Asymmetric features of short-term blood pressure variability

Heart Rate Asymmetry in Healthy Children

Heart rate asymmetry (HRA) is a physiological phenomenon characterized by an unequal contribution of heart rate decelerations and accelerations to different heart rate variability (HRV) features. While HRA has been demonstrated in adults' ECGs of different duration, a similar investigation in healthy children has not been conducted. This study investigated the variance- and number-based HRA features in 96 healthy children (50 girls and 46 boys, aged 3-18 years) using 24-h ECGs. Additionally, we studied sex differences in HRA. To quantify HRA, variance-based and relative contributions of heart rate decelerations to short-term (C1d), long-term (C2d), and total (CTd) HRV, and the number of all heartbeats (Nd) were computed. Heart rate decelerations contributed more to C1d, but less to C2d and CTd, and were less frequent than heart rate accelerations. Short-term HRA was better expressed in boys. The majority of children (93.7%) had short-term HRA, 88.5% had long-term HRA, 88.5% had total HRA, and 99.0% had more accelerations than decelerations. No sex differences were observed for the rate of various HRA features. Heart rate asymmetry is a common phenomenon in healthy children, as observed in 24-h ECGs. Our findings can be used as reference data for future clinical studies on HRA in children.

An assessment of heart rate and blood pressure asymmetry in the diagnosis of vasovagal syncope in females

Introduction: Heart Rate Asymmetry (HRA) describes a phenomenon of differences between accelerations and decelerations in human heart rate. Methods used for HRA assessment can be further implemented in the evaluation of asymmetry in blood pressure variations (Blood Pressure Asymmetry-BPA). Methods: We have analyzed retrospectively the series of heartbeat intervals extracted from ECG and beat-to-beat blood pressure signals from 16 vasovagal patients (age: 32.1 ± 13.3; BMI: 21.6 ± 3.8; all female) and 19 healthy subjects (age: 34.6 ± 7.6; BMI: 22.1 ± 3.4; all female) who have undergone tilt test (70°). Asymmetry was evaluated with Poincaré plot-based methods for 5 min recordings from supine and tilt stages of the test. The analyzed biosignals were heart rate (RR), diastolic (dBP) and systolic Blood Pressure (sBP) and Pulse Pressure (PP). In the paper we explored the differences between healthy and vasovagal women. Results: The changes of HRA indicators between supine and tilt were observed only in the control group (Porta Index p = 0.026 and Guzik Index p = 0.005). No significant differences in beat-to-beat variability (i.e. spread of points across the line of identity in Poincaré plot-SD1) of dBP was noted between supine and tilt in the vasovagal group (p = 0.433 in comparison to p = 0.014 in healthy females). Moreover, in vasovagal patients the PP was significantly different (supine: 41.47; tilt: 39.27 mmHg) comparing to healthy subjects (supine: 35.87; tilt: 33.50 mmHg) in supine (p = 0.019) and in tilt (p = 0.014). Discussion: Analysis of HRA and BPA represents a promising method for the evaluation of cardiovascular response to orthostatic stressors, however currently it is difficult to determine a subject's underlying health condition based only on these parameters.

Alterations in Baroreflex Sensitivity and Blood Pressure Variability Following Sport-Related Concussion

Current methods to diagnose concussions are subjective and difficult to confirm. A variety of physiological biomarkers have been reported, but with conflicting results. This study assessed heart rate variability (HRV), spontaneous baroreflex sensitivity (BRS), and systolic blood pressure variability (BPV) in concussed athletes. The assessment consisted of a 5-min seated rest followed by a 5-min (0.1 Hz) controlled breathing protocol. Thirty participants completed baseline assessments. The protocol was repeated during the post-injury acute phase (days one to five). Total (p = 0.02) and low-frequency (p = 0.009) BPV spectral power were significantly decreased during the acute phase of concussion. BRS down-sequence (p = 0.036) and up-sequence (p = 0.05) were significantly increased in the acute phase of concussion, with a trend towards an increased BRS pooled (p = 0.06). Significant decreases in HRV were also found. Acute concussion resulted in altered BRS and BPV dynamics compared to baseline. These findings highlight objective physiological parameters that could aid concussion diagnosis and return-to-play protocols.

The influence of external stressors on physiological testing: Implication for return-to-play protocols

External stressors such as alcohol, caffeine, and vigorous exercise are known to alter cellular homeostasis, affecting the autonomic nervous system (ANS) and overall physiological function. However, little direct evidence exists quantifying the impact of these external stressors on physiological testing. We assessed the impact of the above-listed stressors on spontaneous baroreflex sensitivity (BRS), heart rate variability (HRV), heart rate asymmetry (HRA), and systolic blood pressure variability (BPV). Seventeen male university varsity American-style football athletes completed two identical assessments on separate days, once presenting with one or more stressors (recent intake of caffeine, alcohol, or exercise participation; contraindicated assessment) and another with no stressors present (repeat assessment). Both assessments were conducted within one week and at the same time of day. The testing protocol consisted of 5-min of rest followed by 5-min of a squat-stand maneuver (0.05 Hz). Continuous beat-to-beat blood pressure and electrocardiogram measurements were collected and allowed for calculations of BRS, HRV, HRA, and BPV. Significant decreases (p < 0.05) in HRV and HRA metrics (SDNN, SD2, SDNNd, SDNNa, SD2a, SD2d), HRV total power, and BRS-up sequence were found during the contraindicated assessment in comparison to the repeat assessment. When assessing those with exercise as their only stressor, high-frequency HRV and BRS-pooled were significantly decreased and increased, respectively, during the contraindicated assessment. Pre-season physiological baseline testing in sport is becoming increasingly prevalent and thus must consider external stressors to ascertain accurate and reliable data. This data confirms the need for stringent and standardized guidelines for pre-participation baseline physiological testing.

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External stressors (exercise participation, caffeine consumption, and alcohol consumption) decrease heart rate variability and the asymmetrical contribution of heart rate accelerations and decelerations (SDNN, SD2, Total Power, SDNNd, SDNNa, SD2d, and SD2a).

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External stressors decrease spontaneous baroreflex sensitivity up-sequence, but no significant changes were found regarding systolic blood pressure variability.

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The establishment of standardized pre-participation guidelines controlling for external stressors would increase the validity and reliability of physiological testing, improving the clinical utility of such data.

Effects of Phytocannabinoids on Heart Rate Variability and Blood Pressure Variability in Female Post-Concussion Syndrome Patients: Case Series

Cannabidiol (CBD) can exert neuroprotective effects without being intoxicating, and in combination with ∆9-tetrahydrocannabinol (THC), CBD has shown to protect against THC psychosis. Acute concussion and post-concussion syndrome (PCS) can result in autonomic dysfunction in heart rate variability (HRV), but less information is available on blood pressure variability (BPV). Furthermore, the effects of phytocannabinoids on HRV and BPV in PCS are unknown. The purpose of this study was to observe the influence of daily administration of CBD or a combination of CBD and THC on HRV and BPV parameters in 4 female PCS participants. Participants completed a seated 5-minute rest followed by 6 breaths per minute paced breathing protocol. Data was collected prior to phytocannabinoid intake and continued over 54 to 70 days. High frequency systolic BPV parameter increased every assessment period, unless altered due to external circumstances and symptoms. HRV parameters showed less consistent and varying responses. These results suggest that CBD can help to improve the altered autonomic dysfunction in those with PCS, and that responses to the drug administration was individualized. Double blinded, randomized controlled trials with greater sample sizes are required to better understand the influences of the varying dosages on human physiology and in PCS.

Hand grip strength variability during serial testing as an entropic biomarker of aging: a Poincaré plot analysis

Background

The Poincaré plot method can be used for both qualitative and quantitative assessment of self-similarity in usually periodic functions, hence the idea of applying it to the study of homeostasis of living organisms. From the analysis of numerous scientific data, it can be concluded that hand functionality can be correlated with the state of the human body as a biological system exposed to various forms of ontogenetic stress.

Methods

We used the Poincaré plot method to analyze the variability of hand grip strength (HGS), as an entropic biomarker of aging, during 60 repetitive tests of the dominant and nondominant hand, in young and older healthy subjects. An observational cross-sectional study was performed on 80 young adults (18–22 years old, mean age 20.01 years) and 80 older people (65–69 years old, mean age 67.13 years), with a sex ratio of 1:1 for both groups. For statistical analysis, we applied univariate descriptive statistics and inferential statistics (Shapiro–Wilk test, Mann–Whitney U-test for independent large samples, with the determination of the effect size coefficient r, and simple linear regression. We calculated the effect of fatigue and the Poincaré indices SD₁, SD₂, SD₁/SD₂ and the area of the fitting ellipse (AFE) for the test values of each subject.

Results

The analysis of the differences between groups revealed statistically significant results for most HGS-derived indices (p ≤ 0.05), and the magnitude of the differences indicated, in most situations, a large effect size (r > 0.5). Our results demonstrate that the proposed repetitive HGS testing indicates relevant differences between young and older healthy subjects. Through the mathematical modeling of data and the application of the concept of entropy, we provide arguments supporting this new design of HGS testing.

Conclusions

Our results indicate that the variability of HGS during serial testing, which reflects complex repetitive biomechanical functions, represents an efficient indicator for differentiation between young and older hand function patterns from an entropic perspective. In practical terms, the variability of HGS, evaluated by the new serial testing design, can be considered an attractive and relatively simple biomarker to use for gerontological studies.

Multistructure index characterization of heart rate and systolic blood pressure reveals precursory signs of syncope

Recurrent syncope - abrupt loss of consciousness - can have a serious impact on patients' quality of life, comparable with chronic illnesses. Vasovagal syncope (VVS) is a specific reflex syncope, in which an inappropriate reaction of the autonomic nervous system (ANS) plays a key role in the pathophysiology. In syncope diagnosis, an ideal diagnostic method should positively identify vasovagal sensitive patients, without the need to perform a specialised head-up tilt table (HUTT) test. We apply a novel methodology of multistructure index (MI) statistics for seamlessly evaluating the size spectrum of the asymmetry properties of magnitudes of neural reflexes responsible for maintaining the homeostatic dynamics of autonomic control. Simultaneous evaluation using the MI of the effects on heart rate and blood pressure involved in achieving homeostasis of contrasting properties of the dynamics of slow and fast neural regulation reveals a clear distinction between vasovagal patients and healthy subjects, who are/are not susceptible to spontaneous fainting. Remarkably, a healthy cardiovascular response to the HUTT test is indeed evident prior to the test, making the MI a robust novel indicator, clearly distinguishing the cardiovascular autonomic regulation of healthy people from that of vasovagal patients without the need to perform an actual HUTT test.

Blood pressure variability and baroreflex sensitivity of a healthy male during cold pressor test that induced development of neurocardiogenic syncope

BACKGROUND

The cold pressor test (CPT) is a recognized physiological technique to evaluate autonomic cardiovascular function. The present case study assessed the cardiovascular response of a healthy adult male during 3 min of CPT.

METHODS

Heart rate (HR) by single-lead electrocardiography and blood pressure (BP) by an arterial tonometer of the participant on a beat-to-beat basis were recorded before and during CPT.

RESULTS

HR during CPT showed a biphasic pattern with an initial increase from baseline (86 bpm) to the first 30 s of CPT (93 bpm) followed by a decrease. It dropped to 51 bpm during the last 30 s of CPT. Systolic blood pressure (SBP) increased from baseline (110 mmHg) to 1 min (122 mmHg) followed by a decrease. SBP immediately after CPT reduced to 57 mmHg. Diastolic blood pressure (DBP) from baseline (71 mmHg) slightly increased to 75 mmHg up to 90 s of the test, thereafter it registered a fall, and during the last 30 s of CPT, DBP fell to 30 mmHg. Stroke volume increased from baseline (75 mL/min) to the first 30 s (99 mL/min), followed by a slight reduction which was maintained till last of the test (70 mL/min). Cardiac output after an initial increase from baseline (6.4 L/min) to the first 30 s (9.2 L/min) decreased to 4.1 L/min during the last 30 s of the test. Baroreflex sensitivity (BRS) from baseline (9.32 ms/mmHg) plummeted to 6.67 ms/mmHg during the first 30 s of CPT followed by an increase, and after CPT, BRS was increased to 15.23 ms/mmHg. Other cardiovascular parameters such as myocardial contractility (dp/dt), total peripheral resistance, and mean arterial pressure were reduced in the individual at the time of loss of consciousness that occurred at the end of the last 30 s of CPT.

CONCLUSIONS

The present case study described the modulation of cardiovascular functions of a healthy male during CPT, which finally led to the development of neurocardiogenic syncope characterized by hypotension and bradycardia.

Abnormal Motor Activity and Thermoregulation in a Schizophrenia Rat Model for Translational Science

Background

Schizophrenia is accompanied by altered motor activity and abnormal thermoregulation; therefore, the presence of these symptoms can enhance the face validity of a schizophrenia animal model. The goal was to characterize these parameters in freely moving condition of a new substrain of rats showing several schizophrenia-related alterations.

Methods

Male Wistar rats were used: the new substrain housed individually (for four weeks) and treated subchronically with ketamine, and naive animals without any manipulations. Adult animals were implanted with E-Mitter transponders intraabdominally to record body temperature and locomotor activity continuously. The circadian rhythm of these parameters and the acute effects of changes in light conditions were analyzed under undisturbed circumstances, and the effects of different interventions (handling, bed changing or intraperitoneal vehicle injection) were also determined.

Results

Decreased motor activity with fragmented pattern was observed in the new substrain. However, these animals had higher body temperature during the active phase, and they showed wider range of its alterations, too. The changes in light conditions and different interventions produced blunted hyperactivity and altered body temperature responses in the new substrain. Poincaré plot analysis of body temperature revealed enhanced short- and long-term variabilities during the active phase compared to the inactive phase in both groups. Furthermore, the new substrain showed increased short- and long-term variabilities with lower degree of asymmetry suggesting autonomic dysregulation.

Conclusions

In summary, the new substrain with schizophrenia-related phenomena showed disturbed motor activity and thermoregulation suggesting that these objectively determined parameters can be biomarkers in translational research.

Investigating foetal heart rate asymmetry

In this study, we have investigated how the asymmetry of beat-to-beat foetal heart rate variability (fHRV) changes during development after 35 weeks and before 32 weeks of gestation. Noninvasive foetal electrocardiogram (fECG) signals from 78 pregnant women at the gestational age from 16 to 41 weeks with normal single pregnancies were analysed. Heart rate asymmetry (HRA) index that measures time asymmetry of RR interval time-series signal was used to understand the dynamics of fHRV. Results indicate that foetal HRA measured by Guzik's Index (GI) and Porta's Index (PI) changes after 35 weeks gestation compared to foetus before 32 weeks of gestation. It might be due to significant amount of maturation of the autonomic nervous system done after 35 and could potentially help identify the pathological autonomic nervous system development.

Multiscale time irreversibility of heart rate and blood pressure variability during orthostasis

Time irreversibility is a characteristic feature of non-equilibrium, complex systems such as the cardiovascular control mediated by the autonomic nervous system (ANS). Time irreversibility analysis of heart rate variability (HRV) and blood pressure variability (BPV) represents a new approach to assess cardiovascular regulatory mechanisms. The aim of this paper was to assess the changes in HRV and BPV irreversibility during the active orthostatic test (a balance of ANS shifted towards sympathetic predominance) in 28 healthy young subjects. We used three different time irreversibility indices-Porta's, Guzik's and Ehler's indices (P%, G% and E, respectively) derived from data segments containing 1000 beat-to-beat intervals on four timescales. We observed an increase in the HRV and a decrease in the BPV irreversibility during standing compared to the supine position. The postural change in irreversibility was confirmed by surrogate data analysis. The differences were more evident in G% and E than P% and for higher scale factors. Statistical analysis showed a close relationship between G% and E. Contrary to this, the association between P% and G% and P% and E was not proven. We conclude that time irreversibility of beat-to-beat HRV and BPV is significantly altered during orthostasis, implicating involvement of the autonomous nervous system in its generation.

Asymmetric properties of long-term and total heart rate variability

We report on two new physiological phenomena: the long-term and total heart rate asymmetry, which describe a significantly larger contribution of heart rate accelerations to long-term and total heart rate variability. In addition to the existing pair of indices, SD1(d); SD1(a); which are based on partitioning short-term variance, we introduce two other pairs of descriptors based on partitioning longterm (SD2(d); SD2(a)) and total (SDNN(d); SDNN(a)) heart rate variability. The new asymmetric descriptors are used to analyze RR intervals time series derived from the 30-min ECG recordings of 241 healthy subjects resting in supine position. It is shown that both new types of asymmetry are present in 76% of the subjects. The new phenomena reported here are real physiological findings rather than artifacts of the method since they vanish after data shuffling.