Low HRV Research Articles

Cardiac sensing at a spinal cord stimulation lead: a promising on-device potential biomarker for pain and wellbeing.

Introduction: In the search for objective measures of therapeutic outcomes for patients with spinal cord stimulation (SCS) devices, various metrics of cardiac performance have been linked to pain as well as overall health. To track such measures at home, recent studies have incorporated wearables to monitor cardiac activity over months or years. The drawbacks to wearables, such as patient compliance, would be obviated by on-device sensing that incorporates the SCS lead. This study sought to evaluate the feasibility of using SCS leads to record cardiac electrograms. Methods: The quality of signals sensed by externalized, percutaneous leads in the thoracic spine of 10 subjects at the end of their SCS trial were characterized across various electrode configurations and postures by detecting R-peaks and calculating signal-to-noise ratio (SNR). In a subset of 5 subjects, cardiac metrics were then compared to those measured simultaneously with a wearable. Results: The average signal quality was acceptable for R-peak detection (i.e., SNR > 5) for all configurations and positions across all 10 subjects, with higher signal quality achieved when recording in resting positions. Notably, the spinal lead recordings enabled more reliable beat detection compared to the wearable (n = 29 recording pairs; p < 0.001). When excluding wearable recordings with over 35% missed beats, the inter-beat intervals across devices were highly correlated (n = 22 recording pairs; Pearson correlation: R = 0.99, p < 0.001). Further comparisons in these aligned wearable and corresponding spinal-lead recordings revealed significant differences in the frequency domain metrics (i.e., absolute and normalized high and low frequency HRV power, p < 0.05), but not in time domain HRV parameters. Discussion: The ability of an implanted SCS system to record electrocardiograms, as demonstrated here, could provide the basis of automated SCS therapy by tracking potential biomarkers of the patient's overall health state without the need for additional external devices.

Analysis of heart rate variability during emergency flight simulator missions in fighter pilots

IntroductionManaging emergency situations in different simulated flight segments can entail a workload that could affect the performance of military pilots. The aim was to analyse the modifications in neurovegetative balance...

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

AimsHeart 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. MethodsThe 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. ResultsLow 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. ConclusionsThe 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.

Associations between physical activity and autonomic function during deep breathing test: the Swedish CArdioPulmonary bioImage Study (SCAPIS).

The deep breathing test (DBT) is a sensitive test of cardiovagal function. The aim of this study was to explore associations between physical activity and sedentary time, measured by accelerometer, and autonomic function, using DBT. In the Swedish Cardio-Pulmonary bioImage Study, men and women aged 50-64 were randomly invited from the general population. A total of 4325 subjects who underwent DBT and assessment of physical activity and sedentary time by accelerometery were included. ECG files from 1-min DBT were used to calculate measures of respiratory sinus arrhythmia [RSA; expiration-inspiration (E-I) difference and E/I ratio], heart rate variability [HRV; root mean square of successive differences (RMSSD), standard deviation of heart rates and mean circular resultant]. Low RSA and HRV was defined as the lowest 10% in the population. For accelerometer-assessed physical activity, there were significant associations between high percentage of sedentary time and low E/I (p < 0.01), and low RMSSD (p < 0.01) in an age- and sex-adjusted model, and between percentage of sedentary time and low RMSSD (p = 0.04) in a risk factor-adjusted model. Low RMSSD was less common in those with a high percentage of moderate to vigorous physical activity (p = 0.04, after risk-factor adjustment). These associations became non-significant when further adjusting for heart rate. We report associations between degree of physical activity and indices of autonomic dysfunction in a large population. The relationships were no longer significant after adjustments for heart rate, indicating that the relationship between physical activity and cardiovagal function partly is accounted for by reduced heart rate.

Effectiveness of emotion regulation strategies measured by self-report and EMG as a result of strategy used, negative emotion strength and participants’ baseline HRV

We investigated how emotion regulation (ER) effectiveness—on both a self-reported rating as well as emotional expression (corrugator supercilii muscle activity) level—is affected by the characteristics of the situation (low vs. high negativity), the strategy used (reinterpretation, distraction, suppression, no regulation control condition) and individual dispositions (low vs. high baseline Heart Rate Variability) as well as their interaction. For this purpose, 54 adult women participated in a laboratory study. All the included factors significantly influenced both corrugator activity and appraisals of pictures’ negativity (in specific experimental conditions). For example, for high HRV participants, (1) distraction, suppression and reinterpretation significantly decreased corrugator activity compared to the control condition, and (2) distraction decreased appraised picture negativity for high negativity photos. For low HRV participants, distraction and suppression were most effective in decreasing corrugator responses, while suppression was more effective than reinterpretation in decreasing perceived picture negativity in the high negativity condition. Subjectively reported effort and success in applying ER strategies were also dependent on manipulated and dispositional factors. Overall, our results lend support to the flexible emotion regulation framework, showing that emotion regulation effectiveness relies on situational context as well as individual dispositions and their interaction.

Enhancing Inhibitory Control in Older Adults: A Biofeedback Study.

Multidomain interventions based on bio-/neurofeedback have proven useful in improving executive functions. The present study aimed to explore the potential efficacy and feasibility of an intervention that combined Heart Rate Variability Biofeedback (HRV-BF) and Near Infrared Hemoencephalography Neurofeedback (nirHEG-NF) on inhibitory control (IC) of healthy older adults. Thirty-four participants were randomly assigned to two groups: the biofeedback group (received a 10-week combined intervention of HRV-BF and nirHEG-NF) and the active control group (received a similar protocol without real-time biofeedback). Besides cognitive outcomes, the study examined pre- and post-changes in autonomic regulation and prefrontal blood oxygenation at rest and during training. Results revealed training-induced inhibitory control gains in one of the two interference tasks, whereas no effect was found on response inhibition. After the intervention, HRV increased in participants with the lowest levels of HRV at baseline. Although older adults increased blood oxygenation during training, no significant pre- and post-changes were found in blood flow oxygenation. These findings not only suggest that HRV-BF and nirHEG-NF potentially improve performance in certain subcomponents of inhibition (i.e., interference vs. response inhibition), but it may also be beneficial for parasympathetic activity in participants with low HRV and for increasing blood flow oxygenation on prefrontal areas during training.

Assessment of Beat-To-Beat Variability in Left Atrial Hemodynamics Using Real Time Phase Contrast MRI in Patients With Atrial Fibrillation.

Hemodynamic assessment of left atrial (LA) flow using phase contrast MRI provides insight into thromboembolic risk in atrial fibrillation (AF). However, conventional flow imaging techniques are averaged over many heartbeats. To evaluate beat-to-beat variability and LA hemodynamics in patients with AF using real time phase contrast (RTPC) MRI. Prospective. Thirty-five patients with history of AF (68 ± 10 years, nine female), 10 healthy controls (57 ± 19 years, four female). 5T, 2D RTPC with through-plane velocity-encoded gradient echo sequence and 4D flow MRI with three-directional velocity-encoded gradient echo sequence. RTPC was continuously acquired for a mid-LA slice in all subjects. 4D flow data were interpolated at the RTPC location and normally projected for comparison with RTPC. RR intervals extracted from RTPC were used to calculate heart rate variability (HRV=interquartile range over median × 100%). Patients were classified into low (<9.7%) and high (>9.7%) HRV groups. LA peak/mean velocity and stasis (%velocities < 5.8cm/sec) were calculated from segmented 2D images. Variability in RTPC flow metrics was quantified by coefficient of variation (CV) over all cycles. Pearson's correlation coefficient (r), Bland-Altman analysis, Kruskal-Wallis test. A P value < 0.05 was considered statistically significant. RTPC and 4D flow measurements were strongly/significantly correlated for all hemodynamic parameters (R2 =0.75-0.83) in controls. Twenty-four patients had low HRV (mean=4 ± 2%) and 11 patients had high HRV (27 ± 9%). In patients, increased HRV was significantly correlated with CV of peak velocity (r=0.67), mean velocity (r=0.51), and stasis (r=0.41). A stepwise decrease in peak/mean velocity and increase in stasis was observed when comparing controls vs. low HRV vs. high HRV groups. Mean velocity and stasis differences were significant for control vs. high HRV groups. RTPC may be suitable for assessing the impact of HRV on hemodynamics and provide insight for AF management in highly arrhythmic patients. 1 TECHNICAL EFFICACY: Stage 2.

Autonomic variability, depression and the disability paradox in spinal cord injury.

Longitudinal. With an increased risk of depression in spinal cord injury, the study longitudinally examines depression to understand how post-injury autonomic regulation and coping might be related to somatic and cognitive manifestations of depression after 3 years. Indian Spinal Injuries Center. Twenty-eight spinal cord injury participants completed the follow-up assessment of the Patient Health Questionnaire 3 years post-injury. The participants were grouped based on post-injury autonomic regulation (high and low HRV) and the somatic and cognitive manifestation of depression reflected in a depression ratio. Wilcoxson signed-rank test tested the post-injury (T1) and 3 year follow-up (T2) depression scores. Depression score reduced after 3 years of injury (p ≤ 0.05). Only the high HRV group showed a higher depression ratio (somatic/ cognitive) atfollow-up (T2) (p ≤ 0.05). No difference was observed in post-injury coping between high and low HRV groups. The reduced depression score at follow-up (T2) aligns with the 'disability paradox' and mightindicate cognitive adaptation, specifically for those who showed autonomic adaptability in the form of post-injury high autonomic variability.

Stress Detection Smartwatch

Abstract: When a person is unable to handle their circumstances, responsibilities, and workload, stress is a natural emotion that is produced. A person's physical and mental health may suffer when the body is triggered, which can be deadly. The physical impacts of stress on a person's body can include an increase in blood pressure, a rapid heartbeat, increased muscle tension, headaches, a decrease in bodily immunity functions, and a decrease in sleepiness, among other things. The latest technology, known as smartwatches, provides the user with easy access to mobile features. Users can employ the stress-detecting capabilities of high-end smartwatches. Although they can be used to understand things better, these stress applications for smartwatches are not precise in how they operate. Heart rate variability, or HRV, is used by smartwatches and involves the intervals between each heartbeat that the sensor records. A person who has a low HRV is likely under stress. Although stress applications may not be as precise as medical equipment, they are dependable when necessary because there is a good likelihood that the data is accurate. An Electro Dermal Activity (EDA) sensor, found in some smartwatches, monitors tension by electrically altering the amount of sweat on our skin. You must spend two minutes with your palm on the watch dial to achieve the same. As an increase in heart rate is a direct outcome of stress, stress is recognized in the project utilizing heart rate. Since it is also an immediate outcome of stress, heart rate is used in the implementation. In this sector, mobile applications give users a way to explore this data graphically or in greater detail. The user of mobile applications might utilize them for medical purposes and to understand the data

Biopsychosocial Contributors to Parent Behaviors during Child Venipuncture.

Children’s needle-related distress is strongly related to parental verbal behaviors. Yet, empirical data supporting theorized contributors to parent behaviors in this context remain limited. This is the first study to collectively measure biological (heart rate variability; HRV), psychological (catastrophizing, anxiety), and social (child behaviors) contributors to parent verbal behaviors throughout pediatric venipuncture. HRV was used as a measure of emotion regulation capacity and examined as a moderator in the associations between parent psychological factors and their behaviors, and between child and parent behaviors. Sixty-one children aged 7 to 12 years who presented at an outpatient blood lab for venipuncture and a parent participated. Parent baseline HRV, state catastrophizing, and anxiety were measured prior to venipuncture. The procedure was video-recorded for later coding of pairs’ verbal behaviors. Strong associations emerged between child behaviors and parent behaviors. Baseline HRV moderated the association between parent catastrophizing and behavior. Social factors remain a strong influence related to parent behaviors. Psychologically, parent negative cognitions differentially related to parent behaviors based on their emotion regulation capacity. Biologically, low baseline HRV may increase the risk that certain parents engage in a constellation of behaviors that simultaneously direct their child’s attention toward the procedure and inadvertently communicate parental worry, fear, or concern.

Abstract P216: Association Of Heart Rate Variability With The Risk Of Heart Failure And Its Sub-types In Post-menopausal Women: A Longitudinal Cohort Study

Background: Previously our research findings revealed that low heart rate variability, a measure of autonomic imbalance, is associated with increased incidence of coronary heart disease (CHD) and heart failure (HF) in a cohort of post-menopausal women. Since CHD is strongly associated with HF, we investigated the effect of CHD on relationship of HRV and HF subtypes, i.e., heart failure with reduced ejection fraction (HFrEF) and heart failure with preserved ejection fraction (HFpEF), in post-menopausal women. Methods: Total of 28,603 post-menopausal women free of baseline CHD, HF and cardiac arrhythmias enrolled in Women’s Health Initiative (WHI) study, were followed for incident hospitalized CHD, HF and its subtypes (HFrEF vs HFpEF). Using multivariate cox proportional hazard model, we estimated the association of above outcomes with baseline quartiles of HRV measures; SDNN (standard deviation of normal-to-normal RR interval) and RMSSD (root mean square of successive difference of RR interval) produced by 10-second twelve-lead ECG on enrollment. We then evaluated the relationship between HRV and HF subtypes stratified by incident CHD. Results: A total of 2279 incident CHD and 1562 incident HF events occurred during a median follow-up duration of 17.5 years. After adjusting for incident CHD in a multivariate cox proportional model, association of low SDNN and RMSSD with incident HF remained significant (SDNN HR 1.19, CI 1.05 - 1.35; RMSSD HR 1.13 (1.00 - 1.29). However, in stratified analysis low SDNN was associated with increased incidence of HFpEF only among participants without incident CHD (HR 1.29, CI 1.05 - 1.58) and not in those with incident CHD (HR 1.06, CI 0.77 - 1.47). Whereas low SDNN was associated with increased incidence of HFrEF only among participants with incident CHD (HR 1.44. CI 1.05 - 1.98) and not in those without incident CHD (HR 1.18, CI 0.87 - 1.61). Conclusion: Post-menopausal women with low HRV who develop CHD have an increased risk of HFrEF while those who don’t develop CHD have an increased risk of HFpEF. The relationship between autonomic imbalance and HF subtypes is dependent on CHD status.

Does the type of seizure influence heart rate variability changes?

ObjectiveHeart rate variability (HRV), an index of the autonomic cardiac activity, is decreased in patients with epilepsy, and a low HRV is associated with a higher risk of sudden death. Generalized tonic-clonic seizures are one of the most consistent risk factors for SUDEP, but the influence (and relative risk) of each type of seizure on cardiac function is still unknown. Our objective was to assess the impact of the type of seizure (focal to bilateral tonic-clonic seizure – FBTCS – versus non-FBTCS) on periictal HRV, in a group of patients with refractory epilepsy and both types of seizures. MethodsWe performed a 48-hour Holter recording on 121 patients consecutively admitted to our Epilepsy Monitoring Unit. We only included patients with both FBTCS and non-FBTCS on the Holter recording and selected the first seizure of each type to analyze. To evaluate HRV parameters (AVNN, SDNN, RMSSD, pNN20, LF, HF, and LF/HF), we chose 5-min epochs pre- and postictally. ResultsWe included 14 patients, with a median age of 36 (min–max, 16–55) years and 64% were female. Thirty-six percent had cardiovascular risk factors, but no previously known cardiac disease.In the preictal period, there were no statistically significant differences in HRV parameters, between FBTCS and non-FBTCS. In the postictal period, AVNN, RMSSD, pNN20, LF, and HF were significantly lower, and LF/HF and HR were significantly higher in FBTCS.From preictal to postictal periods, FBTCS elicited a statistically significant rise in HR and LF/HF, and a statistically significant fall in AVNN, RMSSD, pNN20, and HF. Non-FBTCS only caused statistically significant changes in HR (decrease) and AVNN (increase). Significance/conclusionThis work emphasizes the greater effect of FBTCS in autonomic cardiac function in patients with refractory epilepsy, compared to other types of seizures, with a significant reduction in vagal tonus, which may be associated with an increased risk of SUDEP.

Systematic review on the association between respiratory virus real-time PCR cycle threshold values and clinical presentation or outcomes.

ObjectivesIt is unclear whether real-time (rt)-PCR cycle threshold (Ct) values can be utilized to guide clinical and infection-control decisions. This systematic review assesses the association between respiratory pathogen rt-PCR Ct values and clinical presentation or outcomes.MethodsWe searched MEDLINE, EMBASE and Cochrane library databases on 14–17 January 2020 for studies reporting the presence or absence of an association between Ct values and clinical presentation or outcomes, excluding animal studies, reviews, meta-analyses, and non-English language studies.ResultsAmong 33 studies identified (reporting on between 9 and 4918 participants by pathogen), influenza (n = 11 studies; 4918 participants), human rhinovirus (HRV, n = 11; 2012) and respiratory syncytial virus (RSV, n = 8; 3290) were the most-studied pathogens. Low influenza Ct values were associated with mortality in 1/3 studies, with increased disease severity/duration or ICU admission in 3/9, and with increased hospitalization or length of hospital stay (LOS) in 1/6. Low HRV Ct values were associated with increased disease severity/duration or ICU admission in 3/10 studies, and with increased hospitalization or LOS in 1/3. Low RSV Ct values were associated with increased disease severity/duration or ICU admission in 3/6 studies, and with increased hospitalization or LOS in 4/4. Contradictory associations were also identified for other respiratory pathogens.ConclusionsRespiratory infection Ct values may inform clinical and infection-control decisions. However, the study heterogeneity observed in this review highlights the need for standardized workflows to utilize Ct values as a proxy of genomic load and confirm their value for respiratory infection management.

Correlation between Heart Rate Variability and Claustrum Stimulation – Hypothesis, Experimental Studies and Future Perspectives

Abstract Heart rate variability (HRV) has long been associated with cardiovascular risk, especially after a myocardial infarction, but also in general. HRV reflects and is used as a surrogate for the balance between sympathetic and parasympathetic systems in modulating the cardiovascular activity. A low HRV, traditionally associated to sympathovagal imbalance, is associated with a worse cardiovascular prognosis. Deep brain stimulation (DBS) is a surgical technique used for severe cases of Parkinson's disease and other neurologic pathologies. DBS is performed in various areas of the brain and through different protocols. The claustrum, an area located between the external capsule and the insular cortex, was recently shown to be connected to Parkinson's motor symptoms. As DBS in other regions of the brain has proven non-motor effects, like influencing the HRV, we sought to document the effect of claustrum stimulation on the sympatho-vagal balance (SVB). Our preliminary data indicates that claustrum stimulation inclines the SVB toward the latter, but more studies are required to observe the long-term effects of this type of stimulation.

Integrating Breathing Techniques Into Psychotherapy to Improve HRV: Which Approach Is Best?

IntroductionApproaches to improve heart rate variability and reduce stress such as breathing retraining are more frequently being integrated into psychotherapy but little research on their effectiveness has been done to date. Specifically, no studies to date have directly compared using a breathing pacer at 6 breaths per minute with compassion focused soothing rhythm breathing.Current StudyIn this randomized controlled experiment, 6 breaths per minute breathing using a pacer was compared with compassion focused soothing rhythm breathing, with a nature video being used as a control group condition.MethodsHeart rate variability (HRV) measures were assessed via electrocardiogram (ECG) and respiration belt, and an automated blood pressure machine was used to measure systolic diastolic blood pressure, and heart rate (HR). A total of 96 participants were randomized into the three conditions. Following a 5-min baseline, participants engaged in either 6 breath per minute breathing, soothing rhythm breathing, or watched a nature video for 10 min. To induce a stressful state, participants then wrote for 5 min about a time they felt intensely self-critical. Participants then wrote for 5 min about a time they felt self-compassionate, and the experiment ended with a 10-min recovery period.ResultsConditions did not significantly differ at baseline. Overall, HRV, as measured by standard deviation of NN intervals (SDNN), low frequency HRV (LF HRV), and LF/HF ratio, increased during the intervention period, decreased during self-critical writing, and then returned to baseline levels during the recovery period. High frequency HRV (HF HRV) was not impacted by any of the interventions. The participants in the 6 breath per minute pacer condition were unable to consistently breathe at that rate and averaged about 12 breaths per minute. Time by Condition analyses revealed that both the 6 breaths per minute pacer and soothing breathing rhythm conditions lead to significantly higher SDNN than the nature video condition during breathing practice but there were no significant differences between conditions in response to the self-critical and self-compassionate writing or recovery periods. The 6 breath per minute pacer condition demonstrated a higher LF HRV and LF/HF ratio than the soothing rhythm breathing condition, and both intervention conditions had a higher LF HRV and LF/HF ratio than the nature video.ConclusionsAlthough the 6 breath per minute pacer condition participants were not able to breath consistently at the low pace, both the participants attempting to breathe at 6 breaths per minute as well as those in the soothing rhythm breathing condition effectively increased HR variability as measured by SDNN, and attempting to breathe at 6 breaths per minute led to the highest LF HRV and LF/HF ratio. Both breathing approaches impacted HRV more than watching a relaxing nature video and can potentially be used as key adjuncts in psychotherapy to aid in regulating physiological functioning, although it appears that consistent breathing practice would be needed.

AUTONOMIC AND CARDIOVASCULAR RESPONSES TO ACUTE EXERCISES IN CHILDREN WITH AUTISM SPECTRUM DISORDER

Autism Spectrum Disorder (ASD) is a complex neurological disorder identified in early childhood and is characterized by impaired social interaction and atypical behaviors. Limited studies reported that children with ASD tend to have higher heart rate (HR) and blood pressure (BP) at rest compared to typically developing children (TDC). Previously, we reported that HR and blood flow (BF) did not alter while BP increased from rest to acute exercise in ASD. Thus, we thought that ASD may have impaired autonomic nervous system activity to differentially control HR and stroke volume (SV) to regulate BP through changes in cardiac output. PURPOSE: To determine autonomic and cardiovascular responses to acute dynamic exercise in children with ASD. METHODS: 36 adults, TDC and children with ASD participated in the study. HR from ECG, beat to beat arterial BP from Finapres and brachial BP, and SV from Modelflow, were continuously measured before, during and after 2 minutes of dynamic handgrip exercise at 35% and 50% of maximal voluntary contraction. Diameter, blood velocity, and flow of the brachial artery were measured using Doppler ultrasound on the contracting arm throughout the experiment. Time and frequency domains of HR variability indexes were used. RESULTS: Mean BP was significantly increased to exercise from rest in all groups with no group differences (∆9.8±1.8 adults, ∆8.3±1.2 TDC, and ∆6.9±1.8 ASD, mmHg). HR was significantly increased to exercise from rest in adults and TDC; however, there was no change in HR to exercise from rest in ASD (∆11±1 adults, ∆7±1 TDC, and ∆1±1 ASD, bpm). SV was unaltered from rest to exercise in all groups. Both adults and TDC had similar increase in BF during exercise compared to rest (∆17±3 adults vs. ∆14±2 TDC cm/s); however, BF did not change from rest to exercise (∆0.6±2.2 ASD cm/s) in ASD. The rMSSD and high frequency of HRV were similar in all groups while very low frequency HRV was significantly lower in ASD. CONCLUSION: While HR and BF were altered to exercise in both adults and TDC groups in similar fashion, HR and BF did not change in ASD children indicating impaired autonomic and vascular function. Higher total peripheral resistance may contribute to increase BP during exercise in ASD children without a significant contribution of cardiac output.

Associations Between Heart Rate Variability Measured With a Wrist-Worn Sensor and Older Adults' Physical Function: Observational Study.

BackgroundHeart rate variability (HRV), or variation in beat-to-beat intervals of the heart, is a quantitative measure of autonomic regulation of the cardiovascular system. Low HRV derived from electrocardiogram (ECG) recordings is reported to be related to physical frailty in older adults. Recent advances in wearable technology offer opportunities to more easily integrate monitoring of HRV into regular clinical geriatric health assessments. However, signals obtained from ECG versus wearable photoplethysmography (PPG) devices are different, and a critical first step preceding their widespread use is to determine whether HRV metrics derived from PPG devices also relate to older adults’ physical function.ObjectiveThis study aimed to investigate associations between HRV measured with a wrist-worn PPG device, the Empatica E4 sensor, and validated clinical measures of both objective and self-reported physical function in a cohort of older adults living independently within a continuing care senior housing community. Our primary hypothesis was that lower HRV would be associated with lower physical function. In addition, we expected that HRV would explain a significant proportion of variance in measures of physical health status.MethodsWe evaluated 77 participants from an ongoing study of older adults aged between 65 and 95 years. The assessments encompassed a thorough examination of domains typically included in a geriatric health evaluation. We collected HRV data with the Empatica E4 device and examined bivariate correlations between HRV quantified with the triangular index (HRV TI) and 3 widely used and validated measures of physical functioning—the Short Physical Performance Battery (SPPB), Timed Up and Go (TUG), and Medical Outcomes Study Short Form 36 (SF-36) physical composite scores. We further investigated the additional predictive power of HRV TI on physical health status, as characterized by SF-36 physical composite scores and Cumulative Illness Rating Scale for Geriatrics (CIRS-G) scores, using generalized estimating equation regression analyses with backward elimination.ResultsWe observed significant associations of HRV TI with SPPB (n=52; Spearman ρ=0.41; P=.003), TUG (n=51; ρ=−0.40; P=.004), SF-36 physical composite scores (n=49; ρ=0.37; P=.009), and CIRS-G scores (n=52, ρ=−0.43; P=.001). In addition, the HRV TI explained a significant proportion of variance in SF-36 physical composite scores (R2=0.28 vs 0.11 without HRV) and CIRS-G scores (R2=0.33 vs 0.17 without HRV).ConclusionsThe HRV TI measured with a relatively novel wrist-worn PPG device was related to both objective (SPPB and TUG) and self-reported (SF-36 physical composite) measures of physical function. In addition, the HRV TI explained additional variance in self-reported physical function and cumulative illness severity beyond traditionally measured aspects of physical health. Future steps include longitudinal tracking of changes in both HRV and physical function, which will add important insights regarding the predictive value of HRV as a biomarker of physical health in older adults.

Abstract # 3110 Reward functioning following an acute bout of exercise among healthy adults

Exercise is thought to exert beneficial effects on reward functioning, as it alters neurotransmitter levels in reward-related circuits. However, there has been little investigation of the effect of exercise on reward functions in humans. We hypothesized a bout of exercise would increase motivation for and pleasurable responses to rewards in healthy adults. We also examined possible moderators of exercise’s effects. Thirty-five participants completed exercise (20 min run at 105% of lactate threshold intensity) and rest (20 min sit) sessions in a randomized, counterbalanced order. After each activity, participants completed measures of motivation for (Effort Expenditure for Rewards Task) and pleasurable responses to (International Affective Picture System Task) rewards. Exercise did not increase motivation for or pleasurable responses to rewards on average. However, there was a moderating effect of years running, as individuals who had been runners for more years showed increased motivation for rewards after exercise, while individuals with less years running showed decreases. Further, baseline heart rate variability negatively correlated with the effects of exercise on arousal. As this was not specific to picture type, it suggests a dysregulation of emotional responses after exercise in individuals with low HRV. Our results indicate that baseline characteristics may have important moderating influences on the effect of exercise on emotional functioning. Previous experience with the exercise used should be examined as a possible moderator in exercise interventions.

Cerebral blood flow and heart rate variability predict fatigue severity in patients with chronic fatigue syndrome.

Prolonged, disabling fatigue is the hallmark of chronic fatigue syndrome (CFS). Previous neuroimaging studies have provided evidence for nervous system involvement in CFS etiology, including perturbations in brain structure/function. In this arterial spin labeling (ASL) MRI study, we examined variability in cerebral blood flow (CBFV) and heart rate (HRV) in 28 women: 14 with CFS and 14 healthy controls. We hypothesized that CBFV would be reduced in individuals with CFS compared to healthy controls, and that increased CBFV and HRV would be associated with lower levels of fatigue in affected individuals. Our results provided support for these hypotheses. Although no group differences in CBFV or HRV were detected, greater CBFV and more HRV power were both associated with lower fatigue symptom severity in individuals with CFS. Exploratory statistical analyses suggested that protective effects of high CBFV were greatest in individuals with low HRV. We also found novel evidence of bidirectional association between the very high frequency (VHF) band of HRV and CBFV. Taken together, the results of this study suggest that CBFV and HRV are potentially important measures of adaptive capacity in chronic illnesses like CFS. Future studies should address these measures as potential therapeutic targets to improve outcomes and reduce symptom severity in individuals with CFS.

THE INFLUENCE OF HEART RATE VARIABILITY ON CLINICAL COURSE OF CHRONIC HEART FAILURE AND RENAL FUNCTION IN ATRIAL FIBRILLATION PATIENTS

Aim. Evaluation of structural and functional condition of the left ventricle (LV) and kidneys in permanent atrial fibrillation patients (AF) with ischemic chronic heart failure (CHF) according to mean 24 hour heart rate and heart rate variability. Material and methods . Sixty patients, age 35-60 y. o., with permanent AF of ischemic origin. All patients underwent echocardiography for the dysfunction verification: systolic function was assessed by ejection fraction of the left ventricle by Simpson, diastolic function was assessed via the velocity of transmitral currents and visualization of tissues of the mitral valve; Holter ECG monitoring was done, as volumetric sphygmopletysmography of peripheral arteries, assessment of kidney function by Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) by creatinine and cystatin C, evaluation of the status of collagen production by the tissue inhibitor of matrix metalloproteases type 1 (TIMP-1), measurement of NT-proBNP. In the first part of the study, patients were selected to 3 groups: by GFR 60 mL/min/1,73 m2. In the second — by cystatin C levels below or higher than the referent. Results. There is negative moderate correlation of the heart rate >110 bpm and SDNN (r=-0,64, p=0,040) and 70 bpm (r=0,44, p=0,022); negative moderate correlation of GFR by CKD-EPIcys and mean daily heart rate >110 bpm (r=-0,55, p=0,030). Correlational analysis also showed that in permanent AF and ischemic CHF the mean 24 hour heart rate correlates strongly with E/e’ (r=0,53, р=0,011) and with NT-proBNP (r=0,57, р=0,002). Also the negative strong correlation found for SDNN with mean 24 hour heart rate (r=-0,59, p=0,001), with NT-proBNP (r=-0,65, p=0,002), with EF LV (r=-0,50, p=0,019), with the relation E/e’ (r=-0,61, p 110 bpm. With the increase of mean 24 hour heart rate there was increase of CHF severity, progression of LV diastolic dysfunction and renal dysfunction. Low HRV in a range of mean daily heart rate >110 bpm was associated with adverse cardiac remodeling presenting with LVH, and of kidney remodeling. One of possible mechanisms of the target organs with HRV decline, by our data, might be transformation of collagenolysis towards collagenogenesis in intracellular matrix, according to the dynamics of TIMP-1.