Nonlinear Measures Of Heart Rate Variability Research Articles

Abstract 11632: Altered Autonomic Balance Linked to Arrhythmogenicity in Chronic Myocardial Infarction Ovine Model

Background: Increased sympathetic drive resulting in decreased heart rate variability (HRV), has been linked to cardiovascular diseases such as heart failure and myocardial infarction (MI). Dynamic electrophysiological changes due to acute ischemia and chronic MI are known to be pro-arrhythmic. Objective: Evaluate the changes in autonomic tone resulting from substrate remodeling during the development of chronic MI in an in-vivo ovine model. Methods: ECG recordings were collected at baseline, post occlusion and 6 weeks post MI, in young adult sheep (n=16). Time domain, frequency domain and non-linear measures of HRV were evaluated from 10 minutes of ECG data at the 3 time points. RR interval, heart rate, SDRR (standard deviation of the RR intervals), RMSSD (root mean square of successive differences between normal heartbeats), QTc interval, pNN 50 , LF/HF ratio and SD1/SD2 ratio were calculated and compared between baseline, post acute coronary artery occlusion and after 6 weeks of chronic MI. 24-hour telemetry was also performed in an ambulatory animal for 6 weeks to monitor the progression of alterations in the T-wave morphology or duration, i.e. T-wave alternans, a known marker of ventricular tachyarrhythmias, with chronic MI. Results: Chronic MI led to significantly decreased RR interval (Fig.1A) and increased heart rate (Fig.1B), along with a significant prolongation of the QTc interval (Fig.1C). Significant rise was also observed in the SDRR (Fig1D) and LF/HF ratio (Fig1E) indicating a shift towards increased sympathetic tone and reduced parasympathetic drive. In addition to the autonomic changes, a significant rise in T-wave alternans burden (Fig1F) and localized action potential alternans inducibility was observed with progression of MI indicating increased arrhythmogenicity. Conclusion: Skewed autonomic balance is evident in chronic MI and may be closely linked to increased arrhythmogenicity.

Heart rate variability: reference values and role for clinical profile and mortality in individuals with heart failure.

To establish reference values and clinically relevant determinants for measures of heart rate variability (HRV) and to assess their relevance for clinical outcome prediction in individuals with heart failure. Data from the MyoVasc study (NCT04064450; N = 3289), a prospective cohort on chronic heart failure with a highly standardized, 5h examination, and Holter ECG recording were investigated. HRV markers were selected using a systematic literature screen and a data-driven approach. Reference values were determined from a healthy subsample. Clinical determinants of HRV were investigated via multivariable linear regression analyses, while their relationship with mortality was investigated by multivariable Cox regression analyses. Holter ECG recordings were available for analysis in 1001 study participants (mean age 64.5 ± 10.5years; female sex 35.4%). While the most frequently reported HRV markers in literature were from time and frequency domains, the data-driven approach revealed predominantly non-linear HRV measures. Age, sex, dyslipidemia, family history of myocardial infarction or stroke, peripheral artery disease, and heart failure were strongly related to HRV in multivariable models. In a follow-up period of 6.5years, acceleration capacity [HRperSD 1.53 (95% CI 1.21/1.93), p = 0.0004], deceleration capacity [HRperSD: 0.70 (95% CI 0.55/0.88), p = 0.002], and time lag [HRperSD 1.22 (95% CI 1.03/1.44), p = 0.018] were the strongest predictors of all-cause mortality in individuals with heart failure independently of cardiovascular risk factors, comorbidities, and medication. HRV markers are associated with the cardiovascular clinical profile and are strong and independent predictors of survival in heart failure. This underscores clinical relevance and interventional potential for individuals with heart failure. NCT04064450.

When Heart Beats Differently in Depression: Review of Nonlinear Heart Rate Variability Measures

Disturbed heart dynamics in depression seriously increases mortality risk. Heart rate variability (HRV) is a rich source of information for studying this dynamics. This paper is a meta-analytic review with methodological commentary of the application of nonlinear analysis of HRV and its possibility to address cardiovascular diseases in depression. This paper aimed to appeal for the introduction of cardiological screening to patients with depression, because it is still far from established practice. The other (main) objective of the paper was to show that nonlinear methods in HRV analysis give better results than standard ones. We systematically searched on the web for papers on nonlinear analyses of HRV in depression, in line with PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) 2020 framework recommendations. We scrutinized the chosen publications and performed random-effects meta-analysis, using the esci module in jamovi software where standardized effect sizes (ESs) are corrected to yield the proof of the practical utility of their results. In all, 26 publications on the connection of nonlinear HRV measures and depression meeting our inclusion criteria were selected, examining a total of 1537 patients diagnosed with depression and 1041 healthy controls (N=2578). The overall ES (unbiased) was 1.03 (95% CI 0.703-1.35; diamond ratio 3.60). We performed 3 more meta-analytic comparisons, demonstrating the overall effectiveness of 3 groups of nonlinear analysis: detrended fluctuation analysis (overall ES 0.364, 95% CI 0.237-0.491), entropy-based measures (overall ES 1.05, 95% CI 0.572-1.52), and all other nonlinear measures (overall ES 0.702, 95% CI 0.422-0.982). The effectiveness of the applied methods of electrocardiogram analysis was compared and discussed in the light of detection and prevention of depression-related cardiovascular risk. We compared the ESs of nonlinear and conventional time and spectral methods (found in the literature) and demonstrated that those of the former are larger, which recommends their use for the early screening of cardiovascular abnormalities in patients with depression to prevent possible deleterious events.

The relationship between cardiac damage biomarkers and heart rate variability following 60min of running.

Endurance exercise may cause transient alterations in cardiac tissue. The number of studies evaluating the relationship between changes in heart rate variability (HRV) and cardiac biomarkers following an endurance event is limited. We hypothesized that there would be a time-dependent correlation between biomarkers of cardiac damage and the reduction in parasympathetic indices of HRV within 24h after 60min of running in middle-aged recreational runners. The trained, middle-aged runners who participated in this study ran 60min at a half-marathon pace on a treadmill. Blood samples (before and 0, 4, and 24h after the running test) and HRV data (before and 0, 1, 4, and 24h after the running test) were obtained. After running, cardiac biomarkers (total creatine kinase, cardiac isoform of creatine kinase, creatine kinase-index [CK-Index], cardiac troponin [cTnI]) increased significantly, and HRV measures related to parasympathetic nervous system activity decreased significantly; these measures returned to baseline levels within 24h. Finally, there were significant correlations (all p < 0.05) between the change (4h post-running vs. pre-running) in the CK-Index and the changes (post- vs pre-running) in time-domain and nonlinear measures of HRV (r -0.61 to -0.67). In addition, significant correlations (all p < 0.05) were found between the area under the cTnI curve and change (1-h post- and pre-running) in time-domain and nonlinear measures of HRV (r -0.48 to -0.51). The correlation between HRV and cardiac biomarkers indicates that HRV analysis may be an alternative approach to determine the magnitude of cardiac stress after endurance exercises.

ECG Approximate Entropy in the Elderly during Cycling Exercise.

Approximate entropy (ApEn) is used as a nonlinear measure of heart-rate variability (HRV) in the analysis of ECG time-series recordings. Previous studies have reported that HRV can differentiate between frail and pre-frail people. In this study, EEGs and ECGs were recorded from 38 elderly adults while performing a three-stage cycling routine. Before and after cycling stages, 5-min resting-state EEGs (rs-EEGs) and ECGs were also recorded under the eyes-open condition. Applying the K-mean classifier to pre-exercise rs-ECG ApEn values and body weights revealed nine females with EEG power which was far higher than that of the other subjects in all cycling stages. The breathing of those females was more rapid than that of other subjects and their average heart rate was faster. Those females also presented higher degrees of asymmetry in the alpha and theta bands (stronger power levels in the right frontal electrode), indicating stressful responses during the experiment. It appears that EEG delta activity could be used in conjunction with a very low ECG frequency power as a predictor of bursts in the heart rate to facilitate the monitoring of elderly adults at risk of heart failure. A resting ECG ApEn index in conjunction with the subject’s weight or BMI is recommended for screening high-risk candidates prior to exercise interventions.

Finding a rhythm: Relating ultra-short-term heart rate variability measures in healthy young adults during rest, exercise, and recovery.

Ultra-short-term (UST; <5min) heart rate variability (HRV) is increasingly used to indirectly assess autonomic nervous system modulation and physical health. However, UST HRV estimates may vary with measurement technique, physiological state, and data preprocessing. The purpose of this investigation was to assess the information content of UST HRV and its sensitivity to different physiological states and preprocessing techniques. 26 time, frequency, and non-linear HRV measures were determined in 80 healthy men (age: 22.1±3.7yr) and 25 women (age: 19.4±2.8yr) from 2-min ECG recordings during seated and standing rest, low-intensity exercise, and seated recovery after maximal exercise. For men, HRV measures obtained during each condition were further analyzed with principal component analysis, k-means clustering, and one-way ANCOVAs. Backward stepwise regression was used to determine the ability of UST HRV to predict aerobic fitness. The sensitivity of UST HRV estimates to different artifact correction procedures was determined with intraclass correlation coefficients. Compared with men, women displayed HRV characteristics suggestive of greater vagal modulation. Nearly 80% of HRV information content was distilled into three principal components comprised of similar measures across conditions. K-means clusters varied in composition and HRV characteristics but not aerobic fitness, which was best predicted by HRV during standing rest. HRV estimates differed depending on artifact correction procedures but were generally similar after individualized correction. Our results indicate that UST HRV measures display redundancy but convey state-specific information and do not strongly predict aerobic fitness in healthy men. Most UST HRV measures are robust to slight differences in artifact correction procedures.

Abstract 11057: Measures of Heart Rate Variability as Predictors of Clinical Outcome in Patients with Chronic Heart Failure - Results from the Myovasc Study

Introduction: Evidence supports a potential prognostic value of heart rate variability (HRV) in patients with chronic heart failure (HF). Comprehensive data comparing different domains of HRV in relation to clinical outcome in HF are scarce. Methods: Subjects with chronic HF (i.e. AHA stage C or D) from the MyoVasc study (NCT04064450; N=3,289), a prospective cohort study, were analyzed. Individuals with pacemaker or atrial fibrillation were excluded. All participants received a highly standardized medical-technical examination during a five-hour visit in a dedicated study center. Data from 24-hour Holter ECG recordings were analyzed resulting in HRV markers from the time and frequency domain, and non-linear HRV measures. Information on clinical outcome, i.e. worsening of HF (WoHF), was derived from structured follow-up with subsequent validation and independent adjudication of endpoints. Random forest models were used to identify the most predictive marker of each HRV domain, which were further analyzed with multivariable Cox regression. Results: The analysis sample comprised 554 HF subjects (mean age: 66.4±9.9 years, 34.3% female sex) with HRV data. During a median observational period of 4.08 years (interquartile range 2.22; 5.22), 153 participants experienced WoHF. In random forest analyses, the rMSSD (time domain), high frequency power in normalized units (HF nu ; frequency domain), and SD1/SD2 (non-linear measure) were ranked as most predictive HRV markers for WoHF in each HRV domain. Subsequent Cox regression analysis demonstrated that log(SD1/SD2) (hazard ratio (HR) per standard deviation 1.50, 95%CI 1.29;1.75; P&lt;0.0001), HF nu (HR SD 1.47, 95%CI 1.23;1.77; P&lt;0.0001) and log(rMSSD) (HR SD 1.36, 95%CI 1.17;1.57; P&lt;0.0001) were strong predictors of HF outcome independent of age, sex, clinical profile, and medication. In Cox regression analysis with adjustment for NT-proBNP and the established HF risk score MAGGIC, HF nu (HR SD 1.25, 95%CI 1.05;1.48; P=0.012) and log(SD1/SD2) (HR SD 1.24, 95%CI 1.07;1.43; P=0.005) remained independent predictors of WoHF. Conclusions: Markers of HRV were identified as strong predictors for HF outcome independent of established risk markers, suggesting a potential to advance risk stratification.

Abstract 11025: Markers of Heart Rate Variability Represent Strong and Independent Predictors of All-Cause Death in Heart Failure - Results from the Myovasc Study

Introduction: Although different measures of heart rate variability (HRV) have been proposed as markers of autonomic dysfunction (AD) in heart failure (HF), evidence on their clinical relevance is limited. Methods: Data from the MyoVasc study (NCT04064450; N=3,289), a prospective cohort study on chronic HF, were analyzed. Study participants received a highly standardized, 5-hour examination including 24-hour Holter ECG recording. RR intervals were extracted to evaluate HRV markers from time and frequency domain analyses, and non-linear markers derived via phase space reconstruction, phase-rectified signal averaging, and entropy analyses. HRV markers of interest were selected using a systematic literature screen, and a random survival forest model predicting cardiac death. Reference values were determined in a healthy subsample. To evaluate clinical relevance, HRV markers were investigated in multivariable Cox regression analyses for their relationship to all-cause death considering potential confounders and mediators. Results: Holter ECG recordings were available for analysis in 1,001 study participants (mean age 64.5±10.5 years; female sex: 35.4%). While the top 10 most frequently reported HRV markers in literature screen were from the time and frequency domains, the data-driven approach revealed predominantly non-linear HRV measures. Values outside reference ranges for SDANN, rMSSD, frequency bands (i.e., ULF, VLF, LF, total power, ULF MED wavelet ), acceleration capacity (AC), deceleration capacity (DC), and time lag, were strong predictors of all-cause death in Cox regression analysis (median follow-up time: 6.1 [IQR 4.7/7.1] years) adjusted for age, sex, clinical profile and medication. In linear Cox regression analyses of the total sample, LF/HF (hazard ratio per SD (HR SD ) 0.78 [95% confidence interval (CI) 0.62, 0.98], p=0.034), time lag (HR SD 1.23 [95%CI 1.05, 1.44], p=0.0095), AC (HR SD : 1.57 [95%CI 1.24, 1.99], p=0.0002), and DC (HR SD 0.67 [95%CI 0.53, 0.85], p=0.0012) were strong predictors for all-cause mortality independent of age, sex, clinical profile and medication. Conclusions: HRV markers reflecting AD are strong predictors of all-cause death in HF, suggesting clinical relevance and potential for intervention.

Assessment of cardiac autonomic function in patients with permanent and paroxysmal atrial fibrillation

Abstract Background Atrial fibrillation (AF) is the commonest abnormal heart rhythm with significant related morbidity and mortality. There is increasing evidence that abnormalities of the cardiac autonomic nervous system (ANS) are involved in the pathogenesis of AF. Exploring the ANS is possible through heart rate variability (HRV) evaluation. Purpose To investigate whether HRV is more abnormal in patients with permanent AF compared to paroxysmal AF. Design In a cross-sectional comparison, we studied two patient groups: permanent AF (n=30) and paroxysmal AF (n=31). Time-domain, frequency-domain and non-linear measures of HRV were determined using eMotion Faros ECG sensor. Participant's breathing was controlled with a metronome set at 12 breaths per minute. Data was analysed using SPSS software. Results Time-domain and non-linear indices of HRV were significant higher in permanent AF group compared to paroxysmal AF (table 1). Permanent AF was the only independent predictor of HRV on multivariable analysis in this cohort of patients (p=0.006) Conclusions First study investigating autonomic function in patients with permanent AF and paroxysmal AF. HRV indices were significantly higher in permanent AF compared to paroxysmal AF which may suggest pronounced cardiac autonomic influence in the pathophysiology of permanent AF. Funding Acknowledgement Type of funding sources: None.

The effect of principal component analysis in the diagnosis of congestive heart failure via heart rate variability analysis.

In this study, we investigated the effect of principal component analysis (PCA) in congestive heart failure (CHF) diagnosis using various machine learning algorithms from 5-min HRV data. The extracted 59 heart rate variability (HRV) features consist of statistical time-domain measures, frequency-domain measures (power spectral density estimations from Fourier transform and Lomb-Scargle methods), time-frequency HRV measures (Wavelet transform), and nonlinear HRV measures (Poincare plot, symbolic dynamics, detrended fluctuation analysis, and sample entropy). All these HRV features are the classifiers' inputs. We repeated the study ten times using the first one to the first 10 principal components from PCA instead of all HRV features. Nine different classifiers, namely logistic regression, Naive Bayes, k-nearest neighbors, decision tree, AdaBoost, support vector machines, stochastic gradient descent, random forest, and artificial neuronal network (multilayer perceptron) are examined. The proposed study results in the 100% accuracy, 100% specificity, and 100% sensitivity after utilizing PCA (with the first eight principal components) using the Random Forest classifier where the maximum classifier performances are the 86% accuracy, 79% specificity, and 86% sensitivity before PCA. In conclusion, PCA is beneficial in the diagnosis of patients with CHF. In addition, we experienced the online Python-based visual machine learning tool, Orange, which can implement well-known machine learning algorithms.

Acute effects of high-intensity interval training and moderate-intensity continuous training on linear and nonlinear heart rate variability measures in arterial hypertension

Introduction: Systemic arterial hypertension is a chronic disease worldwide. High-intensity interval training (HIIT) has been described as an effective alternative treatment. Objective: To evaluate the acute effects of one HIIT session versus one moderate-intensity continuous training (MICT) on linear and nonlinear heart rate variability (HRV) measures in hypertension patients. Methods: A preliminary cross-sectional study with 11 non-elderly (35 to 59 years) hypertensive patients using drug therapy from both sexes. They were assigned for cardiological evaluation, ergometric test, echocardiography, and cardiopulmonary exercise test. Patients performed cycling exercise in the conditions HIIT (10 bouts of 1-minute at 85% of the maximum power [Pmax] interspersed with 2 minutes at 50% of Pmax) and MICT (30 minutes at 50% of Pmax). R-R intervals (RRi) of HRV were recorded in the supine position for 10 minutes before and after the two exercise conditions. Results: HIIT and MICT presented a significant reduction (P&lt;0.01) for the RRi between baseline (pre-session) and post-session. All other linear indices presented similar results (P&gt;0.05) between moments. Significant differences (P&lt;0.05) in the symbolic HRV analysis were identified only in the HIIT group for 0V, 2LV, and 2ULV indexes. 0V index increased 2.3-times from pre- to post-session while 2LV and 2ULV indexes reduced to near 50% and 35%, respectively. Conclusion: An increase in sympathetic modulation with a significant decrease in vagal modulation by nonlinear HRV measures was identified in patients with hypertension submitted to one HIIT session.

Decrements in Adolescent Cardiac Complexity During Mother-Adolescent Conflicts.

The present study aimed to provide further evidence on the usefulness of non-linear cardiac measures when examining the output of the cardiac system. Scale-invariant self-similarity and entropy, in addition to heart rate variability (HRV) given by time- and frequency-domain measures were calculated in a sample of N = 55 healthy adolescents (Mage = 14.122, SDage = 0.698) during 10-min positive (non-stressful) and negative (stressful) interactions with their mothers. We also explored sex influence in adolescents' cardiac output using both HRV measures and non-linear cardiac measures. Repeated measures MANOVA revealed a marginal within-group effect for HRV measures, F(3,51) = 2.438, p = 0.075, η2p = 0.125), and a significant within-group effect for non-linear cardiac measures, F(6, 48) = 3.296, p = 0.009, η2p = 0.292, showing a significant decrement in adolescents' cardiac complexity during the negative interaction. No significant effect for sex was found in either non-linear cardiac measures or HRV measures, but results suggest lower cardiac scaling in females than in males. These findings suggest a real-time scale predominance in heart rate output when adolescents face an aversive situation and support the importance of non-linear cardiac measures to gain insight into the cardiac system and its regulatory mechanisms. Further research is needed to examine sex-differences in cardiac complexity during aversive situations.

Heart rate variability in patients with atrial fibrillation and hypertension.

Atrial fibrillation (AF) and hypertension are independently associated with impaired autonomic function determined using heart rate variability (HRV). As these conditions frequently co-exist, we sought to determine whether AF would worsen HRV in hypertensive patients. We studied HRV in AF (and hypertension) (n=61) and hypertension control group (n=33). The AF (and hypertension) group was subdivided into permanent AF (n=30) and paroxysmal AF (n=31) and re-studied. Time-domain, frequency-domain and nonlinear measures of HRV were determined. Permanent AF group (n=30) was followed up after 8weeks following optimisation of their heart rate and blood pressure (BP). Time-domain and nonlinear indices of HRV were higher in AF (and hypertension) group compared to hypertensive controls (P≤.01). Time-domain and nonlinear indices of HRV were higher in permanent AF group compared to paroxysmal AF (P≤.001). Permanent AF was an independent predictor of HRV on multivariable analysis (P=.006). Optimisation of heart rate and BP had no significant impact on HRV in permanent AF. AF, independent of hypertension, is characterised with marked HRV and is possibly related to vagal tone. HRV is higher in permanent AF compared to paroxysmal AF suggesting evident autonomic influence in the pathophysiology of permanent AF. Modulation of autonomic influence on cardiovascular system should be explored in future studies.

Measuring piglet castration pain using linear and non-linear measures of heart rate variability

AbstractThe purpose of this study was to evaluate whether linear and non-linear measures of heart rate variability (HRV) could be used as indicators of piglet castration pain. Thirty piglets were allocated to 1 of 4 treatments: i) sham castrated HRV (SHRV; n = 8); ii) surgical castrated HRV (CHRV; n = 7); iii) sham castrated blood collection (SBC; n = 7); or iv) surgical castrated blood collection (CBC; n = 8). Piglets in the SHRV and CHRV treatment groups underwent a 1-h HRV and postural behaviour evaluation on day-1, day 0 (castration treatment), day 1 and day 3 of the experimental procedure. Piglets in the SBC and CBC groups underwent blood collection for serum cortisol analysis at -0.5, 1, 2, 3, 24, 48 and 72 h relative to castration treatment. Castrated piglets (CHRV) exhibited greater low to high frequency ratio, lower sample entropy and greater percent determinism compared to SHRV piglets, indicating greater pain-related stress due to the surgical castration procedure. Serum cortisol was greater in CBC pigs at 1 h post-castration compared to SBC piglets. No effect of treatment was found for amount of time spent lying post-castration. In conclusion, surgically castrated pigs exhibited greater pain-related stress than their sham castrated counterparts. Additionally, non-linear HRV measures seem to complement traditional linear HRV measures and may be valuable for assessing pain-related stress in future studies investigating swine welfare.

Effect of music therapy on heart rate variability in generalized anxiety disorder: A poincaré analysis

Background: Poincare plot analysis of heart rate variability (HRV) is a complex nonlinear method for assessing cardiac autonomic nerve function (CANF) in generalized anxiety disorder (GAD).&#x0D; Objective: This study aimed to observe the effect of music therapy on HRV by poincaré plot analysis in GAD patients.&#x0D; Methods: This prospective Interventional study was done in 2019 on 60 newly diagnosed GAD patients aged 20- 40 years, both male and female. Among them, 30 patients were under music therapy with Raga Bhairabi based Rabindra Sangeet for 3 months and 30 patients were without music therapy and both patient groups were studied over three months. Healthy controls, who were enrolled in this study, were Age, sex and BMI matched. Poincaré plot (non linear measure) of HRV of all GAD patients and control were recorded at baseline and after three months of follow up. HRV were recorded by Power Lab 8/ 35. For statistical analysis Bonferroni’s Post Hoc test and paired sample ‘t’ test were done.&#x0D; Results:Standard deviation of the points perpendicular to the axis of line of identity(SD1), standard deviation of the points along the axis of line of identity (SD2) SD and SD1/SD2 were significantly lower in all GAD patients compared to healthy control at baseline. After 3 months of music therapy, significant increment of these parameters occurred in GAD patients, whereas no changes of these except SD1 were noted in patients without music therapy after 3 months. Moreover, these parameters were not significantly different in patients under music therapy compared to control at the end of three months.&#x0D; Conclusion: This study concluded that music therapy can improve cardiac autonomic dysfunction in GAD patients.&#x0D; J Bangladesh Soc Physiol. 2020, June; 15(1): 39-45

Nonlinear analysis of heart rate variability for evaluating the growing pig stress response to an acute heat episode

Heart rate variability (HRV) is a proxy measure of autonomic function and can be used as an indicator of swine stress. While traditional linear measures are used to distinguish between stressed and unstressed treatments, inclusion of nonlinear HRV measures that evaluate data structure and organization shows promise for improving HRV interpretation. The objective of this study was to evaluate the inclusion of nonlinear HRV measures in response to an acute heat episode. Twenty 12- to 14-week-old growing pigs were individually housed for 7 days and acclimated to thermoneutral conditions (20.35°C ± 0.01°C; 67.6% ± 0.2% RH) before undergoing one of the two treatments: (1) thermoneutral control (TN; n = 10 pigs) or (2) acute heat stress (HS; n = 10 pigs; 32.6°C ± 0.1°C; 26.2% ± 0.1% RH). In Phase 1 of the experimental procedure (P1; 60 min), pigs underwent a baseline HRV measurement period in thermoneutral conditions before treatment [Phase 2; P2; 60 min once gastrointestinal temperature (Tg) reached 40.6°C], where HS pigs were exposed to heated conditions and TN pigs remained in thermoneutral conditions. After P2, all pigs were moved back to thermoneutral conditions (Phase 3; P3; 60 min). During each phase, Tg data were collected every 5 min and behavioural data were collected to evaluate the amount of time each pig spent in an active posture. Additionally, linear (time and frequency domain) and nonlinear [sample entropy (SampEn), de-trended fluctuation analysis, percentage recurrence, percentage determinism (%DET), mean diagonal line length in a recurrence plot] HRV measures were quantified. Heat stressed pigs exhibited greater Tg (P = 0.002) and spent less time in an active posture compared to TN pigs during P2 (P = 0.0003). Additionally, low frequency to high frequency ratio was greater in HS pigs during P3 compared to TN pigs (P = 0.02). SampEn was reduced in HS pigs during P2 (P = 0.01) and P3 (P = 0.03) compared to TN pigs. Heat stressed pigs exhibited greater %DET during P3 (P = 0.03) and tended to have greater %DET (P = 0.09) during P2 than TN pigs. No differences between treatments were detected for the remaining HRV measures. In conclusion, linear HRV measures were largely unchanged during P2. However, changes to SampEn and %DET suggest increased heat stress as a result of the acute heat episode. Future work should continue to evaluate the benefits of including nonlinear HRV measures in HRV analysis of swine heat stress.

Automated assessment of pulmonary patients using heart rate variability from everyday wearables

Abstract Everyday wearables with enhanced computational capacity, good quality sensors, and machine learning/artificial intelligence enabled algorithms have the potential to play a key role not only in the fitness and wellness sector but also in the field of disease diagnostics and monitoring. The major challenges are a limited number of sensors, reliable data collection and processing, and deployment of computationally efficient algorithms. In this multi-cohort study, we have used everyday wearables such as chest band and smartwatch to investigate the heart rate variability (HRV) of 131 subjects which include 40 healthy controls, 69 asthma patients, 9 COPD patients and 13 patients with a co-morbidity of asthma and COPD. We aimed at a comprehensive investigation by exploring a total of 58 features including time domain, frequency domain, non-linear and entropy measures of HRV to identify the HRV indices that provide significant discriminatory information for classification between healthy and pulmonary patients. Feature ranking has been done by the area under the receiver operating characteristics curve. Classification of patients with the 15 top ranked features using data from the chest band heart rate sensor as well as estimated HRV parameters from smartwatch PPG signal have been investigated separately. Using the chest band data, a classification accuracy of 82.07%, precision of 83.13%, recall of 81.53% and F-1 score of 81.7% have been achieved; whereas using the smartwatch data, a classification accuracy of 80%, precision of 79.9%, recall of 80% and F-1 score of 79.94% have been achieved for the test set with an AdaBoost classifier. Heart rate variability metrics also showed significant correlation with disease severity and impact on health-related quality of life as measured by pulmonary function test, Asthma Symptoms Utility Index and COPD assessment test score respectively. The results indicate that HRV analysis using everyday wearables may be helpful in the assessment and management of asthma and COPD.

Short communication: Assessment of disbudding pain in dairy calves using nonlinear measures of heart rate variability

The purpose of this study was to evaluate whether pain-related stress caused by disbudding could be detected using nonlinear measures of heart rate variability (HRV). Twenty-five female Holstein calves (4-7 wk of age) were randomly assigned to 1 of 3 treatments: (1) sham disbud (SHAM; n = 9), (2) disbud with lidocaine-meloxicam pain mitigation (MED; n = 8), or (3) disbud without pain mitigation (NoMED; n = 8). Heart rate variability (sample entropy, percentage determinism, percentage recurrence, or mean length of diagonal lines in a recurrence plot) was recorded on d -1, 0, 1, 3, and 5 relative to the experimental procedure, with disbudding taking place on d 0. The short-term detrended fluctuation analysis scaling exponent was greater in MED calves than in SHAM calves, indicating a greater stress response to the disbudding procedure regardless of pain mitigation. These results indicate that calves in the MED group may have experienced pain-related stress as a result of the disbudding procedure. The remaining nonlinear HRV measures did not differ by treatment. Future research on this topic should address additional potential confounding factors, such as the effect of pain-mitigating drugs on autonomic function or the influence of the autonomic nervous system on wound healing, that may prohibit HRV measurement as an indicator of disbudding pain severity.

Music therapy on non linear assessment of cardiac autonomic function in patients with major depressive disorder

Background :Non linear measure of heart rate variability (HRV) is an emerging method to detect changes in cardiac autonomic nerve function in major depressive disorder (MDD).&#x0D; Objective: To observe the effect of music therapy on non linear measures of HRV in newly diagnosed MDD patients.&#x0D; Methods: This prospective interventional study was done in the Department of Physiology, Bangabandhu Sheikh Mujib Medical University (BSMMU), Shahbag, Dhaka in 2018 on 60 newly diagnosed MDD patients aged 20-40 years, both male and female. They were further subdivided into 30 patients with only antidepressant medication (Mirtazapine) and 30 patients received music therapy with Raga kafi (Rabindrasangeet) along with the same medication for 3 months. Age, sex and BMI matched healthy control were also enrolled. HRV non linear parameters were recorded by Power Lab 8/35. For statistical analysis paired sample ‘t’ test and independent sample ‘t’ test were done.&#x0D; Result: SD1, SD2 and SD1/SD2 were found significantly lower in MDD patients compared to healthy control at baseline. After 3 months of music therapy, significant increment of these parameters occurred with trend of improvement in cardiac autonomic nerve function (CANF) in these patients.&#x0D; Conclusion: This study concluded that music therapy can improve CANF by increasing parasympathetic and reducing sympathetic activity in MDD patients.&#x0D; J Bangladesh Soc Physiol. 2019, June; 14(1): 7-13

Effect of slow breathing exercise on non linear Heart rate variability in transfusion dependent thalassemic patients

Background: Nonlinear measure of heart rate variability (HRV) is an emerging tool to detect changes in cardiac autonomic nerve function (CANF) in transfusion dependent thalassemic (TDT) patients. Slow breathing exercise (SBE) can significantly improve HRV in health and various diseases.&#x0D; Objective: To observe the effect of slow breathing exercise (SBE) on non linear measures of HRV in TDT patients.&#x0D; Methods: This prospective interventional study was done in the Department of Physiology, Bangabandhu Sheikh Mujib Medical University (BSMMU), Dhaka in 2018 on 60 male TDT patients aged 15-30 years. Thirty patients received conventional treatment and 30 patients performed slow breathing exercise along with the conventional treatment for 3 months. Age and sex matched 30 healthy control were enrolled. All subjects were followed up at baseline and after 3 months. Non linear (Poincare) HRV parameters were recorded by Power Lab 8/35 AD Instrument, Australia. For statistical analysis paired sample ‘ t’ test and independent sample ‘t’ test were used.&#x0D; Result: SD1, SD2 and SD1/SD2 were found significantly lower in TDT patients compared to healthy control at baseline. After 3 months of slow breathing exercise, significant increment of these parameters occurred with trend of improvement in cardiac autonomic nerve function in this group of patients.&#x0D; Conclusion: Slow breathing exercise may improve cardiac autonomic nerve function and sympathovagal balance in transfusion dependent thalassemic patients.&#x0D; J Bangladesh Soc Physiol. 2019, June; 14(1): 26-32