Standard Deviation Of Successive Differences Research Articles

Assessment of the relationship of systemic vascular dysfunction and cardiac autonomic neuropathy (CAN) with diabetic retinopathy.

Diabetic retinopathy, a form of microvasculopathy, is the leading cause of the visual abnormality. However, there is no conclusive evidence of the relationship of systemic vascular dysfunction with retinal microvasculopathy. In addition, diabetes-associated cardiac autonomic neuropathy may also compromise vascular function. The present study intends to correlate arterial stiffness, endothelial function, and heart rate variability (HRV) as a standardized measure of cardiac autonomic neuropathy with diabetic retinopathy. The present cross-sectional, observational study was conducted in the Department of Physiology. Twenty subjects were recruited in group 1 (T2DM, type 2 diabetes mellitus patients, without retinopathy) and group 2 (T2DM with retinopathy). The vascular parameters such as heart rate, peripheral and central blood pressure, augmentation index [AIx (%)], brachial -ankle pulse wave velocity (baPWV), and reactive hyperaemia index (RHI) were recorded. Independent sample t-test (for parametric data) and Mann-Whitney U test (for non-parametric data) were employed to compare the variables of two groups. Spearman correlation was used to examine the relationship among the parameters. Linear regression analysis was performed to examine the important vascular predictor for diabetic retinopathy. baPWV was significantly higher in group 2 than in group 1 and positively associated with group 2. RHI was significantly less in group 2 than group 1 and negatively associated with group 2. Among HRV metrics, standard deviation of successive differences (SDSD), root mean square of successive differences between normal heartbeats (RMSSD), and high frequency (HF) power were significantly decreased in group 2 than in group 1. SDSD, RMSSD, and HF power were negatively associated with group 2. RHI emerged as a significant predictor of diabetic retinopathy following linear regression. Overall, the result of the present study indicates that metabolic dysregulation of glucose may affect the normal functioning of the autonomic nervous system and vascular function. Therefore, screening of vascular function and cardiac autonomic tone may be advocated in diabetic patients in routine clinics to examine the existence of any comorbid condition, such as diabetic retinopathy, as systemic vascular changes may also affect ophthalmic vasculature.

Lower ultra-short-term heart rate variability can predict worse mucosal healing in ulcerative colitis

BackgroundPsychological stress has been proved to be a risk factor for exacerbation for ulcerative colitis (UC). However, traditional approaches of quantifying psychological stress using psychological scales are time-consuming and the results may not be comparable among patients with different educational levels and cultural backgrounds. Alternatively, heart rate variability (HRV) is an indicator for psychological stress and not biased by educational and cultural backgrounds.AimsIn this study, we try to explore the relationship between psychological stress and UC by analyzing the effect of ultra-short-term HRV on mucosal and histological remission status of UC.MethodsThis is a retrospective case–control study on UC inpatients from 2018 through 2020. Ultra-short-term HRV were calculated using baseline electrocardiography. Patients were divided intocase and control groups according to their Mayo endoscopic scores or histological Geboes scores. Three variables of ultra-short-term HRV (the standard deviation of normal to normal R-R intervals (SDNN), the standard deviation of successive differences between adjacent normal to normal R-R intervals (SDSD), the root mean square of successive differences of normal to normal R-R intervals (RMSSD)) were compared between different groups. And for those variables with significant differences, we built univariate and multivariate logistic regressions to depict the relationship between HRV variables and remission status of UC.ResultsAll three HRV variables showed significant differences between the mucosal groups. However, none of them showed significant difference between the histological groups. In further logistic regression analyses, smaller RMSSD can predict severe mucosal healing status (OR = 5.21).ConclusionsLower ultra-short-term HRV (i.e. smaller RMSSD) is shown to positively correlate with worse mucosal healing status. However, ultra-short-term HRV cannot predict histological healing status according to our data.

Effects of Different Doses of Caffeinated Coffee on Muscular Endurance, Cognitive Performance, and Cardiac Autonomic Modulation in Caffeine Naive Female Athletes

Caffeine is widely consumed among elite athletes for its well-known ergogenic properties, and its ability to increase exercise performance. However, studies to date have predominantly focused on the anhydrous form of caffeine in male participants. The aim of the study was to investigate the effect of caffeinated coffee ingestion on lower-upper body muscular endurance, cognitive performance, and heart rate variability (HRV) in female athletes. A total of 17 participants (mean ± standard deviation (SD): age = 23 ± 2 years, body mass = 64 ± 4 kg, height = 168 ± 3 cm) in a randomized cross-over design completed three testing sessions, following the ingestion of 3 mg/kg/bm of caffeine (3COF), 6 mg/kg/bm of caffeine (6COF) provided from coffee or decaffeinated coffee (PLA) in 600 mL of hot water. The testing results included: (1) repetition number for muscular endurance performance; (2): reaction time and response accuracy for cognitive performance; (3): HRV parameters, such as standard deviation of normal-to-normal (NN) intervals (SDNN), standard deviation of successive differences (SDSD), root mean square of successive differences (RMSSD), total power (TP), the ratio of low- and high-frequency powers (LF/HF), high-frequency power (HF), normalized HF (HFnu), low-frequency power (LF), and normalized LF (LFnu). A one-way repeated measures ANOVA revealed that 3COF (p = 0.024) and 6COF (p = 0.036) improved lower body muscular endurance in the first set as well as cognitive performance (p = 0.025, p = 0.035 in the post-test, respectively) compared to PLA. However, no differences were detected between trials for upper body muscular endurance (p = 0.07). Lastly, all HRV parameters did not change between trials (p > 0.05). In conclusion, ingesting caffeinated coffee improved lower body muscular endurance and cognitive performance, while not adversely affecting cardiac autonomic function.

Predictors of atrial mechanical sensing and atrioventricular synchrony with a leadless ventricular pacemaker: Results from the MARVEL 2 Study

The MARVEL (Micra Atrial TRacking Using a Ventricular AccELerometer) 2 study assessed the efficacy of atrioventricular (AV) synchronous pacing with a Micra leadless pacemaker. Average atrioventricular synchrony (AVS) was 89.2%. Previously, low amplitude of the Micra-sensed atrial signal (A4) was observed to be a factor of low AVS. The purpose of this study was to identify predictors of A4 amplitude and high AVS. We analyzed 64 patients enrolled in MARVEL 2 who had visible P waves on electrocardiogram for assessing A4 amplitude and 40 patients with third-degree AV block for assessing AVS at rest. High AVS was defined as >90% correct atrial-triggered ventricular pacing. The association between clinical factors and echocardiographic parameters with A4 amplitude was investigated using a multivariable model with lasso variable selection. Variables associated with A4 amplitude together with premature ventricular contraction burden, sinus rate, and sinus rate variability (standard deviation of successive differences of P-P intervals [SDSD]) were assessed for association with AVS. In univariate analysis, low A4 amplitude was inversely related to atrial function assessed by E/A ratio and e'/a' ratio, and was directly related to atrial contraction excursion (ACE) and atrial strain (Ɛa) on echocardiography (all P ≤.05). The multivariable lasso regression model found coronary artery bypass graft history, E/A ratio, ACE, and Ɛa were associated with low A4 amplitude. E/A ratio and SDSD were multivariable predictors of high AVS, with >90% probability if E/A <0.94 and SDSD <5 bpm. Clinical parameters and echocardiographic markers of atrial function are associated with A4 signal amplitude. High AVS can be predicted by E/A ratio <0.94 and low sinus rate variability at rest.

Effects of a 75-km mountain ultra-marathon on heart rate variability in amateur runners.

This study examined the effects of a mountain ultra-marathon (MUM) on the activity of the autonomous nervous system through heart rate variability (HRV) monitoring and determined whether this variable related to final performance. Heart rate and HRV were measured in eight male amateur runners (aged 37-60 years). Measurements were recorded before and after the event, in resting conditions, as well as continuously throughout the whole MUM. In addition, percentage (%) of heart rate reserve (HR<inf>res</inf>) and partial and total times during the race were analyzed. Average heart rate (HR<inf>avg</inf>) measured at rest was increased after the event (+37%). Standard deviation of successive differences (SDSD) and the square root of the mean squared differences of successive NN intervals (RMSSD) were reduced after the MUM (-56% and -59%, respectively). There was a positive relationship between the frequency-domain index normalized low frequency power (PLFn) measured at rest before the event and race time (0.79) while there was a negative relationship between race time and the difference in HR<inf>avg</inf> before and after the event. In the last half of the event, there was a high correlation (Spearman coefficient of correlation >0.9) between race time and the standard deviation of the NN intervals (SDNN) registered during the race. Autonomous cardiac regulation can be related to the performance in a mountain ultra-marathon. HRV monitoring could represent a practical tool for the evaluation of the relationship between the autonomous nervous system activity and performance in a mountain ultra-marathon.

Effect of Acute Elevations in Serum Phosphate on Cardiac Baroreflex Sensitivity in Young Healthy Adults

Over the last 20 years, with the growing abundance of processed foods in the United States, dietary intake of inorganic phosphate (Pi) has more than doubled the daily‐recommended allowance. Importantly, chronic consumption of Pi is associated with an increased risk of cardiovascular diseases in the general population, such as atherosclerosis, hypertension, and stroke. However, investigation of the potential underlying mechanisms by which high Pi intake affects the cardiovascular system has been limited. Given the strong link between impairments in cardiac baroreflex sensitivity (cBRS) and reductions in heart rate variability (HRV) to greater cardiovascular morbidity and mortality, we examined the impact of acute high Pi consumption on cBRS and HRV. We tested the hypotheses that acute high Pi consumption attenuates cBRS and decreases HRV in young adults. Fourteen young men were studied on two separate days in which they consumed either a phosphate drink containing 2,000 mg Phosphorus and 1,520 sodium (n=13; 23 ± 1 yrs; mean ± SEM) or a sodium chloride drink (NaCl) containing 1,520 mg sodium (n=5; 23 ± 2 yrs) to match the sodium in the phosphate drink and to serve as a control. Resting heart rate (ECG) and arterial blood pressure (finger photoplethysmography and automated sphygmomanometer) were measured for a 10 min period before and 60 min post‐Pi (a time period known to elicit peak elevations in serum phosphate following Pi consumption) or post‐NaCl consumption. Blood draws were performed at baseline, 60 min, and 120 min to measure serum phosphate. The Sequence Method was used to estimate spontaneous cBRS separately for up sequences (increase systolic blood pressure: increase R‐R interval), down sequences (decrease systolic blood pressure: decrease R‐R interval), and for all sequences combined (overall cBRS). HRV was determined in the time‐domain as Root Mean Square of the Successive Differences (RMSSD), Standard Deviation of Successive Differences (SDSD), and Standard Deviation of Normal to Normal R‐R intervals (SDNN). Serum phosphate was significantly elevated at 60 min (baseline: 3.2 ± 0.2 mg/dL; 60 min: 4.5 ± 0.2 mg/dL; p&lt;0.01) and was maintained at 120 min post‐ Pi consumption. Resting blood pressure was not affected by Pi consumption (mean BP: pre 84 ± 2 vs. post 85 ± 2; p=0.23). Overall cBRS showed no differences between pre‐and post‐Pi (25.1 ± 2.4 vs. 26.1 ± 2.9 ms/mmHg; p=0.50). Up sequences and down sequences were also not different pre‐ and post‐Pi. The number of sequences were similar pre‐ and post‐Pi. For HRV, no differences were observed pre‐and post‐Pi (e.g. RMSSD: 93.9 ± 15.06 vs. 86.4 ± 13.67 ms; p=0.37). NaCl consumption had no effect on serum phosphate (p=0.51), or any measured cardiovascular variable. These preliminary data suggest that acute exposure to high Pi is not directly associated with an impairment in resting cBRS or decrease in HRV in young, healthy men.Support or Funding InformationSupported by UTA College of Nursing and Health InnovationThis abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

220 Daphnia magna as a model for quantifying chaos in cardiac arrhythmia

IntroductionDaphnia magna are an established model in ecology for the investigation of toxins in freshwater systems, as well as an emerging model in medical science. Daphnia have a myogenic heart,...

Abstract 9234: Ventricular Irregularity, but not Ventricular Rate, is Important for Determination of NT-ProBNP Levels in Chronic Atrial Fibrillation: Evidence for Lenient Rate Control in Atrial Fibrillation

Background Adequate rate control has been a concern in management of patients with atrial fibrillation(AF). Role of ventricular rate(VR) and its irregularity have not been well studied with respect to the elevation of NT-proBNP level. VR at which NT-proBNP level is lowest would be the optimal heart rate in patients with AF. Methods and Results In 85 patients with AF(69.8±9.0 years, 43 men), NT-proBNP level, indices of VR irregularity(mean VR, standard deviation(SD) of VR, SD of successive differences and SD of 5-minute averages(SDAVR)) derived from 24-hour ambulatory ECG and transthoracic echocardiographic parameters(early mitral inflow velocity(e)/mitral annular velocity(e′), left atrial volume index and left ventricular ejection fraction(LVEF)) were measured. Potential determinants of NT-proBNP level were identified by univariate and multivariate linear analysis. Age, e/e’ and SDAVR were significant univariate predictors of NT-proBNP level, but mean VR did not. e/e′and SDAVR remained as significant predictors after multivariate adjustment(β=0.028, P =0.004, and β=-0.002, P =0.008, respectively). When the patients were stratified with the 33rd and 67th percentile values of e/e′(10.62 and 14.63, respectively), a significant positive correlation between mean VR and NT-proBNP level was present in patients with higher e/e(N=57, β=0.007, P =0.043). Conclusions LV diastolic function and VR irregularity rather than VR were associated with elevation of NT-proBNP level in AF. Key words : Atrial fibrillation, NT-proBNP

The Relationship between Heart Rate Variability and Adiposity Differs for Central and Overall Adiposity

While frank obesity is associated with reduced HRV, indicative of poorer autonomic nervous system (ANS) function, the association between body mass index (BMI) and HRV is less clear. We hypothesized that effects of adiposity on ANS are mostly mediated by visceral fat and less by subcutaneous fat; therefore, centrally distributed adipose tissue, that is, waist circumference (WC), should be more strongly associated with HRV than overall adiposity (BMI). To examine this hypothesis, we used data collected in a subset of the Baltimore Longitudinal Study of Aging to compare strength of association between HRV and WC to that of HRV and BMI. Time domain HRV variables SDNN (standard deviation of successive differences in normal-to-normal (N-N) intervals) and RMSSD (root mean square of successive differences in N-N intervals) were calculated from 24-hour Holter recordings in 159 participants (29–96 years). Increasing WC was associated with decreasing SDNN and RMSSD in younger but not older participants (P value for WC-by-age interaction = 0.003). BMI was not associated with either SDNN or RMSSD at any age. In conclusion, central adiposity may contribute to sympathetic and parasympathetic ANS declines early in life.

Ventricular Irregularity, But Not Ventricular Rate, Is Important for Determination of NT-ProBNP Levels in Chronic Atrial Fibrillation: Evidence for Lenient Rate Control in Atrial Fibrillation

Background: Role of ventricular rate (VR) and its irregularity in AF have not been well studied with respect to the elevation of NT-proBNP. Methods and Results: In 66 patients with AF (71±9 years, 32 men), NT-proBNP, indices of VR irregularity (mean VR, standard deviation (SD) of VR, SD of successive differences and SD of 5-minute averages (SDAVR)) derived from 24-hour Holter and transthoracic echocardiographic parameters (early mitral inflow velocity (e)/mitral annular velocity (e′), left atrial volume index and left ventricular ejection fraction (LVEF)) were measured. Mean VR, LVEF, e/e′, SDVR and SDAVR were significant univariate predictors of NT-proBNP. e/e′ and SDAVR remained as significant predictors after multivariate adjustment (standardized β=0.306, P=0.007, and β=−0.362, P=0.002, respectively), but mean VR did not. By partial correlation, e/e′ was found to be independently correlated with NT-proBNP (r=0.283, P=0.031), but mean VR was not (r=0.032, P=0.811). When the patients were stratified with the 33rd and 67th percentile values of e/e′ (11.8 and 15.4, respectively), a significant positive correlation between mean VR and NT-proBNP was present only in patients with the upper tertile value. Conclusions: VR is not as important as LV diastolic function and VR irregularity in the elevation of NT-proBNP in AF. VR control may be needed in patients with severe LV diastolic dysfunction. Our results support the findings of RACE II trial.

An electrocardiogram marker to detect paroxysmal atrial fibrillation

An electrocardiogram marker to detect patients who have paroxysmal atrial fibrillation (PAF) is reported. The data set of ECG records made available by PhysioNet for Cardiology Challenge 2001 was used. The method uses a filtered time series with a frequency range between 3 and 9 Hz obtained from the electrocardiogram record. Typically, frequencies observed when a patient is in atrial fibrillation and atrial flutter is within this frequency range. Filtering was done using wavelets. Thereafter, the temporal properties of this filtered time series are studied. The temporal properties studied are the standard deviation, standard deviation of successive differences, and the length of the ellipse in the Poincare plot. The results indicate that these temporal properties of patients with PAF are depressed compared to the healthy group. A marker based on these temporal properties shows promise in detecting PAF when patients are in normal sinus rhythm. Results also show that the values for these temporal properties for a patient with PAF show little variation with time, and its measure is not dependent on the time of occurrence of a PAF episode.

The effect of autonomic manipulation on heart rate variability in dogs

Beat-to-beat variation of heart rate is reflective of autonomic balance and has been used to assess pain and stress in human beings. The purpose of this investigation was to pharmacologically manipulate the autonomic nervous system and to determine the effect of these manipulations on heart rate variability (HRV) in dogs. Four adult male hound dogs (27 ± 1 kg) were used in the investigation. Each dog was given five treatments: Parasympathetic blockade (glycopyrrolate; 0.01 mg kg−1 IV and 0.01 mg kg−1 IM), parasympathetic stimulation (phenylephrine; 0.005 mg kg−1 IV + 0.05 mg kg−1hour−1), sympathetic blockade (propranolol; 0.11 mg kg−1 IV), sympathetic stimulation propranolol; 0.01 μg kg−1 minute−1), and saline control. At least 48 hours were allowed between treatments. ECG recordings were obtained using an ambulatory ECG monitor. A 5-minutes period of continuous recording obtained ~30 minutes after initiation of drug administration was used for data analysis. Changes in HRV were evaluated by time and frequency-domain analysis. The standard deviation of normal R-R intervals (SDNN), as well as the standard deviation of successive differences in RR intervals (SDSD) were assessed for each treatment. Low frequency (LFP; 0.05–0.15 Hz), high frequency (HFP; 0.15–0.35 Hz), and total (TP; 0.017–0.5 Hz) spectral power were also determined. The LFP:HFP ratio was also evaluated. A two-way anovawith a Tukey's test was used to detect differences (p < 0.05). Administration of glycopyrrolate or isoproterenol increased HR and decreased SDNN and SDSD below control levels. Phenylephrine or propranolol administration were without effect. LFP was diminished by glycopyrrolate and isoproterenol, but was unaffected by phenylephrine and propranolol. HFP, TP, and LFP:HFP were unaffected by treatment. Both branches of the autonomic nervous system influence SDNN and LFP. SDSD, in contrast, is altered primarily by parasympathetic activity. Thus, it appears that parasympathetic activity modulates HRV in the resting dog, as either withdrawal of parasympathetic influence or accentuated sympathetic activity led to significant changes in these measures of HRV. Conversely, augmentation of parasympathetic activity or withdrawal of sympathetic tone minimally affected HRV.

The effect of anesthesia and surgery on heart rate variability in dogs

Heart rate variability (HRV) may be useful for objective assessment of stress and pain in animals. The objective of this study was to describe the effect of anesthesia and surgery on HRV in dogs. We hypothesized that surgery would decrease HRV to a greater degree and for a longer duration than anesthesia alone. Four healthy male dogs (29 ± 2 kg) were instrumented for ambulatory ECG monitoring. Continuous ECG data was obtained for 1 day prior to, and 6 days following anesthesia alone (ANES) or anesthesia plus unilateral stifle arthrotomy (ANSX). The anesthetic protocol included xylazine (0.5 mg kg–1 IM), morphine (0.5 mg kg–1 IM), atropine (0.04 mg kg–1 IM), thiopental (10 mg kg–1 IV) and isoflurane in oxygen. A single dose of morphine (0.5 mg kg–1 IM) was administered at extubation. Time domain analysis of HRV was performed on 5 minutes epochs of artefact- and arrhythmia-free ECG data obtained at 12 noon and 12 midnight on each of the seven experimental days. Mean RR interval, standard deviation of normal R-R intervals (SDNN), and the standard deviation of successive differences in RR intervals (SDSD) were compared to baseline for ANES and ANSX. Pain scores obtained during the day were also evaluated. Significance was set at p < 0.01. There were no differences between groups for any baseline data. Mean RR interval did not differ from baseline on days 1–6 in ANES or ANSX. SDNN and SDSD values at noon were not different from baseline on days 1–6 in ANES or ANSX. At midnight on days 1 and 2, SDNN was significantly decreased from baseline in ANSX, and on day 1 a significant difference between groups existed. ANSX values of SDSD at midnight were significantly decreased from baseline and ANES on day 1. Pain scores for ANSX were significantly greater than baseline on days 1–3, and different from ANES on days 1–5. These results suggest that HRV is decreased following anesthesia plus surgery, and that changes in HRV may be associated with pain.

Vagal changes following cancer chemotherapy: Implications for the development of nausea

Many physiological changes that occur contemporaneously with nausea are mediated by the autonomic nervous system, but the specific autonomic changes associated with nausea have not been characterized. Cardiac parasympathetic (vagal) activity as indicated by heart rate variability, measured as the standard deviation of successive differences (SDSD) in beat-to-beat intervals, was assessed in 24 women with ovarian cancer immediately prior to and accompanying nausea that occurred following anticancer chemotherapy. A progressive increase in SDSD followed infusion of the chemotherapy agent, indicating a rise in cardiac parasympathetic (vagal) activity, with onset of nausea consistently occurring after the peak activity had been reached, at a time when SDSD was decreasing. An increase in parasympathetic activity seems to set the stage for the expression of nausea but an additional stimulus is apparently needed to finally trigger the event.

Psychosocial Issues: Autonomic Measures Associated with Chemotherapy-Related Nausea: Techniques and Issues

Advances in antiemetic therapy for cancer patients have been hindered by a lack of understanding of the physiological mechanisms associated with nausea and their corresponding measurement techniques. Here we review conceptual and methodological issues involved in developing an autonomic frame of reference for nausea and outline two strategies for assessing autonomic function. A primarily research-oriented strategy uses heart rate, blood volume pulse, pallor, and skin temperature to assess autonomic activity and reactivity over 24 hr. Peak values of these measures relative to time of emesis, heart rate spectral analyses of autonomic activity, and analyses of the standard deviation of successive differences of beat-to-beat intervals were all associated with subsequent nausea. A primarily clinically oriented strategy assesses normal and abnormal results on eight common bedside clinical tests of autonomic function. The total number of abnormal tests was associated with subsequent nausea. A better understanding of chemotherapy side effect mechanisms is likely to result in less polypharmacy and more effective individualized treatment for cancer patients.