Differences in autonomic balance in patients with cardioinhibitory and vasodepressor type of reflex syncope during head-up tilt test and active standing

Prognostic value of heart rate variability for risk of serious adverse events in continuously monitored hospital patients

Technological advances allow continuous vital sign monitoring at the general ward, but traditional vital signs alone may not predict serious adverse events (SAE). This study investigated continuous heart rate variability (HRV) monitoring's predictive value for SAEs in acute medical and major surgical patients. Data was collected from four prospective observational studies and two randomized controlled trials using a single-lead ECG. The primary outcome was any SAE, secondary outcomes included all-cause mortality and specific non-fatal SAE groups, all within 30 days. Subgroup analyses of medical and surgical patients were performed. The primary analysis compared the last 24 h preceding an SAE with the last 24 h of measurements in patients without an SAE. The area under a receiver operating characteristics curve (AUROC) quantified predictive performance, interpretated as low prognostic ability (0.5-0.7), moderate prognostic ability (0.7-0.9), or high prognostic ability (> 0.9). Of 1402 assessed patients, 923 were analysed, with 297 (32%) experiencing at least one SAE. The best performing threshold had an AUROC of 0.67 (95% confidence interval (CI) 0.63-0.71) for predicting cardiovascular SAEs. In the surgical subgroup, the best performing threshold had an AUROC of 0.70 (95% CI 0.60-0.81) for neurologic SAE prediction. In the medical subgroup, thresholds for all-cause mortality, cardiovascular, infectious, and neurologic SAEs had moderate prognostic ability, and the best performing threshold had an AUROC of 0.85 (95% CI 0.76-0.95) for predicting neurologic SAEs. Predicting SAEs based on the accumulated time below thresholds for individual continuously measured HRV parameters demonstrated overall low prognostic ability in high-risk hospitalized patients. Certain HRV thresholds had moderate prognostic ability for prediction of specific SAEs in the medical subgroup.

Relationship between hemodynamic type and syncopal symptoms in pediatric vasovagal syncope

Vasovagal syncope (VVS) is a clinically common neurally mediated syncope. The relationship between different hemodynamic types of VVS and clinical syncopal symptoms has not been reported. The purpose of this research is to explore relationship between hemodynamic types and syncopal symptoms in pediatric VVS. Two thousand five hundred thirteen patients diagnosed with VVS at the age of 3-18 years, average age was 11.76 ± 2.83 years, including 1124 males and 1389 females, due to unexplained syncope and pre-syncope from single-center of January 2001 to December 2021 were retrospectively analyzed. Subjects were divided into two groups according to the presence or absence of syncopal symptoms: syncope group (1262 cases) and pre-syncope group (1251 cases). (1) Baseline characteristics: age, height, weight, systolic blood pressure (SBP), and diastolic blood pressure (DBP) increased in the syncope group compared with the pre-syncope group; the composition ratio of females was more than that of males in the syncope group; and the composition ratio of VVS-cardioinhibited (VVS-CI) and VVS-mixed (VVS-M) was more in the syncope group than that of the pre-syncope group (all P < 0.05). (2) Univariate analysis: age, height, weight, SBP, DBP, female, VVS-CI, and VVS-M were potential risk factors for the presence of syncopal symptoms (all P < 0.05). (3) Multivariate analysis: VVS-CI and VVS-M were independent risk factors for the presence of syncopal symptoms, with an increased probability of 203% and 175%, respectively, compared to VVS-vasoinhibited (VVS-VI) (all P < 0.01).

CONCLUSION

The hemodynamic type of pediatric VVS is closely related to the syncopal symptoms.

WHAT IS KNOWN

• There are varying probabilities of syncopal episodes in different hemodynamic types of VVS, and there is a lack of research to assess the comparative risk of syncope in children with different hemodynamic types of VVS.

WHAT IS NEW

• The probability in presence of syncopal symptoms varies greatly between different hemodynamic types of VVS. • VVS-CI and VVS-M had a 203% and 175% increased risk in presence of syncopal symptoms compared with VVS-VI, respectively.

Predictive Value of Blood Pressure, Heart Rate, and Blood Pressure/Heart Rate Ratio in a Chinese Subpopulation with Vasovagal Syncope

Objective: The head-up tilt test (HUTT) is widely used but is time-consuming and not cost-effective to evaluate patients with vasovagal syncope (VVS). The present study aims to verify the hypothesis that ambulatory blood pressure (BP) monitoring (ABPM) and the simplistic tilt test may be potential alternatives to the HUTT.Methods: The study consecutively enrolled 360 patients who underwent the HUTT to evaluate VVS. BP), heart rate (HR), and BP/HR ratios derived from ABPM and the simplistic tilt test were evaluated to predict the presence, pattern, and stage of syncope during the HUTT.Results: Mixed response was the commonest pattern, and syncope occurred frequently with infusion of isoproterenol at a rate of 3 μg/min. During the simplistic tilt test, the cardioinhibitory group had higher tilted BP/HR ratios than the vasodepressor group, while the vasodepressor group had a faster tilted HR and a larger HR difference than the cardioinhibitory group. The higher the BP/HR ratio in the tilted position, the higher the isoproterenol dosage needed to induce a positive response. During ABPM, BP/HR ratios were significantly higher in the cardioinhibitory group than in the vasodepressor group. The higher the ABPM-derived BP, the higher the dosage of isoproterenol needed to induce syncope. There were significant correlations in BP/HR ratios between ABPM and the supine position in the vasodepressor group, while significant correlation was found only for the diastolic BP/HR ratio between ABPM and the tilted position in the cardioinhibitory group. The mixed pattern shared correlative features of the other two patterns.Conclusion: ABPM and the simplistic tilt test might be used as promising alternatives to the HUTT in VVS evaluation in clinical settings.

Cardiac Autonomic Response to Active Standing in Adults With Vasovagal Syncope

PURPOSE

Little is known about the autonomic response to active standing in vasovagal syncope, and most works have focused on children or adolescents. The aim of this work was to study the changes in cardiac autonomic modulation in adult patients with vasovagal syncope through heart rate variability analysis with linear and short-term complexity (alpha-1) indexes during supine position and active standing, in patients with positive or negative head-up tilt test (HUTT).

METHODS

Twenty-five patients with vasovagal syncope were included. Heart rate variability linear and short-term complexity (alpha-1) indexes were recorded during an active standing test (15 minutes in each position) and compared among patients grouped by HUTT outcome and between positions.

RESULTS

During supine position, positive HUTT (+HUTT) patients had longer mean RR (1016 [850-1051] milliseconds), higher pNN50 (17.7 [9.2-26.2]), lower sympathovagal balance (1.3 [0.5-1.7]), and alpha-1 (0.9 [0.8-1.0]) than negative HUTT (-HUTT) patients (871 [776-969] milliseconds, 8.8 [2.1-14.5], 2.9 [1.3-3.9], and 1.2 [1.0-1.1], respectively). During active standing, heart rate and alpha-1 increased in both groups; in +HUTT patients, pNN50 decreased, whereas sympathovagal balance increased. The magnitude of change between positions of sympathovagal balance and alpha-1 was 6.1 and 4.8 times larger in +HUTT than -HUTT patients, respectively.

CONCLUSIONS

The underlying cardiac autonomic mechanism in vasovagal syncope may involve different autonomic patterns in subjects with a history of recurrent syncope and +HUTT or -HUTT.

Orthostatic Changes in Hemodynamics and Cardiovascular Biomarkers in Dysautonomic Patients

Background

Impaired autonomic control of postural homeostasis results in orthostatic intolerance. However, the role of neurohormones in orthostatic intolerance has not been explained.

Methods

Six-hundred-and-seventy-one patients (299 males; 55±22 years) with unexplained syncope underwent head-up tilt (HUT) with serial blood sampling. Systolic blood pressure (SBP) and heart rate (HR) supine, after 3min, and lowest BP/highest HR during HUT were recorded. Plasma levels of epinephrine, norepinephrine, renin, C-terminal-pro-arginine-vasopressin (CT-proAVP), C-terminal- endothelin-1 (CT-proET-1), and mid-regional-fragment of pro-atrial-natriuretic-peptide (MR-proANP) were determined at supine and 3min of HUT. Multivariate-adjusted logistic regression model was applied to compare 1^st (reference) with 4^th quartile of 3 min and maximal ΔSBP/ΔHR (i.e. pronounced hypotension or tachycardia) vs. changes in neuroendocrine biomarkers, respectively.

Results

Higher resting CT-proET-1 predicted BP fall at 3min (Odds ratio (OR) per 1 SD: 1.62, 95%CI 1.18–2.22; p = 0.003), and max BP fall during HUT (1.82, 1.28–2.61; p = 0.001). Higher resting CT-proAVP predicted BP fall at 3min (1.33, 1.03–1.73; p = 0.03), which was also associated with increase in CT-proAVP (1.86, 1.38–2.51; p = 0.00005) and epinephrine (1.47, 1.12–1.92; p = 0.05) during HUT. Lower resting MR-proANP predicted tachycardia at 3min (0.37, 0.24–0.59; p = 0.00003), and max tachycardia during HUT (0.47, 0.29–0.77; p = 0.002). Further, tachycardia during HUT was associated with increase in epinephrine (1.60, 1.15–2.21; p = 0.005), and norepinephrine (1.87, 1.38–2.53; p = 0.005).

Conclusions

Resting CT-proET-1 and CT-proAVP are increased in orthostatic hypotension, while resting MR-proANP is decreased in postural tachycardia. Moreover, early BP fall during orthostasis evokes increase in CT-proAVP and epinephrine, while postural tachycardia is associated with increase in norepinephrine and epinephrine.

Kernel based support vector machine for the early detection of syncope during head-up tilt test

This study aims to analyze the autonomic nervous system response during head-up tilt test (HUTT), by exploring the changes in dynamic properties of heart rate variability in subjects with and without syncopes, to predict the outcome of HUTT. Baroreflex response, as well as linear and non-linear parameters of RR-interval time series, have been extracted from the ECG of 66 subjects: 35 with and 31 without syncope during HUTT. The results show that, when considering the first 15 min of tilting position, the total power spectrum, the standard deviation, the long-term fractal scale of RR-interval and ΔRR-interval of time series increase, while the sample entropy decreases in the positive group compared to the negative one. These indices may be good predictors of positive response in patients with reflex syncope. Additionally, an analysis of the first 15 min of tilting position using kernel support vector machines leads to a correct classification of 85% of patients, within negative and positive response groups (specificity = 80.6% and sensitivity = 88.5%). In medical applications, it is important to avoid false negative diagnosis of syncopes during HUTT. Taking this into account, an overall accuracy of 72.1% can be obtained in the same window allowing the reduction of the examination time in the clinical domain.

Onset of sweating depends on the type of reflex syncope

Reflex syncope is classified based on the efferent autonomic system as vasodepressant type, cardioinhibitory type and mixed type. We employed quantitative sweat testing to assess differences in sudomotor sympathetic activity in relation to the type of reflex syncope. In cardioinhibitory type sweating started in 7/9 patients after and in vasodepressor type in 11/12 patients before syncope. In mixed type sweating in 20 patients started before and in 10 after syncope. The onset of sweating correlated significantly with the onset of syncope symptoms. These results possibly reflect different onsets of emotional sweating.

Natriuretic peptides in the evaluation of syncope in children and adolescents

INTRODUCTION

Natriuretic peptides have an increasing role in assessing cardiovascular conditions. The number of papers addressing their role in the evaluation of children with syncope of unclear etiology is sparse. The aim of this study was to determine whether measuring atrial natriuretic peptide (ANP) and the inactive form, N-terminal prohormone of brain natriuretic peptide (NT-proBNP) concentration in children admitted due to differential diagnosis of syncope can be helpful in establishing the most probable cause of this condition.

METHODS

The study included 88 patients between 9 and 18 years of age hospitalized due to syncope. The control group comprised 25 healthy children. In order to identify the cause of syncope, children with this condition were subjected to cardiologic and neurologic evaluation, and ANP and NT-proBNP concentrations were determined.

RESULTS

The syncope group and the controls did not differ significantly in terms of natriuretic peptides concentrations. Similarly, no significant intergroup differences in natriuretic peptide concentrations were documented between children representing various types of response to the tilt test, and between the subgroups of patients with syncope of various origins.

CONCLUSION

Analysis of natriuretic peptides concentrations in children with syncope does not result in unambiguous findings that would enable establishing accurate diagnosis.