Significant Decrease In Heart Rate Variability Research Articles

Assessing the Sympathetic Response of Medical Doctors and Trainees when Exposed to a Virtual Realty Mass Casualty Incident Simulation

Introduction:The occurrence of disasters and mass casualty incidents (MCIs) is on the rise, thus training and rehearsal for disaster response remain paramount. Virtual reality (VR) platforms have previously been shown to be well-received, engaging, and immersive for disaster training. The primary objective of this study was to ascertain if a human actor-based VR MCI scenario could elicit a sympathetic response, as measured by heart rate variability (HRV), in medical doctors and trainees compared to a baseline state.Method:A simulation was filmed with students, residents, and surgeons on a GoPro 360 camera. Subjects (n=35) were recruited to sufficiently power (1-b=0.8) a Wilcoxon matched-pairs test and Welch’s t-test. Subjects watched the simulation on an Oculus Quest headset while having HRV recorded. Multivariate logistic regression was performed to identify factors associated with increased odds of significant sympathetic activation. Statistical significance was established at p<0.05.Results:Thirty-five subjects were enrolled and included three trauma surgeons, three emergency medicine (EM) attendings, eight EM residents, six surgery residents, and 15 medical students. A significant decrease in HRV was observed across all groups in the MCI (median 20 ms IQR 16.2, 31.4 ms) compared to baseline (33.2 ms IQR 27.2, 44.1 ms; p<0.0001). Sympathetic activation was most pronounced in students, then attendings, then residents. There was no significant difference in the fold-difference of sympathetic activation of EM physicians (-48.5% +/- 32.1%) versus surgeons (-49.5% +/- 25.2%; p=0.57). In all groups, SNS activation occurred independently of heart rate, age, sex, number of years in practice, first responder experience, or prior MCI response.Conclusion:Live-actor VR MCI simulation elicited a strong sympathetic response from students, residents, and attending physicians. By recruiting and disinhibiting essential neural pathways via controlled SNS activation, VR MCI training has the potential to enhance the encoding and consolidation of disaster training in a low-cost and reproducible manner.

PO-01-078 THE ACUTE PHYSIOLOGIC EFFECTS OF OSTEOPATHIC MANIPULATIVE TREATMENT IN PATIENTS WITH CARDIAC IMPLANTABLE ELECTRONIC DEVICES: A RANDOMIZED CONTROLLED TRIAL

Osteopathic manipulative treatment (OMT) is a procedure used to improve physiologic function and maintain homeostasis. OMT modulates the autonomic nervous system (ANS) and augments heart rate variability (HRV) in healthy subjects. The acute physiologic effects of OMT have been reported in patients with heart failure, but not in those with cardiac implantable electronic devices (CIEDs). To assess the short-term physiologic effects of OMT on heart rate, respiratory rate, arterial blood pressure, and HRV in patients with CIEDs. Cardiac patients with CIEDs at an osteopathic medical center were recruited into a randomized controlled trial (ClinicalTrials.gov ID: NCT0400474) and assigned to either OMT or light touch (control) groups. Short-term physiologic data was recorded pre and post intervention (including one minute HRV via photoplethysmography). HRV was calculated using root mean square of successive RR interval differences (RMSSD). Student’s t-test was used to compare groups; p < 0.05. 20 subjects were enrolled (10 OMT/10 control). Table 1 shows physiologic measurements prior to and post intervention. Changes in HR, RR, BP, and SpO2 were no different between groups before and after intervention; OMT HRV decreased by 12.39 + 34.05 ms, whereas control HRV increased by 19.94 + 18.54 ms (p=0.022). There was a significant decrease in HRV in the OMT group, but no difference in the remaining standard physiologic variables. The difference in HRV is opposite of what would be expected, and could be due to the effects of OMT on the ANS, altered cardiac response in this population, and possibly a decrease in ectopy. Further evaluation of CIED data (arrhythmias, HRV and activity level) may be helpful in determining the long-term effects of OMT on cardiac arrhythmia patients.

Heart rate variability in people with metabolic syndrome

Metabolic syndrome (MS) is characterized by disorders of carbohydrate and fat metabolism, which can lead to the development of cardiac autonomic neuropathy (CAN). Heart rate variability (HRV) analysis is used to assess the state of autonomic regulation. A decrease in HRV indicates unfavourable changes in autonomic regulation and the development of CAN. The purpose of this study was to compare HRV parameters in patients with metabolic syndrome and healthy individuals without signs of MS. We examined 74 patients with metabolic syndrome (mean age 54.4 ± 1.1 years) and 61 healthy subjects (without signs of MS) (mean age 57.0 ± 1.6 years). The results of the study indicate a significant decrease in HRV in people with MS. However, they had significantly lower values of the SDNN index (by 26%), which characterizes the overall power of neurohumoral regulation of heart rate. Differences in the indicators characterizing short-term, vagal influences were especially pronounced: in patients with MS, RMSSD (by 44%) and HF (by 69%) were lower than in controls. The activity of the baroreflex center of the medulla oblongata, assessed by the spectral power of low-frequency waves (LF), was 55% lower in patients with MS compared to controls. There were no significant differences in the mean duration of the R-R interval, the spectral power of very low frequency (VLF) waves, or the ratio of the spectral powers of low and high frequencies (LF/HF, LFn, HFn) in patients with MS compared to controls. No significant shift in the autonomic balance towards sympathicotonia was found in patients with MS. The analysis of variance confirmed the significant effect of the metabolic syndrome factor on HRV. Thus, the data obtained indicate the development of CAN in people with metabolic syndrome, which is an unfavourable prognostic sign. To assess the effect of MS on the rate of ageing, the biological age (BA) of the examined people with MS was calculated. The formula for calculating BA was obtained on a group of people without MS. The method of multiple stepwise regression was used. The ageing rate was calculated as the difference between biological and chronological age (CA). The average BA in the group of people with MS was 63,20 ± 1,81 years, and in the control group – 53.99 ± 1.71 years (p&lt; 0.05). The difference between BA and CA is 8,81 ± 0,94 years in the group of people with MS and -1.01 ± 0.61 in the control group (p&lt; 0.05). From this we can conclude that MS can be a factor accelerating ageing. _________________________________________________________________________________________ Keywords: metabolic syndrome, heart rate variability, biological age

Heart rate variability in people with metabolic syndrome

Metabolic syndrome (MS) is characterized by disorders of carbohydrate and fat metabolism, which can lead to the development of cardiac autonomic neuropathy (CAN). Heart rate variability (HRV) analysis is used to assess the state of autonomic regulation. A decrease in HRV indicates unfavourable changes in autonomic regulation and the development of CAN. The purpose of this study was to compare HRV parameters in patients with metabolic syndrome and healthy individuals without signs of MS. We examined 74 patients with metabolic syndrome (mean age 54.4 ± 1.1 years) and 61 healthy subjects (without signs of MS) (mean age 57.0 ± 1.6 years). The results of the study indicate a significant decrease in HRV in people with MS. However, they had significantly lower values of the SDNN index (by 26%), which characterizes the overall power of neurohumoral regulation of heart rate. Differences in the indicators characterizing short-term, vagal influences were especially pronounced: in patients with MS, RMSSD (by 44%) and HF (by 69%) were lower than in controls. The activity of the baroreflex center of the medulla oblongata, assessed by the spectral power of low-frequency waves (LF), was 55% lower in patients with MS compared to controls. There were no significant differences in the mean duration of the R-R interval, the spectral power of very low frequency (VLF) waves, or the ratio of the spectral powers of low and high frequencies (LF/HF, LFn, HFn) in patients with MS compared to controls. No significant shift in the autonomic balance towards sympathicotonia was found in patients with MS. The analysis of variance confirmed the significant effect of the metabolic syndrome factor on HRV. Thus, the data obtained indicate the development of CAN in people with metabolic syndrome, which is an unfavourable prognostic sign. To assess the effect of MS on the rate of aging, the biological age (BA) of the examined people with MS was calculated. The formula for calculating BA was obtained on a group of people without MS. The method of multiple stepwise regression was used. The aging rate was calculated as the difference between biological and chronological age (CA). The average BA in the group of people with MS was 63,20 ± 1,81 years, in the control group – 53.99 ± 1.71 years (p&lt; 0.05). The difference between BA and CA is 8,81 ± 0,94 years in the group of people with MS and -1.01 ± 0.61 in control group (p&lt; 0.05). From this we can conclude that MS can be a factor accelerating aging. _________________________________________________________________________________________ Keywords: metabolic syndrome, heart rate variability, biological age

Acute Effects of a Single-Session of Full-Body Foam Rolling on Heart Rate Variability.

Self-myofascial release has been demonstrated to increase relaxation and improve blood flow, yet it is unknown if it can elicit an acute effect on heart rate variability (HRV). This study aimed to determine if a single-bout of foam rolling could increase parasympathetic activity as measured by HRV. Twenty (20) participants volunteered and their baseline HRV was assessed using a finger sensor while lying supine, and then a second measure was recorded with them sitting upright with feet on the ground. This study utilized a practical HRV collection method designed for use in the field settings, and the data is recorded in arbitrary units (A.U.). Participants then oscillated on a closed-cell cylindrical foam roller using their body weight on the triceps surae, hamstrings, quadriceps, lumbar spine, and pectoral muscles each for 60 sec. Participants first massaged the right limb and then repeated on the matching muscle group on the left before continuing to the next region. Follow-up HRV measurements were recorded using the same procedures. Paired samples t tests assessing pre- and post-foam-rolling HRV measures in supine and seated positions revealed no difference between supine measures (p = .05, d = 0.21), nor the seated measures (p = .27, d = 0.17) among all participants. When sexes were analyzed separately, males showed a significant decrease in HRV in supine positions (p = .03, d = 0.33), but females did not (p = .55, d = 0.09). The single bout of foam rolling on large muscle groups did not increase parasympathetic activity as hypothesized. Males and females responded differently in supine positions, but no difference was present in seated positions across sexes. The task of self-massage may have prevented the anticipated response from the massage. Further research should investigate if passive massage is more effective on HRV response.

A Micro-Level Analysis of Physiological Responses to COVID-19: Continuous Monitoring of Pregnant Women in California.

Continuous monitoring of perinatal women in a descriptive case study allowed us the opportunity to examine the time during which the COVID-19 infection led to physiological changes in two low-income pregnant women. An important component of this study was the use of a wearable sensor device, the Oura ring, to monitor and record vital physiological parameters during sleep. Two women in their second and third trimesters, respectively, were selected based on a positive COVID-19 diagnosis. Both women were tested using the polymerase chain reaction method to confirm the presence of the virus during which time we were able to collect these physiological data. In both cases, we observed 3–6 days of peak physiological changes in resting heart rate (HR), heart rate variability (HRV), and respiratory rate (RR), as well as sleep surrounding the onset of COVID-19 symptoms. The pregnant woman in her third trimester showed a significant increase in resting HR (p = 0.006) and RR (p = 0.048), and a significant decrease in HRV (p = 0.027) and deep sleep duration (p = 0.029). She reported experiencing moderate COVID-19 symptoms and did not require hospitalization. At 38 weeks of gestation, she had a normal delivery and gave birth to a healthy infant. The participant in her second trimester showed similar physiological changes during the 3-day peak period. Importantly, these changes appeared to return to the pre-peak levels. Common symptoms reported by both cases included loss of smell and nasal congestion, with one losing her sense of taste. Results suggest the potential to use the changes in cardiorespiratory responses and sleep for real-time monitoring of health and well-being during pregnancy.

Effects of agomelatine on heart rate variability in patients with coronary artery disease and depression

Aim. To determine heart rate variability (HRV) in depressed patients with chronic coronary artery disease (CAD) and to assess the effects of agomelatine on HRV.Methods. 74 patients with CAD (class 3-4 angina pectoris) were recruited in a study. Patients (n = 45) with CAD and depression were assigned to Group 1, whereas CAD patients (n = 29) without any signs of depression were assigned to Group 2. 17 patients received agomelatine (Subgroup 1) and 28 patients did not take any antidepressants (Subgroup 2). HRV was measured using SCHILLER MT-200 Holter-ECG apparatus at baseline and after 6 months.Results. Patients with depression demonstrated a significant decrease in HRV compared to non-depressed patients (pNN50% (3.9 [2.2; 5.4] vs 5.7 [2.9; 12.6], p = 0.03), SDANN (81 [63; 97] ms vs 91 [79; 102] ms, p = 0.06), SDNNindx (46 [36; 56] ms vs 55 [48; 66] ms, p = 0.002), rMSSD (28 [21; 36] ms vs 33 [ 29; 45] ms, p = 0.02), SDNN (97 [75; 121] ms vs 110 [98; 127] ms, p = 0.02). Subgroups 1 and 2 did not differ in HRV (p&gt;0.05). After 6 months, significant differences in the following parameters were found in those patients who received agomelatine therapy and those who did not: rMSSD (36.5 [28.5; 51] ms vs 26.5 [25; 32] ms, p = 0.02), SDANN (88 [72,5; 114,5] ms vs 67,5 [58; 83] ms, p = 0.03), SDNN strives to a significant difference - 100 [87; 133.5] ms vs 85.5 [75; 103] ms, p = 0.07.Conclusion. HRV significantly decreased in depressed patients with CAD suggesting autonomic dysfunction and worsening their prognosis. Agomelatine therapy in patients with CAD is effective in treating heart rate variability and reducing the risk of developing life-threatening arrhythmias.Key

Autonomic Nervous System Activity during Refractory Rise in Intracranial Pressure.

Refractory intracranial hypertension (RIH) is a dramatic increase in intracranial pressure (ICP) that cannot be controlled by treatment. Recent reports suggest that the autonomic nervous system (ANS) activity may be altered during changes in ICP. Our study aimed to assess ANS activity during RIH and the causal relationship between rising in ICP and autonomic activity. We reviewed retrospectively 24 multicenter (Cambridge, Tromso, Berlin) patients in whom RIH developed as a pre-terminal event after acute brain injury (ABI). They were monitored with ICP, arterial blood pressure (ABP), and electrocardiography (ECG) using ICM+ software. Parameters reflecting autonomic activity were computed in time and frequency domain through the measurement of heart rate variability (HRV) and baroreflex sensitivity (BRS). Our results demonstrated that a rise in ICP was associated to a significant rise in HRV and BRS with a higher significance level in the high-frequency HRV (p < 0.001). This increase was followed by a significant decrease in HRV and BRS above the upper-breakpoint of ICP where ICP pulse-amplitude starts to decrease whereas the mean ICP continues to rise. Temporality measured with a Granger test suggests a causal relationship from ICP to ANS. The above results suggest that a rise in ICP interacts with ANS activity, mainly interfacing with the parasympathetic-system. The ANS seems to react to the rise in ICP with a response possibly focused on maintaining the cerebrovascular homeostasis. This happens until the critical threshold of ICP is reached above which the ANS variables collapse, probably because of low perfusion of the brain and the central autonomic network.

Acute Electrocardiographic Changes during Smoking and Tobacco Chewing

Background: Smoking increases the risk of coronary artery disease. Very few studies have evaluated the temporal relationship of electrocardiographic changes with smoking. We sought to study and compare the electrocardiogram (ECG) changes during smoking and tobacco chewing in current smokers and tobacco chewers presenting with atypical chest pain with either negative or mild positive exercise ECG test (treadmill test [TMT]). Materials and Methods: We screened male smokers and tobacco chewers with atypical chest pain with TMT. A total of 60 patients, 30 in each group in whom TMT was either negative or mildly positive, underwent a 24-h Holter monitoring. We asked patients to note down their time of smoking and tobacco chewing along with the timing of symptoms if any. Results: All patients were male with an average age of 45 years in smokers and 42 years in the tobacco chewer group. The mean number of cigarettes consumed was 6 ± 2.8 and tobacco chewed was 5 ± 4.7 g/day. Heart rate (HR) in smokers increased from 82.5 ± 14.56/min 10 min before smoking to 90.63 ± 15.34/min, during smoking with peak HR achieved at the time of smoking (P &lt; 0.0001). HR in the tobacco chewers peaked at 10 min after chewing from 80.62 ± 13.52/min 10 min before to 87.89 ± 13.86/min 10 min after chewing (P &lt; 0.0001). Smoking was associated with a significant increase in supraventricular ectopics (VEs) from 3.98/h before smoking to 7.43/h during and 6.92/h after smoking (P &lt; 0.0001). Two patients in the smoker subgroup had spontaneous smokeless tobacco -T changes lasting for 10–25 min. Smoking was associated with a significant decrease in HR variability (HRV) index than the controls (P = 0.023). Tobacco chewing was not associated with any significant changes in the HRV parameter. Conclusions: Smoking and tobacco chewing both significantly increase the HR acutely. Smoking leads to an increase in both supraventricular and VEs. We observed reduced HRV in patients who smoked cigarettes.

Impact of a 12-Week Group-Based Compassion Focused Therapy Intervention on Heart Rate Variability.

Heart rate variability (HRV) is considered an index of self-regulatory capacity, and trait compassion predicts healthy HRV and self-regulation. Compassion focused psychotherapy interventions have been shown to increase levels of compassion in the general population but no studies to date have examined if these interventions also increase HRV in a distressed clinical sample. The present study examined whether a 12-week compassion focused therapy intervention administered in group format would improve resting HRV and impact HRV reactivity during self-critical writing and self-compassion writing tasks administered before and after the intervention. A total of 31 participants in a university counseling center completed the intervention and HRV assessments. Resting HRV did not significantly change over the course of the intervention in the overall sample. Only those who showed a reliable increase in self-compassion also had a significant increase in resting HRV post-intervention. Additionally, the self-critical writing task was associated with a significant decrease in HRV, with HRV staying low during self-compassionate writing and then significantly increasing during recovery. Reliable change in self-compassion predicted increased HRV reactivity to self-critical and self-compassion writing tasks following the intervention, indicating greater engagement with the task. Findings support the idea that increased self-compassion increases HRV reactivity and potentially strengthens ability to engage with difficult emotions in psychotherapy.

573-P: Diagnostic Performance of Heart Rate Variability for Detecting Diabetic Cardiac Autonomic Neuropathy

Heart rate variability (HRV) has been considered as a useful tool for detecting cardiac autonomic neuropathy (CAN) and predicting mortality in individuals with diabetes. We evaluated its diagnostic performance for CAN in a hospital-based cohort. CAN was defined and classified according to Ewing’s criteria using standard 5 cardiovascular reflex test. HRV and power spectral density (PSD) were assessed by DiCAN (Medicore, Seoul, Korea); and diagnostic performance of Standard Deviation Normal to Normal (SDNN) and each PSD domain (total power, TP; very low frequency, VLF; low frequency, LF; high frequency, HF) were evaluated using receiver operating characteristic (ROC) analysis and Youden's index. After excluding subjects with insufficient data, 2,209 diabetic patients were included the analyses (mean age, 60 ± 11 years; men, 49.6%). Early, definite, and severe CAN were detected in 38.7%, 10.4%, and 4.1% in them. Multivariable Poisson regression adjusted for age and sex showed that all SDNN, TP, VLF, LF, and HF were decreased as severity of CAN increased (P&amp;lt;0.001). Their area under curve of ROC for diagnosis of definite CAN was 0.67 (95% confidence interval, 0.64 - 0.70), 0.71 (0.68 - 0.74), 0.68 (0.65 - 0.71), 0.73 (0.70 - 0.75), and 0.68 (0.65 - 0.71), respectively; and their sensitivity was 0.74, 0.80, 0.70, 0.70, and 0.79, respectively in this analysis. For detection of early CAN, their sensitivity was more decreased to 0.71, 0.64, 0.52, 0.64, and 0.74, respectively. In conclusion, even though there was significant decrease in HRV according to severity of CAN, HRV could not detect about 30% of diabetic subjects with CAN especially in the case with early impairment. Further studies evaluating diagnostic performance of HRV in various populations are needed. Disclosure B. Koo: None. M. Moon: None.

Pediatric cardio-autonomic response to variable effort after severe traumatic brain injury

Aim: To assess heart rate (HR) and heart rate variability (HRV) at rest, during exercise and during the recovery phase post-exercise in children at the chronic phase post-severe TBI as compared to age-matched typically-developed (TD) controls.Setting: Out-patient clinic.Participants: Ten children (two girls, eight boys), 3–5 years post-severe TBI, aged 7–11 years with residual deficits and 20 TD children matched for age.Interventions: HR and HRV were determined at rest, during step test for 3 minutes, during walking on a treadmill for 6 minutes and during the recovery periods post-exercise sessions.Main outcome measures: HR and HRV parameters.Results: Children post-TBI demonstrated higher mean HR values and lower HRV at rest compared to controls (p < 0.05). During exercise a significant increase in HR and significant decrease in HRV was noted in both groups. A significant interaction was noted (p < 0.01); HR and HRV parameters in response to exercise and to exercise cessation were significantly lower among children post-TBI as compared to the controls.Conclusions: The findings of this study show that, in children, post-severe TBI at the chronic phase, the cardiac autonomic system is less efficient at rest and less adaptive to exercise and activity as compared to TD children.

Spinal cord stimulation protects against ventricular arrhythmias by suppressing left stellate ganglion neural activity in an acute myocardial infarction canine model.

Previous studies have shown that spinal cord stimulation (SCS) may reduce ventricular arrhythmias (VAs) induced by acute myocardial infarction (AMI). Furthermore, activation of left stellate ganglion (LSG) appears to facilitate VAs after AMI. The purpose of this study was to investigate whether pretreatment with SCS could protect against VAs by reducing LSG neural activity in an AMI canine model. Thirty dogs were anesthetized and randomly divided into SCS group (with SCS, n = 15) and sham group (sham operation without SCS, n = 15). SCS was performed for 1 hour before AMI. Heart rate variability (HRV), ventricular effective refractory period (ERP), serum norepinephrine level, LSG function measured by blood pressure increases in response to LSG stimulation, and LSG neural activity were measured for 1 minute at baseline and 1 hour after SCS. AMI was induced by left anterior descending coronary artery ligation, and then HRV, LSG neural activity, and VAs were measured. Compared to baseline, SCS for 1 hour significantly prolonged ventricular ERP, increased HRV, and attenuated LSG function and LSG activity in the SCS group, whereas no significant change was shown in the sham group. AMI resulted in a significant decrease in HRV and increase in LSG neural activity in the sham group, which were attenuated in the SCS group (frequency: 99 ± 34 impulses/min vs 62 ± 22 impulses/min; amplitude: 0.41 ± 0.12 mV vs 0.18 ± 0.05 mV; both P <.05). The incidence of VAs was significantly lower in the SCS group than in the sham group. SCS may prevent AMI-induced VAs, possibly by suppressing LSG activity.

Heart rate variability and cognitive function following a multi-vitamin and mineral supplementation with added guarana (Paullinia cupana).

The aim of this study was to assess cognitive performance and heart rate variability (HRV) following the ingestion of either a multi-vitamin-mineral preparation supplemented with 300 mg guarana (Ac); a caffeine supplement (C) or a placebo supplement (Pl). Fifty-six subjects took part in a randomized, double-blind crossover design, consisting of three experimental sessions ran on a different day. Cognitive performance was assessed using a go/no-go task and a simple reaction time (SRT) task. HRV was assessed in the time domain (RMSSD) and in the frequency domain (HF) and cognitive tasks were performed before ingestion, 15 min after ingestion and then every 15 min over the course of 3 h. Responses were faster (without change in accuracy) when the go/no-go task was performed between 30 and 90 min after ingestion of Ac (4.6% ± 0.8%, p < 0.05). No effect was observed on SRT task. A significant decrease in HRV was observed during the first hour under C and Pl, whereas HRV remained stable under Ac. The results suggest that the ingestion of a multi-vitamin-mineral with added guarana improves decision-making performance and is accompanied by a stable autonomic nervous system regulation during the first hour.

Decreased heart rate variability in surgeons during night shifts.

Heart rate variability (HRV) has been used as a measure of stress and mental strain in surgeons. Low HRV has been associated with death and increased risk of cardiac events in the general population. The aim of this study was to clarify the effect of a 17-hour night shift on surgeons' HRV. Surgeons were monitored prospectively with an ambulatory electrocardiography device for 48 consecutive hours, beginning on a precall day and continuing through an on-call (17-h shift) day. We measured HRV by frequency domain parameters. We included 29 surgeons in our analysis. The median pulse rate was decreased precall (median 64, interquartile range [IQR] 56-70 beats per minute [bpm]) compared with on call (median 81, IQR 70-91 bpm, p < 0.001). Increased high-frequency (HF) activity was found precall (median 199, IQR 75-365 ms2) compared with on call (median 99, IQR 48-177 ms2, p < 0.001). The low-frequency:high-frequency (LF:HF) ratio was lower precall (median 2.7, IQR 1.9-3.9) than on call (median 4.9, IQR 3.7-6.5, p < 0.001). We found no correlation between the LF:HF ratio and performance in laparoscopic simulation. Surgeons working night shifts had a significant decrease in HRV and a significant increase in pulse rate, representing sympathetic dominance in the autonomic nervous system. NCT01623674 (www.clinicaltrials.gov).

Cardiac autonomic dysfunction in type 2 diabetes - effect of hyperglycemia and disease duration.

Heart rate variability (HRV) is reduced in diabetes mellitus (DM) patients, suggesting dysfunction of cardiac autonomic regulation and an increased risk for cardiac events. The aim of this paper was to examine the associations of blood glucose level (BGL), glycated hemoglobin (HbA1c), and duration of diabetes with cardiac autonomic regulation assessed by HRV analysis. Resting electrocardiogram (ECG), recorded over 20 min in supine position, and clinical measurements of 189 healthy controls and 93 type 2 DM (T2DM) patients were analyzed. HRV was assessed using several time-domain, frequency-domain, and non-linear methods. HRV parameters showed a clear difference between healthy controls and T2DM patients. Hyperglycemia was associated with increase in mean heart rate and decrease in HRV, indicated by negative correlations of BGL and HbA1c with mean RR interval and most of the HRV parameters. Duration of diabetes was strongly associated with decrease in HRV, the most significant decrease in HRV was found within the first 5–10 years of the disease. In conclusion, elevated blood glucose levels have an unfavorable effect on cardiac autonomic function and this effect is pronounced in long-term T2DM patients. The most significant decrease in HRV related to diabetes and thus presence of autonomic neuropathy was observed within the first 5–10 years of disease progression.

Heart rate and blood pressure variability in children with chronic kidney disease: a report from the CKiD study

Autonomic nervous system dysfunction and sympathetic nervous system over-activity play important roles in the development of hypertension associated with chronic kidney disease (CKD). In adults, increased blood pressure variability (BPV) appears to be directly related to sympathetic over-activity with increased risk of end-organ damage and cardiovascular events. Decreased heart rate variability (HRV) has been observed in adults with CKD, and is an independent predictor of mortality. The purpose of this study was to evaluate BPV and HRV in pediatric patients enrolled in the Chronic Kidney Disease in Children Study. Ambulatory blood pressure monitoring data were available for analysis of 215 person-visits from 144 children that were not receiving antihypertensive medications. BPV and HRV were determined by standard deviation and coefficient of variation for heart rate and systolic and diastolic blood pressure for each patient averaged for wake/sleep periods during 24-h monitoring. Uniformly lower values were displayed during sleep versus wake periods: BPV was 20% lower during sleep (p < 0.001) and HRV was 30% lower during sleep (p < 0.001). A significant increase in systolic BPV was observed in hypertensive children compared to children with normal blood pressure (6.9%, p = 0.009). Increased diastolic BPV was detected among hypertensive children during sleep period compared to children with normal blood pressure (11.5%, p = 0.008). There was a significant decrease in HRV in hypertensive compared to normotensive children (-8.2%, p = 0.006). These findings are similar to those in adult patients and may underscore childhood origin and natural progression of adverse cardiovascular outcomes in adults with CKD.

Diminazene Aceturate Improves Autonomic Modulation in Pulmonary Hypertension

Our studies have demonstrated that diminazene aceturate (DIZE) protects rats from monocrotaline (MCT)-induced pulmonary hypertension (PH). The present study was conducted to determine if these effects of DIZE are associated with improvements in autonomic nervous system (ANS) modulation. A single dose of MCT (50mg/kg) was subcutaneously injected to induce PH. A subset of MCT rats were treated with DIZE (15mg/kg/day) for 21 days. ANS control was evaluated by spectral and symbolic analysis of heart rate variability (HRV). MCT induced a significant (p<0.001) increase in right ventricular systolic pressure (62±14mmHg) when compared to all other groups (Control: 26±6; DIZE alone: 29±5; MCT+DIZE: 31±7). MCT treatment was associated with a significant decrease in HRV versus control (s2; Control: 93±32; DIZE: 64±58; MCT+DIZE: 41±15 and MCT: 14±11) and with an increase in the cardiac sympathetic modulation, observed by 0V pattern of symbolic analysis (Control: 4±1; DIZE: 8.8±6.1; MCT+DIZE: 2.9±2.4 and MCT: 11±6.3). This observation was confirmed by the LF/HF index of spectral analysis (Control: 0.4±0.09; DIZE: 0.06±0.007; MCT+DIZE: 0.14±0.1and MCT: 1.0±0.7) which showed that DIZE was able to recover the ANS balance. Thus, our results demonstrate that MCT-induced PH is associated with a significant increase in sympathetic modulation and a decrease in HRV. Furthermore, DIZE was able to reestablish the ANS balance.

Risk Compensation and Bicycle Helmets

This study investigated risk compensation by cyclists in response to bicycle helmet wearing by observing changes in cycling behavior, reported experience of risk, and a possible objective measure of experienced risk. The suitability of heart rate variability (HRV) as an objective measure of experienced risk was assessed beforehand by recording HRV measures in nine participants watching a thriller film. We observed a significant decrease in HRV in line with expected increases in psychological challenge presented by the film. HRV was then used along with cycling pace and self-reported risk in a field experiment in which 35 cyclist volunteers cycled 0.4 km downhill, once with and once without a helmet. Routine helmet users reported higher experienced risk and cycled slower when they did not wear their helmet in the experiment than when they did wear their helmet, although there was no corresponding change in HRV. For cyclists not accustomed to helmets, there were no changes in speed, perceived risk, or any other measures when cycling with versus without a helmet. The findings are consistent with the notion that those who use helmets routinely perceive reduced risk when wearing a helmet, and compensate by cycling faster. They thus give some support to those urging caution in the use of helmet laws.

Endotoxin depresses heart rate variability in mice: cytokine and steroid effects

Heart rate variability (HRV) falls in humans with sepsis, but the mechanism is not well understood. We utilized a mouse model of endotoxemia to test the hypothesis that cytokines play a role in abnormal HRV during sepsis. Adult male C57BL/6 mice underwent surgical implantation of probes to continuously monitor electrocardiogram and temperature or blood pressure via radiotelemetry. Administration of high-dose LPS (Escherichia coli LPS, 10 mg/kg, n = 10) caused a biphasic response characterized by an early decrease in temperature and heart rate at 1 h in some mice, followed by a prolonged period of depressed HRV in all mice. Further studies showed that LPS doses as low as 0.01 mg/kg evoked a significant decrease in HRV. With high-dose LPS, the initial drops in temperature and HR were temporally correlated with peak expression of TNFalpha 1 h post-LPS, whereas maximal depression in HRV coincided with peak levels of multiple other cytokines 3-9 h post-LPS. Neither hypotension nor hypothermia explained the HRV response. Pretreatment with dexamethasone prior to LPS significantly blunted expression of 7 of the 10 cytokines studied and shortened the duration of depressed HRV by about half. Interestingly, dexamethasone treatment alone caused a dramatic increase in both low- and high-frequency HRV. Administration of recombinant TNFalpha caused a biphasic response in HR and HRV similar to that caused by LPS. Understanding the role of cytokines in abnormal HRV during sepsis could lead to improved strategies for detecting life-threatening nosocomial infections in intensive care unit patients.