Evaluating reliability of ultra-short ECG indices of heart rate variability in diabetes mellitus patients

Relationship between ultra-short heart rate variability and short-term mortality in hospitalized COVID-19 patients

OBJECTIVE

To assess the association between ultra-short heart rate variability (US-HRV) and short-term mortality in patients with COVID-19 and develop prognostic prediction models to identify high-risk patients as early as possible.

METHODS

A retrospective cohort study was performed on 488 patients diagnosed with COVID-19 and hospitalized in the First Affiliated Hospital of Fujian Medical University from December 2022 to January 2023. 10-s electrocardiogram (ECG) data were available for these patients. The US-HRV parameters including standard deviation of all normal-to-normal R-R intervals (SDNN) and root mean square of successive differences between normal-to-normal R-R intervals (rMSSD) were calculated using Nalong ECG software. The endpoint was short-term mortality, including in-hospital mortality or mortality within 1 week after discharge.

RESULTS

Of the 488 patients, 76 (15.6%) died. The SDNN and rMSSD in the death group were significantly lower than those in the survival group (P < 0.001). The area under the receiver operating characteristic (ROC) curve (AUC) for SDNN and rMSSD to predict mortality was 0.761 and 0.715, respectively. The combined use of SDNN and rMSSD had an AUC of 0.774. The mortality rate in the group with SDNN ≤7.5 ms was higher than that of SDNN >7.5 ms group (P < 0.05). With the decrease of SDNN, the mortality of patients showed an upward trend, and the mortality of patients with SDNN ≤2 ms was the highest (66.7%). Multivariate logistic regression analysis identified SDNN as an independent predictor of prognosis (odds ratio (OR) = 5.791, 95% confidential interval (CI) 1.615-20.765, P = 0.007). The AUC of Model 1 (simple model) was 0.866 (95% CI 0.826-0.905). The AUC of Model 2 (comprehensive model) was 0.914 (95% CI 0.881-0.947).

CONCLUSION

SDNN was associated with short-term mortality and provided the additional discriminatory power of the risk stratification model for hospitalized COVID-19 patients.

Interplay of heart rate variability and resting heart rate on mortality in type 2 diabetes

AIMS

Heart rate variability (HRV) and resting heart rate (RHR) are usually analyzed and interpreted separately. We aimed to assess the interplay of HRV and RHR on mortality in type 2 diabetes.

METHODS

The study included 7,529 participants from the Action to Control Cardiovascular Risk in Diabetes (ACCORD) trial. HRV metrics included standard deviation of all normal-to-normal intervals (SDNN) and root mean square of successive differences between normal-to-normal intervals (rMSSD). Abnormal values were defined based on <25th percentile for HRV and >75th percentile for RHR. Interactions of HRV status and RHR status were tested on multiplicative and additive scales. Results were validated in a subset of patients with type 2 diabetes (n = 745) from the Multi-Ethnic Study of Atherosclerosis.

RESULTS

Low SDNN was associated with increased all-cause mortality in the high RHR group (HR 1.60; 95% CI 1.29-1.97), but not in the normal RHR group. Compared with those who had neither low SDNN nor high RHR, the presence of either low SDNN or high RHR was not significantly associated with an increased risk of all-cause mortality. In contrast, the combination of low SDNN and high RHR was associated with a significantly increased risk of all-cause mortality (HR 1.68; 95% CI 1.43-1.97). Significant multiplicative and additive interactions were found between HRV status and RHR status on risk of all-cause mortality (all Pinteraction < 0.05). Similar findings were observed for cardiovascular mortality, in analyses using rMSSD, and in the Multi-Ethnic Study of Atherosclerosis.

CONCLUSIONS

The association between HRV and mortality risk is modified by RHR levels. Furthermore, low HRV and high RHR have interdependent and synergistic associations with mortality risk.

Intensive Glycemic Therapy in Type 2 Diabetes Patients With Cardiac Autonomic Dysfunction: The ACCORD Trial

OBJECTIVE

To assess whether the presence of cardiac autonomic dysfunction denoted by low heart rate variability (HRV) modifies the effect of intensive glycemic therapy on outcomes in patients with type 2 diabetes.

PATIENTS AND METHODS

This study included 7946 participants in the ACCORD (Action to Control Cardiovascular Risk in Diabetes) trial from January 2001 through June 2009. Heart rate variability measures included standard deviation of all normal-to-normal intervals (SDNN) and root mean square of successive differences between normal-to-normal intervals (rMSSD). Abnormal values were defined based on less than the 10th percentile for SDNN and rMSSD.

RESULTS

Compared with standard therapy, intensive therapy was associated with improved primary outcome (composite of cardiovascular events) in the low-HRV group (SDNN: HR, 0.57; 95% CI, 0.39 to 0.84; rMSSD: HR, 0.57; 95% CI, 0.38 to 0.84), but not in the normal-HRV group (SDNN: HR, 0.90; 95% CI, 0.77 to 1.05; rMSSD: HR, 0.90; 95% CI, 0.77 to 1.05). A similar pattern was found for coronary heart disease. Conversely, intensive therapy had a neutral effect on all cause death in the low-HRV group (SDNN: HR, 0.88; 95% CI, 0.54 to 1.41; rMSSD: HR, 0.71; 95% CI, 0.43 to 1.17;), but increase risk of all-cause death in the normal-HRV group (SDNN: HR, 1.21; 95% CI, 1.00 to 1.46; rMSSD: HR, 1.25; 95% CI, 1.03 to 1.51). Intensive therapy induced a greater risk of hypoglycemia in the normal-HRV group than that in the low-HRV group.

CONCLUSION

Cardiac autonomic dysfunction expressed as low HRV identified subpopulations in ACCORD with more benefits and less harms from intensive therapy.

Cardiac Autonomic Dysfunction and Risk of Silent Myocardial Infarction Among Adults With Type 2 Diabetes

Background There is a paucity of large-scale epidemiological studies on the link between cardiac autonomic neuropathy (CAN) and the risk of silent myocardial infarction (SMI) in type 2 diabetes. We evaluated the association between CAN and the risk of SMI in a large sample of adults with type 2 diabetes. Methods and Results Participants with type 2 diabetes from the ACCORD (Action to Control Cardiovascular Risk in Diabetes) study without atherosclerotic cardiovascular disease at baseline were included. CAN was ascertained using heart rate variability indices calculated from 10-s resting electrocardiograms. The heart rate variability indices included standard deviation of all normal-to-normal R-R intervals and root mean square of successive differences between normal-to-normal R-R intervals. CAN was defined as both the standard deviation of all normal-to-normal R-R intervals and root mean square of successive differences between normal-to-normal R-R intervals less than the fifth percentile of the general population. We used Cox proportional hazards regression to generate hazard ratios (HRs) for incident SMI in relation to CAN measures. Among 4842 participants (mean age, 62.5 years; 46.6% women; 60.2% White), there were 73 incident SMI cases over a median follow-up of 4.9 years (incidence rate 3.1 out of 1000 person-years [95% CI, 2.5-3.9]). After adjusting for confounders, low heart rate variability was associated with a higher risk of SMI (HR, 1.67 [95% CI, 1.02-2.72] and HR, 1.56 [95% CI, 0.94-2.58] for low standard deviation of all normal-to-normal R-R intervals and root mean square of successive differences between normal-to-normal R-R intervals, respectively). Participants with CAN had a 1.9-fold greater risk of SMI (HR, 1.91 [95% CI, 1.14-3.20]). Conclusions In a large cohort of adults with type 2 diabetes, CAN was significantly associated with an increased risk of incident SMI.

Boosting affective control with bifrontal transcranial direct current stimulation (tDCS): a proof-of-concept study in healthy individuals

Affective control refers to the ability to regulate emotions and is considered a marker of mental health. Transcranial direct current stimulation (tDCS), a non-invasive brain stimulation technique, holds promise to enhance affective control. In this between-subjects study in healthy individuals, we investigated the effects of bifrontal tDCS on core processes and higher-level markers of affective control. As such, we assessed direct tDCS effects on emotional interference during an affective control task and indirect effects on an instructed reappraisal task afterward. Results showed that the affective control task combined with active tDCS, compared to sham, resulted in enhanced cognitive emotion regulation. Specifically, participants in the active tDCS condition showed an increased propensity to use reappraisal and were more successful in doing so. Moreover, there was reduced vagally mediated heart rate variability indicative of attenuated emotion and self-regulation, in the sham, but not in the active condition. Surprisingly, there were no effects of tDCS on emotional interference during the affective control task, with Bayesian analyses showing extreme evidence against these effects. Nevertheless, there was a positive association between the emotional interference during the affective control task and participants' reappraisal success afterward for the active, but not the sham tDCS condition. The study offers valuable insights to guide future work on combined tDCS with affective control tasks or training on the ability to regulate emotions.

Exploring Autonomic Alterations during Seizures in Temporal Lobe Epilepsy: Insights from a Heart-Rate Variability Analysis

Epilepsy's impact on cardiovascular function and autonomic regulation, including heart-rate variability, is complex and may contribute to sudden unexpected death in epilepsy (SUDEP). Lateralization of autonomic control in the brain remains the subject of debate; nevertheless, ultra-short-term heart-rate variability (HRV) analysis is a useful tool for understanding the pathophysiology of autonomic dysfunction in epilepsy patients. A retrospective study reviewed medical records of patients with temporal lobe epilepsy who underwent presurgical evaluations. Data from 75 patients were analyzed and HRV indices were extracted from electrocardiogram recordings of preictal, ictal, and postictal intervals. Various HRV indices were calculated, including time domain, frequency domain, and nonlinear indices, to assess autonomic function during different seizure intervals. The study found significant differences in HRV indices based on hemispheric laterality, language dominancy, hippocampal atrophy, amygdala enlargement, sustained theta activity, and seizure frequency. HRV indices such as the root mean square of successive differences between heartbeats, pNN50, normalized low-frequency, normalized high-frequency, and the low-frequency/high-frequency ratio exhibited significant differences during the ictal period. Language dominancy, hippocampal atrophy, amygdala enlargement, and sustained theta activity were also found to affect HRV. Seizure frequency was correlated with HRV indices, suggesting a potential relationship with the risk of SUDEP.

Prognostic implications of ultra-short heart rate variability indices in hospitalized patients with infective endocarditis

BACKGROUND

Infective endocarditis (IE) is a disease that poses a serious health risk. It is important to identify high-risk patients early in the course of their treatment. In the current study, we evaluated the prognostic value of ultra-short heart-rate variability (HRV), an index of vagal nerve activity, in IE.

METHODS

Retrospective analysis was performed on adult patients admitted to a tertiary hospital due to IE. A logistic regression (LR) was used to determine whether clinical, laboratory, and HRV parameters were predictive of specific clinical features (valve type, staphylococcal infection) or severe short-term complications (cardiac, metastatic infection, and death). The accuracy of the model was evaluated through the measurement of the area under the curve (AUC) of the receiver operating characteristic curve (ROC). An analysis of survival was conducted using Cox regression. A number of HRV indices were calculated, including the standard deviation of normal heart-beat intervals (SDNN) and the root mean square of successive differences (RMSSD).

RESULTS

75 patients, aged 60.3(±18.6) years old, were examined. When compared with published age- and gender-adjusted HRV norms, SDNN and RMSSD were found to be relatively low in our cohort (75%-76% lower than the median; 33%-41% lower than the 2nd percentile). 26(34.6%) patients developed a metastatic infection, with RMSSD<7.03ms (adjusted odds ratio (aOR) 9.340, p = 0.002), incorporated in a multivariate LR model (AUC 0.833). Furthermore, 27(36.0%) patients were diagnosed with Staphylococcus IE, with SDNN<4.92ms (aOR 5.235, p = 0.004), a major component of the multivariate LR model (AUC 0.741). Multivariate Cox regression survival model, included RMSSD (HR 1.008, p = 0.012).

CONCLUSION

SDNN, and particularly RMSSD, derived from ultra-short ECG recordings, may provide prognostic information about patients presenting with IE.

Evaluating heart rate variability with 10 second multichannel electrocardiograms in a large population-based sample

Introduction

Heart rate variability (HRV), defined as the variability of consecutive heart beats, is an important biomarker for dysregulations of the autonomic nervous system (ANS) and is associated with the development, course, and outcome of a variety of mental and physical health problems. While guidelines recommend using 5 min electrocardiograms (ECG), recent studies showed that 10 s might be sufficient for deriving vagal-mediated HRV. However, the validity and applicability of this approach for risk prediction in epidemiological studies is currently unclear to be used.

Methods

This study evaluates vagal-mediated HRV with ultra-short HRV (usHRV) based on 10 s multichannel ECG recordings of N = 4,245 and N = 2,392 participants of the Study of Health in Pomerania (SHIP) from two waves of the SHIP-TREND cohort, additionally divided into a healthy and health-impaired subgroup. Association of usHRV with HRV derived from long-term ECG recordings (polysomnography: 5 min before falling asleep [N = 1,041]; orthostatic testing: 5 min of rest before probing an orthostatic reaction [N = 1,676]) and their validity with respect to demographic variables and depressive symptoms were investigated.

Results

High correlations (r = .52-.75) were revealed between usHRV and HRV. While controlling for covariates, usHRV was the strongest predictor for HRV. Furthermore, the associations of usHRV and HRV with age, sex, obesity, and depressive symptoms were similar.

Conclusion

This study provides evidence that usHRV derived from 10 s ECG might function as a proxy of vagal-mediated HRV with similar characteristics. This allows the investigation of ANS dysregulation with ECGs that are routinely performed in epidemiological studies to identify protective and risk factors for various mental and physical health problems.

Driver Stress Detection Using Ultra-Short-Term HRV Analysis under Real World Driving Conditions

Considering that driving stress is a major contributor to traffic accidents, detecting drivers' stress levels in time is helpful for ensuring driving safety. This paper attempts to investigate the ability of ultra-short-term (30-s, 1-min, 2-min, and 3-min) HRV analysis for driver stress detection under real driving circumstances. Specifically, the t-test was used to investigate whether there were significant differences in HRV features under different stress levels. Ultra-short-term HRV features were compared with the corresponding short-term (5-min) features during low-stress and high-stress phases by the Spearman rank correlation and Bland-Altman plots analysis. Furthermore, four different machine-learning classifiers, including a support vector machine (SVM), random forests (RFs), K-nearest neighbor (KNN), and Adaboost, were evaluated for stress detection. The results show that the HRV features extracted from ultra-short-term epochs were able to detect binary drivers' stress levels accurately. In particular, although the capability of HRV features in detecting driver stress also varied between different ultra-short-term epochs, MeanNN, SDNN, NN20, and MeanHR were selected as valid surrogates of short-term features for driver stress detection across the different epochs. For drivers' stress levels classification, the best performance was achieved with the SVM classifier, with an accuracy of 85.3% using 3-min HRV features. This study makes a contribution to building a robust and effective stress detection system using ultra-short-term HRV features under actual driving environments.

Ultra Short Heart Rate Variability Predicts Clinical Outcomes in Patients with a Clinical Presentation Consistent with Myocarditis: A Derivation Cohort Analysis

Myocarditis prognosis varies substantially, hence identification of novel prognostic factors is crucial. The prognostic role of ultra-short heart-rate variability (HRV) in myocarditis remains unknown. In a retrospective study, adult patients admitted to a tertiary hospital due to clinically suspected myocarditis were included. Clinical, laboratory and HRV parameters were assessed as predictors of severe short term complications (heart failure (HF), dilated cardiomyopathy—DCM, ventricular arrhythmia—VA and death), utilizing logistic regression (LR). Accuracy was evaluated with receiver operating characteristic (ROC) curve area under the curve (AUC). HRV indices included standard deviation of normal beat intervals (SDNN) and root mean square of successive differences (RMSSD). 115 patients, aged 34 (±13) years old, were examined. Six patients (5%) developed severe HFrEF. RMSSD was included in a multivariate LR model (RMSSD < 10.72 ms adjusted odds ratio (AOR) 14.056, p-value 0.024). Model classification accuracy was very good, with an AUC of 86%. Eight patients (7%) developed DCM. RMSSD < 10.72 ms was included in a multivariate classification model (AOR 8.826, p-value 0.013); model classification AUC of 82%. HRV did not predict development of VA or death. SDNN and especially RMSSD may be prognostic indicators in myocarditis.

Ear your heart: transcutaneous auricular vagus nerve stimulation on heart rate variability in healthy young participants

Background

Transcutaneous auricular vagus nerve stimulation (taVNS) stimulating the auricular branch of the vagus nerve along a well-defined neuroanatomical pathway, has promising therapeutic efficacy. Potentially, taVNS can modulate autonomic responses. Specifically, taVNS can induce more consistent parasympathetic activation and may lead to increased heart rate variability (HRV). However, the effects of taVNS on HRV remain inconclusive. Here, we investigated changes in HRV due to brief alteration periods of parasympathetic-vagal cardiac activity produced by taVNS on the cymba as opposed to control administration via the helix.

Materials and Methods

We compared the effect of 10 min of active stimulation (i.e., cymba conchae) to sham stimulation (i.e., helix) on peripheral cardiovascular response, in 28 healthy young adults. HRV was estimated in the time domain and frequency domain during the overall stimulation.

Results

Although active-taVNS and sham-taVNS stimulation did not differ in subjective intensity ratings, the active stimulation of the cymba led to vagally mediated HRV increases in both the time and frequency domains. Differences were significant between active-taVNS and both sham-taVNS and resting conditions in the absence of stimulation for various HRV parameters, but not for the low-frequency index of HRV, where no differences were found between active-taVNS and sham-taVNS conditions.

Conclusion

This work supports the hypothesis that taVNS reliably induces a rapid increase in HRV parameters when auricular stimulation is used to recruit fibers in the cymba compared to stimulation at another site. The results suggest that HRV can be used as a physiological indicator of autonomic tone in taVNS for research and potential therapeutic applications, in line with the established effects of invasive VNS. Knowledge of the physiological effect of taVNS short sessions in modulating cardiovagal processing is essential for enhancing its clinical use.

Diabetes without Overt Cardiac Disease Is Associated with Markers of Abnormal Repolarization: A Case-Control Study

Patients with diabetes mellitus (DM) are prone to advanced atherosclerosis, microvascular disease, and tissue fibrosis. Despite the increased risk for arrhythmias, little is known about cardiac repolarization abnormalities in DM. We aimed to determine whether abnormal T-wave morphology markers are common among patients with DM and no known cardiac disease. Patients were recruited and classified as having DM or impaired fasting glucose (IFG) according to accepted guidelines. Total cosine R to T (TCRT) and T-wave morphology dispersion (TMD) were computed with custom-designed software for randomly selected and averaged beats. Among 124 patients recruited; 47 were diagnosed with DM and 3 IFG. DM patients and the control group had similar clinical characteristics, other than statins and anti-diabetic drugs, which were more common among DM patients. Patients with DM/IFG had decreased TCRT values computed from a random beat (0.06 ± 0.10 vs. 0.43 ± 0.07, p < 0.01) and an average beat (0.08 ± 0.09 vs. 0.44 ± 0.06, p < 0.01), when compared with the control group. TMD parameters did not differ. In conclusion, TCRT is reduced in patients with DM and no known cardiac diseases. Further research is required to investigate whether repolarization-associated changes in DM are the consequence of subclinical atherosclerosis, diabetic cardiomyopathy, or a combination of the two.

Reduced heart rate variability is related to the number of metabolic syndrome components and manifest diabetes in the sixth Tromsø study 2007-2008

Both diabetes mellitus (DM) and the metabolic syndrome (MetS) are associated with autonomic neuropathy, which predisposes to cardiac events and death. Measures of heart rate variability (HRV) can be used to monitor the activity of the autonomic nervous system (ANS), and there are strong indications that HRV can be used to study the progression of ANS-related diabetes complications. This study aims to investigate differences in HRV in healthy, MetS and diabetic populations. Based on 7880 participants from the sixth health survey in Tromsø (Tromsø 6, 2007–2008), we found a significant negative association between the number of MetS components and HRV as estimated from short-term pulse wave signals (PRV). This decrease in PRV did not appear to be linear, instead it leveled off after the third component, with no significant difference in PRV between the MetS and DM populations. There was a significant negative association between HbA1c and PRV, showing a decrease in PRV occurring already within the normal HbA1c range. The MetS and DM populations are different from healthy controls with respect to PRV, indicating impaired ANS in both conditions. In the future, a study with assessment of PRV measurements in relation to prospective cardiovascular events seems justified.

Cardiac Autonomic Neuropathy and Risk of Incident Heart Failure Among Adults with Type 2 Diabetes

AIMS

Community-based data on the association between cardiac autonomic neuropathy (CAN) and incident heart failure (HF) in type 2 diabetes are limited. We evaluated the association of CAN with incident HF in adults with type 2 diabetes.

METHODS AND RESULTS

This analysis included participants from the Action to Control Cardiovascular Risk in Diabetes (ACCORD) study without HF at baseline. CAN was assessed by electrocardiogram-based measures of heart rate variability (HRV) and QT interval index (QTI). HRV was measured using standard deviation of all normal-to-normal intervals (SDNN) and root mean square of successive differences between normal-to-normal intervals (rMSSD). CAN was defined using composite measures of the lowest quartile of SDNN and highest quartiles of QTI and heart rate. Multivariable Cox regression models were used to generate adjusted hazard ratios (aHR) for HF in relation to various CAN measures. A total of 7160 participants (mean age 62.3 [standard deviation 6.4] years, 40.8% women, 61.9% white) were included. Over a median follow-up of 4.9 years (interquartile range 4.0-5.7), 222 participants developed incident HF. After multivariable adjustment for relevant confounders, lower HRV as assessed by SDNN was associated with a higher risk of HF (aHR for the lowest vs highest quartile of SDNN: 1.70, 95% confidence interval [CI] 1.14-2.54). Participants with CAN (defined as lowest quartile of SDNN and highest quartiles of QTI and heart rate) had a 2.7-fold greater risk of HF (aHR 2.65, 95% CI 1.57-4.48).

CONCLUSIONS

In a large cohort of adults with type 2 diabetes, CAN was independently associated with higher risk of incident HF.

Interactive Effects of Heart Rate Variability and P-QRS-T on the Power Density Spectra of ECG Signals

Different from the traditional methods of assessing the cardiac activities through heart rhythm statistics or P-QRS-T complexes separately, this study demonstrates their interactive effects on the power density spectrum (PDS) of ECG signal with applications for the diagnosis of ST-segment elevation myocardial infarction (STEMI) diseases. Firstly, a mathematical model of the PDS of ECG signal with a random pacing pulse train (PPT) mimicking S-A node firings was derived. Secondly, an experimental PDS analysis was performed on clinical ECG signals from 49 STEMI patients and 42 healthy subjects in PTB Diagnostic Database. It was found that besides the interactive effects which are consistent between theoretical and experimental results, the ECG PDSs of STEMI patients exhibited consistently significant power shift towards lower frequency range in ST-elevated leads in comparison with those of reference leads and leads of health subjects with the highest median frequency shift ratios at 51.39 12.94% found in anterior MI. Thirdly, the results of ECG simulation with systematic changes in PPT firing statistics over various lengths of ECG data ranging from 10s to 60 mins revealed that the mean and median frequency parameters were less affected by the heart rhythm statistics and the data length but more depended on the alterations of P-QRS-T complexes, which were further confirmed on 33 more STEMI patients in European ST-T Database, demonstrating that the frequency indexes could be potentially used as alternative indicators for STEMI diagnosis even with ultra-short-term ECG recordings suitable for wearable and mobile health applications in living-free environments.

Comparing Ictal Cardiac Autonomic Changes in Patients with Frontal Lobe Epilepsy and Temporal Lobe Epilepsy by Ultra-Short-Term Heart Rate Variability Analysis

Background and Objectives: Abnormal epileptic discharges in the brain can affect the central brain regions that regulate autonomic activity and produce cardiac symptoms, either at onset or during propagation of a seizure. These autonomic alterations are related to cardiorespiratory disturbances, such as sudden unexpected death in epilepsy. This study aims to investigate the differences in cardiac autonomic function between patients with temporal lobe epilepsy (TLE) and frontal lobe epilepsy (FLE) using ultra-short-term heart rate variability (HRV) analysis around seizures. Materials and Methods: We analyzed electrocardiogram (ECG) data recorded during 309 seizures in 58 patients with epilepsy. Twelve patients with FLE and 46 patients with TLE were included in this study. We extracted the HRV parameters from the ECG signal before, during and after the ictal interval with ultra-short-term HRV analysis. We statistically compared the HRV parameters using an independent t-test in each interval to compare the differences between groups, and repeated measures analysis of variance was used to test the group differences in longitudinal changes in the HRV parameters. We performed the Tukey-Kramer multiple comparisons procedure as the post hoc test. Results: Among the HRV parameters, the mean interval between heartbeats (RRi), normalized low-frequency band power (LF) and LF/HF ratio were statistically different between the interval and epilepsy types in the t-test. Repeated measures ANOVA showed that the mean RRi and RMSSD were significantly different by epilepsy type, and the normalized LF and LF/HF ratio significantly interacted with the epilepsy type and interval. Conclusions: During the pre-ictal interval, TLE patients showed an elevation in sympathetic activity, while the FLE patients showed an apparent increase and decrease in sympathetic activity when entering and ending the ictal period, respectively. The TLE patients showed a maintained elevation of sympathetic and vagal activity in the pos-ictal interval. These differences in autonomic cardiac characteristics between FLE and TLE might be relevant to the ictal symptoms which eventually result in SUDEP.

Suitability of Ultra-Short-Term Heart Rate Variability in Military Trainees

We aimed to (a) evaluate the agreement between ultra-short-term and criterion resting heart rate variability (HRV) measures in military trainees, and (b) compare associations between HRV recording lengths and body composition. HRV recordings were performed for 10 min in 27 military male students. Mean RR interval, the root-mean square of successive differences (RMSSD), RMSSD:RR interval ratio, standard deviation of normal-to-normal RR intervals (SDNN), and SDNN:RR interval ratio were determined from the last 5 min of the 10-min recording and considered the criterion. Parameters were also recorded in successive 1-min epochs from the 5-min stabilization period. No differences were observed between criterion values and any of the 1-min epochs (p > 0.05). Effect sizes ranged from -0.36-0.35. Intra-class correlations ranged from 0.83-0.99. Limits of agreement ranged from 38.3-78.4 ms for RR interval, 18.8-30.0 ms for RMSSD, 1.9-3.1 for RMSSD:RR, 24.1-31.4 ms for SDNN, and 2.5-3.0 for SDNN:RR. Body fat% was associated (p < 0.05) with all HRV parameters at varying time segments. A 1-min HRV recording preceded by a 1-min stabilization period seems to be a suitable alternative to criterion measures. Ultra-short procedures may facilitate routine HRV tracking in tactical populations for status-monitoring purposes.

A Novel Smartphone App for the Measurement of Ultra-Short-Term and Short-Term Heart Rate Variability: Validity and Reliability Study

Background

Smartphone apps for heart rate variability (HRV) measurement have been extensively developed in the last decade. However, ultra–short-term HRV recordings taken by wearable devices have not been examined.

Objective

The aims of this study were the following: (1) to compare the validity and reliability of ultra–short-term and short-term HRV time-domain and frequency-domain variables in a novel smartphone app, Pulse Express Pro (PEP), and (2) to determine the agreement of HRV assessments between an electrocardiogram (ECG) and PEP.

Methods

In total, 60 healthy adults were recruited to participate in this study (mean age 22.3 years [SD 3.0 years], mean height 168.4 cm [SD 8.0 cm], mean body weight 64.2 kg [SD 11.5 kg]). A 5-minute resting HRV measurement was recorded via ECG and PEP in a sitting position. Standard deviation of normal R-R interval (SDNN), root mean square of successive R-R interval (RMSSD), proportion of NN50 divided by the total number of RR intervals (pNN50), normalized very-low–frequency power (nVLF), normalized low-frequency power (nLF), and normalized high-frequency power (nHF) were analyzed within 9 time segments of HRV recordings: 0-1 minute, 1-2 minutes, 2-3 minutes, 3-4 minutes, 4-5 minutes, 0-2 minutes, 0-3 minutes, 0-4 minutes, and 0-5 minutes (standard). Standardized differences (ES), intraclass correlation coefficients (ICC), and the Spearman product-moment correlation were used to compare the validity and reliability of each time segment to the standard measurement (0-5 minutes). Limits of agreement were assessed by using Bland-Altman plot analysis.

Results

Compared to standard measures in both ECG and PEP, pNN50, SDNN, and RMSSD variables showed trivial ES (<0.2) and very large to nearly perfect ICC and Spearman correlation coefficient values in all time segments (>0.8). The nVLF, nLF, and nHF demonstrated a variation of ES (from trivial to small effects, 0.01-0.40), ICC (from moderate to nearly perfect, 0.39-0.96), and Spearman correlation coefficient values (from moderate to nearly perfect, 0.40-0.96). Furthermore, the Bland-Altman plots showed relatively narrow values of mean difference between the ECG and PEP after consecutive 1-minute recordings for SDNN, RMSSD, and pNN50. Acceptable limits of agreement were found after consecutive 3-minute recordings for nLF and nHF.

Conclusions

Using the PEP app to facilitate a 1-minute ultra–short-term recording is suggested for time-domain HRV indices (SDNN, RMSSD, and pNN50) to interpret autonomic functions during stabilization. When using frequency-domain HRV indices (nLF and nHF) via the PEP app, a recording of at least 3 minutes is needed for accurate measurement.

Post-Exercise Recovery of Ultra-Short-Term Heart Rate Variability after Yo-Yo Intermittent Recovery Test and Repeated Sprint Ability Test

This study aimed to examine the agreement and acceptance of ultra-short-term heart rate (HR) variability (HRV_UST) measures during post-exercise recovery in college football players. Twenty-five male college football players (age: 19.80 ± 1.08 years) from the first division of national university championship voluntarily participated in the study. The participants completed both a repeated sprint ability test (RSA) and a Yo-Yo intermittent recovery test level 1 (YYIR1) in a randomized order and separated by 7 days. Electrocardiographic signals (ECG) were recorded in a supine position 10 min before and 30 min after the exercise protocols. The HR and HRV data were analyzed in the time segments of baseline 5~10 min (Baseline), post-exercise 0~5 min (Post 1), post-exercise 5~10 min (Post 2), and post-exercise 25~30 min (Post 3). The natural logarithm of the standard deviation of normal-to-normal intervals (LnSDNN), root mean square of successive normal-to-normal interval differences (LnRMSSD), and LnSDNN:LnRMSSD ratio was compared in the 1st min HRV_UST and 5-min criterion (HRV_criterion) of each time segment. The correlation of time-domain HRV variables to 5-min natural logarithm of low frequency power (LnLF) and high frequency power (LnHF), and LF:HF ratio were calculated. The results showed that the HRV_UST of LnSDNN, LnRMSSD, and LnSDNN:LnRMSSD ratio showed trivial to small effect sizes (ES) (−0.00~0.49), very large and nearly perfect interclass correlation coefficients (ICC) (0.74~0.95), and relatively small values of bias (RSA: 0.01~−0.12; YYIR1: −0.01~−0.16) to the HRV_criterion in both exercise protocols. In addition, the HRV_UST of LnLF, LnHF, and LnLF:LnHF showed trivial to small ES (−0.04~−0.54), small to large ICC (−0.02~0.68), and relatively small values of bias (RSA: −0.02~0.65; YYIR1: 0.03~−0.23) to the HRV_criterion in both exercise protocols. Lastly, the 1-min LnSDNN:LnRMSSD ratio was significantly correlated to the 5-min LnLF:LnHF ratio with moderate~high level (r = 0.43~0.72; p < 0.05) during 30-min post-exercise recovery. The post-exercise 1-min HRV assessment in LnSDNN, LnRMSSD, and LnSDNN:LnRMSSD ratio was acceptable and accurate in the RSA and YYIR1 tests, compared to the 5-min time segment of measurement. The moderate to high correlation coefficient of the HRV_UST LnSDNN:LnRMSSD ratio to the HRV_criterion LnLF:LnHF ratio indicated the capacity to facilitate the post-exercise shortening duration of HRV measurement after maximal anaerobic or aerobic shuttle running. Using ultra-short-term record of LnSDNN:LnRMSSD ratio as a surrogate for standard measure of LnLF:LnHF ratio after short-term bouts of maximal intensity field-based shuttle running is warranted.

Determination of minimal recording period to assess resting heart rate variability during pregnancy

Traditionally, resting heart rate variability (rHRV) is measured for 10 min using the last 5 min for analyses (e.g., criterion period). It is unknown whether the measurement period can be shortened in pregnant women as there are currently no established standards. We aimed to compare shorter time segments (e.g., from the 1st to 10th minutes) of the parasympathetic index natural logarithm transformation of root mean square of successive R–R differences (Ln rMSSD) with the criterion period in pregnant and nonpregnant women. Twelve pregnant (age: 30.8 ± 3.4 years; gestational age: 20.1 ± 5.0 weeks) and 15 nonpregnant women (age: 29.8 ± 4.0 years) were included. rHRV was measured using a portable heart rate monitor for 10 min while sitting. Ln rMSSD difference/agreement between shorter time segments and criterion period was analyzed. The result observed between the 4th–5th minutes was the shortest time segment not different from/highly agreed with the criterion period in pregnant women (difference [95% confidence interval (CI)]: −0.10 [−0.22 to 0.02]/bias ± 1.96 × SD: −0.06 [−0.38 to 0.25]). In nonpregnant women, the 2nd–3rd-minute segment was the shortest with similar results (difference [95% CI]: −0.04 [−0.15 to 0.07]/bias ± 1.96 × SD: −0.03 [−0.39 to 0.32]). The Ln rMSSD was found to be stable from the 5th–10th minutes and the 3rd–10th minutes in pregnant and nonpregnant women, respectively. A shortened rHRV assessment can increase its applicability in clinical/exercise-training settings.

Novelty Ln rMSSD can be measured for 5 min in pregnant women, with the last 1-min segment analyzed. The last 1-min segment from 3 min can be used for rHRV measurement in nonpregnant women. The shortened rHRV assessment can facilitate its applicability in clinical/exercise-training settings.

Ultra-short-term and Short-term Heart Rate Variability Recording during Training Camps and an International Tournament in U-20 National Futsal Players

The aim of this study was to examine ultra-short-term and short-term heart rate variability (HRV) in under-20 (U-20) national futsal players during pre-tournament training camps and an official tournament. Fourteen male U-20 national futsal players (age = 18.07 ± 0.73 yrs; height = 169.57 ± 8.40 cm; body weight = 64.51 ± 12.19 kg; body fat = 12.42% ± 3.18%) were recruited to participate in this study. Early morning 10 min resting HRV, Borg CR-10 scale session rating of perceived exertion (sRPE), and general wellness questionnaire were used to evaluate autonomic function, training load, and recovery status, respectively. Log-transformed root mean square of successive normal-to-normal interval differences (LnRMSSD) was used to compare the first 30 s, first 1 min, first 2 min, first 3 min, and first 4 min with standard 5 min LnRMSSD. Mean (LnRMSSD_mean) and coefficient of variation (LnRMSSD_cv) of LnRMSSD were used to compare the different time segments of HRV analysis. The result of LnRMSSD_mean showed nearly perfect reliability and relatively small bias in all comparisons. In contrast, LnRMSSD_cv showed nearly perfect reliability and relatively small bias from 2-4 min time segments in all study periods. In conclusion, for accuracy of HRV measures, 30 s or 1 min ultra-short-term record of LnRMSSD_mean and short-term record of LnRMSSD_cv of at least 2 min during the training camps are recommended in U-20 national futsal players.

Assessment of Ultra-Short Heart Variability Indices Derived by Smartphone Accelerometers for Stress Detection

Body acceleration due to heartbeat-induced reaction forces can be measured as mobile phone accelerometer (m-ACC) signals. Our aim was to test the feasibility of using m-ACC to detect changes induced by stress by ultra-short heart rate variability (USV) indices (standard deviation of normal-to-normal interval—SDNN and root mean square of successive differences—RMSSD). Sixteen healthy volunteers were recruited; m-ACC was recorded while in supine position, during spontaneous breathing at rest conditions (REST) and during one minute of mental stress (MS) induced by arithmetic serial subtraction task, simultaneous with conventional electrocardiogram (ECG). Beat occurrences were extracted from both ECG and m-ACC and used to compute USV indices using 60, 30 and 10 s durations, both for REST and MS. A feasibility of 93.8% in the beat-to-beat m-ACC heart rate series extraction was reached. In both ECG and m-ACC series, compared to REST, in MS the mean beat duration was reduced by 15% and RMSSD decreased by 38%. These results show that short term recordings (up to 10 s) of cardiac activity using smartphone’s accelerometers are able to capture the decrease in parasympathetic tone, in agreement with the induced stimulus.

Cultural Differences in Interpersonal Emotion Regulation

Cultural differences exist in the use of emotion regulation (ER) strategies, but the focus to date has been on intrapersonal ER strategies such as cognitive reappraisal. An emerging literature highlights the importance of interpersonal ER, which utilizes social cues to facilitate the regulation of emotional states. In cultures that place high value on social interconnectedness as integral to their collectivistic self-construal, including East Asian cultures, interpersonal ER strategies may be particularly effective in reducing negative affect but this has not been previously tested. In this study, two groups comprising East Asian (n = 48) and Western European (n = 38) participants were randomly assigned to receive a priming narration depicting the use of either interpersonal (e.g., social modeling, perspective taking) or intrapersonal (e.g., cognitive reappraisal) ER strategies during a stressful experience. They were then instructed to utilize similar ER strategies in an emotion reactivity task during which they viewed high arousing negative pictorial stimuli while their heart rate (HR), heart rate variability (high frequency power - HF-HRV) and subjective affective states were measured. First we found that the East Asian group reported higher use of interpersonal ER strategies of social modeling and perspective taking in daily life. During the experimental interpersonal prime exposure, the East Asian group showed elevated HF-HRV (relative to baseline) compared to the Western European group, indicating more adaptive ER, but this pattern was not sustained during the reactivity or recovery phases. Instead, the East Asian group demonstrated increased HF-HRV and decreased HR across both prime conditions. The East Asian group also showed greater decreases in positive affect across the course of the experiment. Furthermore, individual differences in social modeling and individualistic self-construal moderated the effect of the ER prime in the East Asian group at trend levels, and main effects for perspective taking and reappraisal were observed in the Western European group. The findings support the notion that engaging in interpersonal ER strategies may be more beneficial for East Asian groups when immediately exposed to a stressful situation, as these strategies are congruent with cultural context and preferences, but our priming methodology may have limited the longer-term benefits.

Inter and Intra-Rater Reliability of Short-Term Measurement of Heart Rate Variability on Rest in Diabetic Type 2 Patients

Heart rate variability (HRV) among other methods can be used to assess diabetic cardiac autonomic neuropathy by cardiac intervals were recorded. However, the amount of error depending on this measurement methodology is unclear. To evaluate the intra- and inter-rater reliability to calculate HRV indices, comparing different times and by different trained examiners in patients with type 2 diabetes mellitus (T2DM). Thirty individuals of both genders, aged between 18 and 45 years, with T2DM. The RR interval (RRi) were recorded during a 10 min period on supine position using a portable heart rate monitor (Polar® S810i model). HRV indices were calculated by the software Kubios® HRV analysis (version 2.2). Linear (Mean RRi; STD RR; Mean HR; rMSSD; RR Tri; TINN LF; HF; total power) and non-linear (SD1; SD2; DFα1; DFα2, ApEn and, SampEn) indices were calculated by two examiners with an interval of one week between them. Substantial to excellent was found for reliability of the intra-examiner, with intraclass correlation coefficient (ICC) values ranging from 0.79 to 0.99, standard error of measurement (SEM) between 0.02 and 123.49 (in percentage: 1.83 and 16.67), and minimum detectable change (MDC) between 0.07 and 342.30. Regarding the inter-examiner reliability, substantial to excellent reliability was found, with ICC values ranging from 0.73 to 0.97, SEM between 0.04 and 178.13 (in percentage: 3.26 and 24.18), and MDC between 0.11 and 493.77. The use of the portable heart rate monitor to measure HRV showed acceptable intra and inter reliability in individuals with T2DM, supporting the use of this method of evaluation in research and clinical practice.

Validity of spectral analysis based on heart rate variability from 1-minute or less ECG recordings

BACKGROUND

To broaden the utility of heart rate variability (HRV) in clinical medicine and mass screening, results based on shorter electrocardiogram (ECG) recordings require validation with those based on standard 5-minute recordings. We investigated the association between HRV variables obtained from 5-minute ECGs with those obtained from ECGs shorter than 5 minutes.

METHODS

Twenty-two participants aged 20-69 years underwent 5-minute resting ECG recordings in the supine position with natural breathing. Spectral analysis using MemCalc method was performed to calculate high-frequency (HF, which required at least 10 seconds) and low-frequency (LF, which required at least 30 seconds) components. Participants were not strictly preconditioned as in previous experimental studies in order to simulate a setting similar to that of a general health checkup. Associations of each variable between the 5-minute ECG recordings and those for shorter recordings were examined by Pearson's correlation coefficients and Bland-Altman plots.

RESULTS

HF and LF components were log-transformed based on their distributions. Correlation coefficients between 5-minute data and shorter recordings in the supine position with natural breathing ranged from 0.80 to 0.91 (HF by 10-second recording, 0.80; LF by 30-second recording, 0.83, respectively). Bland-Altman plots showed that gaps between the values from both methods slightly increased as the HF and LF component values increased.

CONCLUSIONS

Although slight proportional errors were possible, values from standard 5-minute and shorter recordings in the supine position were strongly correlated. Our findings suggest that shorter ECG data without strict preconditioning can be reliably used for spectral analysis.

Ultra-short-term heart rate variability during resistance exercise in the elderly

Despite the appeal of ultra-short-term heart rate variability (HRV) methods of analysis applied in the clinical and research settings, the number of studies that have investigated HRV by analyzing R-R interval (RRi) recordings shorter than 5 min is still limited. Moreover, ultra-short-term HRV analysis has not been extensively validated during exercise and, currently, no indications exist for its applicability during resistance exercise. The aim of the present study was to compare ultra-short-term HRV analysis with standard short-term HRV analysis during low-intensity, dynamic, lower limb resistance exercise in healthy elderly subjects. Heart rate (HR) and RRi signals were collected from 9 healthy elderly men during discontinuous incremental resistance exercise consisting of 4-min intervals at low intensities (10, 20, 30, and 35% of 1-repetition maximum). The original RRi signals were segmented into 1-, 2-, and 3-min sections. HRV was analyzed in the time domain (root mean square of the of differences between adjacent RRi, divided by the number of RRi, minus one [RMSSD]), RRi mean value and standard deviation [SDNN] (percentage of differences between adjacent NN intervals that are greater than 50 ms [pNN50]), and by non-linear analysis (short-term RRi standard deviation [SD1] and long-term RRi standard deviation [SD2]). No significant difference was found at any exercise intensity between the results of ultra-short-term HRV analysis and the results of standard short-term HRV analysis. Furthermore, we observed excellent (0.70 to 0.89) to near-perfect (0.90 to 1.00) concordance between linear and non-linear parameters calculated over 1- and 2-min signal sections and parameters calculated over 3-min signal sections. Ultra-short-term HRV analysis appears to be a reliable surrogate of standard short-term HRV analysis during resistance exercise in healthy elderly subjects.

Evolving changes in fetal heart rate variability and brain injury after hypoxia-ischaemia in preterm fetal sheep

KEY POINTS

Fetal heart rate variability is a critical index of fetal wellbeing. Suppression of heart rate variability may provide prognostic information on the risk of hypoxic-ischaemic brain injury after birth. In the present study, we report the evolution of fetal heart rate variability after both mild and severe hypoxia-ischaemia. Both mild and severe hypoxia-ischaemia were associated with an initial, brief suppression of multiple measures of heart rate variability. This was followed by normal or increased levels of heart rate variability during the latent phase of injury. Severe hypoxia-ischaemia was subsequently associated with the prolonged suppression of measures of heart rate variability during the secondary phase of injury, which is the period of time when brain injury is no longer treatable. These findings suggest that a biphasic pattern of heart rate variability may be an early marker of brain injury when treatment or intervention is probably most effective.

ABSTRACT

Hypoxia-ischaemia (HI) is a major contributor to preterm brain injury, although there are currently no reliable biomarkers for identifying infants who are at risk. We tested the hypothesis that fetal heart rate (FHR) and FHR variability (FHRV) would identify evolving brain injury after HI. Fetal sheep at 0.7 of gestation were subjected to either 15 (n = 10) or 25 min (n = 17) of complete umbilical cord occlusion or sham occlusion (n = 12). FHR and four measures of FHRV [short-term variation, long-term variation, standard deviation of normal to normal R-R intervals (SDNN), root mean square of successive differences) were assessed until 72 h after HI. All measures of FHRV were suppressed for the first 3-4 h in the 15 min group and 1-2 h in the 25 min group. Measures of FHRV recovered to control levels by 4 h in the 15 min group, whereas the 25 min group showed tachycardia and an increase in short-term variation and SDNN from 4 to 6 h after occlusion. The measures of FHRV then progressively declined in the 25 min group and became profoundly suppressed from 18 to 48 h. A partial recovery of FHRV measures towards control levels was observed in the 25 min group from 49 to 72 h. These findings illustrate the complex regulation of FHRV after both mild and severe HI and suggest that the longitudinal analysis of FHR and FHRV after HI may be able to help determine the timing and severity of preterm HI.

Relations of Demographic and Clinical Factors With Cardiovascular Autonomic Function in a Population-Based Study: An Assessment By Quantile Regression

BACKGROUND

The relationships of many factors with cardiovascular autonomic function (CVAF) outcome parameters may not be uniform across the entire distribution of the outcome. We examined how demographic and clinical factors varied with different subgroups of CVAF parameters.

METHODS

Quantile regression was applied to a cross-sectional analysis of 4,167 adults (56% male; age range, 50-84 years) from 4 ethnic groups (3,419 New Zealand European, 303 Pacific, 227 Maori, and 218 South Asian) and without diagnosed cardiac arrhythmia. Pulse rate variability (root mean square of successive differences (RMSSD) and SD of pulse intervals) and baroreflex sensitivity were response variables. Independent variables were age, sex, ethnicity, brachial and aortic blood pressure (BP) variables, body mass index (BMI), and diabetes.

RESULTS

Ordinary linear regression showed that age, sex, Pacific and Maori ethnicity, BP variables, BMI, and diabetes were associated with CVAF parameters. But quantile regression revealed that, across CVAF percentiles, the slopes for these relationships: (i) varied by more than 10-fold in several cases and sometimes changed direction and (ii) noticeably differed in magnitude often (by >3-fold in several cases) compared to ordinary linear regression coefficients. For instance, age was inversely associated with RMSSD at the 10th percentile of this parameter (β = -0.12 ms/year, 95% confidence interval = -0.18 to -0.09 ms/year) but had a positive relationship at the 90th percentile (β = 3.17 ms/year, 95% confidence interval = 2.50 to 4.04 ms/year).

CONCLUSIONS

The relationships of demographic and clinical factors with CVAF parameters are, in many cases, not uniform. Quantile regression provides an improved assessment of these associations.

Estimation of the Driving Style Based on the Users' Activity and Environment Influence

New models and methods have been designed to predict the influence of the user's environment and activity information to the driving style in standard automotive environments. For these purposes, an experiment was conducted providing two types of analysis: (i) the evaluation of a self-assessment of the driving style; (ii) the prediction of aggressive driving style based on drivers' activity and environment parameters. Sixty seven h of driving data from 10 drivers were collected for analysis in this study. The new parameters used in the experiment are the car door opening and closing manner, which were applied to improve the prediction accuracy. An Android application called Sensoric was developed to collect low-level smartphone data about the users' activity. The driving style was predicted from the user's environment and activity data collected before driving. The prediction was tested against the actual driving style, calculated from objective driving data. The prediction has shown encouraging results, with precision values ranging from 0.727 up to 0.909 for aggressive driving recognition rate. The obtained results lend support to the hypothesis that user's environment and activity data could be used for the prediction of the aggressive driving style in advance, before the driving starts.

Effects of visual flow direction on signs and symptoms of cybersickness

Our objective was to assess the influence of visual flow direction on physiological changes and symptoms elicited by cybersickness. Twelve healthy subjects (6 male and 6 female) were exposed to a 15-min virtual ride on a rollercoaster on two different days in a counterbalanced manner, such half of participants were facing forward during the first ride while another half was facing backward. Forehead skin conductance, heart rate and HRV parameters (SDRR, RMSSD) were collected as objective measures; subjective symptoms were assessed with the Motion Sickness Assessment Questioner immediately after exposure. We found that while nausea ratings at which participants terminated the experiment did not differ between forward/backward rides, the mean ride tolerance time was significantly longer during reverse ride compared to forward ride (6.1±0.4 vs 5.0±0.5 min, respectively, p = 0.01, η² = 0.45). Analysis of HRV parameters revealed significant reduction in both RMSSD (p = 0.02, t = 2.62, η2 = 0.43) and SDRR (p = 0.01, t = 2.90, η2 = 0.45) in the forward ride; no such changes were found in the backward ride. We also found that amplitude of phasic changes in forehead skin conductance increased significantly in both ride directions. This increase however was significantly lower (p<0.05) in backward ride when compared to the forward ride. When assessed immediately post-ride, subjects reported significantly lower (p = 0.04) subjective symptom intensity after the reverse ride compared to the forward ride. We conclude that the direction of visual flow has a significant effect on the symptoms reported by the subjects and on the physiological changes during cybersickness.

Blunted Autonomic Responses and Low-Grade Inflammation in Mongolian Adults Born at Low Birth Weight

Low birth weight (LBW) has been considered as a risk factor for adult hypertension that is associated with deterioration of autonomic functions and low-grade inflammation. To explore the above effects of LBW, we measured blood pressure (BP) and heart rate variability during postural change from a supine position to a sitting position in 21 healthy Mongolian adults aged 23-34 years: 4 with LBW (birth weight < 2,500 g), 13 with normal birth weight (NBW, 2,500 g ≤ birth weight < 4,000 g), and 4 with high birth weight (HBW, ≥ 4,000 g). Mongolian population is known to have higher prevalence of hypertension. The ratio of low frequency (LF, 0.04-0.15 Hz) to high frequency components (HF, 0.15-0.40 Hz) was used as an index of sympathetic nerve activity, and HF was used as an index of parasympathetic nerve activity. In contrast to the NBW group, the LBW and HBW groups showed no significant increase in heart rate, systolic BP and LF/HF following postural change. We also measured blood cell counts and other blood parameters related to inflammation. After adjusting for age, BMI, sex and family history of hypertension, LBW was retained as an independent predictor only for higher counts of leukocytes (β = -0.51, p < 0.05), basophils (β = -0.62, p < 0.01), eosinophils (β = -0.83, p < 0.001), and platelets (β = -0.61, p < 0.05). We propose that LBW leads to blunted autonomic responses and low-grade inflammation in seemingly healthy Mongolian adults.

Statin utilisation in a real-world setting: a retrospective analysis in relation to arterial and cardiovascular autonomic function

Randomized trials suggest that statin treatment may lower blood pressure and influence cardiovascular autonomic function (CVAF), but the impact of duration of usage, discontinuation, and adherence to this therapy is unknown. We examined these issues with regard to blood pressure (BP)-related variables in a large, population-based study. Participants were 4942 adults (58% male; aged 50-84 years): 2179 on statin treatment and 2763 untreated. Days of utilization, adherence (proportion of days covered ≥0.8), and discontinuation (non-use for ≥30 days immediately prior to BP measurement) of three statins (atorvastatin, pravastatin, and simvastatin) over a period of up to 2 years was monitored retrospectively from electronic databases. Systolic BP (SBP), diastolic BP (DBP), augmentation index, excess pressure, reservoir pressure, and CVAF (pulse rate and BP variability) parameters were calculated from aortic pressure waveforms derived from suprasystolic brachial measurement. Days of statin treatment had inverse relationships with pulse rate variability parameters in cardiac arrhythmic participants (20-25% lower than in statin non-users) and with most arterial function parameters in everyone. For example, compared to untreated participants, those treated for ≥659 days had 3.0 mmHg lower aortic SBP (P < 0.01). Discontinuation was associated with higher brachial DBP and aortic DBP (for both, β = 2.0 mmHg, P = 0.008). Compared to non-adherent statin users, adherent users had lower levels of brachial SBP, brachial DBP, aortic DBP, aortic SBP, and peak reservoir pressure (β = -1.4 to -2.6 mmHg). In conclusion, in a real-world setting, statin-therapy duration, non-discontinuation and adherence associate inversely with BP variables and, in cardiac arrhythmias, CVAF parameters.

The Promise of Ultra-Short-Term (UST) Heart Rate Variability Measurements

Researchers have investigated whether ultra-short-term (UST) heart rate variability values can replace traditional 5-minute values in clinical and optimal performance settings. Concurrent validity is the extent to which the results of a measurement correspond to a previously validated assessment of the same construct. Several studies either failed to specify their concurrent validity criteria or used an inappropriate statistical test. The authors proposed a rigorous standard and demonstrated that artifacted resting ultra-short-term heart rate variability values can achieve strong concurrent validity for diverse time-domain, frequency-domain, and nonlinear measurements in healthy undergraduates. Based on these findings, resting baselines as brief as 1 minute should be sufficient to measure heart rate, the standard deviation of the interbeat interval for normal beats (SDNN), and the square root of the mean squared difference of adjacent NN intervals (RMSSD) in clinical, optimal performance, and personal health assessment with individuals who resemble Truman State University undergraduates.

Alterations in Amygdala-Prefrontal Functional Connectivity Account for Excessive Worry and Autonomic Dysregulation in Generalized Anxiety Disorder

BACKGROUND

Generalized anxiety disorder (GAD) is characterized by the core symptom of uncontrollable worry. Functional magnetic resonance imaging studies link this symptom to aberrant functional connectivity between the amygdala and prefrontal cortex. Patients with GAD also display a characteristic pattern of autonomic dysregulation. Although frontolimbic circuitry is implicated in the regulation of autonomic arousal, no previous study to our knowledge combined functional magnetic resonance imaging with peripheral physiologic monitoring in these patients to test the hypothesis that core symptoms of worry and autonomic dysregulation in GAD arise from a shared underlying neural mechanism.

METHODS

We used resting-state functional magnetic resonance imaging and the measurement of parasympathetic autonomic function (heart rate variability) in 19 patients with GAD and 21 control subjects to define neural correlates of autonomic and cognitive responses before and after induction of perseverative cognition. Seed-based analyses were conducted to quantify brain changes in functional connectivity with the right and left amygdala.

RESULTS

Before induction, patients showed relatively lower connectivity between the right amygdala and right superior frontal gyrus, right paracingulate/anterior cingulate cortex, and right supramarginal gyrus than control subjects. After induction, such connectivity patterns increased in patients with GAD and decreased in control subjects, and these changes tracked increases in state perseverative cognition. Moreover, decreases in functional connectivity between the left amygdala and subgenual cingulate cortex and between the right amygdala and caudate nucleus predicted the magnitude of reduction in heart rate variability after induction.

CONCLUSIONS

Our results link functional brain mechanisms underlying worry and rumination to autonomic dyscontrol, highlighting overlapping neural substrates associated with cognitive and autonomic responses to the induction of perseverative cognitions in patients with GAD.

A novel cardiovascular risk stratification model incorporating ECG and heart rate variability for patients presenting to the emergency department with chest pain

BACKGROUND

Risk stratification models can be employed at the emergency department (ED) to evaluate patient prognosis and guide choice of treatment. We derived and validated a new cardiovascular risk stratification model comprising vital signs, heart rate variability (HRV) parameters, and demographic and electrocardiogram (ECG) variables.

METHODS

We conducted a single-center, observational cohort study of patients presenting to the ED with chest pain. All patients above 21 years of age and in sinus rhythm were eligible. ECGs were collected and evaluated for 12-lead ECG abnormalities. Routine monitoring ECG data were processed to obtain HRV parameters. Vital signs and demographic data were obtained from electronic medical records. Thirty-day major adverse cardiac events (MACE) were the primary endpoint, including death, acute myocardial infarction, and revascularization. Candidate variables were identified using univariate analysis; the model for the final risk score was derived by multivariable logistic regression. We compared the performance of the new model with that of the thrombolysis in myocardial infarct (TIMI) score using receiver operating characteristic (ROC) analysis.

RESULTS

In total, 763 patients were included in this study; 254 (33 %) met the primary endpoint, the mean age was 60 (σ = 13) years, and the majority was male (65 %). Nineteen candidate predictors were entered into the multivariable model for backward variable elimination. The final model contained 10 clinical variables, including age, gender, heart rate, three HRV parameters (average R-to-R interval (RR), triangular interpolation of normal-to-normal (NN) intervals, and high-frequency power), and four 12-lead ECG variables (ST elevation, ST depression, Q wave, and QT prolongation). Our proposed model outperformed the TIMI score for prediction of MACE (area under the ROC curve 0.780 versus 0.653). At the cutoff score of 9 (range 0-37), our model had sensitivity of 0.709 (95 % CI 0.653, 0.765), specificity of 0.674 (95 % CI 0.633, 0.715), positive predictive value of 0.520 (95 % CI 0.468, 0.573), and negative predictive value of 0.823 (95 % CI 0.786, 0.859).

CONCLUSIONS

A non-invasive and objective ECG- and HRV-based risk stratification tool performed well against the TIMI score, but future research warrants use of an external validation cohort.

Heart Rate Variability as Early Biomarker for the Evaluation of Diabetes Mellitus Progress

According to the American Diabetes Association (ADA), the side effects of diabetes mellitus have recently increased the global health expenditure each year. Of these, the early diagnostic can contribute to the decrease on renal, cardiovascular, and nervous systems complications. However, the diagnostic criteria, which are commonly used, do not suggest the diabetes progress in the patient. In this study, the streptozotocin model in mice (cDM) was used as early diagnostic criterion to reduce the side effects related to the illness. The results showed some clinical signs similarly to five-year diabetes progress without renal injury, neuropathies, and cardiac neuropathy autonomic in the cDM-model. On the other hand, the electrocardiogram was used to determine alterations in heart rate and heart rate variability (HRV), using the Poincaré plot to quantify the HRV decrease in the cDM-model. Additionally, the SD1/SD2 ratio and ventricular arrhythmias showed increase without side effects of diabetes. Therefore, the use of HRV as an early biomarker contributes to evaluating diabetes mellitus complications from the diagnostic.

Neurostructural abnormalities associated with axes of emotion dysregulation in generalized anxiety

BACKGROUND

Despite the high prevalence of generalized anxiety disorder (GAD) and its negative impact on society, its neurobiology remains obscure. This study characterizes the neurostructural abnormalities associated with key symptoms of GAD, focusing on indicators of impaired emotion regulation (excessive worry, poor concentration, low mindfulness, and physiological arousal).

METHODS

These domains were assessed in 19 (16 women) GAD patients and 19 healthy controls matched for age and gender, using questionnaires and a low demand behavioral task performed before and after an induction of perseverative cognition (i.e. worry and rumination). Continuous pulse oximetry was used to measure autonomic physiology (heart rate variability; HRV). Observed cognitive and physiological changes in response to the induction provided quantifiable data on emotional regulatory capacity. Participants underwent structural magnetic resonance imaging; voxel-based morphometry was used to quantify the relationship between gray matter volume and psychological and physiological measures.

RESULTS

Overall, GAD patients had lower gray matter volume than controls within supramarginal, precentral, and postcentral gyrus bilaterally. Across the GAD group, increased right amygdala volume was associated with prolonged reaction times on the tracking task (indicating increased attentional impairment following the induction) and lower scores on the 'Act with awareness' subscale of the Five Facets Mindfulness Questionnaire. Moreover in GAD, medial frontal cortical gray matter volume correlated positively with the 'Non-react mindfulness' facet. Lastly, smaller volumes of bilateral insula, bilateral opercular cortex, right supramarginal and precentral gyri, anterior cingulate and paracingulate cortex predicted the magnitude of autonomic change following the induction (i.e. a greater decrease in HRV).

CONCLUSIONS

Results distinguish neural structures associated with impaired capacity for cognitive, attentional and physiological disengagement from worry, suggesting that aberrant competition between these levels of emotional regulation is intrinsic to symptom expression in GAD.

Heart rate variability stabilization in athletes: towards more convenient data acquisition

Resting heart rate variability (HRV) is a potentially useful marker to consider for monitoring training status in athletes. However, traditional HRV data collection methodology requires a 5-min recording period preceded by a 5-min stabilization period. This lengthy process may limit HRV monitoring in the field due to time constraints and high compliance demands of athletes. Investigation into more practical methodology for HRV data acquisitions is required. The aim of this study was to determine the time course for stabilization of ECG-derived lnRMSSD from traditional HRV recordings. Ten-minute supine ECG measures were obtained in ten male and ten female collegiate cross-country athletes. The first 5 min for each ECG was separately analysed in successive 1-min intervals as follows: minutes 0-1 (lnRMSSD0-1 ), 1-2 (lnRMSSD1-2 ), 2-3 (lnRMSSD2-3 ), 3-4 (lnRMSSD3-4 ) and 4-5 (lnRMSSD4-5 ). Each 1-min lnRMSSD segment was then sequentially compared to lnRMSSD of the 5- to 10-min ECG segment, which was considered the criterion (lnRMSSDC riterion ). There were no significant differences between each 1-min lnRMSSD segment and lnRMSSDC riterion , and the effect sizes were considered trivial (ES ranged from 0·07 to 0·12). In addition, the ICC for each 1-min segment compared to the criterion was near perfect (ICC values ranged from 0·92 to 0·97). The limits of agreement between the prerecording values and lnRMSSDC riterion ranged from ±0·28 to ±0·45 ms. These results lend support to shorter, more convenient ECG recording procedures for lnRMSSD assessment in athletes by reducing the prerecording stabilization period to 1 min.

Heart rate variability in children with type 1 diabetes mellitus

OBJECTIVE

To gather current information about the effects of type 1 diabetes mellitus on children's cardiac autonomic behavior.

DATA SOURCES

The search of articles was conducted on PubMed, Ibecs, Medline, Cochrane, Lilacs, SciELO and PEDro databases using the MeSH terms: "autonomic nervous system", "diabetes mellitus", "child", "type 1 diabetes mellitus", "sympathetic nervous system" and "parasympathetic nervous system", and their respective versions in Portuguese (DeCS). Articles published from January 2003 to February 2013 that enrolled children with 9-12 years old with type 1 diabetes mellitus were included in the review.

DATA SYNTHESIS

The electronic search resulted in four articles that approached the heart rate variability in children with type 1 diabetes mellitus, showing that, in general, these children present decreased global heart rate variability and vagal activity. The practice of physical activity promoted benefits for these individuals.

CONCLUSIONS

Children with type 1 diabetes mellitus present changes on autonomic modulation, indicating the need for early attention to avoid future complications in this group.

Validity of the ithlete™ Smart Phone Application for Determining Ultra-Short-Term Heart Rate Variability

The purpose of this investigation was to cross-validate the ithlete™ heart rate variability smart phone application with an electrocardiograph for determining ultra-short-term root mean square of successive R-R intervals. The root mean square of successive R-R intervals was simultaneously determined via electrocardiograph and ithlete™ at rest in twenty five healthy participants. There were no significant differences between the electrocardiograph and ithlete™ derived root mean square of successive R-R interval values (p > 0.05) and the correlation was near perfect (r = 0.99, p < 0.001). In addition, the ithlete™ revealed a Standard Error of the Estimate of 1.47 and Bland Altman plot showed that the limits of agreement ranged from 2.57 below to 2.63 above the constant error of −0.03. In conclusion, the ithlete™ appeared to provide a suitably accurate measure of root mean square of successive R-R intervals when compared to the electrocardiograph measures obtained in the laboratory within the current sample of healthy adult participants. The current study lays groundwork for future research determining the efficacy of ithlete™ for reflecting athletic training status over a chronic conditioning period.