The Efficiency of 10-Second Resting Heart Rate for the Evaluation of Short-Term Heart Rate Variability Indices

A new algorithm for fetal heart rate detection: Fractional order calculus approach

OBJECTIVES

A new modified Pan-Tompkins' (mPT) method for fetal heart rate detection is presented. The mPT method is based on the hypothesis that optimal fractional order derivative and optimal window width of the moving average filter would enable efficient estimation of fetal heart rate from surface abdominal electrophysiological recordings with relatively low signal-to-noise ratios.

METHODS

The algorithm is tested on signals recorded from the abdomen of pregnant women available from the PhysioNet Computing in Cardiology Challenge database. Fetal heart rate detection is performed on 10-s long segments selected by the estimation of signal-to-noise ratios (the extravagance of the fetal QRS peak to its surroundings and to the whole signal; and the mean ratio of fetal and maternal QRS peaks) and on the manually selected segments.

RESULTS

The best results are obtained via criteria based on the extravagance of the fetal QRS peak to its surroundings that reached average sensitivity of 97%, positive predictive value of 97%, error rate of ∼3.5%, and F1 score of 97%. The obtained averaged optimal parameters for mPT are 0.51 for fractional order and 24.5 ms for the window width of the moving average filter.

CONCLUSION

Proposed mPT algorithm showed satisfactory performance for fetal heart rate detection. Further adaptations of the presented mPT method could be used for peak detection in noisy environments in biomedical signal analysis in general.

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.

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.

Neuromodulation Applied to Diseases: The Case of HRV Biofeedback

The vagus or “wandering” nerve is the main branch of the parasympathetic nervous system (PNS), innervating most internal organs crucial for health. Activity of the vagus nerve can be non-invasively indexed by heart-rate variability parameters (HRV). Specific HRV parameters predict less all-cause mortality, lower risk of and better prognosis after myocardial infarctions, and better survival in cancer. A non-invasive manner for self-activating the vagus is achieved by performing a slow-paced breathing technique while receiving visual feedback of one’s HRV, called HRV-biofeedback (HRV-B). This article narratively reviews the biological mechanisms underlying the role of vagal activity and vagally mediated HRV in hypertension, diabetes, coronary heart disease (CHD), cancer, pain, and dementia. After searching the literature for HRV-B intervention studies in each condition, we report the effects of HRV-B on clinical outcomes in these health conditions, while evaluating the methodological quality of these studies. Generally, the levels of evidence for the benefits of HRV-B is high in CHD, pain, and hypertension, moderate in cancer, and poor in diabetes and dementia. Limitations and future research directions are discussed.

The Effect of High-Altitude Acclimatisation on Ultra-Short Heart Rate Variability

Introduction

High-altitude (HA) exposure affects heart rate variability (HRV) and has been inconsistently linked to acute mountain sickness (AMS). The influence of increasing HA exposure on ultra-short HRV and its relationship to gold standard HRV measures at HA has not been examined.

Methods

This was a prospective observational study of adults aged ≥ 18 years undertaking a HA trek in the Dhaulagiri region of the Himalayas. Cardiac inter-beat-intervals were obtained from a 10-s recording of supra-systolic blood pressure (Uscom BP⁺ device) immediately followed by 300 s single lead ECG recording (CheckMyHeart device). HRV was measured using the RMSSD (root mean square of successive differences of NN intervals) at sea level (SL) in the United Kingdom and at 3,619, 4,600, and 5,140 m at HA. Oxygen saturations (SpO₂) were measured using finger-based pulse oximetry. The level of agreement between the 10 and 300 s RMSSD values were examined using a modified Bland–Altman relative-difference analysis.

Results

Overall, 89 participants aged 32.2 ± 8.8 years (range 18–56) were included of which 70.8% were men. HA exposure (SL vs. 3,619 m) was associated with an initial increase in both 10 s (45.0 [31.0–82.0]) vs. 58.0 [33.0–119.0] ms) and 300 s (45.67 [33.24–70.32] vs. 56.48 [36.98–102.0] ms) in RMSSD. Thereafter at 4,600 and 5,140 m both 10 and 300 s RMSSD values were significantly lower than SL. From a total of 317 paired HRV measures the 10 and 300 s RMSSD measures were moderately correlated (Spearman r = 0.66; 95% CI: 0.59–0.72; p < 0.0001). The median difference (bias) in RMSSD values (300 s − 10 s) was −2.3 ms with a lower and upper limit of agreement of −107.5 and 88.61 ms, respectively with no differences with altitude. Overall, 293/317 (92.4%) of all paired HRV values fell within the 95% CI limits of agreement. Neither HRV method was predictive of AMS.

Conclusion

Increasing HA affects ultra-short HRV in a similar manner to gold-standard 300 s. Ultra-short HRV has a moderate agreement with 300 s measurements. HRV did not predict AMS.

Ten-Second Heart Rate Variability, Its Changes Over Time, and the Development of Hypertension

BACKGROUND

The role of ultrashort-term heart rate variability (HRV) and its temporal changes in incident hypertension are unknown. We aimed to investigate the association between 10-second HRV, its changes, and incident hypertension in adults aged <40 years and older.

METHODS

This cohort study included 232 587 Koreans (mean age 37.6 years) without hypertension. Hypertension was defined according to the 2017 American College of Cardiology and American Heart Association hypertension guidelines. HRV, including the root mean square of successive RR interval differences and the SD of normal-to-normal RR intervals, was estimated using standard 12-lead, 10-second electrocardiography.

RESULTS

During a median follow-up of 3.8 years, 40 268 hypertension cases were identified (incidence rates: 36.1 and 67.9 per 1000 person-years for young and older participants, respectively). An inverse association was observed between HRV and hypertension risk, in a dose-dependent manner. The multivariable-adjusted hazard ratios (95% CIs) for hypertension comparing the first to the fifth quintiles of root mean square of successive RR interval difference and SD of normal-to-normal RR interval were 1.58 (1.52-1.63) and 1.35 (1.30-1.39), respectively. These associations were stronger in young adults than in older adults. In a subsample of 150 301 participants, compared with stable HRV, an increase in HRV over time was also inversely associated with incident hypertension.

CONCLUSIONS

A higher HRV and its increase over time on a 10-second electrocardiography were associated with a lower risk of hypertension. Our findings indicate that autonomic function, estimated using 10-second standard electrocardiography, plays a role in predicting hypertension, with a stronger effect in young adults.

Measuring Mental Stress During Otologic Surgery Using Heart Rate Variability Analysis

OBJECTIVES

Healthy individuals have significant beat-to-beat variability in heart rate, and this variability decreases with mental stress. We aim to use heart rate variability (HRV) to objectively compare mental stress levels in otologic surgeons at rest and during key portions of procedures.

DESIGN

Pilot study.

SETTING

Operating room and laboratory.

PARTICIPANTS

Two neurotology fellows performed six mastoidectomy and facial nerve (FN) dissections in the operating room and six in a cadaver lab while continuous electrocardiograms were measured wirelessly. Five-minute samples were recorded during resting, preoperative, mastoidectomy, and FN dissection. Beat-to-beat time intervals were analyzed in time and frequency domains. The standard deviation of normal beat-to-beat intervals (SDNN) and the ratio of low frequency to high frequency power (LF/HF, measure of sympathetic tone) were calculated. Decreases in SDNN and increases in LF/HF indicate elevated mental stress.

RESULTS

Mean resting SDNN was 43.9 ± 9.2 ms, not statistically different from preoperative SDNN (34.1 ± 8.2 ms, p = 0.13). SDNN decreased during mastoidectomy (29.4 ± 11.7 ms) and FN dissection (22.8 ± 3.1 ms), which was significant compared to preoperative values (p = 0.03). Intraoperative LF/HF increased for FN dissection (6.8 ± 2.6) compared to resting (2.2 ± 0.7, p = 0.004), indicating increased sympathetic tone. Mastoid and FN cadaveric procedures resulted in SDNN of 33.6 ± 3.8 and 32.9 ± 4.7 ms, respectively, not statistically different from preoperative values (p = 0.82 and p = 0.94, respectively). Cadaveric FN dissection did not result in increased LF/HF (2.4 ± 0.9) compared to resting (p = 0.94).

CONCLUSIONS

Decreased HRV and increased sympathetic tone were observed intraoperatively, indicating high levels of mental stress, particularly with FN dissection. Similar changes were not found during cadaveric dissections.

The age-dependent relationship between resting heart rate variability and functional brain connectivity

Resting heart rate variability (HRV), an index of parasympathetic cardioregulation and an individual trait marker related to mental and physical health, decreases with age. Previous studies have associated resting HRV with structural and functional properties of the brain - mainly in cortical midline and limbic structures. We hypothesized that aging affects the relationship between resting HRV and brain structure and function. In 388 healthy subjects of three age groups (140 younger: 26.0 ± 4.2 years, 119 middle-aged: 46.3 ± 6.2 years, 129 older: 66.9 ± 4.7 years), gray matter volume (GMV, voxel-based morphometry) and resting state functional connectivity (eigenvector centrality mapping and exploratory seed-based functional connectivity) were related to resting HRV, measured as the root mean square of successive differences (RMSSD). Confirming previous findings, resting HRV decreased with age. For HRV-related GMV, there were no statistically significant differences between the age groups, nor similarities across all age groups. In whole-brain functional connectivity analyses, we found an age-dependent association between resting HRV and eigenvector centrality in the bilateral ventromedial prefrontal cortex (vmPFC), driven by the younger adults. Across all age groups, HRV was positively correlated with network centrality in the bilateral posterior cingulate cortex. Seed-based functional connectivity analysis using the vmPFC cluster revealed an HRV-related cortico-cerebellar network in younger but not in middle-aged or older adults. Our results indicate that the decrease of HRV with age is accompanied by changes in functional connectivity along the cortical midline. This extends our knowledge of brain-body interactions and their changes over the lifespan.

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.

Reliability and validity of time domain heart rate variability during daily routine activities – an alternative to the morning orthostatic test?

Study aim: To determine the reliability and validity of a time domain heart rate variability (HRV) index during free-living physical activity (FLPA).

Material and methods: Eight white-collar workers participated in this study. RR intervals (time between consecutive R-peaks of the PQRS complex) were recorded using the Polar V800 heart rate (HR) monitor upon awakening and at work on 16 different days. A total of 127 cycles of sitting periods followed by walking breaks were included for consecutive pairwise analysis for reliability. The HR values from the orthostatic test (OT) were compared with the corresponding values at work.

Results: The HR values showed high levels of repeatability [the coefficient of variation (CV) during sitting and walking at work was 4.71 and 3.99%, respectively, with a typical error (TE) of 3.73 (3.34-4.25) and 3.65 (3.31-4.09)], but they did not correlate with the corresponding OT HR upon awakening (r = 0.28 for supine vs. sitting and r = 0.05 for standing vs. walking, p > 0.05). The root-mean-square difference of successive normal RR (RMSSD) was revealed not to be repeatable [CV values during sitting and walking were 19.99 and 29.05%, respectively, with a TE of 7.9 (7.15-8.85) and 9.43 (8.53-10.57)].

Conclusions: Analyzing RMSSD from daily routine activities was not reliable, and therefore validity cannot be assumed. RMSSD should therefore be calculated from RR intervals recorded in standardized conditions, such as during the OT upon awakening.

Monitoring peri-ictal changes in heart rate variability, oxygen saturation and blood pressure in epilepsy monitoring unit

PURPOSE

The peri-ictal autonomic disturbances have been studied as predictors of seizure outcome and as markers of seizure onset. We studied the changes in heart rate (HR), HRV, oxygen saturation and blood pressure (BP) in the peri-ictal period in patients with drug-resistant localization-related epilepsy.

METHODOLOGY

Ninety one subjects undergoing video-EEG monitoring, underwent continuous HR, SpO2, BP and Lead II ECG monitoring. The changes during the preictal, ictal and postictal periods were analyzed for 57 seizures in 42 patients with artifact-free recordings and correlated with VEEG ictal onset and MRI characteristics.

RESULTS

Ictal tachycardia was noted in 15 (26.3%) seizures, of which, 60% had temporal lobe onset. HR increased by an average of 20.1% from pre-ictal to ictal phases (p=0.04). Ictal bradycardia was noted in one event with right temporal seizure onset. Heart rate variability (HRV) analysis of the preictal, ictal and postictal phases showed an increase in the sympathetic and decrease in parasympathetic activity during the ictus with relatively preserved total power. Ictal oxygen desaturation (84.1%±3.5%) was noticed in 10 (17.5%) seizures. Ictal hypertension was observed in 15 (26.3%); ictal hypotension was noted in 5 (8.7%) seizures. Both the systolic BP and diastolic BPs increased from the pre-ictal to ictal phase (p=0.01).

CONCLUSIONS

Peri-ictal dysautonomia can present in variable patterns and can be measured and compared over different modalities such as BP, HR and HRV. Though degree of tachycardia and increase in BP were higher during extratemporal onset of seizures, a fall in variability was noted in seizures of temporal lobe origin. Oxygen desaturation is not an uncommon event during the peri-ictal period in localization related epilepsy.

Cognitive flexibility, heart rate variability, and resilience predict fine-grained regulation of arousal during prolonged threat

Emotion regulation in the ongoing presence of a threat is essential for adaptive behavior. Threatening situations change over time and, as a consequence, require a fine-tuned, dynamic regulation of arousal to match the current state of the environment. Constructs such as cognitive flexibility, heart rate variability, and resilience have been proposed as resources for adaptive emotion regulation, especially in a moment-to-moment fashion. Nevertheless, none of these constructs has been empirically related to the dynamic regulation of arousal as it unfolds over the course of a prolonged threatening episode. Here, we do so by placing participants in a threatening and evolving immersive virtual environment called Room 101, while recording their skin conductance. Subsequently, participants rated their subjective arousal continuously over the course of the experience. Participants who had shown greater cognitive flexibility in a separate task (i.e., fewer task-switching costs when switching to evaluating the valence of positive stimuli) showed better regulation of physiological arousal (skin conductance level), during less-threatening phases of Room 101. Individuals with higher trait resilience and individuals with higher resting heart rate variability showed more regulation in terms of their subjective arousal experience. The results indicate that emotional, cognitive, and physiological flexibility support nuanced adaptive regulation of objective and experienced arousal in the ongoing presence of threats. Furthermore, the results indicate that these forms of flexibility differentially affect automatic and objective versus reflective and subjective processes.

Determinants of All-Cause Mortality and Incidence of Cardiovascular Disease (2009 to 2013) in Older Adults

Aim:

Ikaria Island (North-East Aegean, Greece) has been recognized as one of the places with the highest life expectancy around the world (the Blues Zones). Risk factors in relation to 4-year all-cause mortality and cardiovascular disease (CVD) incidence in elders were studied.

Methods:

From June to October 2009, 330 men and 343 women, aged 65 to 100 years, were enrolled, and in June to July 2013, they were reevaluated.

Results:

Age-standardized, gender-specific, all-cause mortality rate was 790 deaths per 10 000 inhabitants, and causes of death were CVD (36%), cancer (21%), infection (10%), respiratory disease (2%), and other (31%). Incidence of CVDwas 520 cases per 10 000 men inhabitants and 320 cases per 10 000 women ( P = .03). Age, male gender, heart rate, urea levels, left atrial maximum volume, left ventricular hypertrophy, thyroid-stimulating hormone, and moderate to severe depression were positively associated with mortality, whereas left ventricular ejection fraction as well as coffee and tea drinking, fruit intake, and exclusive olive oil use were inversely associated with CVD.

Conclusion:

Heart function markers in addition to antioxidant dietary factors were placed in this puzzle of CVD morbidity.

Monitoring training status with HR measures: do all roads lead to Rome?

Measures of resting, exercise, and recovery heart rate are receiving increasing interest for monitoring fatigue, fitness and endurance performance responses, which has direct implications for adjusting training load (1) daily during specific training blocks and (2) throughout the competitive season. However, these measures are still not widely implemented to monitor athletes' responses to training load, probably because of apparent contradictory findings in the literature. In this review I contend that most of the contradictory findings are related to methodological inconsistencies and/or misinterpretation of the data rather than to limitations of heart rate measures to accurately inform on training status. I also provide evidence that measures derived from 5-min (almost daily) recordings of resting (indices capturing beat-to-beat changes in heart rate, reflecting cardiac parasympathetic activity) and submaximal exercise (30- to 60-s average) heart rate are likely the most useful monitoring tools. For appropriate interpretation at the individual level, changes in a given measure should be interpreted by taking into account the error of measurement and the smallest important change of the measure, as well as the training context (training phase, load, and intensity distribution). The decision to use a given measure should be based upon the level of information that is required by the athlete, the marker's sensitivity to changes in training status and the practical constrains required for the measurements. However, measures of heart rate cannot inform on all aspects of wellness, fatigue, and performance, so their use in combination with daily training logs, psychometric questionnaires and non-invasive, cost-effective performance tests such as a countermovement jump may offer a complete solution to monitor training status in athletes participating in aerobic-oriented sports.

Effect of castration method on neurohormonal and electroencephalographic stress indicators in Holstein calves of different ages

As public concern for food animal welfare increases, a need to validate objective pain assessment tools exists in order to formulate animal welfare policies and facilitate regulatory approval of compounds to alleviate pain in livestock in the United States. The aims of this study were (1) to compare the physiological response to pain induced by surgical and nonsurgical (band) castration in calves and (2) to elucidate age-related differences in pain response of calves subjected to different castration methods. Seventy-six Holstein bull calves were blocked by age (≤8-wk and ≥6-mo-old) and randomly assigned to 1 of 4 treatment groups: control (n=20), castration by banding (n=18), cut-and-clamp surgical castration (n=20), and cut-and-pull surgical castration (n=18). Measurements included electroencephalogram, heart rate variability, infrared thermography, electrodermal activity, and concentrations of serum cortisol and plasma substance P before, during, and within 20min following castration. Electroencephalogram recordings showed desynchronization for all treatments, consistent with increased arousal; yet the magnitude of desynchronization was greatest for 6-mo-old calves castrated by cut-and-clamp. Additionally, older calves in the cut-and-pull group showed greater desynchronization than younger calves in the same group. Based on the heart rate variability analysis, 6-mo-old calves in the control or cut-and-pull castration groups showed greater sympathetic tone than younger calves in the same treatment groups. Overall, younger calves showed lower electrodermal activity than older calves. Regardless of treatment, concentrations of cortisol and plasma substance P were greater in 6-mo-old calves relative to their younger counterparts, indicating a more robust response to all treatments in older calves. In summary, neurohormonal and electroencephalographic stress responses of calves to castration were age-specific. Castration by cut-and-clamp showed the most pronounced stress response in 6-mo-old calves. These findings provide evidence that support welfare policies recommending castration at an early age and the use of analgesic compounds at the time of surgical castration especially in older calves. However, the potential long-term negative consequences of early untreated pain must be considered and warrant further investigation.