regulation, determining a patient's risk for unfavorable events. This study set out to determine the changes in the ANS by participating in a 3-day mountain bike cycling race in amateur cyclists using HRV as an outcome measure.

METHODS

Sixteen healthy participants (male and female) participating in a 3-day mountain bike cycling race underwent five-minute resting electrocardiography recordings in a supine position 2 days before the race (baseline testing). In addition, HRV measurements were recorded after each race day and 24 h post-race (recovery).

RESULTS

Time-domain and frequency-domain measures showed significant changes from baseline HRV parameters after each race day (p ≤ 0.05). In addition, our data revealed that the mean heart rate and R-R variability intervals did not return to baseline values after 24 h of recovery. Thus, autonomic nervous system (ANS) alterations may be due to changes in cardiac sympatho-vagal balance.

CONCLUSIONS

The main strength of this study is using HRV as a measuring and screening tool to assess cardiac autonomic activity, whereby the state of the ANS before and after endurance races can be measured. Thus, physicians, athletes, and coaches can determine the stress of endurance races on the ANS and plan recovery strategies. The reasoning is that if the ANS is in a state of sub-optimal function, susceptible amateur athletes might be at risk for a cardiovascular event or maladaptation due to the endurance race.

ECG performance in simultaneous recordings of five wearable devices using a new morphological noise-to-signal index and Smith-Waterman-based RR interval comparisons

Background

Numerous wearables are used in a research context to record cardiac activity although their validity and usability has not been fully investigated. The objectives of this study is the cross-model comparison of data quality at different realistic use cases (cognitive and physical tasks). The recording quality is expressed by the ability to accurately detect the QRS complex, the amount of noise in the data, and the quality of RR intervals.

Methods

Five ECG devices (eMotion Faros 360°, Hexoskin Hx1, NeXus-10 MKII, Polar RS800 Multi and SOMNOtouch NIBP) were attached and simultaneously tested in 13 participants. Used test conditions included: measurements during rest, treadmill walking/running, and a cognitive 2-back task. Signal quality was assessed by a new local morphological quality parameter morphSQ which is defined as a weighted peak noise-to-signal ratio on percentage scale. The QRS detection performance was evaluated with eplimited on synchronized data by comparison to ground truth annotations. A modification of the Smith-Waterman algorithm has been used to assess the RR interval quality and to classify incorrect beat annotations. Evaluation metrics includes the positive predictive value, false negative rates, and F1 scores for beat detection performance.

Results

All used devices achieved sufficient signal quality in non-movement conditions. Over all experimental phases, insufficient quality expressed by morphSQ values below 10% was only found in 1.22% of the recorded beats using eMotion Faros 360°whereas the rate was 8.67% with Hexoskin Hx1. Nevertheless, QRS detection performed well across all used devices with positive predictive values between 0.985 and 1.000. False negative rates are ranging between 0.003 and 0.017. eMotion Faros 360°achieved the most stable results among the tested devices with only 5 false positive and 19 misplaced beats across all recordings identified by the Smith-Waterman approach.

Conclusion

Data quality was assessed by two new approaches: analyzing the noise-to-signal ratio using morphSQ, and RR interval quality using Smith-Waterman. Both methods deliver comparable results. However the Smith-Waterman approach allows the direct comparison of RR intervals without the need for signal synchronization whereas morphSQ can be computed locally.

Validation of a Low-Cost Electrocardiography (ECG) System for Psychophysiological Research

BACKGROUND AND OBJECTIVE

The reliability of low-cost mobile systems for recording Electrocardiographic (ECG) data is mostly unknown, posing questions regarding the quality of the recorded data and the validity of the extracted physiological parameters. The present study compared the BITalino toolkit with an established medical-grade ECG system (BrainAmp-ExG).

METHODS

Participants underwent simultaneous ECG recordings with the two instruments while watching pleasant and unpleasant pictures of the "International Affective Picture System" (IAPS). Common ECG parameters were extracted and compared between the two systems. The Intraclass Correlation Coefficients (ICCs) and the Bland-Altman Limits of Agreement (LoA) method served as criteria for measurement agreement.

RESULTS

All but one parameter showed an excellent agreement (>80%) between both devices in the ICC analysis. No criteria for Bland-Altman LoA and bias were found in the literature regarding ECG parameters.

CONCLUSION

The results of the ICC and Bland-Altman methods demonstrate that the BITalino system can be considered as an equivalent recording device for stationary ECG recordings in psychophysiological experiments.

The validity and reliability of an open source biosensing board to quantify heart rate variability

Background

Heart rate variability (HRV) is a popular tool to quantify autonomic function. However, this typically requires an expensive 3-12 lead electrocardiogram (ECG) and BioAmp system. This investigation sought to determine the validity and reliability of an OpenBCI cyton biosensing board (open source) for accurately quantifying HRV.

New method

A cyton board with a 3-lead ECG was employed to acquire heart rate waveform data, which was processed to obtain HRV within both time- and frequency-domains. The concurrent validity was compared to a simultaneous recording from an industry-standard 3-lead ECG (ADInstruments) (n = 15). The reliability of the cyton board was compared between three days within a 7-day timespan (n = 10). Upright quiet-stance short-term HRV metrics were quantified in time- and frequency-domains.

Results

The two devices displayed excellent limits of agreements (all log mean differences ±0.4) and very high between-device variable associations (all r ² > 0.98). Between the three time points in the same subjects, no differences were noted within time- (all p > 0.71) or frequency-domains (all p > 0.88) across testing points. Finally, all HRV metrics exhibited excellent levels of reliability through high Cronbach's Alpha (all ≥0.916) and intraclass correlation coefficients (all ≥0.930); and small standard error of the measurement (all ≤0.7) and typical error of the measurement (all ≤0.1) metrics.

Comparison with existing methods

The cyton board with 3-lead ECG was compared with an industry-standard ADInstruments ECG during HRV assessments. There were no significant differences between devices with respect to time- and frequency-domains. The cyton board displayed high-levels of between-day reliability and provided values harmonious to previous ECG literature highlighting the applicability for longitudinal studies.

Conclusion

With proper background knowledge regarding ECG principles and a small degree of set-up complexity, an open source cyton board can be created and employed to perform multimodal HRV assessments at a fraction of the cost (~4%) of an industry-standard ECG setup.

Reproducibility for Heart Rate Variability Analysis during 6-Min Walk Test in Patients with Heart Failure and Agreement between Devices

Heart rate variability (HRV) analysis is a useful method to assess abnormal functioning in the autonomic nervous system and to predict cardiac events in patients with heart failure (HF). HRV measurements with heart rate monitors have been validated with an electrocardiograph in healthy subjects but not in patients with HF. We explored the reproducibility of HRV in two consecutive six-minute walk tests (6MW), 60-minute apart, using a heart rate monitor (PolarS810i) and a portable electrocardiograph (called Holter) in 50 HF patients (mean age 59 years, NYHA II, left ventricular ejection fraction ~35%). The reproducibility for each device was analysed using a paired t-test or the Wilcoxon signed-rank test. Additionally, we assessed the agreement between the two devices based on the HRV indices at rest, during the 6MW and during recovery using concordance correlation coefficients (CCC), 95% confidence intervals and Bland-Altman plots. The test-retest for the HRV analyses was reproducible using Holter and PolarS810i at rest but not during recovery. In the second 6MW, patients showed significant increases in rMSSD and walking distance. The PolarS810i measurements had remarkably high concordance correlation [0.86 Collapse

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MESH Headings

• Aged
• Electrocardiography
• Female
• Heart Failure/diagnosis
• Heart Failure/physiopathology
• Heart Rate
• Humans
• Male
• Reproducibility of Results
• Walk Test

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Grants

• Fundação de Amparo à Pesquisa do Estado de São Paulo

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Affiliation(s)

Lays Magalhães Braga Department of Physiotherapy, Faculdade de Medicina da Universidade de São Paulo, São Paulo, Brazil
Gustavo Faibischew Prado Pulmonary Division of Heart Institute (InCor) do Hospital das Clínicas da Faculdade de Medicina da Universidade de São Paulo, São Paulo, Brazil
Iracema Ioco Kikuchi Umeda Dante Pazzanese Institute of Cardiology São Paulo State, São Paulo, Brazil
Tatiana Satie Kawauchi Department of Physiotherapy, Faculdade de Medicina da Universidade de São Paulo, São Paulo, Brazil
Adriana Marques Fróes Taboada Dante Pazzanese Institute of Cardiology São Paulo State, São Paulo, Brazil
Raymundo Soares Azevedo Department of Pathology, University of São Paulo Medical School, São Paulo, Brazil
Horacio Gomes Pereira Filho Cardiology Division of Heart Institute (InCor) do Hospital das Clínicas da Faculdade de Medicina da Universidade de São Paulo, São Paulo, Brazil
César José Grupi Cardiology Division of Heart Institute (InCor) do Hospital das Clínicas da Faculdade de Medicina da Universidade de São Paulo, São Paulo, Brazil
Hayala Cristina Cavenague Souza Dante Pazzanese Institute of Cardiology São Paulo State, São Paulo, Brazil
Dalmo Antônio Ribeiro Moreira Dante Pazzanese Institute of Cardiology São Paulo State, São Paulo, Brazil
Naomi Kondo Nakagawa Department of Physiotherapy, Faculdade de Medicina da Universidade de São Paulo, São Paulo, Brazil

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[Options and limitations of heart rate measurement and analysis of heart rate variability by mobile devices: A systematic review]

BACKGROUND

Heart rate (HR) and heart rate variability (HRV) have been established in the last few years as a non-invasive method for recording the demands on the cardiovascular system. The development enables us today to measure the interbeat intervals with different technologies for calculating HR and HRV.

MATERIALS AND METHODS

This review is based on a systematic literature search in PubMed for validity of different measurement techniques and their pros and cons for the measurement of HR and the analysis of HRV.

RESULTS

Measurement equipment for recording of interbeat intervals should have a high storage capacity and a sampling rate of 1000 Hz ideally. The quality criteria of freedom of feedback (small, little disruptive), robustness and a non-invasive measurement (e. g. freeze-electrodes or sensors) have to be fulfilled. In addition to the Holter ECG, several portable heart rate watch and chest belt systems provide adequate validity and good applicability.

DISCUSSION

The Holter ECG is still the gold standard for the measurement of NN intervals and for the analysis of HRV. Modern heart rate watches show a good correlation with the conformance of freedom from discomfort, robustness and non-invasive measurement and are a good alternative due to the lower disturbance of test persons.

A quantitative systematic review of normal values for short-term heart rate variability in healthy adults

Heart rate variability (HRV) is a known risk factor for mortality in both healthy and patient populations. There are currently no normative data for short-term measures of HRV. A thorough review of short-term HRV data published since 1996 was therefore performed. Data from studies published after the 1996 Task Force report (i.e., between January 1997 and September 2008) and reporting short-term measures of HRV obtained in normally healthy individuals were collated and factors underlying discrepant values were identified. Forty-four studies met the pre-set inclusion criteria involving 21,438 participants. Values for short-term HRV measures from the literature were lower than Task Force norms. A degree of homogeneity for common measures of HRV in healthy adults was shown across studies. A number of studies demonstrate large interindividual variations (up to 260,000%), particularly for spectral measures. A number of methodological discrepancies underlined disparate values. These include a systematic failure within the literature (a) to recognize the importance of RR data recognition/editing procedures and (b) to question disparate HRV values observed in normally healthy individuals. A need for large-scale population studies and a review of the Task Force recommendations for short-term HRV that covers the full-age spectrum were identified. Data presented should be used to quantify reference ranges for short-term measures of HRV in healthy adult populations but should be undertaken with reference to methodological factors underlying disparate values. Recommendations for the measurement of HRV require updating to include current technologies.

Comparison of three mobile devices for measuring R-R intervals and heart rate variability: Polar S810i, Suunto t6 and an ambulatory ECG system

The first aim of this study was to compare an ambulatory five-lead ECG system with the commercially available breast belt measuring devices; Polar S810i and Suunto t6, in terms of R-R interval measures and heart rate variability (HRV) indices. The second aim was to compare different HRV spectral analysis methods. Nineteen young males (aged between 22 and 31 years, median 24 years) underwent simultaneous R-R interval recordings with the three instruments during supine and sitting rest, moderate dynamic, and moderate to vigorous static exercise of the upper and lower limb. For each subject, 17 R-R interval series of 3-min length were extracted from the whole recordings and then analyzed in frequency domain using (1) a fast Fourier transform (FFT), (2) an autoregressive model (AR), (3) a Welch periodogram (WP) and (4) a continuous wavelet transform (CWT). Intra-class correlation coefficients (ICC) and Bland-Altman limits of agreement (LoA) method served as criteria for measurement agreement. Regarding the R-R interval recordings, ICC (lower ICC 95% confidence interval >0.99) as well as LoA (maximum LoA: -15.1 to 14.3 ms for ECG vs. Polar) showed an excellent agreement between all devices. Therefore, the three instruments may be used interchangeably in recording and interpolation of R-R intervals. ICCs for HRV frequency parameters were also high, but in most cases LoA analysis revealed unacceptable discrepancies between the instruments. The agreement among the different frequency transform methods can be taken for granted when analyzing the normalized power in low and high frequency ranges; however, not when analyzing the absolute values.

Levels of agreement for RR intervals and short-term heart rate variability obtained from the Polar S810 and an alternative system

The aim of this study was to assess the agreement between HRV measures derived from a time series of RR intervals recorded by a standard 12-lead ECG (CP) and a commercially available RR interval recorder (S810). Thirty-three participants (19 males) (median age 36, range 20-63) underwent simultaneous, 5-min, supine RR-interval recordings. Each RR interval time series was analysed using the software supplied with the recording equipment. Two comparisons were then made. First, a comparison of RR interval data recording and editing only was made. Second, comparisons were made for measures of HRV derived from edited RR interval data. Agreement between RR intervals and standard HRV measures were assessed using intraclass correlation coefficient and limits of agreement. Agreement of HRV measures derived from RR intervals recorded and edited by individual systems was not acceptable. Agreement analyses for the number of RR intervals recorded and edited by each systems software showed excellent intraclass correlation coefficients (ICC lower 95% CI > 0.75) and acceptably narrow limits of agreement (LoA). These data indicate that the number of RR intervals recorded by S810 can agree well those recorded from a standard 12-lead ECG. This is true even after application of system specific data editing procedures. Commercial RR-interval recorders may offer a simple, inexpensive alternative to full 12-lead ECG in the recording and editing of RR intervals for subsequent HRV analysis in healthy populations.

Is aerobic endurance a determinant of cardiac autonomic regulation?

The aim of this study was to determine if subjects matched for VO2max but with differing aerobic endurance displayed similar heart rate variability (HRV) at rest and heart rate recovery (HRR) after maximal exercise. We hypothesized that the higher the aerobic endurance, the higher the HRV and the faster the HRR. Twenty-eight well trained middle- and long-distance runners (24 men and 4 women) performed a maximal continuous graded exercise test for the determination of maximal oxygen consumption (VO2max), ventilatory threshold (VT), peak treadmill velocity (PTV) and HRR, as well as a test to measure the autonomic regulation of heart rate during supine rest, using HRV analysis. Once both tests were completed, subjects were matched for VO2max and assigned to the low endurance or the high endurance group, depending on the %PTV at which VT occurred (81.9 +/- 2.9 and 88.3 +/- 3.1%PTV for both groups, respectively; P < 0.0001). Contrary to our hypotheses, neither HRV nor HRR parameters were different between groups or associated with aerobic endurance. VO2max (59.0+/-7.3 ml min(-1) kg(-1)) was inversely correlated with ln SDNN (r = -0.44, P < 0.05), ln HF (r = -0.52, P < 0.05), ln LF + HF (r = -0.53, P < 0.05). These results suggest that aerobic endurance is not associated with cardiovascular autonomic control, as measured by HRV and HRR.

Heart rate variability: comparison among devices with different temporal resolutions

Several devices based on ECG can acquire beat-to-beat intervals, and some of these devices may be used for heart rate variability (HRV) analysis. Most of these devices and their methods to acquire the beat-to-beat intervals need to be validated for HRV analysis by comparing them against traditional methods. Some of these methods have low temporal resolution, which may be sufficient for certain studies. HRV analysis parameters obtained from two methods differing in temporal resolution were compared to the HRV analysis parameters obtained from a referent method (ECG). One of the methods had a high resolution (<1 ms) and the other method had a low resolution (10 ms). Seven healthy male volunteers participated in the study. The beat-to-beat intervals were collected simultaneously from the three methods and the HRV parameters derived from them were used for our comparisons. The Pearson product-moment correlations were used, which demonstrated an excellent correlation (r > 0.99) in time domain, frequency domain and some non-linear HRV measures. The HRV measures were further analyzed using the one-way repeated-measures analysis of variance (ANOVA) and statistically significant differences were observed in some of the HRV parameters obtained from the low-resolution method, especially the mean RR (p < 0.001) and the mean heart rate (p < 0.001). Since the same software was used for HRV analysis of the three methods, any differences were due to the temporal resolution of the RR intervals measured by the methods. Overall, both the methods correlated very well with the referent method among healthy volunteers in resting conditions and may be used by researchers for HRV studies.