Deviation Of Normal RR Intervals Research Articles

Abstract 4136776: Prognostic Value of Resting Heart Rate and Heart Rate Variability in the 12-lead Electrocardiogram: Mortality Data From the CODE Nationwide Database

Introduction: Resting Heart Rate (HR) and Heart Rate Variability (HRV) reflect autonomic control, and are implicated as prognostic factors. We aimed to evaluate the prognostic value of HR and HRV in a cohort from a nationwide telemedicine network. Methods: We assessed unique ECGs recorded from patients ≥16 years-old, from the tele-ECG database of the Telehealth Network of Minas Gerais, Brazil, between 2010 and 2017. Variables of interest were HR and standard deviation of normal RR intervals (SDNN). Self-informed data were collected: sex, age, risk factors (hypertension, dyslipidemia, diabetes, smoking) and comorbidities (myocardial infarction, Chronic Obstructive Pulmonary Disease, and Chagas disease). Outcomes of interest were all-cause and cardiovascular mortality, assessed by ICD codes reported in death certificates, through linkage with the Mortality Information System. Cox regression was applied to evaluate the association between HR and HRV and the outcomes, in 4 models: 1. Unadjusted; 2. Adjusted for sex and age; 3. Model 2 + risk factors + clinical comorbidities; 4. Model 3 + HRV or HR, respectively. Results: At total 992.611 individuals were included, median age of 55 years, 60% women. In 6 years, there were 33.292 deaths (3,37%), 21% due to cardiovascular causes. Patients who died had higher prevalence of all risk factors and comorbidities, as well as higher HR: 76 (IQR 66-87) vs. 74 (IQR 65-83) bpm, p<0.001 and lower HRV: 84 (IQR 51-127) vs. 114 (IQR 74-153), p<0.001. After adjustments (model 4), all HR quartiles were independently associated a progressively increased risk of all-cause mortality, being 88% higher for the 4 th quartile (HR=1.88 (95%CI 1.77–1.89). Similarly, the 1 st and 2 nd HRV quartiles remained associated with increased all-cause mortality (1 st quartile HR=1.42 (95%CI 1.37–1.47) in the final model. For cardiovascular mortality, HR was also an independent predictor, with a progressively higher risk, with a 77% increase (HR=1.77 95%CI 1.65–1.91) in the 4 th quartile. HRV was also an independent predictor of cardiovascular death, with a 33% risk increase (HR=1.33, 95%CI 1.23–1.44) for the 1 st quartile. Male gender, age, and all risk factors and comorbidities were also independent predictors of all-cause and cardiovascular mortality. Conclusions: In a large cohort of Brazilian adults, baseline HR and HRV were independent predictors of all-cause and cardiovascular mortality, after adjustment for clinical variables and autonomic indexes.

Relationship between heart rate variability and echocardiography indices of cardiac function in healthy individuals.

This study evaluated the relationship between HRV and echocardiography indices of cardiac function. Healthy individuals (N = 30) aged 33 ± 10 years old, underwent short-term resting HRV assessment and transthoracic echocardiography with speckle tracking analysis. Time domain - (i.e. R-R interval, root mean square of successive RR interval difference (RMSSD), standard deviation of normal RR intervals (SDNN) and frequency domain-measures of HRV (i.e. high-frequency power (HF), low-frequency power (LF), high-frequency normalised (HFnorm) and low-frequency normalised (LFnorm)). Echocardiography indices of cardiac function included; Left ventricular ejection fraction (LVEF), left- and right-ventricular global longitudinal strain (LV-GLS, and RV GLS), left atrial strain: left atrial reservoir (LAres), left atrial conduit (LAcon) and left atrial contraction (LACT). The mean values for HRV time-domain measures were: R-R (991 ± 176 ms), SDNN (50.9 ± 21.5 ms), and RMSSD (46.8 ± 29.4 ms); and frequency-domain: LF (727 ± 606 ms2), HF (415 ± 35 ms2), LFnorm (56 ± 19.4) and HFnorm (36.5 ± 18.8). Mean values for indices of cardiac function were LVEF (59.9% ± 2.8%), LV-GLS (19.2% ± 1.4%), RV-GLS (21.7% ± 2.7%), LAres (36.8% ± 6.99%), LAcon (26.2% ± 6.95%) and LACT (12.3% ± 3.56%). There was a significant negative relationship between HF and LV-GLS (r = -0.47, p = 0.01) and RMSSD and LVEF (r = -0.39, p = 0.03) respectively. Heart rate variability measures such as high frequency power and RMSSD are associated with left ventricle systolic function in healthy individuals.

How did coronavirus disease 2019 affect autonomic balance in young individuals? Analysis by heart rate variability.

The aim of this study was to demonstrate the effect of coronavirus disease 2019 on the cardiovascular autonomic system using heart rate variability in young individuals. The study was designed retrospectively by scanning the 24-h Holter electrocardiography records of patients who applied to the Ankara Abdurrahman Yurtaslan Oncology Education and Research Hospital Cardiology outpatient clinic. The study group consisted of 492 patients under the age of 40 years, who did not have additional comorbidities or medication use and had prolonged symptoms after coronavirus disease 2019 during the pandemic. The control group, including 401 patients, was determined during the pre-pandemic period (before December 2019). Heart rate variability parameters were evaluated by scanning the 24-h Holter electrocardiography records of the patients and compared with the non-coronavirus disease 2019 group. The median age of participants was 30 years. Standard deviation of normal RR intervals (SDNN) ≤100 ms was more prevalent in the study group (27 (6.7%) vs 73 (14.8%), p<0.001). In univariate logistic regression analysis, the presence of coronavirus disease 2019 [(OR 2.41, 95%CI 1.52-3.83), p<0.001] and age [(OR 1.04, 95%CI 1.01-1.07), p=0.016] had a significant effect on the probability of SDNN≤100. In multivariate logistic regression analysis, the presence of coronavirus disease 2019 [(OR 2.42, 95%CI 1.52-3.85), p<0.001] and age [(OR 2.42, 95%CI 1.52-3.85), p=0.016] had a significant effect on the probability of SDNN≤100. Frequency domain measures such as, high-frequency values were significantly higher in the study group (p=0.029). The study group's low-frequency/high frequency ratio was significantly lower (p=0.019). The low-frequency/high-frequency ratio's cut-off value was ≤2.77. for determining the differentiation between coronavirus disease 2019 positive and negative cases in the receiver operating characteristic analysis. The sensitivity rate was 80.7%. The area under the curve value is 0.546 (p=0.019). This study showed that coronavirus disease 2019 causes reduced heart rate variability and increased parasympathetic activity in young patients. This may explain the prolonged symptoms after coronavirus disease 2019 infection.

An exploratory investigation of heart rate and heart rate variability responses to daylong heat exposure in young and older adults.

Heart rate variability (HRV) has shown potential as a tool for monitoring thermal strain, but there is limited data to support its efficacy in older adults during prolonged heat exposures. We compared HRV between young (19-31 years, n=20) and older (61-78 years, n=39) adults during 9 hours of heat exposure (40°C, 9% RH). We also explored whether heart rate (HR) and/or HRV could be used to distinguish older adults who achieved elevated thermal strain, defined as either 1) an increase in core temperature >1.0°C (occurring in 39% [15/39]) or 2) a reduction in systolic blood pressure >10 mm Hg (occurring in 67% [26/39]). Percentage of age-predicted maximal HR and percentage of heart rate reserve (HRR) were higher, whereas standard deviation of normal RR intervals (SDNN), the square root of the mean of squared differences between successive RR intervals (RMSSD), high frequency power (HF), and cardiac vagal index (CVI) were lower in older compared to young adults (P≤0.004) during heat exposure. In older adults, increases in core temperature were correlated with percentage of age-predicted maximal HR, percentage of HRR, RMSSD, and CVI (P≤0.031), whereas changes in systolic blood pressure were not significantly associated with HR or HRV indices (P≤0.327). Receiver operating characteristic curve analysis indicated that HR and HRV indices had generally poor ability to identify older adults with elevated thermal strain (area under the curve ≤0.65). Age-related differences in HRV, consistent with vagal withdrawal among older adults, remained during daylong heat exposure, but marked heterogeneity of response likely contributed to HRV providing limited discriminatory value in identifying changes in core temperature or blood pressure in older adults.

Resting Heart Rate Variability is Independently Associated with Visceral Fat Rating Scores in Saudi Adult Males.

Visceral adipose tissue (VAT) may be a specific modifiable contributor to body composition-related autonomic impairment. To compare heart rate variability (HRV) between groups stratified by visceral fat rating (VFR) and compare associations between HRV and body composition metrics. A cross-sectional study was conducted on healthy men (n=99,age=37.8±13.4 years, body mass index [BMI]=26.9±4.6 kg/m2). HRV was derived from 5-minute electrocardiographic recordings. Body composition (body fat percentage, VFR, and muscle mass to visceral fat ratio [MMVFR]) was estimated using tetrapolar bioelectrical impedance analysis. Participants were categorized into groups according to VFR: G1 (VFR=1-8); G2(VFR=9-12); and G3(VFR>12). Age-adjusted comparisons were made between groups. Independent associations were quantified with multiple linear regressions. P <0.05 was significant. Root-mean square of successive differences (RMSSD) and standard deviation of normal RR intervals (SDNN) were higher for G1 vs. G2 and G3 (p<0.05). Low-frequency power (LF) was higher in G1 than in G2 (p<0.05). VFR and MMVFR were negatively associated with SDNN, RMSSD, LF, and HF (p<0.05). After adjusting for age, BMI, and systolic and diastolic blood pressure, VFR was significantly predictive of RMSSD, SDNN, and HF (p=0.002,-0.027), and MMVFR was significantly predictive of RMSSD and SDNN (p=0.020,-0.023). Men in the lowest VFR category had the highest HRV. VFR was more strongly associated with HRV than body fat percentage and MMVR. Time domain parameters were more sensitive to VAT than frequency domain parameters. HRV parameters could be the primary parameters of interest in tracking cardiac-autonomic status in response to interventions targeting VAT reduction.

Increased Parasympathetic Activity as a Fall Risk Factor Beyond Conventional Factors in Institutionalized Older Adults with Mild Cognitive Impairment

This study aimed to investigate autonomic nervous function during the orthostatic challenge and its relationship with depression and fall, and to elucidate fall-associated factors, including autonomic function, executive function, and depression among institutionalized older adults with mild cognitive impairment (MCI). The study is a cross-sectional descriptive study. Fall experiences in the current institutions were researched. Heart rate variability (HRV) during the orthostatic challenge was measured. Executive function was evaluated using the semantic verbal fluency test and clock drawing test. Depression was assessed using the Geriatric Depression Scale. Of the 115 older adults, 17 (14.8%) experienced falls in the current institution. None of the HRV indices during the orthostatic challenge showed any significant changes except for the standard deviation of normal RR intervals (SDNN, p=.037) in the institutionalized older adults with MCI. None of the HRV indices was significantly related to the depressive symptoms. Multivariate logistic regression analysis showed that normalized high frequency on lying was independently associated with falls (OR=1.027, p=.049) after adjusting for other conventional fall risk factors, although executive function and depressive symptoms were not significant factors for fall. Institutionalized older adults with MCI were vulnerable to autonomic nervous modulation, especially to sympathetic modulation, during the orthostatic challenge, which was not associated with depressive symptoms. As increased resting parasympathetic activity seemed to play a key role in association with falls, autonomic nervous function assessment should be considered for fall risk evaluation.

Heart Rate Variability and Somatization in Adolescents With Irritable Bowel Syndrome

Changes in autonomic regulation and psychological distress play an important role in the pathobiology of irritable bowel syndrome (IBS). The aim of the current study is to evaluate the autonomic function and to link it to the levels of somatization in adolescents with IBS. We enrolled 30 adolescents with various types of IBS and 35 healthy controls. Time and frequency domain indexes of heart rate variability (HRV) were measured in supine (baseline) and standing (orthostasis) positions using short-term electrocardiographic recordings. The somatic symptoms index was assessed with the modified Screening for Somatoform Symptoms questionnaire. Adolescents with IBS showed no differences of HRV parameters in the supine position compared to healthy control. In orthostasis, a decrease in the standard deviation of normal RR intervals as well as main spectral index total power (TP) were observed. The reduction of TP was attributed to the reduced activities of the high- and low frequency components. Increased somatic symptoms index in IBS patients negatively correlated with TP in orthostasis (r = -0.485, P = 0.007). A subgroup analysis revealed that adolescents with IBS with TP values either < 2500 msec2 or > 5500 msec2 in the supine position demonstrated significantly reduced activity of the low frequency component. Adolescents with IBS showed signs of autonomic dysfunction only during the orthostatic test, which were associated with increased somatization scores. Further research is needed to establish the links between emotional wellbeing and autonomic function in this population.

Impaired heart rate variability one and six months post acute COVID-19

Abstract Background Long COVID-19 syndrome is an increasingly recognized problem. Post-infectious cardiac autonomic dysfunction is commonly reported. This study aims to evaluate autonomic dysfunction by means of Heart rate variability (HRV) on post-COVID-19 patients. Methods Hospitalized patients for COVID-19 (either at the medical ward or Intensive Care Unit (ICU)) were followed up at 1 and 6 months after hospital discharge. Medical history and clinical information were collected. HRV was assessed by 24-hour ambulatory electrocardiography Holter, with the measure of the standard deviation of normal RR intervals in 24 h, ms (SDNN). The comparison was conducted with age and sex-matched non-COVID-19 controls. Results Thirty-four patients hospitalized with COVID-19 (20.6% admitted in ICU) were examined 1-month and 6-months post-hospital discharge. SDNN was significantly (p&amp;lt;0.001) reduced in the COVID-19 group (111±23 ms) compared to the control subjects (152±24 ms) 1-month after discharge. Subgroup analysis between COVID-19 group revealed that ICU subjects presented significantly (p&amp;lt;0.001) reduced SDNN compared to the medical ward, respectively (83±20 ms vs. 118±17 ms). At 6-months, an improvement was noted at SDNN 24h (6-month: 133±24 vs. control: 151±24 ms, p=0.004; 1-month: 111±23 ms vs. 6-month: 133±24 ms, p&amp;lt;0.001). Also at 6-months, ICU subjects noted significantly (p=0.003) reduced SDNN 24h compared to medical ward subjects (107±17 ms vs. 140±20 ms). On the 6-months follow-up, 32% of the subjects had “long-COVID-19” symptoms. Subjects with long COVID-19 symptoms had low SDNN values (“long-COVID-19”: 112±17 ms vs. non-“long-COVID-19”: 142±20 ms, p=0.001) Conclusion Patients hospitalized for COVID-19 have reduced SDNN, at one month post-hospital discharge which is improved at the six months follow-up. These findings emphasize the increased sympathetic drive activity in the post-acute COVID-19 phase and imply a link between autonomic dysfunction and long COVID-19. Funding Acknowledgement Type of funding sources: None.

Impaired left ventricular deformation and ventricular-arterial coupling in post-COVID-19: association with autonomic dysregulation.

Coronavirus disease-19 (COVID-19) has extended implications namely the long COVID-19 syndrome. We assessed over-time changes in left ventricular (LV) function, aortic stiffness, autonomic function, and ventricular-arterial coupling (VAC) in post-COVID-19 patients. We followed 34 post-COVID-19 subjects, up to 6 months post-hospital discharge. Subjects without COVID-19 served as control. We evaluated LV global longitudinal strain (LV-GLS), arterial stiffness [carotid-femoral pulse wave velocity (cf-PWV)], and heart rate variability -standard deviation of normal RR intervals (SDNN). VAC was estimated as the ratio of cf-PWV to LV-GLS. Post-COVID-19 individuals (1-month post-hospital discharge) presented with impaired LV-GLS [−18.4%(3.1) vs. −22.0%(2.7), P < 0.001], cf-PWV [12.1 m/s (3.2) vs. 9.6 m/s (1.9), P < 0.001], SDNN [111.3 ms (22.6) vs. 147.2 ms (14.0), P < 0.001], and VAC [−0.68 (0.22) vs. −0.44 (0.10), P < 0.001] compared to control. LV-GLS, SDNN, and VAC improved at the 6-month follow-up however they did not reach control levels. In post-COVID-19 subjects, SDNN and VAC were correlated at the 1-month (R = 0.499, P = 0.003) and 6-month (R = 0.372, P = 0.04) follow-up. Long COVID-19 syndrome was associated with impaired LV-GLS, SDNN, and VAC. Post-COVID-19 subjects presented with autonomic dysregulation associated with aortic stiffness, ventricular-arterial impairment, and LV dysfunction, even 6-months post-hospital discharge. These abnormalities may be related to the presence of long COVID-19 syndrome.Graphical abstract

Heart rate variability and atrial fibrillation in the general population: a longitudinal and Mendelian randomization study

BackgroundSex differences and causality of the association between heart rate variability (HRV) and atrial fibrillation (AF) in the general population remain unclear.Methods12,334 participants free of AF from the population-based Rotterdam Study were included. Measures of HRV including the standard deviation of normal RR intervals (SDNN), SDNN corrected for heart rate (SDNNc), RR interval differences (RMSSD), RMSSD corrected for heart rate (RMSSDc), and heart rate were assessed at baseline and follow-up examinations. Joint models, adjusted for cardiovascular risk factors, were used to determine the association between longitudinal measures of HRV with new-onset AF. Genetic variants for HRV were used as instrumental variables in a Mendelian randomization (MR) analysis using genome-wide association studies (GWAS) summary-level data.ResultsDuring a median follow-up of 9.4 years, 1302 incident AF cases occurred among 12,334 participants (mean age 64.8 years, 58.3% women). In joint models, higher SDNN (fully-adjusted hazard ratio (HR), 95% confidence interval (CI) 1.24, 1.04–1.47, p = 0.0213), and higher RMSSD (fully-adjusted HR, 95% CI 1.33, 1.13–1.54, p = 0.0010) were significantly associated with new-onset AF. Sex-stratified analyses showed that the associations were mostly prominent among women. In MR analyses, a genetically determined increase in SDNN (odds ratio (OR), 95% CI 1.60, 1.27–2.02, p = 8.36 × 10–05), and RMSSD (OR, 95% CI 1.56, 1.31–1.86, p = 6.32 × 10–07) were significantly associated with an increased odds of AF.ConclusionLongitudinal measures of uncorrected HRV were significantly associated with new-onset AF, especially among women. MR analyses supported the causal relationship between uncorrected measures of HRV with AF. Our findings indicate that measures to modulate HRV might prevent AF in the general population, in particular in women.Graphical abstractAF; atrial fibrillation, GWAS; genome-wide association study, IVW; inverse variance weighted, MR; Mendelian randomization, MR-PRESSO; MR-egger and mendelian randomization pleiotropy residual sum and outlier, RMSSD; root mean square of successive RR interval differences, RMSSDc; root mean square of successive RR interval differences corrected for heart rate, SDNN; standard deviation of normal to normal RR intervals, SDNNc; standard deviation of normal to normal RR intervals corrected for heart rate, WME; weighted median estimator.aRotterdam Study n=12,334bHRV GWAS n=53,174cAF GWAS n=1,030,836

Heart rate variability and cardiac autonomic functions in post-COVID period.

BackgroundThe heart rate variability (HRV) is a non-invasive, objective and validated method for the assessment of autonomic nervous system. Although acute manifestations of COVID-19 were widely researched, long-term sequela of COVID-19 are still unknown. This study aimed to analyze autonomic function using HRV indices in the post-COVID period that may have a potential to enlighten symptoms of COVID long-haulers.MethodsThe 24-h ambulatory electrocardiography (ECG) recordings obtained >12 weeks after the diagnosis of COVID-19 were compared with age–gender-matched healthy controls. Patients who used drugs or had comorbidities that affect HRV and who were hospitalized with severe COVID-19 were excluded from the study.ResultsTime domain indices of HRV analysis (standard deviation of normal RR intervals in 24 h (SDNN 24 h) and root mean square of successive RR interval differences (RMSSD)) were significantly higher in post-COVID patients (p < 0.05 for all). Among frequency domain indices, high frequency and low frequency/high frequency ratio was significantly higher in post-COVID patients (p = 0.037 and p = 0.010, respectively). SDNN >60 ms [36 (60.0%) vs. 12 (36.4%), p = 0.028)] and RMSSD >40 ms [31 (51.7%) vs. 7 (21.2%), p = 0.003)] were more prevalent in post-COVID patients. Logistic regression models were created to evaluate parasympathetic overtone in terms of SDNN >60 ms and RMSSD >40 ms. After covariate adjustment, post-COVID patients were more likely to have SDNN >60 msn (OR: 2.4, 95% CI:1.2–12.8) and RMSSD >40 ms (OR: 2.5, 95% CI: 1.4–9.2).ConclusionThis study revealed parasympathetic overtone and increased HRV in patients with history of COVID-19. This may explain the unresolved orthostatic symptoms occurring in post-COVID period which may be associated with autonomic imbalance.Supplementary InformationThe online version contains supplementary material available at 10.1007/s10840-022-01138-8.

Heart Rate Variability on 10-Second Electrocardiogram and Risk of Acute Exacerbation of COPD: A Secondary Analysis of the BLOCK COPD Trial.

Autonomic dysfunction is common in chronic obstructive pulmonary disease (COPD), and worse autonomic function may be a marker of risk for acute exacerbations of COPD (AECOPD). Heart rate variability (HRV) is a measure of autonomic function. Our objective was to test whether lower (worse) HRV is a risk factor for AECOPD. We measured standard deviation of normal RR intervals (SDNN) and root mean square of successive RR interval differences (RMSSD) on 10-second electrocardiograms (ECGs) performed at screening and day 42 in participants in the Beta Blockers for the Prevention of Acute Exacerbations of COPD trial ( BLOCK-COPD), a placebo-controlled trial of metoprolol for prevention of AECOPD. We used Cox-proportional hazards models to test if these HRV measures were associated with risk of any AECOPD, and separately, hospitalized AECOPD. We tested associations using baseline HRV measures and incorporating HRV measures from day 42 as a time-varying covariate. We also tested for interactions with metoprolol assignment. Of 532 trial participants, 529 (forced expiratory volume in 1 second [FEV1 ]41 ± 16.3 % predicted) were included in this analysis. We did not find a significant association between HRV measures and risk of AECOPD when all participants were analyzed together. There was a significant interaction between RMSSD and assignment to metoprolol on time to first hospitalized AECOPD; in the placebo group greater RMSSD was associated with a lower risk of hospitalized AECOPD (adjusted hazard ratio0.71, 95% confidence interval: 0.52 to 0.96, per 10 ms increase) but there was no association in the metoprolol group. Autonomic dysfunction as measured by HRV may be a risk factor for AECOPD. Future studies should analyze longer HRV recordings and their performance in broader samples of people with COPD, including those on beta-blockers.

HEART RATE VARIABILITY ON 10-SECOND ECG AND RISK OF ACUTE EXACERBATIONS OF COPD: A SECONDARY ANALYSIS OF BLOCK COPD

HEART RATE VARIABILITY ON 10-SECOND ECG AND RISK OF ACUTE EXACERBATIONS OF COPD: A SECONDARY ANALYSIS OF BLOCK COPD

Cardiac-autonomic and hemodynamic responses to a hypertonic, sugar-sweetened sports beverage in physically active men

Hydration practices may confound heart rate variability (HRV) measurements when collected in the pre-training period. We aimed to determine the effects of ingesting a hypertonic, sugar-sweetened sports beverage on HRV and hemodynamic parameters in physically active young men. Fifteen subjects consumed 591mL of Gatorade (6% carbohydrate, ∼330 mOsmol/kg), 591mL water, or 10mL water (control) in random order on separate days following overnight fasting. HRV and hemodynamics were evaluated in 5-min windows immediately before (T1) and 5-10min (T2), 25-30min (T3), 40-45min (T4), and 55-60min (T5) post-drinking. Root-mean square of successive differences and the standard deviation of normal RR intervals increased post-water intake at all time-points relative to T1 (P< 0.05). No increases were observed post-Gatorade intake, though small effect sizes were noted at T2 and T3 (P> 0.05, ES = 0.27-0.32). Systemic vascular resistance increased at T2 post-Gatorade intake and at T2 and T3 post-water intake (P< 0.05). No interactions were observed for blood pressure measures, stroke volume, or cardiac output. Gatorade does not evoke cardiovascular adjustments to the same magnitude as water. Practitioners should wait at least 45min to record HRV post-Gatorade intake and >60min post-water intake. Novelty: Equal volumes of cold water and Gatorade produce inequivalent cardiac-autonomic and hemodynamic responses. HRV responses of greater amplitude and duration were observed following intake of water versus Gatorade. Failure to account for recent fluid intake may result in misinterpretation of autonomic status.

Global and Transient Effects of Intermittent Hypoxia on Heart Rate Variability Markers: Evaluation Using an Obstructive Sleep Apnea Model

Intermittent hypoxia (IH) produces autonomic dysfunction that promotes the development of arrhythmia and hypertension in patients with obstructive sleep apnea (OSA). This paper investigated different heart rate variability (HRV) indices in the context of IH using a rat model for OSA. Linear and non-linear HRV parameters were assessed from ultra-short (15-s segments) and short-term (5 min) analyses of heartbeat time-series. Transient changes observed from pre-apnea segments to hypoxia episodes were evaluated, besides the relative and global impact of IH, as a function of its severity. Results showed an overall increase in ultra-short HRV markers as immediate response to hypoxia: standard deviation of normal RR intervals, SDNN = 1.2 ms (IQR: 1.1-2.1) vs 1.4 ms (IQR: 1.2-2.2), p = 0.015; root mean square of the successive differences, RMSSD = 1.7 ms (IQR: 1.5-2.2) vs 1.9 ms (IQR: 1.6-2.4), p = 0.031. The power in the very low frequency (VLF) band also showed a significant increase: 0.09 ms <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> (IQR: 0.05-0.20) vs 0.16 ms <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> (IQR: 0.12-0.23), p = 0.016, probably associated with the potentiation of the carotid body chemo-sensory response to hypoxia. Moreover, a clear link between severity of IH and short-term HRV measures was found in VLF and LF power, besides their progressive increase seen throughout the experiment after each apnea sequence. However, only those markers quantifying fragmentation levels in RR series were significantly affected when the experiment ended, as compared to baseline measures: percentage of inflection points, PIP = 49% (IQR: 45-51) vs 53% (IQR: 47-53), p = 0.031; percentage of short (geq 3 RR intervals) accelerated/decelerated segments, PSS = 75% (IQR: 51-81) vs 87% (IQR: 51-90), p = 0.046. These findings suggest a significant deterioration of cardiac rhythm with a more erratic behavior beyond the normal sinus arrhythmia, that may lead to a future cardiac condition.

Potassium excretion and blood pressure are associated with heart rate variability in healthy black adults: The African-PREDICT study

Background and aimsHeart rate variability (HRV) is a main determinant of autonomic function and related to the development of hypertension and cardiovascular (CV) disease. Hypertension develops in black populations at an earlier age, which could be due to differences in the autonomic nervous system activity and sodium/potassium handling in black and white populations. We investigated whether HRV is associated with 24 h urinary sodium and potassium excretion and blood pressure (BP) in a young bi-ethnic cohort. Methods and resultsWe examined 423 black and 483 white healthy adults (aged 24.5 ± 3.1 years) for 24 h HRV, including standard deviation of normal RR intervals (SDNN) reflecting autonomic variations over time, and root mean square of successive differences (RMSSD) reflecting parasympathetic activity. We measured 24 h urinary sodium and potassium concentration and BP. The black group had lower SDNN and potassium excretion as well as higher RMSSD, sodium and Na/k ratio compared to the white group (all p < 0.05). Only in black individuals, urinary potassium excretion was independently and negatively associated with SDNN (β[95% CI];-0.26[-0.50;-0.02]ms) and RMSSD (−0.14[-0.27;-0.01]ms, p < 0.05). One unit increase in sodium/potassium (Na/K) ratio was associated with higher SDNN (β[95% CI]; 3.04[0.89; 5.19]ms) and RMSSD (1.60[0.41; 2.78]ms) in the black cohort only (both p < 0.001). In both groups elevated 24 h diastolic BP was associated with lower RMSSD (p < 0.05). ConclusionLower potassium excretion and higher Na/K ratio related independently to higher HRV in young and healthy black adults. A better ethnic-specific understanding of sodium and potassium handling is required as part of preventive cardiology, especially in black individuals. Clinical trial registrationClinicalTrials.gov Identifier: NCT03292094; URL: https://clinicaltrials.gov/ct2/show/NCT03292094.

Age-Related Change in Heart Rate Variability at Resting in Thai Professional Athletes

Background: Although regular exercise is beneficially acknowledged in promoting general health status, the cardiovascular risk of sudden cardiac death in highly training athletes has been reported. Unfortunately, the primary key factor in inducing cardiac problems in athletic populations is still questioned. Objectives: In the present study, we aim to determine factors that could affect the relationship between physical activity level and cardiac autonomic function in the Thai population. Methods: Forty participants were recruited and classified into three groups based on their physical activity level and sport profession, including sedentary men, elite handball players, and professional futsal players. In all participants, we measured predicted maximal oxygen consumption, time- and frequency- domain heart rate variability (HRV) variables at rest. Results: Results demonstrated a positive correlation between time-domain HRV and estimated maximal oxygen consumption, but not with frequency-domain HRV, in which athletes aged lower than 25 years old (18 - 25 years old) had a significantly higher in the standard deviation of normal RR intervals (SDNN) and root mean square of the successive differences (RMSSD) than that in age-matched sedentary subjects. Interestingly, athletes aged above 25 years old (25 - 32 years old) had lower SDNN and RMSSD with higher low frequency/high-frequency ratio than those athletes aged under 25. Since all athletes aged above 25 years old were world-class national futsal players, stress due to the competitive level might be another factor influencing cardiac autonomic activity in athletes. Conclusions: In conclusion, the study suggested the importance of age and stress exposure on cardiac autonomic regulation in elite athletes. The observed correlation also reinforced HRV as a potential marker in detecting abnormal changes in cardiac health even in an athletic population.

Adiposity and physical activity are related to heart rate variability: the African-PREDICT study.

Physical inactivity contributes significantly to the development of obesity-related cardiovascular disease. Adiposity may lead to reduced heart rate variability (HRV), whereas increased physical activity (PA) has the potential to improve autonomic activity. These associations remain largely unexplored in healthy individuals. We therefore investigated whether adiposity and physical activity (PA) are associated with reduced heart rate variability (HRV) in young adults. We examined 403 black and 461 white healthy adults (aged 20-30years) for HRV, including standard deviation of normal RR intervals (SDNN) and root mean square of successive differences (RMSSD). We measured adiposity, PA levels and blood pressure (BP). Body mass index (BMI) of≥30kg/m2 indicated obesity. Participants with obesity had lower mean HRV than normal weight (SDNN [95% CI]; 138 [131-145]s vs 161 [158-165]ms), where those with the highest PA had higher SDNN (164 [160-169]ms) and RMSSD (51 [49-53]ms) than the least active individuals (150 [146-155]s) and 46 [44-48]ms)(all P<.01). BMI, waist circumference and body fat associated with lower SDNN (P<.001). With each unit increase of vigorous PA, a favourable higher RMSSD was found (P<.05). One unit increase in diastolic BP was associated with decreased SDNN and RMSSD (P<.001). These findings remained significant in multivariable-adjusted analyses. Adiposity and low PA associated independently with depressed autonomic activity in young healthy adults. Sympathovagal imbalance seems to already contribute to elevated diastolic BP at young ages. Our study supports population-based prevention programmes in young adults, improving PA and healthy diet, to curb the development of cardiovascular disease.

Heart Rate Variability, HIV and the Risk of Cardiovascular Diseases in Rural South Africa

Background:Antiretroviral therapy (ART) transformed human immunodeficiency virus (HIV) infection into a chronic disease. Possible HIV-associated complications have emerged including cardiovascular diseases (CVD).Objectives:This study aims to determine the heart rate variability (HRV) distribution and association between HRV and HIV treated with ART in a rural African population.Methods:This cross-sectional study included 325 participants of the Ndlovu Cohort Study, South Africa. HRV was measured using a standardized five-minute resting ECG and assessed by the standard deviation of normal RR intervals (SDNN), root of mean squares of successive RR differences (RMSSD), percentage of RR intervals greater than 50 milliseconds different from its predecessor (pNN50), total-, low- and high-frequency power. CVD risk factors were assessed using measurements (blood pressure, anthropometry, cholesterol) and questionnaires (e.g. socio-demographics, alcohol, smoking, physical activity, age, diabetes). We used a Wilcoxon rank test to assess differences in medians between HIV-infected and HIV-uninfected participants and multivariable linear regression to investigate associations between HRV and HIV treated with ART.Conclusions:Of the participants, 196 (61.4%) were HIV-infected treated with ART and 123 (38.6%) were HIV-uninfected. HIV-infected consumed less alcohol, 52% versus 35%, smoked less, were less physically active, more often attained lower education, 26% versus 14%, and had lower systolic blood pressure, 134 mmHg versus 140 mmHg, compared to HIV-uninfected. Medians of all HRV parameters were lower for HIV-infected participants. The model fully adjusted for CVD risk factors showed a significant inverse association between HIV treated with ART and log RMSSD (–0.16) and log pnn50 (–0.61). Although HIV-infected participants treated with ART presented with less CVD risk factors they had a lower HRV indicating an increased risk of CVD.Highlights– African HIV-infected participants on ART had less conventional CVD risk factors than HIV-uninfected.– However, HIV-infected participants had lower HRV than HIV-uninfected participants.– Lower HRV of the HIV-infected participants indicates that they are at a higher risk for CVD.

553-P: Differential Effects of High-Intensity Interval Training on Somatosensory and Autonomic Nerve Function in Patients with Type 2 Diabetes

It remains unclear, whether exercise training as part of lifestyle intervention has favorable effects on the development or progression of diabetic neuropathy in patients with type 2 diabetes (T2D). Therefore, we assessed peripheral and autonomic nerve fiber function and morphology in patients with T2D as well as in individuals with normal glucose tolerance (CON) before and after a high intensity interval training (HIIT) intervention program over 12 weeks. The T2D group included 20 male individuals ([median (1st; 3rd quartile)] age: 56 (53; 63) years; diabetes duration: 5 (2; 9) years; BMI: 31.2 (28.6; 32.8) kg/m²; HbA1c: 6.9 (6.4; 8.0)%). The CON group was matched for age, sex, and BMI (n=23; age: 57 (53; 60) years; BMI: 30.3 (28.4; 32.2) kg/m²; HbA1c: 5.4 (5.2; 5.7)). Somatosensory and autonomic nerve tests included nerve conduction velocity, quantitative sensory testing, skin biopsy, corneal confocal microscopy, cardiovascular autonomic function tests (CAFT), and spontaneous baroreflex sensitivity (BRS). After 12 weeks of HIIT, no improvement in somatosensory nerve tests was detected in T2D or CON. In both groups, resting heart rate decreased ([mean±SEM] baseline vs. follow-up: T2D: 68.8±2.3 vs. 63.4±1.8 bpm; CON: 65.1±1.8 vs. 60.2±1.9 bpm; both P&amp;lt;0.05). The change in systolic blood pressure after standing up (-13.9±2.6 vs. -9.4±2.2 mmHg) and three BRS sequence analysis indices (e.g., BRS-slope: 7.9±1.9 vs. 12.6±5.1 ms/mmHg) improved in T2D (P&amp;lt;0.05), while the standard deviation of normal RR intervals (SDNN; 36.1±2.6 vs. 55.3±8.8 ms; P&amp;lt;0.05) and coefficient of variation (CV; 3.8±0.3 vs. 5.2±0.7%; P&amp;lt;0.05) improved in CON. In conclusion, while cardiovascular autonomic function improved moderately after 12 weeks of HIIT in male T2D patients, a longer training period may be required to achieve favorable effects on somatosensory nerve function or morphology. Disclosure G.J. Bönhof: None. A. Strom: None. M. Apostolopoulou: None. D. Pesta: None. M. Roden: Advisory Panel; Self; Boehringer Ingelheim Pharmaceuticals, Inc., Poxel SA, Servier. Board Member; Self; Eli Lilly and Company. Research Support; Self; Boehringer Ingelheim Pharmaceuticals, Inc., Sanofi. Speaker's Bureau; Self; Novo Nordisk Inc. D. Ziegler: Advisory Panel; Self; Allergan, TrigoCare. Consultant; Self; Mitsubishi Tanabe Pharma Corporation, Mylan, Novartis Pharmaceuticals Corporation, Wörwag. Speaker's Bureau; Self; Berlin-Chemie AG. Funding German Ministry of Culture and Science of the State of North Rhine-Westphalia; German Federal Ministry of Health; German Federal Ministry of Education and Research