Inadequate sympathovagal balance in response to orthostatism in patients with unexplained syncope and a positive head up tilt test

Unraveling Autonomic Dysfunction in GBA-Related Parkinson's Disease

Background

Patients with Parkinson's disease (PD) and GBA gene mutations (GBA-PD) develop nonmotor complications more frequently than noncarriers. However, an objective characterization of both cardiovascular and sudomotor autonomic dysfunction using extensive clinical and instrumental measures has never been provided so far. Survival is reduced in GBA-PD regardless of age and dementia, suggesting that other hitherto unrecognized factors are involved.

Objectives

To provide instrumental measures of pattern and severity of autonomic dysfunction in GBA-PD and explore their correlation with other non-motor symptoms and implications for clinical practice.

Methods

In this cross-sectional study, 21 GBA-PD and 24 matched PD noncarriers underwent extensive assessment of motor and non-motor features, including neuropsychological testing. Cardiovascular autonomic function was explored through a comprehensive battery of indexes, including power spectral analysis of the R-R intervals and blood pressure short-term variability during resting state and active maneuvers. Dynamic Sweat Test was used to assess post-ganglionic sudomotor dysfunction.

Results

Despite minimal or absent clinical correlates, cardiovagal and sympathetic indexes, heart rate variability parameters and sudomotor postganglionic function were more severely impaired in GBA-PD than noncarriers (overcoming relatively preserved compensatory peripheral sympathetic function), suggesting more prominent cardiac sympatho-vagal demodulation, efferent baroreflex failure and peripheral sympathetic dysfunction in GBA-PD. Cardiovascular dysautonomia showed marginal correlations with cognitive impairment.

Conclusions

Compared to PD noncarriers, GBA-PD display more severe instrumental autonomic abnormalities, which may be underestimated by purely clinical measures, despite their relevance on morbidity and mortality. This supports the necessity of implementing instrumental autonomic assessment in all GBA-PD, regardless of clinically overt symptoms.

Simultaneous beat-to-beat heart rate and systolic blood pressure variability in patients with and without neurally mediated syncope

Introduction: Autonomic changes play an essential role in the genesis of neurally mediated syncope (NMS). The aim of this study was to compare the changes of the autonomic nervous system (ANS) by measuring spectral indices of beat-to-beat systolic blood pressure and heart rate variability (SBPV and HRV) in ranges of low frequency (LF), high frequency (HF), and the LF/HF ratio during head-up tilt test (HUTT) in patients with and without a syncope response.

Methods: In this case-control study of 46 patients with a suspected history of unexplained syncope, data were recorded separately during the typical three phases of HUTT. Patients who developed syncope were designated as the case group and the rest as the control group.

Results: Thirty one patients experienced syncope during HUTT. Resting HRV and SBPV indices were significantly lower in cases than controls. After tilting in the syncope group, both HF and LF powers of SBPV showed a significant and gradual decrease. LF/HF in HRV increased in both groups similarly during the test but in SBPV, mainly driven by oscilations in its LF power, it increased significantly more during the first two phases of the test in syncope patients only to paradoxically decrease during active tilt (P< 0.001).

Conclusion: Our findings show an abnormal autonomic function in patients with syncope, both at rest and tilting. Fluctuations of spectral indices of beat-to-beat SBPV, a potential noval index of pure sympathetic activity, show an exaggerated response during tilt and its withdrawal before syncope.

A randomized study of yoga therapy for the prevention of recurrent reflex vasovagal syncope

AIMS

Vasovagal syncope (VVS) is a common cardiovascular dysautonomic disorder that significantly impacts health and quality of life (QoL). Yoga has been shown to have a positive influence on cardiovascular autonomics. This study assessed the effectiveness of yoga therapy on the recurrence of VVS and QoL.

METHODS AND RESULTS

We randomized subjects with recurrent reflex VVS (>3 episodes in the past 1 year) and positive head-up tilt test to guideline-directed therapy (Group 1) or yoga therapy (Group 2). Patients in Group 1 were advised guideline-directed treatment and Group 2 was taught yoga by a certified instructor. The primary endpoint was VVS recurrences and QoL. Between June 2015 and February 2017, 97 highly symptomatic VVS patients were randomized (Group 1: 47 and Group 2: 50). The mean age was 33.1 ± 16.6 years, male:female of 40:57, symptom duration of 17.1 ± 20.7 months, with a mean of 6.4 ± 6.1 syncope episodes. Over a follow-up of 14.3 ± 2.1 months Group 2 had significantly lower syncope burden compared with Group 1 at 3 (0.8 ± 0.9 vs. 1.8 ± 1.4, P < 0.001), 6 (1.0 ± 1.2 vs. 3.4 ± 3.0, P < 0.001), and at 12 months (1.1 ± 0.8 vs. 3.8 ± 3.2, P < 0.001). The Syncope functional score questionnaire was significantly lower in Group 2 compared with Group 1 at 3 (31.4 ± 7.2 vs. 64.1 ± 11.5, P < 0.001), 6 (26.4 ± 6.3 vs. 61.4 ± 10.7, P < 0.001), and 12 months (22.2 ± 4.7 vs. 68.3 ± 11.4, P < 0.001).

CONCLUSION

For patients with recurrent VVS, guided yoga therapy is superior to conventional therapy in reducing symptom burden and improving QoL.

Are women really more affected by vasovagal syncope than men?

It is commonly reported that vasovagal syncope (VVS) is more frequent in women. Presently, this issue has never been investigated. The purpose of this review was to evaluate, through an extensive review of the literature, whether women are really more affected by VVS than men. The gender distribution was investigated in individuals with classical and nonclassical VVS. The database PubMed was searched using the terms 'syncope', 'vasovagal syncope', 'neurally mediated syncope' and 'tilt testing'. Twelve studies dealing with classical and 75 with nonclassical VVS were eligible. In the individuals with classical (N = 1861) and nonclassical VVS (N = 9696), a trend towards a greater percentage of women emerged (P = 0.14 and 0.07, respectively). In the total population with VVS (N = 11 557), the percentage of women was significantly higher than that of men (58 versus 42%, P = 0.03). Most of the individuals were young or middle-aged. In 84% of the studies, the percentage of women was greater than that of men. A separate analysis was carried out in older VVS patients (≥60 years) and only two studies were eligible to be evaluated. Considering that almost all the studies were carried out in the western nations, where the number of men and women is almost superimposable until the age of 65 years and a bias by gender has never been reported in the management of VVS, these data strongly suggest that young and middle-aged women are more affected by VVS than their male counterparts. At present, data are too scant to draw a definitive conclusion in older VVS patients.

Preliminary Comparison of Zero-Gravity Chair With Tilt Table in Relation to Heart Rate Variability Measurements

Heart rate variability (HRV) measurements are performed using a tilt-table (TT) to diagnose dysfunctionality in the autonomic nervous system (ANS) and the cardiovascular system. To maintain homeostasis, the ANS adapts to body position changes through alterations in sympathetic and parasympathetic responses that can be quantified by extracting time-domain and frequency-domain parameters from the heart rate signal. When body position is changed from supine to erect, a healthy subject’s response also shows changes in ANS activity. However, TT can be unsafe or uncomfortable for elderly or overweight subjects. Furthermore, it may induce anxiety which alters the HRV measurements. This study proposes an alternative strategy to replace the TT with a zero-gravity chair (ZGC). The statistical analysis between HRV parameters from the TT and the ZGC shows that ZGC can be a feasible alternative to TT. Therefore, ZGC can be used as a more convenient, secure, stable and safer option to the traditional HRV analysis with TT.

Entropy Measures in Analysis of Head up Tilt Test Outcome for Diagnosing Vasovagal Syncope

The paper presents possible applications of entropy measures in analysis of biosignals recorded during head up tilt testing (HUTT) in patients with suspected vasovagal syndrome. The study group comprised 80 patients who developed syncope during HUTT (57 in the passive phase of the test (HUTT(+) group) and 23 who had negative result of passive phase and developed syncope after provocation with nitroglycerine (HUTT(−) group)). The paper focuses on assessment of monitored signals’ complexity (heart rate expressed as R-R intervals (RRI), blood pressure (sBP, dBP) and stroke volume (SV)) using various types of entropy measures (Sample Entropy (SE), Fuzzy Entropy (FE), Shannon Entropy (Sh), Conditional Entropy (CE), Permutation Entropy (PE)). Assessment of the complexity of signals in supine position indicated presence of significant differences between HUTT(+) versus HUTT(−) patients only for Conditional Entropy (CE(RRI)). Values of CE(RRI) higher than 0.7 indicate likelihood of a positive result of HUTT already at the passive phase. During tilting, in the pre-syncope phase, significant differences were found for: (SE(sBP), SE(dBP), FE(RRI), FE(sBP), FE(dBP), FE(SV), Sh(sBP), Sh(SV), CE(sBP), CE(dBP)). HUTT(+) patients demonstrated significant changes in signals’ complexity more frequently than HUTT(−) patients. When comparing entropy measurements done in the supine position with those during tilting, SV assessed in HUTT(+) patients was the only parameter for which all tested measures of entropy (SE(SV), FE(SV), Sh(SV), CE(SV), PE(SV)) showed significant differences.

Unconstrained Estimation of HRV Indices After Removing Respiratory Influences From Heart Rate

OBJECTIVE

This paper proposes an approach to better estimate the sympathovagal balance (SB) and the respiratory sinus arrhythmia (RSA) after separating respiratory influences from the heart rate (HR).

METHODS

The separation is performed using orthogonal subspace projections and the approach is first tested using simulated HR and respiratory signals with different spectral properties. Then, RSA and SB are estimated during autonomic blockade and stress using the proposed approach and the classical heart rate variability (HRV) analysis. Both real- and ECG-derived respiration (EDR) are used and the reliability of the EDR is evaluated.

RESULTS

Mean absolute percentage errors lower than [Formula: see text] were obtained after removing previously known respiratory signals from simulated HR. The proposed indices were able to improve the quantification of SB during autonomic withdrawal. In the stress data, differences ( ) among relaxed and stressful phases were found with the proposed approach, using both the real respiration and the EDR, but they disappeared when using the classical HRV.

CONCLUSION

A better assessment of the autonomic nervous system' response to pharmacological blockade and stress can be achieved after removing respiratory influences from HR, and this can be done using either the real respiration or the EDR.

SIGNIFICANCE

This work can be used to better identify vagal withdrawal and increased sympathetic activation when the classical HRV analysis fails due to the respiratory influences on HR. Furthermore, it can be computed using only the ECG, which is an advantage when developing wearable systems with limited number of sensors.

The complexity of hemodynamic response to the tilt test with and without nitroglycerine provocation in patients with vasovagal syncope

The paper presents a comparison of vasovagal syndrome occurrence in a head up tilt table test between patients with a positive result of passive tilt test and those with a positive result after pharmacological provocation. The study group consisted of 80 patients: 57 patients who experienced syncope in the passive phase of the test (43 women (aged: 35.6 ± 16.2) and 14 men (aged: 41.7 ± 15.6) and 23 patients who experienced syncope after pharmacological provocation (17 women (age: 32.3 ± 12) and 6 men (age: 43 ± 15). The main investigation was based on the assessment of monitored signals complexity: heart rate, blood pressure and stroke volume. The analysis of complexity in chosen measurement phases was performed with Sample Entropy. The investigation showed that the reactions of autonomic nervous system during tilt test and before syncope are similar for positive result of passive tilt test and positive result of tilt test with provocation. The differences in supine position occurred only in analysis based on impedance measurement (SV: p = 0.01). Significant differences were denoted for all signals just before the syncope (RRI, sBP, dBP: p = 0,00001 and SV: p = 0.01). In analysis of signals complexity the significant differences occurred just before the syncope for Sample Entropy of blood pressure (SampEn (sBP): p = 0.0008, SampEn (dBP): p = 0,0001).

Modulation of the orthostatic blood pressure response by acute nitrate consumption is dependent upon ethnic origin

Orthostatic stress triggers a response to maintain cerebral perfusion and prevent syncope. Given the hypotensive effects of inorganic nitrate this response to orthostasis may be altered by acute supplementation with inorganic nitrate and modified by ethnic origin. Caucasian and SE Asian (n = 30 for both), were recruited and subjected to an 'active stand test' and brachial artery blood pressure (BP), digit blood flow and ECG were recorded. Following inorganic nitrate supplementation, (10 mg/kg body mass) the tests were repeated. For both Caucasian and SE Asians transition to standing increased diastolic pressure (DP) and heart rate (HR) (P < 0.001 for both) and by calculation increased rate-pressure product (P < 0.001) and decreased pulse pressure (P < 0.01 for both) indicative of decreased ventricular filling. Nitrate supplementation decreased both DP (P < 0.001) and HR (P < 0.001). Assessment of HR variability suggested sympathetic nerve activity, was higher throughout in Caucasians (P < 0.05) coupled with higher parasympathetic tone (P < 0.01). Nitrate had no effect on cardiac autonomic nerve activity, as estimated using HR variability, for supine or standing subjects. The tachycardia and hypertension associated with orthostatic stress were preserved in both Caucasian and SE Asian subjects, however, we highlight possible differences in autonomic nervous system activity between Caucasians and SE Asians. SE Asians are resistant to the hypotensive effects of inorganic nitrate supplementation suggesting the absence of a crucial mechanism for activation of the nitrate-nitrite-nitric oxide system.

Predictive value of very low frequency at spectral analysis among patients with unexplained syncope assessed by head-up tilt testing

BACKGROUND

The role of heart rate variability (HRV) in the prediction of vasovagal syncope during head-up tilt testing (HUTt) is unclear.

AIM

To evaluate the ability of the spectral components of HRV at rest to predict vasovagal syncope among patients with unexplained syncope referred for HUTt.

METHODS

Twenty-six consecutive patients with unexplained syncope were enrolled in the study. All patients underwent HRV evaluation at rest (very low frequency [VLF], low frequency [LF], high frequency [HF] and LF/HF ratio) and during HUTt. HUTt was performed using the Westminster protocol. Continuous electrocardiogram and blood pressure monitoring were performed throughout the test.

RESULTS

Eight (31%) patients developed syncope during HUTt. There were no baseline differences in terms of clinical features and HRV variables among patients who developed syncope and those who did not, except for VLF (2421 vs 896ms²; P<0.001). In the multivariable logistic regression analysis, including age and sex, VLF was the only independent variable associated with syncope during HUTt (odds ratio 1.002, 95% confidence interval 1.0003-1.0032; P=0.02). The area under the curve at rest was 0.889 for VLF, 0.674 for HF and 0.611 for LF. A value of VLF>2048ms² was the optimal cut-off to predict syncope during HUTt (sensitivity 87.5%, specificity 72.2%).

CONCLUSIONS

VLF at rest predicted the incidence of syncope during HUTt. Further studies are warranted to confirm these preliminary data.

Analysis of Heart Rate Variability Before and During Tilt Test in Patients with Cardioinhibitory Vasovagal Syncope

BACKGROUND

Cardioinhibitory vasovagal response is uncommon during the tilt test (TT). Heart rate variability (HRV) by use of spectral analysis can distinguish patients with that response.

OBJECTIVE

To compare the HRV in patients with cardioinhibitory vasovagal syncope (case group - G1) with that in patients without syncope and with negative response to TT (control group - G2).

METHODS

64 patients were evaluated (mean age, 36.2 years; 35 men) and submitted to TT at 70 degrees, under digital Holter monitoring. The groups were paired for age and sex (G1, 40 patients; G2, 24).

RESULTS

In G1, 21 patients had a type 2A response and 19 had type 2B, with mean TT duration of 20.4 minutes. There was a greater low frequency (LF) component (11,6 versus 4,5 ms2, p=0.001) and a lower low/high frequency ratio in the supine position (3,9 versus 4,5 ms2, p=0.008) in G1, with no difference during TT between the groups. Applying the receiver operating characteristic curve for cardioinhibitory response, the area under the curve was 0.74 for the LF component in the supine position (p = 0.001). The following were observed for the cutoff point of 0.35 ms(2) for the LF component: sensitivity, 97.4%; specificity, 83.3%; positive predictive value, 85.3%; negative predictive value, 96.9%; and positive likelihood ratio, 5.8.

CONCLUSION

HRV in the supine position allowed identifying patients with syncope and cardioinhibitory response with a high negative predictive value and likelihood ratio of 5.8.

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.

The Role of the Baroreflex in Tilt Table Testing: Outcome and Type of Response

OBJECTIVES

The purpose of this study was to better understand the role of the baroreflex in tilt-induced vasovagal syncope (VVS).

BACKGROUND

The role of the baroreflex in tilt-induced VVS remains controversial. The authors hypothesized that: 1) patients with positive tilt table test (TTT) results have greater baroreflex gain (BRG) compared with patients with negative TTT results; and 2) patients with tilt-induced asystole have greater BRG compared with patients without asystole.

METHODS

Using the sequence method, BRG measurements were obtained in 438 consecutive patients undergoing TTT. Two hundred sixty-eight patients (61%) had positive TTT results (mean age 50 ± 21 years; 34% men), and 170 patients (39%) had negative TTT results (mean age 48 ± 21 years; 35% men).

RESULTS

Mean BRG was significantly higher in patients with positive TTT results compared with those with negative TTT results (12.9 ± 6.0 ms/mm Hg vs. 11.5 ± 6.0 ms/mm Hg; p = 0.01). Among the 268 patients with positive TTT results, 23 (9%) had more than 3 s of asystole (mean age 37 ± 17; 30% men), and 245 patients had a mixed vasodepressor or cardioinhibitory response without asystole (mean age 51 ± 17 years; 34% men). Mean BRG was greater in patients with tilt-induced asystole (>3 s) compared with patients without asystole (15.3 ± 5.9 ms/mm Hg vs. 12.7 ± 5.9 ms/mm Hg; p = 0.03).

CONCLUSIONS

The results of this study demonstrate that baseline BRG was higher in patients with positive TTT results compared with those with negative TTT results, with greater values noted in patients with tilt-induced asystole (>3 s) compared with those without asystole.

Cerebral blood flow during HUTT in young patients with orthostatic intolerance

PURPOSE

To investigate patterns of change in cerebral perfusion during head-up tilt testing (HUTT) in children and young adults with autonomic dysfunction.

METHODS

We utilized near-infrared spectroscopy (NIRS) to estimate bilateral cerebral perfusion patterns during HUTT in 71 adolescents and young adults with a diagnosis of autonomic dysfunction. In addition, we used transthoracic impedance to measure cardiac stroke volume and thus infer autonomic tone, heart rate, and blood pressure during the test. Cerebral blood-flow wave-patterns were then visually analyzed and associated with clinical symptoms and measures of cardiovascular and autonomic function.

RESULTS

Visual analysis of contour changes in head NIRS values during phases of HUTT revealed variable patterns of cerebral blood flow, some specifically associated with severe symptomatology (i.e., syncope). We also observed an inequality in blood flow of the cerebral hemispheres in many patients. Finally, we observed changes in cardiac stroke volume during HUTT, as previously reported, that related to changes in head NIRS.

CONCLUSION

These results confirm a decrease in cerebral blood flow during HUTT as assessed by head NIRS in patients with autonomic dysfunction. Specifically, we have profiled the cerebral blood flow contours throughout the phases of HUTT, which add insight into the clinical spectrum of the disorder and may correlate with clinical severity.

Real-Time Prediction of Neurally Mediated Syncope

Neurally mediated syncope (NMS) patients suffer from sudden loss of consciousness, which is associated with a high rate of falls and hospitalization. NMS negatively impacts a subject's quality of life and is a growing cost issue in our aging society, as its incidence increases with age. In this paper, we present a solution for prediction of NMS, which is based on the analysis of the electrocardiogram (ECG) and photoplethysmogram (PPG) alone. Several parameters extracted from ECG and PPG, associated with reflectory mechanisms underlying NMS in previous publications, were combined in a single algorithm to detect impending syncope. The proposed algorithm was evaluated in a population of 43 subjects. The feature selection, distance metric selection, and optimal threshold were performed in a subset of 30 patients, while the remaining data from 13 patients were used to test the final solution. Additionally, a leave-one-out cross-validation scheme was also used to evaluate the performance of the proposed algorithm yielding the following results: sensitivity (SE)--95.2%; specificity (SP)--95.4%; positive predictive value (PPV)--90.9%; false-positive rate per hour (FPRh)-0.14 h(-1), and prediction time (aPTime)--116.4 s.

Biogenic amine metabolism in juvenile neurocardiogenic syncope with dysautonomia

OBJECTIVE

Biogenic amine brain levels and their cerebral metabolism are frequently studied by quantitation of biogenic amine metabolites in cerebrospinal fluid (CSF) compared to age-matched controls. There is a paucity of studies in adolescents and young adults investigating the potential role of disordered cerebral biogenic amine metabolism in young patients who have dysautonomia based on abnormal head-up tilt table (HUTT).

METHODS

In a cohort of juvenile patients with neurocardiogenic syncope and dysautonomia documented by abnormal HUTT, biogenic amine metabolites of dopamine and serotonin were quantitated in 18 patients (15 females). HUTT testing is an effective clinical method to evaluate posturally induced physiological events in patients suspected of neurocardiogenic syncope with dysautonomia.

RESULTS

Levels of the dopamine metabolite (homovanillic acid: HVA) and/or the serotonin metabolite (5-hydroxyindoleacetic acid: 5HIAA) were significantly reduced in 13 patients compared to age-matched controls.

INTERPRETATION

Peripheral biogenic amines and their metabolites have been extensively studied in adults with dysautonomia due to various neurodegenerative disorders (Parkinson disease, multiple system atrophy, primary autonomic failure). Our findings indicate that more than two-thirds of this cohort of young patients with dysautonomia of variable severity have a defect in cerebral biogenic amines, particularly in dopamine and serotonin metabolism.

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.

Heart rate variability analysis during head-up tilt test predicts nitroglycerine-induced syncope

Objective

The aim of this study was to determine whether or not heart rate variability (HRV) analysis during the first 20 min of head-up tilt testing could predict whether patients will develop syncope after nitroglycerine administration.

Design

64 patients with previous loss of consciousness underwent head-up tilt testing with the Italian protocol, which involves the administration of nitroglycerine after 20 min of tilt. HRV parameters were analysed from 5 min intervals selected during pretest supine rest (phase 1), the first 5 min (phase 2) and the last 5 min (phase 3) of passive 20 min of tilting, prior to the administration of nitroglycerine. Differences in power (ms²) of the spectral components between the various phases of tilting were calculated for each patient and expressed as Δ.

Results

20 patients (group 1, 9 women, mean age 43.2±24.5 years) had a syncope during tilt testing after nitroglycerine, while the other 44 (group 2, 24 women, mean age 41±20.5 years) did not. In group 1, the HRV spectral parameters high frequency (HF) and total power (TP) had a significant decrement from phases 2 to 3 (p=0.012 and 0.027, respectively), while in group 2 the average HF and TP values did not change. The Δ of spectral parameters between phases 2 and 3 were able to differentiate between the two groups and to predict syncope after nitroglycerine administration (p<0.05).

Conclusions

HRV analysis within the first 20 min of passive tilting demonstrated that patients with nitroglycerine-induced syncope are characterised by a progressive decrement of parasympathetic activity, which does not occur in patients with a negative response to nitroglycerine. If confirmed on a wider population, HRV analysis could replace nitroglycerine administration and shorten the duration of the tilt test.

Usability of QTc dispersion for the prediction of orthostatic intolerance syndromes

BACKGROUND

Syncope is defined as transient loss of consciousness and muscle tone, usually of short duration. Noncardiac causes of syncope are classified as orthostatic intolerance syndromes (OIS). QT and QTc (corrected QT) dispersions are the measurements of myocardial instability and show predisposition to arrhythmias. In this study; clinical findings, QT and QTc dispersions of the patients who were diagnosed as OIS were evaluated retrospectively. Also, the aim of the study is to clarify the association of clinical characteristics of unexplained syncope with the outcome of the QT and QTc dispersions in children.

METHODS

We designed a retrospective study including 152 children and adolescents who had repeated unexplained syncope or presyncope between June 2002 and August 2010. Head-up Tilt table test (HUTT) were performed for all patients. Control group consisted of 67 healthy children. The QT and QTc dispersions were measured from the 12 ECG leads.

RESULTS

Eighty-four (55.2%) patients had positive and 68 (44.8%) had negative response to HUTT. QT and QTc dispersions were significantly higher in HUTT-positive group than in negative (p < 0.01, p < 0.001 respectively). Also, QTc dispersion was significantly higher in both vasovagal syncope and postural orthostatic tachycardia syndrome groups than in HUTT-negative group (p < 0.001, p < 0.05 respectively). Specifity and sensitivity of QTc dispersion for predicting positive HUTT are 76.5% and 59.5% respectively. The positive predictive value of the test calculated as 75.8%.

CONCLUSIONS

These results revealed that we can use QTc dispersion measurement as a noninvasive electrocardiographic test to evaluate OIS for predicting positive result before performing HUTT.

[Orthostatic hypotension: which initial cardiovascular and biological explorations? Which therapeutic solutions? The place of recommendations]

Orthostatic hypotension (OHT) is a common symptom that affects about 1% of the population. Its prevalence increases with age. In addition to the morbidity related to falls and syncope, OHT is a risk factor for cognitive decline and cerebrovascular morbidity and mortality. In most cases, its cause is easily found by the examination and some simple explorations. For severe and/or less obvious mechanism, some paraclinical methods of investigation can be proposed. These include head upright tilt-test and Valsalva maneuver. Both explore the entire baroreflex arc, and are realised by non-invasive measurements of heart rate and blood pressure. Other tests explore more specifically the parasympathetic outflow tract or sympathetic. In some situations cardiac MIBG scintigraphy and urinary catecholamines may be useful. The respective choice of these tests depends on the clinical setting and suspected type of dysautonomic lesion. Identifying the cause and assessment of functional impairment guide the therapeutic choices, which are primarily based on non-pharmacological approach.

Orthostatic tolerance is difficult to predict in recurrent syncope patients

OBJECTIVES

We tested the hypothesis that detailed anthropometric and hemodynamic measurements predict orthostatic tolerance in neurally mediated syncope patients. In addition, we tested whether orthostatic tolerance is related to syncope frequency in real life.

BACKGROUND

Earlier studies in patients with neurally mediated syncope suggested that orthostatic heart rate and blood pressure responses predict the tilt table responses with high sensitivity and specificity.

METHODS

We analyzed data from 157 consecutive patients (n = 100 exploratory cohort, n = 57 confirmatory cohort) with recurrent syncope in whom orthostatic tolerance was quantified as the time to (pre)syncope during head-up tilt testing combined with lower body negative pressure. We measured heart rate, brachial blood pressure, cardiac stroke volume, heart rate and blood pressure variability, and spontaneous baroreflex sensitivity supine and early during head-up tilt.

RESULTS

The orthostatic heart rate increase showed the strongest correlation with orthostatic tolerance. The best multivariate model including age, supine diastolic blood pressure, supine blood pressure variability, as well as tilt-induced changes in diastolic blood pressure and heart rate explained no more that 40% of the variability in orthostatic tolerance. The model failed to predict orthostatic tolerance in the confirmatory cohort. Frequency or number of free-living syncopal episodes were only weakly related to orthostatic tolerance.

CONCLUSIONS

In patients with neurally mediated syncope, orthostatic tolerance in the clinical laboratory is difficult to predict with a wide range of anthropometric and cardiovascular measurements and correlates poorly with syncope occurrence in real life.

The autonomic nervous system dysregulation in response to orthostatic stress in children with neurocardiogenic syncope

Neurocardiogenic syncope is a common disorder, which is considered as a benign condition. However, sudden loss of conscience and muscle tone causes anxiety among the family members due to its similarity to sudden death. Autonomic nervous system dysregulation is thought to be responsible in the aetiology. Heart rate variability is used for assessment of autonomic nervous system.We evaluated 24 children between 6 and 18 years (mean plus or minus standard deviation is equal to 12.5 plus or minus 3.28, with neurocardiogenic syncope and 10 healthy controls, mean plus or minus standard deviation is equal to 12.48 plus or minus 3.27) by using 24 hour Holter monitorisation and head-up tilt test. Heart rate variability analysis was performed using the Holter recordings obtained both during head-up tilt test and throughout the day.Our results revealed that, there is no significant difference between the study and the control groups in terms of the mean heart rate and all indices of the heart rate variability (p > 0.05). However, during the first 5 minutes of the head-up tilt test, standard deviation of all RR intervals and root mean square of successive differences were significantly lower in the syncope group compared with the control group, 42.17 plus or minus 12.56 versus 60.10 plus or minus 33.10 and 21.26 plus or minus 8.87 versus 36.80 plus or minus 31.03; p-values 0.02 and 0.03, respectively.In conclusion; autonomic functions in children with neurocardiogenic syncope are similar to healthy children. However, sympathetic hyperactivation occurs during the early phase of orthostatic stress in children with neurocardiogenic syncope comparing to healthy controls. Parasympathetic innervation is not sufficient in compensation of this sympathetic hyperactivation. Management strategy in neurocardiogenic syncope should be based on these pathophysiologic mechanisms.

Vulnerability to simple faints is predicted by regional differences in brain anatomy

Neurocardiogenic syncope (NCS, simple fainting) is a common and typically benign familial condition, which rarely may result in traumatic injury or hypoxic convulsions. NCS is associated with emotional triggers, anxiety states and stress. However, the etiology of NCS, as a psychophysiological process, is poorly understood. We therefore investigated the relationship between NCS and brain anatomy. We studied a non-clinical sample of eighteen individuals with histories characteristic of NCS, and nineteen matched controls who had never fainted. We recorded fainting frequency, resting heart rate variability measures and anxiety levels. Structural T1-weighted magnetic resonance images (MRI) were acquired at 1.5 T. Associations between brain morphometry (regional gray and white matter volumes) and NCS, resting physiology and anxiety were tested using voxel-based morphometry (VBM). Compared to controls, NCS participants had lower regional brain volume within medulla and midbrain (a priori regions of interest). Moreover, across NCS individuals, lower gray matter volume in contiguous regions of left caudate nucleus predicted enhanced parasympathetic cardiac tone, fainting frequency and anxiety levels. Our findings provide preliminary evidence for a hierarchical anatomical basis to NCS. First, differences in the volume of brainstem centers supporting cardiovascular homeostasis may relate to constitutional predisposition to NCS. Second, differences in the structural organization of the caudate nucleus in NCS individuals may relate to fainting frequency via interactions between emotional state and parasympathetic control of the heart. These observations highlight the application of VBM to the identification of neurovisceral mechanisms relevant to psychosomatic medicine and the neuroscience of emotion.

Recurrent unexplained syncope may have a cerebral origin: report of 10 cases of arrhythmogenic epilepsy

BACKGROUND

Despite thorough investigation, approximately 15-20% of syncope cases remain unexplained. An underrecognized cause of syncope may occur when partial epileptic discharges profoundly disrupt normal cardiac rhythm, including cardiac asystole, the so-called arrhythmogenic epilepsy (AE).

AIM

To report initial results of observations of AE in patients with recurrent, unexplained, traumatic and/or convulsive syncope.

METHODS

Ten patients aged 49+/-20 years (median 49.5 years; nine women) underwent complete cardiological (including ambulatory Holter electrocardiogram (ECG), echocardiography and head-up tilt test [plus electrophysiology in four patients]) and neurological (including standard electroencephalogram [EEG], computed tomography [CT] and magnetic resonance imaging scan [MRI]) assessments.

RESULTS

After initial evaluation, neurocardiogenic syncope was suspected in six patients with tilt-induced hypotension+/-bradycardia. Further evaluation (prolonged inpatient video-EEG/ECG monitoring) was undertaken because of non-diagnostic syncope or uncertainty about the diagnosis of neurocardiogenic syncope. While monitored in the neurophysiology lab, a syncopal episode similar to the spontaneous episodes recurred in all 10 patients. Cardiac asystole preceded by partial seizure of temporal onset was documented in nine patients; a second-degree atrioventricular (AV) block with a cardiac rhythm of 30 beats per minute preceded by partial seizure of temporal onset was noted in one patient. Eight patients were treated successfully with antiepileptic drugs; two were refractory to antiepileptic therapy and required pacemaker implantation. No patient had recurrent syncope during a median follow-up of 102.5 months (mean 82.2+/-42; range 16-128 months).

CONCLUSIONS

In patients with recurrent, unexplained, traumatic and/or convulsive syncope, AE should be considered as a possible aetiology.

Precursors of syncope in linear and non-linear parameters of heart rate variability during pediatric head-up tilt test

The aim of this study was to identify precursors of neurocardiogenic syncope (NCS) in ECG parameters of children and adolescents who undergo head-up tilt testing (HUTT). Established linear and non-linear parameters of heart rate variability (HRV) were calculated minute-by-minute in 44 young patients with an NCS history (age 7-20 years, 22 female, 22 male, positive HUTT) and 34 age-matched healthy controls (age 7-20 years, 17 female, 17 male, negative HUTT) during 60 degrees HUTT. The influence of age and gender on the response to tilting was studied using the Wilcoxon rank sum test. We also assessed the predictive power of individual features with respect to HUTT outcome within three temporal windows (0-2 min after tilt; 2-5 min after tilt, and 5-2 min before tilt-back) by means of receiver operating characteristics analysis. Our results indicate that prediction of HUTT outcome should be restricted to subjects in or after puberty. In this group, descriptors based on co-occurrence or joint-recurrence analysis in recurrence plots showed promising predictive power (up to 86% sensitivity and 90% specificity, area under the curve 0.91). Time-domain parameters (standard deviation of differences for successive RR intervals) reached 75% sensitivity and 80% specificity. We conclude that HRV analysis within the first 5 min after tilting provides significant information on HUTT outcome and may be useful in conjunction with more sophisticated classification strategies for shortening HUTT duration in subjects after puberty.

[Heart rate variability and vasovagal syncope]

OBJECTIVE

Tilt Table testing is widely used for the diagnosis and evaluation of vasovagal syncope. By evaluating the fluctuations of the autonomic nervous system that play an important role in syncope genesis, heart rate variability (HRV) can be considered as a tool of added value.

METHODS

We evaluated prospectively 123 patients admitted for recurrent syncope with a positive tilt Table testing. A time domain analysis of a 24 hours ambulatory electrocardiography was used in all patients to asses the particularities of their autonomic function. We compared their results with those obtained from a group of 82 healthy volunteers.

RESULTS

Statistical analysis of the results showed a significant increase of all HRV parameters in the group of vasovagal syncope compared to the healthy volunteers. SDNNidx (58 vs 42; p < 0.001), rMSSD (40 vs 27; p < 0.001), SDNN (102 vs 83; p < 0.001), SDANN (79 vs 67; p< 0.001), pNN50 (11 vs 4.9; p <0.001).

CONCLUSION

Time domain analysis of heart rate variability reveals increased values in patients with vasovagal syncope. It seems to be an interesting, easy and complementary test in the evaluation of syncope of unknown etiology.

Time-frequency analysis of the ECG in the diagnosis of vasovagal syndrome in older people

The Smoothed Pseudo Wigner-Ville Distribution (SPWVD) is used for the time-frequency analysis of variations in RR interval. A novel technique to determine the smoothing window lengths is implemented, and a new heart rate variability (HRV) metric is developed, instantaneous center frequency variability (ICFV), which uses the time-frequency map generated by the SPWVD. The technique is then applied to 50 patients with unexplained falls and age > 60, undergoing head-upright tilt table testing (HUT). Eighteen of the patients were diagnosed with vasovagal syndrome. Attempts at syncope prediction using the new metric is an improvement on traditional techniques: an ICFV less than 0.07 Hz from 90 s to 180 s after tilt is predictive of a negative test (negative predictive value: 0.77). The comorbidity and autonomic degeneration present in elderly patients are thought to be responsible for lowering the negative predictive value.

Orthostatic decrease in cardiac chaos during the head-up tilt test in patients with vasovagal syncope

BACKGROUND

Autonomic dysfunction contributes to orthostatic intolerance in vasovagal syncope (VVS), but as it has not been identified by spectral analysis of heart rate variability (HRV) in previous studies, the present hypothesis was that nonlinear analysis of HRV would identify the orthostatic intolerance in VVS.

METHODS AND RESULTS

Twenty-six patients with VVS and 14 matched controls were subjected to 80-degree head-up tilt test (positive: 13 patients; negative: 13 patients and 14 controls). There were no differences in the orthostatic changes in the indices of spectral analyses of HRV among the 3 groups. The Lyapunov exponent (LE) was calculated from 200 consecutive RR-intervals to investigate chaotic behavior, and cardiac chaos was defined as the incidence of the presence of a positive finite LE. Orthostatic decreases in cardiac chaos were observed in the VVS patients (both the positive and negative groups), although there was no orthostatic decrease in the control group (ANOVA: p = 0.008). The receiver-operator characteristic curve indicated that cardiac chaos during the tilt identified VVS regardless of the results of the tilt (p < 0.001, sensitivity: 85.7%, specificity: 96.2%).

CONCLUSIONS

The decrease in cardiac chaos during the tilt test was specific to patients with VVS, even if their response to the test was negative.

Short-term heart rate variability response to head-up tilt in young syncope patients and controls with respect to age

This study aims at characterizing the short-term time-courses of time- and frequency-domain heart rate variability (HRV) parameters during head-up tilt test (HUTT). Data from 44 young patients with a history of syncope and 34 age-matched controls was analysed in two age-groups related to puberty (< or =13 and > or =14 years), and separately for gender, by extracting minute-by-minute progression of mean RR-interval, standard deviation of RR-intervals (SDNN) and their first difference (SDSD) as well as low-frequency (LF, 0.05-0.15 Hz) energy, high-frequency (HF, 0.15-0.4 Hz) energy and the LF/HF-ratio. Time-courses were individually normalized and averaged after synchronization to the events of tilt and tilt-back/syncope. We observed remarkable age-related differences not only with respect to response to tilting but also regarding the differentiation of patients with positive HUTT from controls with negative HUTT. ROC-analysis in three regions of interest (0-2 min after tilt, 2-5 min after tilt, 5-2 min before tilt-back) revealed generally much weaker and less persistent differences in younger subjects whereas in elders the differences were clearer and often most pronounced immediately before syncope. For both age-groups, the relative change of mean RR provided best separation, however in elders in the ROI just before syncope (sensitivity: 74%, specificity 80%) in young immediately after tilt (sens.: 71%, spec.: 74%). In elder subjects, the relative reduction of SDNN 2-5 minute after tilt achieved almost the same performance (sens.: 74%, spec. 80%) as in the ROI before syncope (sens. 78%, spec. 73%), indicating the existence of rather early precursors of syncope that might help to predict the outcome of the HUTT in subjects in or after puberty.

Causal Cross-Spectral Analysis of Heart Rate and Blood Pressure Variability for describing the Impairment of the Cardiovascular Control in Neurally Mediated Syncope

A causal approach to the calculation of coherence and transfer function between systolic pressure (SP) and RR interval variability was applied in eight patients and eight control subjects during prolonged tilt test for investigating the impairment of cardiovascular control related to neurally mediated syncope. The causal analysis showed a depressed baroreflex regulation in resting patients, with reduced gain and increased latency from SP to RR, and a drop of the baroreflex coupling immediately before syncope. These findings, which were not elicited by traditional cross-spectral analysis, strongly suggest the use of the causal approach for the study of syncope mechanisms.

Heart Rate Variability During Sleep in Patients with Vasovagal Syncope

BACKGROUND

There are a few studies showing no significant heart rate variability (HRV) over a 24-hour period in vasovagal syncope (VVS) patients, but no research has examined HRV and its sympathetic and parasympathetic components during rapid eye movement (REM) and non-REM sleep. The authors hypothesized that REM sleep might be a critical state in which VVS patients would show abnormal responses.

OBJECTIVES

To analyze the sympathetic and parasympathetic components of HRV during REM and SWS in patients with VVS compared to normal subjects, and in patients with positive HUTT compared to negative ones.

METHODS

Thirty-seven VVS patients and 20 normal age-matched controls were submitted to polysomnography with 24-hour Holter monitoring to assess HRV. Time and frequency domain techniques were carefully performed for 24 hours and during Stages 3 and 4 of REM and non-REM sleep. Variation of sympathetic activity index (VSAI) was defined as the difference in the low frequency (LF) component of HRV between REM and Stages 3 and 4 of non-REM sleep. An analysis of variance was performed to compare patients and controls; patients with positive and negative head-up tilt testing.

RESULTS

The LF component was lower in syncope compared to normal patients (1,769.54 +/- 1,738.17, 3,225.37 +/- 2,585.05, respectively, P = 0.03). There was a significant decrease in VSAI in the syncope group compared to the control group (-539.39 +/- 1,930.78, 1,268.10 +/- 2,420.20, respectively, P = 0.01). The other sleep variables analyzed including very LF, high frequency, low frequency/high frequency and time domain parameters did not reach statistical significance. Syncope patients also showed an increase in slow wave sleep (28.2 +/- 10.5, 19.7 +/- 7.8, P = 0.01).

CONCLUSIONS

VVS patients exhibited sympathetic suppression during REM sleep. Possible mechanisms are discussed in this article.

Prognostic value of head-up tilt test with intravenous beta-blocker administration in assessing the efficacy of therapy in patients with vasovagal syncope

BACKGROUND

Although beta-blockers are frequently used in order to prevent the recurrence of vasovagal syncope, the efficacy of this treatment is difficult to determine.

OBJECTIVES

To determine if the result of a tilt test with an intravenously administered beta-blocker can predict the long-term efficacy of beta-blockade.

METHODS

The study group consisted of 62 patients (29 females, mean age 32.8 +/- 12.3 years and 33 males, mean age 35.9 +/- 18.2 years) with at least two syncopal episodes during 6 months preceding the positive tilt test. After the baseline tilt test, propranolol (0.1 mg/kg BW) was administered intravenously and the tilt test was repeated. Beta-blockade was considered effective if the subsequent tilt test proved negative (complete efficacy) or if the time until the occurrence of syncope at the subsequent tilt test was longer compared to the baseline test (partial efficacy). All the patients were put on continuous propranolol treatment and were followed up for a period of 1 year or until the time when syncope recurred.

RESULTS

Intravenously administered propranolol prevented (n = 33) or delayed (n = 18) the occurrence of syncope at the tilt test in 51 patients (82%), while it was found ineffective in the remaining 11 patients (18%). During the 8.6 +/- 6.7 months (range 1-14) of the follow-up period, the syncope recurred in 20 patients (32%), with 13 patients (25%) in the group where intravenously administered propranolol proved effective versus 7 patients (64%) for whom intravenously administered propranolol did not prevent syncope during the tilt test (P < 0.015). The survival analysis with respect to the recurrence of syncope revealed a significant correlation between the results of the tilt test with intravenously administered propranolol and the efficacy of the long-term beta-blocker therapy (P < 0.003). There were no significant differences with respect to the predictive value of the tilt test with propranolol between the patients showing complete and partial propranolol efficacy (ns), while significant differences were observed between these two groups on one hand and the patients in whom intravenously administered propranolol was found ineffective on the other (P < 0.04 and P < 0.002, respectively).

CONCLUSIONS

Intravenous propranolol prevents tilt-induced syncope in a significant percentage of patients. The results of the tilt tests combined with the administration of propranolol predict the efficacy of a continuous propranolol treatment. Both complete and partial propranolol efficacy at tilt test can successfully identify those patients who will benefit from continuous beta blockade.

Heart rate and blood pressure variability in subjects with vasovagal syncope

Autonomic nervous system control in subjects with vasovagal syncope is controversial. In the present study, we used short-term spectral analysis to evaluate autonomic control in subjects with recurrent vasovagal syncope. We assessed the ability of spectral indices of HR (heart rate) variability to predict tilt-test responses. A series of 47 outpatients with recurrent vasovagal syncope and with positive responses to head-up tilt testing underwent a further study of RR variability during controlled breathing at rest and during tilt testing. During controlled breathing, RR interval variability of total power (TPRR; P<0.001), low-frequency power (LFRR; P<0.05), high-frequency power (HFRR; P<0.001) and HF expressed in normalized units (HFnuRR; P<0.001) were all higher, and LF expressed in normalized units (LFnuRR) and LF/HF ratio were lower in subjects with vasovagal syncope than in controls (P<0.001). To assess the ability of spectral components of RR variability to predict tilt-test responses, we prospectively studied 109 subjects with recurrent vasovagal syncope. The two normalized measures, HFnuRR and LFnuRR, determined during controlled breathing alone predicted a positive tilt-test response (sensitivity, 76%; specificity, 99%; positive predictive value, 96%; and negative predictive value, 90%). During tilting, subjects with vasovagal syncope had lower SBP (systolic blood pressure; P<0.05), LF component of peak SBP variability (LFSBP) and LFnuRR than controls, and higher TPRR, HFRR, HFnuRR and α HF (P<0.001). These spectral data indicate that vagal sinus modulation is increased at rest in subjects with vasovagal syncope. Spectral analysis of RR variability during controlled breathing, a procedure that predicts tilt-test responses, could be a useful guide in choosing the method of tilt testing.

Vestibular function interferes in cardiovascular reflexes [corrected]

BACKGROUND

Experimental work indicates that the vestibular system participates in autonomic reflexes during body movement and postural changes. However, there are no studies of cardiovascular reflexes during vertigo due to human acute vestibular lesions.

METHODS

We assessed the response to active change of posture and hand immersion in cold water in seven patients with unilateral peripheral vestibular failure (vestibular neuritis) and seven age/sex-matched healthy subjects in acute phase (72 h from vertigo onset) and at 2 weeks of follow-up.

RESULTS

During acute phase, patients showed decreased blood pressure response during cold hand test (p < 0.05). Upright stance induced deficient decrease of the respiratory component of heart rate variability (p < 0.05) with lack of increase in low frequency/high frequency (LF/HF) ratio. At 2 weeks of follow-up, these abnormalities improved.

CONCLUSIONS

Results suggest that acute vestibular lesions can interfere with cardiovascular autonomic responses in humans. This may reflect disruption of normal vestibulo-autonomic reflexes.

Role of vagal control in vasovagal syncope

The vasovagal reaction is thought to be caused by sympathetic withdrawal and vagal augmentation. While measurements of muscle sympathetic nerve activity support sympathetic withdrawal in tilt induced syncope, the results of previous attempts to quantify vagal control using spectral analyses of heart rate variability (HRV) remain controversial. The sampling period used in the HRV studies is related to the discordant results. In the present study, HRV was computed every second using wavelet transformation to clarify the role of vagal control in tilt induced syncope during the 80-degree head-up tilt test (positive: 10 patients with vasovagal syncope; negative: 10 patients with vasovagal syncope, and 10 control subjects). Autonomic modulations were assessed using the absolute power of the low frequency (LF) (0.04-0.15 Hz) and high frequency (HF) (0.15-2.00 Hz) oscillatory components of R-R variability. Although the LF did not change during the tilt procedure, a decrease in the systolic arterial pressure (SAP) and increases in the R-R interval and HF were observed for the last 30 seconds before the tilt induced syncope in the tilt-positive group. Analyzing the hemodynamic measurements and spectral indices for the last 5 minutes preceding the tilt induced syncope, the study found that the SAP, R-R interval, and HF changed simultaneously during the 30-second period immediately before the tilt induced syncope. Further, the HF was positively correlated with the R-R interval and negatively correlated with the SAP. In conclusion, continuous spectral analysis of the R-R interval demonstrated increased vagal influence on the heart in tilt induced syncope.

Shortened head-up tilting test guided by systolic pressure reductions in neurocardiogenic syncope

BACKGROUND

Asymptomatic reductions in arterial pressure have been reported to occur before the onset of tilt-induced syncope. We investigated the predictive value of these reductions for a positive tilt result.

METHODS AND RESULTS

In a first study, 238 consecutive healthy subjects with unexplained syncope underwent a passive tilt table test. Finger systolic arterial pressure (SAP) recordings made it possible to calculate how many of the beat-to-beat SAP values during the first 15 minutes of tilt were lower than the lowest value recorded at baseline. Neurocardiogenic syncope was diagnosed in 73 subjects; 28 fainted after 15 minutes of tilt and experienced more pressure reductions than did the subjects with a negative test (328+/-400 versus 119+/-284; P<0.01). More than 14 SAP reductions during the first 15 minutes of tilt allowed us to predict a positive test with 93% sensitivity, 58% specificity, and positive and negative predictive values of 28% and 98%, respectively. In a second prospective study (80 consecutive subjects), the online analysis of this criterion by visually inspecting a Finapres monitor showed 80% sensitivity, 85% specificity, and positive and negative predictive values of 57% and 94%.

CONCLUSIONS

In healthy subjects with unexplained syncope, the evaluation of SAP reductions during the first 15 minutes of tilt is a marker of systolic pressure instability preceding syncope and constitutes a simple and good predictor of tilt outcome that could be used to guide test duration.

Beta blockade in neurocardiogenic dysfunction: results of a clinical study

BACKGROUND

Few placebo-controlled studies with β-blockers have been performed in patients suffering from neurocardiogenic syncope.

METHODS

We investigated the efficacy of metoprolol in 26 patients with recurrent syncope, suspected to be of neurocardiogenic origin, and positive tilt table test (TTT) outcome in a single-centre, double-blind, placebo-controlled, crossover study, with treatment periods of two weeks. Therapeutic efficacy was defined as a negative TTT after metoprolol and a positive TTT after placebo. Therapeutic failure was defined as a positive TTT after metoprolol and a positive or negative TTT after placebo. Patients with a negative TTT test after both metoprolol and placebo comprised the third group.

RESULTS

The 24 patients who completed the study consisted of 14 females and 10 males, mean age 53 years, range 18-75 years. Therapeutic efficacy was observed in nine patients, therapeutic failure in eight patients and seven patients had a negative TTT after both placebo and metoprolol. According to the exact binomial test for paired proportions, the 95% confidence interval is 12 to 38% and p<0.01 in favour of treatment with metoprolol.

CONCLUSION

These findings indicate a favourable effect of metoprolol.

Decreased entropy of symbolic heart rate dynamics during daily activity as a predictor of positive head-up tilt test in patients with alleged neurocardiogenic syncope

Entropy measures of RR interval variability during daily activity over a 24h period were compared in 30 patients with a positive head-up tilt (HUT) test and 30 patients with a negative HUT test who had a history of alleged neurocardiogenic syncope. Two different entropies, approximate entropy (ApEn) and entropy of symbolic dynamics (SymEn), were employed. In patients showing a positive HUT test, the entropies were significantly decreased when compared with the patients with a negative HUT test. In addition, SymEn in the patients with a negative HUT test was significantly lower than in the normal controls. Discriminant analysis using SymEn could correctly identify 89.3% (520/582) of the 1 h RR interval data of the patients with a positive HUT test regardless of the time of day. Baseline entropies of heart rate dynamics during daily activity were found to be significantly lower in patients with alleged neurocardiogenic syncope and a positive HUT test than in those with the same history but with a negative HUT test. The decreased entropy of symbolic heart rate dynamics may be of predictive value of a positive HUT test in patients with alleged neurocardiogenic syncope.