Vasovagal syncope: a prospective, randomized, crossover evaluation of the effect of propranolol, nadolol and placebo on syncope recurrence and patients' well-being

Markers for predicting the efficacy of beta-blockers in vasovagal syncope management in children: A mini-review

Vasovagal syncope (VVS) is a common subtype of neurally mediated syncope. It is prevalent in children and adolescents, and critically affects the quality of life of patients. In recent years, the management of pediatric patients with VVS has received extensive attention, and β-blocker serves as an important choice of the drug therapy for children with VVS. However, the empirical use of β-blocker treatment has limited therapeutic efficacy in patients with VVS. Therefore, predicting the efficacy of β-blocker therapy based on biomarkers related to the pathophysiological mechanism is essential, and great progress has been made by applying these biomarkers in formulating individualized treatment plans for children with VVS. This review summarizes recent advances in predicting the effect of β-blockers in the management of VVS in children.

Pharmacologic prevention of recurrent vasovagal syncope: A systematic review and network meta-analysis of randomized controlled trials

Vasovagal syncope (VVS) is a transient loss of consciousness that currently imposes a high burden on health care systems with limited evidence of the comparative efficacy of available pharmacologic interventions. This study aims to compare all pharmacologic therapies suggested in randomized controlled trials (RCTs) through systematic review and network meta-analysis. A systematic search in PubMed, Embase, Web of Science, and Cochrane Library was conducted to identify RCTs evaluating pharmacologic therapies for patients with VVS. The primary outcome was spontaneous VVS recurrence. The secondary outcome was a positive head-up tilt test (HUTT) after receiving intervention, regarded as a lower level of evidence. Pooled risk ratio (RR) with 95% confidence interval (CI) was calculated using random-effect network meta-analysis. Pairwise meta-analysis for comparison with placebo was also performed when applicable. The surface under the cumulative ranking curve analysis was conducted to rank the treatments for each outcome. Twenty-eight studies with 1744 patients allocated to different medications or placebo were included. Network meta-analysis of the reduction in the primary outcome showed efficacy for midodrine (RR 0.55; 95% CI 0.35-0.85) and fluoxetine (especially in patients with concomitant anxiety) (RR 0.36; 95% CI 0.16-0.84). In addition, midodrine and atomoxetine were superior to other treatment options, considering positive HUTT (RR 0.37; 95% CI 0.23-0.59; and RR 0.49; 95% CI 0.28-0.86, respectively). Overall, midodrine was the only agent shown to reduce spontaneous syncopal events. Fluoxetine also seems to be beneficial but should be studied further in RCTs. Our network meta-analysis did not find evidence of the efficacy of any other medication.

Current approach to the treatment of vasovagal syncope in adults

Vasovagal syncope (VVS) is the most common cause of transient loss of consciousness. Although not associated with mortality, it causes injuries, reduces quality of life, and is associated with anxiety and depression. The European and North American cardiac societies recently published syncope clinical practice guidelines. Most patients with VVS do well after specialist evaluation, reassurance and education. Adequate hydration, increased salt intake when not contraindicated, and careful withdrawal of diuretics and specific hypotension-inducing drugs are a reasonable initial strategy. Physical counterpressure maneuvers might be helpful but can be of limited efficacy in older patients and those with short or no prodromes. Orthostatic training lacks long term efficacy and is troubled by non-compliance. Yoga might be helpful, although the biomedical mechanism is unknown. Almost a third of VVS patients continue to faint despite these conservative measures. Metoprolol was not helpful in a pivotal randomized clinical trial. Fludrocortisone and midodrine significantly reduce syncope recurrences with tolerable side effects, when titrated to target doses. Pacing therapy with specialized sensors appears promising in carefully selected population who have not responded conservative measures. Cardioneuroablation may be helpful but has not been studied in a formal clinical trial.

Biomarkers and Hemodynamic Parameters in the Diagnosis and Treatment of Children with Postural Tachycardia Syndrome and Vasovagal Syncope

In children, vasovagal syncope and postural tachycardia syndrome constitute the major types of orthostatic intolerance. The clinical characteristics of postural tachycardia syndrome and vasovagal syncope are similar but their treatments differ. Therefore, their differential diagnosis is important to guide the correct treatment. Therapeutic methods vary in patients with the same diagnosis because of different pathomechanisms. Hence, in patients with vasovagal syncope or postural tachycardia syndrome, routine treatments have an unsatisfactory efficacy. However, biomarkers could increase the therapeutic efficacy significantly, allowing for an accurate and detailed assessment of patients and leading to improved therapeutic effects. In the present review, we aimed to summarize the current state of research into biomarkers for distinguishing the diagnosis of pediatric vasovagal syncope from that of postural tachycardia syndrome. We also discuss the biomarkers that predict treatment outcomes during personalized therapy for each subtype.

Pathophysiology and Individualized Management of Vasovagal Syncope and Postural Tachycardia Syndrome in Children and Adolescents: An Update

Vasovagal syncope (VVS) and postural tachycardia syndrome (POTS) are the main forms of orthostatic intolerance in pediatrics and both are underlying causes of neurally-mediated syncope. In recent years, increasing attention has been paid to the management of VVS and POTS in children and adolescents. A number of potential mechanisms are involved in their pathophysiology, but the leading cause of symptoms varies among patients. A few studies thus have focused on the individualized treatment of VVS or POTS based on selected hemodynamic parameters or biomarkers that can predict the therapeutic effect of certain therapies and improve their effectiveness. This review summarizes the latest developments in individualized treatment of VVS and POTS in children and indicates directions for further research in this field.

Diagnostic and therapeutic approach to cardioinhibitory reflex syncope: A complex and controversial issue

Syncope is defined as a transient loss of consciousness due to global cerebral hypoperfusion and is one of the leading causes of emergency department admission. The initial approach should focus on excluding non-syncopal causes for loss of consciousness and risk stratification for cardiac cause, in order to ensure an appropriate etiological investigation and therapeutic approach. Vasovagal syncope (VVS), the most common type of syncope, should be assumed once other causes are excluded. Pathophysiologically, the vasovagal reflex is the result of a paradoxical autonomic response, leading to hypotension and/or bradycardia. VVS has not been shown to affect mortality, but morbidity may be considerable in those with recurrent syncopal episodes. The management of VVS includes both non-pharmacological and pharmacological measures that act on various levels of the reflex arc that triggers the syncopal episode. However, most are of uncertain benefit given the scarcity of high-quality supporting evidence. Pacemaker therapy may be considered in recurrent refractory cardioinhibitory reflex syncope, for which it is currently considered a robust intervention, as noted in the European guidelines. Non-randomized and unblinded studies have shown a potential benefit of pacing in recurrent VVS, but double-blinded randomized controlled trials have not consistently demonstrated positive results. We performed a comprehensive review of the current literature and recent advances in cardiac pacing and pacing algorithms in VVS, and discuss the diagnostic and therapeutic approach to the complex patient with recurrent VVS and reduced quality of life.

Skin sympathetic nerve activity as a biomarker for syncopal episodes during a tilt table test

BACKGROUND

Autonomic imbalance is the proposed mechanism of syncope during a tilt table test (TTT). We have recently demonstrated that skin sympathetic nerve activity (SKNA) can be noninvasively recorded using electrocardiographic electrodes.

OBJECTIVE

The purpose of this study was to test the hypothesis that increased SKNA activation precedes tilt-induced syncope.

METHODS

We studied 50 patients with a history of neurocardiogenic syncope undergoing a TTT. The recorded signals were band-pass filtered at 500-1000 Hz to analyze nerve activity.

RESULTS

The average SKNA (aSKNA) value at baseline was 1.38 ± 0.38 μV in patients without syncope and 1.42 ± 0.52 μV in patients with syncope (P = .77). On upright tilt, aSKNA was 1.34 ± 0.40 μV in patients who did not have syncope and 1.39 ± 0.43 μV in patients who had syncope (P = .65). In all 14 patients with syncope, there was a surge of SKNA before an initial increase in heart rate followed by bradycardia, hypotension, and syncope. The peak aSKNA immediately (<1 minute) before syncope was significantly higher than baseline aSKNA (2.63 ± 1.22 vs 1.39 ± 0.43 μV; P = .0005). After syncope, patients were immediately placed in the supine position and aSKNA dropped significantly to 1.26 ± 0.43 μV; (P = .0004). The heart rate variability during the TTT shows a significant increase in parasympathetic tone during syncope (low-frequency/high-frequency ratio: 7.15 vs 2.21; P = .04).

CONCLUSION

Patients with syncope do not have elevated sympathetic tone at baseline or during the TTT except immediately before syncope when there is a transient surge of SKNA followed by sympathetic withdrawal along with parasympathetic surge.

Treatment of Neurocardiogenic Syncope: From Conservative to Cutting-edge

Neurocardiogenic syncope is the most frequent cause of syncope in the general population. Many years have been spent on determining an effective treatment for this condition. Conventional treatment usually follows a tiered approach for neurocardiogenic syncope, as follows: first, lifestyle modification, including increased fluid intake and the introduction of physical counterpressure maneuvers, is tried; then the use of targeted pharmacologic therapy, particularly agents that support blood pressure or that drive blood pressure is attempted; and, finally, pacemaker implantation in patients with a predominant cardioinhibitory component to their syncopal episodes is performed. More recently, autonomic modulation with cardiac ganglion ablation has emerged as a promising treatment modality for patients refractory to traditional approaches. In this review, we sought to summarize the existing therapies for neurocardiogenic syncope and explore the latest research on new modalities of treatment.

Reflex syncope: Diagnosis and treatment

For the diagnosis of reflex syncope, diligent history-building with the patient and a witness is required. In the Emergency Department (ED), the assessment of syncope is a challenge which may be addressed by an ED Observation Unit or by a referral to a Syncope Unit. Hospital admission is necessary for those with life-threatening cardiac conditions although risk stratification remains an unsolved problem. Other patients may be investigated with less urgency by carotid sinus massage (>40 years), tilt testing, and electrocardiogram loop recorder insertion resulting in a clear cause for syncope. Management includes, in general terms, patient education, avoidance of circumstances in which syncope is likely, increase in fluid and salt consumption, and physical counter-pressure maneuvers. In older patients, those that will benefit from cardiac pacing are now well defined. In all patients, the benefit of drug therapy is often disappointing and there remains no ideal drug. A role for catheter ablation may emerge for the highly symptomatic reflex syncope patient.

Therapy for Syncope

The diagnostic process in patients with syncope is not always easy and includes a detailed clinical history, physical examination and baseline electrocardiogram; according to the results of these initial approaches, some additional tests must be performed. Using this strategy, the cause of syncope is diagnosed in 60% to 80% of patients; in the remaining patients, risk stratification can be established to identify those patients at risk of having cardiac events or death at midterm follow-up. This article reviews the treatment of patients with syncope according to the different causes.

Non-invasive management of vasovagal syncope

Vasovagal syncope (VVS) is a common disorder of the autonomic nervous system. While recurrent syncope can cause very impaired quality of life, the spells are not generally life-threatening. Both non-pharmacological and pharmacological approaches can be used to treat patients. Conservative management with education, exercise and physical maneuvers, and aggressive volume repletion is adequate for controlling symptoms in most patients. Unfortunately, a minority of patients will continue to have recurrent syncope despite conservative therapy, and they may require medications. These could include vasopressor agents, beta-blockers, or neurohormonal agents. Some patients may require more aggressive device based therapy with pacemakers or radiofrequency ablation, which are emerging therapies for VVS. This paper will review non-procedure based treatments for VVS.

[Treatment of syncope]

The therapy of patients with syncope is oriented to the underlying pathophysiological mechanisms. Patients with reflex syncope require careful education regarding recognition of warning signs and the avoidance of trigger factors. Treatment with beta blockers is nowadays obsolete. Even other drugs have failed to show any benefit. Pacemaker therapy should only be considered if syncope attacks are frequent and if there is a correlation between symptoms and the electrocardiogram (ECG). Because autonomic failure in patients with orthostatic hypotension is often drug-induced, reduction of the dosage or the complete elimination is the treatment of choice in these patients. A higher than normal salt and fluid intake as well as general measures to avoid delayed venous backflow, e.g. elastic stockings, may also be helpful. A change in blood pressure medication can be decisive for therapy success, especially in elderly patients with arterial hypertension. Pacemaker and defibrillator therapy is the treatment of choice in patients with bradycardia and tachycardia arrhythmias, respectively. Although these measures are simple but effective, in individual cases it is still difficult to find clinical proof that arrhythmic disorders are the causal factors for the syncope. However, also in these patients cardiac pacing should be based on a symptom ECG correlation. The recently conducted market release of the injectable miniaturized ECG recorder will alleviate the diagnostic process. The limits of this approach, however, become obvious when there is the suspicion of a life-threatening rhythm disorder, because the only difference between syncope and sudden cardiac death is that in one case the patient wakes up again.

The impacts of dispositional optimism and psychological resilience on the subjective well-being of burn patients: a structural equation modelling analysis

Burn wounds are severely stressful events that can have a significant impact on the mental health of patients. However, the impact of burns on individuals with different personality traits can be different. The present study aimed to investigate the impact of dispositional optimism on the subjective well-being of burn patients, and mainly focused on the confirmation of the mediator role of psychological resilience. 410 burn patients from five general hospitals in Xi'an accomplished the revised Life Orientation Test, Connor-Davidson Resilience Scale, and Subjective Well-Being (SWB) scale. The results revealed that both dispositional optimism and psychological resilience were significantly correlated with SWB. Structural equation modelling indicated that psychological resilience partially mediated the relationship between dispositional optimism and SWB. The current findings extended prior reports and shed some light on how dispositional optimism influenced SWB. Limitations of the study were considered and suggestions for future studies were also discussed.

Autonomic nerve activity and blood pressure in ambulatory dogs

BACKGROUND

The relationship between cardiac autonomic nerve activity and blood pressure (BP) changes in ambulatory dogs is unclear.

OBJECTIVE

The purpose of this study was to test the hypotheses that simultaneous termination of stellate ganglion nerve activity (SGNA) and vagal nerve activity (VNA) predisposes to spontaneous orthostatic hypotension and that specific β₂-adrenoceptor blockade prevents the hypotensive episodes.

METHODS

We used a radiotransmitter to record SGNA, VNA, and BP in eight ambulatory dogs. Video imaging was used to document postural changes.

RESULTS

Of these eight dogs, five showed simultaneous sympathovagal discharges in which the minute-by-minute integrated SGNA correlated with integrated VNA in a linear pattern (group 1). In these dogs, abrupt termination of simultaneous SGNA-VNA at the time of postural changes (as documented by video imaging) was followed by abrupt (>20 mm Hg over four beats) drops in BP. Dogs without simultaneous on/off firing (group 2) did not have drastic drops in pressure. ICI-118,551 (ICI, a specific β₂-blocker) infused at 3 µg/kg/h for 7 days significantly increased BP from 126 mm Hg (95% confidence interval 118-133) to 133 mm Hg (95% confidence interval 125-141; P = .0001). The duration of hypotension (mean systolic BP <100 mm Hg) during baseline accounted for 7.1% of the recording. The percentage was reduced by ICI to 1.3% (P = .01).

CONCLUSION

Abrupt simultaneous termination of SGNA-VNA was observed at the time of orthostatic hypotension in ambulatory dogs. Selective β₂-adrenoceptor blockade increased BP and reduced the duration of hypotension in this model.

Treatment of neurally mediated reflex syncope

Neurally mediated reflex syncope, more commonly known as vasovagal syncope (VVS), remains the most common cause of transient loss of consciousness and syncope in all age groups. Most evidence assessing treatment of VVS derived from randomized clinical trials is limited. Multiple modalities of both nonpharmacologic and pharmacologic strategies have been tested, with conflicting results. The treatment of VVS has been directed toward interventions that interrupt the reflex response at different levels, hypothetically preventing the onset of syncope. This article reviews the available evidence of the different nonpharmacologic and pharmacologic therapies available for the treatment of recurrent VVS.

Overview of the contribution of recent clinical trials to advancement of syncope management

In this communication we review those trials that have contributed in recent years to improving our knowledge on the management (diagnosis and treatment) of syncope. In this regard, most recent trials focus on vasovagal syncope (VVS) and consequently these will be the focus of this manuscript. In essence, from a diagnostic perspective the ISSUE studies demonstrate the value of insertable loop recorders (ILR), while in terms of treatment, in the case of VVS current data strongly support use of non-pharmacologic treatment as a primary approach. There is no clear evidence supporting pharmacologic treatment with the possible exception of midodrine. Further, the most recent ISSUE trials suggest that in older very symptomatic patients with VVS in whom an asystole has been documented during spontaneous episode or possibly after ATP administration, implantation of a permanent pacemaker (PPM) can be effective. Which pacing or programming mode will be the more beneficial has not been completely clarified. Management of other forms of neurally-mediated syncope (e.g., carotid sinus syndrome) or other causes of syncope has not been addressed by clinical trials. In those cases, direction is provided by older evidence, the vast majority of which is based on observational reports or small non-randomized patient series.

Medical therapy and physical maneuvers in the treatment of the vasovagal syncope and orthostatic hypotension

Patients with vasovagal syncope and neurogenic orthostatic hypotension can both present with pre-syncope and syncope resulting from systemic hypotension. While not directly responsible for increased mortality, both of these conditions can have a tremendous deleterious impact on the daily lives of patients. This negative impact can take the form of both physical symptoms and injury, but also a psychological impact from living in fear of the next syncopal episode. Despite these similarities, these are different disorders with fixed damage to the autonomic nerves in neurogenic orthostatic hypotension, as opposed to a transient reflex hypotension in "neurally mediated" vasovagal syncope. The treatment approaches for both disorders are parallel. The first step is to educate the patient about the pathophysiology and prognosis of their disorder. Next, offending medications should be withdrawn when possible. Non-pharmacological therapies and maneuvers can be used, both in an effort to prevent the symptoms and to prevent syncope at the onset of presyncope. This is all that is required in many patients with vasovagal syncope. If needed, pharmacological options are also available for both vasovagal syncope and neurogenic orthostatic hypotension, many of which are focused on blood volume expansion, increasing cardiac venous return, or pressor agents to increase vascular tone. There is a paucity of high-quality clinical trial data to support the use of these pharmacological agents. We aim to review the literature on these different therapy choices and to give recommendations on tailored approaches to the treatment of these conditions.

The effect of paediatric syncope on health-related quality of life

BACKGROUND

Syncope is common in children and adolescents and most commonly represents neurocardiogenic syncope. No information has been reported regarding the effect of syncope on health-related quality of life in children.

METHODS

This was a retrospective cohort study of patients seen in the Heart Institute Syncope Clinic at Cincinnati Children's Hospital Medical Center between July, 2009 and June, 2010. Health-related quality of life was assessed using the PedsQL™ tool. PedsQL™ scores were compared with both healthy historical controls and historical controls with chronic illnesses.

RESULTS

A total of 106 patients were included for analysis. In all, 90% were Caucasian and 63% were girls. The median age was 15.1 years (8.2-21.6). Compared with healthy controls, patients had lower PedsQL™ scores: Total score (75.2 versus 83.8, p < 0.0001); Physical Health Summary (78.8 versus 87.5, p < 0.0001); Psychosocial Health Summary (73.9 versus 81.9, p < 0.001), Emotional Functioning (68.9 versus 79.3, p < 0.001); and School Functioning (66.4 versus 81.1, p < 0.001). No difference was seen in Social Functioning (86.2 versus 85.2, p = 0.81). Patients also had lower PedsQL™ Total scores than patients with diabetes mellitus (p < 0.0001) and similar scores to patients with asthma, end-stage renal disease, obesity, and structural heart disease.

CONCLUSION

Children with syncope, although typically benign in aetiology, can have low health-related quality of life.

Age-dependence of relative change in circulating epinephrine and norepinephrine concentrations during tilt-induced vasovagal syncope

BACKGROUND

Although vasovagal syncope (VVS) is preceded by a surge of circulating catecholamines (epinephrine [Epi] and norepinephrine [NE]) of adrenal/renal and synaptic origin, prevention of VVS with β-adrenergic blockade has been ineffective except in "older" VVS patients.

OBJECTIVE

We hypothesized that age-related differences of β-blocker effect may be due in part to differences in the relative magnitudes of Epi and NE release during an evolving faint, specifically, greater Epi/NE ratio in younger fainters compared to older patients. To assess this hypothesis, we measured changes in Epi/NE ratios in younger (<40 years) vs older (≥40 years) patients during head-up tilt-table test-induced VVS.

METHODS

The study comprised 29 patients (12 patients ≥40 years [mean 56 ± 10.7 years] and 17 patients <40 years mean 25 ± 5.7 years]) with recurrent suspected VVS in whom 70° head-up tilt testing reproduced symptoms. Arterial Epi and NE concentrations were measured at baseline (supine), 2 minutes of head-up tilt, and syncope.

RESULTS

Baseline Epi and NE concentrations and the Epi/NE ratio did not differ in younger and older groups (Epi: 90 ± 65 pg/mL vs 70 ± 32 pg/mL; NE: 226 ± 122 pg/mL vs 244 ± 183 pg/mL). However, Epi/NE ratio increased to a greater extent in younger fainters during head-up tilt and tended to be greater in younger patients at both 2 minutes (<40: 1.02 ± 1.29 vs ≥40: 0.40 ± 0.27, P = .11) and at symptoms (<40: 2.6 ± 1.26 vs ≥40: 1.6 ± 0.71, P = .03). At symptoms, Epi/NE ratio ≥2.5 was observed in 9 of 17 younger patients vs 1 of 12 older patients (P = .02).

CONCLUSION

Epi/NE ratios tend to be greater in younger fainters, a finding that may account in part for the observation that β-blocker therapy is less effective in reducing VVS susceptibility in younger individuals.

The Management of Vasovagal Syncope in a Patient with Brugada Syndrome

Vasovagal syncope is the most common cause of the neurally mediated reflex syncopes. A higher susceptibility to vasovagal syncope has been reported in patients with Brugada syndrome (BrS) and may be caused by associated autonomic dysfunction. It is unclear what risk vasovagal syncope confers to patients with BrS. This article reviews the pathophysiology of vasovagal syncope and autonomic dysfunction in patients with BrS and its association with BrS, treatment options for patients with BrS with vasovagal syncope, specific therapies and those that may be harmful in patients with BrS, and potential therapies and monitoring for patients with BrS with vasovagal syncope.

Are treatments for vasovagal syncope effective? A meta-analysis

BACKGROUND

Therapies used to treat vaso-vagal syncope (VVS) recurrence have not been proven effective in single studies.

METHODS

Comprehensive search of PubMed, EMBASE and Cochrane Central databases of published trials was done. Randomized or non-randomized studies, comparing the intervention of interest to control group(s), with the endpoint of spontaneous recurrence or syncope on head-up tilt test, were included. Data were extracted on an intention-to-treat basis. Study heterogeneity was analyzed by Cochran's Q statistics. A random-effect analysis was used.

RESULTS

α-adrenergic agonists were found effective (n=400, OR 0.19, CI 0.06-0.62, p<0.05) in preventing VVS recurrence. β-blockers were not found to be effective when only randomized studies comparing β-blockers to non-pharmacologic agents were assessed (9 studies, n=583, OR 0.48, CI 0.22-1.04, p=0.06). Tilt-training had no effect when only randomized studies were considered (4 studies, n=298, OR 0.47, CI 0.21-1.05, p=0.07). Selective serotonin reuptake inhibitors were found effective (n=131, OR 0.28, CI 0.10-0.74, p<0.05), though the analysis contained only 2 studies. Pacemakers were found effective in preventing syncope recurrence when all studies were analyzed (n=463, OR 0.13, CI 0.05-0.36, p<0.05). However, studies comparing active pacemaker to sensing mode only did not show benefit (3 studies, n=162, OR 0.45, CI 0.09-2.14, p=0.32).

CONCLUSIONS

This meta-analysis highlights the totality of evidence for commonly used medications used to treat VVS, and the requirement for larger, double-blind, placebo controlled trials with longer follow-up.

Recent history of vasovagal syncope in a young, referral-based population is a stronger predictor of recurrent syncope than lifetime syncope burden

INTRODUCTION

accurate selection of patients for vasovagal syncope studies requires strong risk stratification and knowledge of the natural history of syncope. We aimed to test the hypothesis that recent history of vasovagal syncope compared to distant history better predicts subsequent recurrence of syncope.

METHODS AND RESULTS

in all, 208 subjects with a positive tilt test and ≥ 3 lifetime syncope spells were followed for 1 year. Syncope episodes in the preceding year and total historical spells were compared for their ability to predict a syncope recurrence using the criteria of optimal statistical significance, best linear separation of risk populations, and impact on power calculations. The number of vasovagal syncope spells in the preceding year better predicted syncope recurrence when compared to total number of historical spells (likelihood ratio statistic 28.4, P < 0.0001; versus 20.4, P = 0.001), and showed a substantial effect as the number of syncope events increased. For example, syncope recurred in 22% of those with <2 spells in the previous year compared to 69% in those with >6 spells. A history of no syncope compared to any syncope in the preceding year was associated with a 1-year probability of 7% versus 46% for syncope recurrence. A study designed to detect a 50% decrease in syncope recurrence at P = 0.05 with 80% power would require 159 patients with at least 3 lifetime spells, and only 108 patients with at least 3 spells in the previous year.

CONCLUSIONS

the number of syncope events in the year preceding clinical evaluation is the best predictor of syncope recurrence.

Drugs and pacemakers for vasovagal, carotid sinus and situational syncope

BACKGROUND

Neurally mediated reflex syncope is the most common cause of transient loss of consciousness. In patients not responding to non-pharmacological treatment, pharmacological or pacemaker treatment might be considered.

OBJECTIVES

To examine the effects of pharmacological therapy and pacemaker implantation in patients with vasovagal syncope, carotid sinus syncope and situational syncope.

SEARCH STRATEGY

We searched the Cochrane Central Register of Controlled Trials (CENTRAL) on The Cochrane Library (Issue 1, 2008), PubMed (1950 until February 2008), EMBASE on OVID (1980 until February 2008) and CINAHL on EBSCOhost (1937 until February 2008). No language restrictions were applied.

SELECTION CRITERIA

We included parallel randomized controlled trials and randomized cross-over trials of pharmacological treatment (beta-blockers, fludrocortisone, alpha-adrenergic agonists, selective serotonine reuptake inhibitors, ACE inhibitors, disopyramide, anticholinergic agents or salt tablets) or dual chamber pacemaker treatment. Studies were included if pharmacological or pacemaker treatment was compared with any form of standardised control treatment (standard treatment), placebo treatment, or (other) pharmacological or pacemaker treatment. We did not include non-randomized studies.

DATA COLLECTION AND ANALYSIS

Two reviewers independently assessed the risk of bias. Using a standardised data extraction form, they extracted characteristics and results of the various studies. In a consensus meeting they discussed any disagreements that had occurred during data extraction. If no agreement could be reached, a third reviewer was asked to make a decision. Summary estimates with 95% confidence intervals of treatment effect were calculated using relative risks, rate ratios or weighted means differences depending on the type of outcome reported.

MAIN RESULTS

We included 46 randomized studies, 40 on vasovagal syncope and six on carotid sinus syncope. No studies on situational syncope matched the criteria for inclusion in our review. Studies in general were small with a median sample size of 42. A wide range of control treatments were used with 22 studies using a placebo arm. Blinding of patients and treating physicians was applied in eight studies. Results varied considerably between studies and between types of outcomes.For vasovagal syncope, the occurrence of syncope upon provocational head-up tilt testing was lower upon treatment with beta-blockers, ACE-inhibitors and anticholinergic agents compared to standard treatment. For carotid sinus syncope, the occurrence of syncope upon carotid sinus massage was lower on midodrine treatment compared to placebo treatment in one study.

AUTHORS' CONCLUSIONS

There is insufficient evidence to support the use of any of the pharmacological or pacemaker treatments for vasovagal syncope and carotid sinus syncope. Larger studies using patient relevant outcomes are needed.

Management and therapy of vasovagal syncope: A review

Vasovagal syncope is a common cause of recurrent syncope. Clinically, these episodes may present as an isolated event with an identifiable trigger, or manifest as a cluster of recurrent episodes warranting intensive evaluation. The mechanism of vasovagal syncope is incompletely understood. Diagnostic tools such as implantable loop recorders may facilitate the identification of patients with arrhythmia mimicking benign vasovagal syncope. This review focuses on the management of vasovagal syncope and discusses the non-pharmacological and pharmacological treatment options, especially the use of midodrine and selective serotonin reuptake inhibitors. The role of cardiac pacing may be meaningful for a subgroup of patients who manifest severe bradycardia or asystole but this still remains controversial.

Neurocardiogenic syncope: mechanisms, evaluation and treatment

Syncope is the abrupt and transient loss of consciousness due to a temporary reduction in cerebral blood flow, associated with an absence of postural tone, followed by a rapid and usually complete recovery. It may result from several possible etiologies, ranging from the benign to the potentially fatal. Neurocardiogenic (vasovagal) syncope is the most common of a group of neurally mediated syncopes, characterized by a sudden failure of autonomic regulatory mechanisms to maintain adequate blood pressure and, occasionally, heart rate, to sustain cerebral perfusion and consciousness. The diagnosis may be suggested by a characteristic history and by exclusion of other causes of syncope; however, in some cases, upright tilt table testing may be required to provoke typical hemodynamic responses. Cardiologists and cardiac electrophysiologists are frequently expected to manage patients with suspected neurocardiogenic syncope. The following review aims to provide a basic framework for understanding its pathophysiology, clinical presentations, diagnosis and treatment.

Clinical efficacy of beta1 selective adrenergic blockers in the treatment of neurocardiogenic syncope - a meta-analysis

BACKGROUND

Beta1 (B(1)) selective blockers have been widely used for the treatment of neurocardiogenic syncope though clinical trials have shown conflicting degrees of efficacy.

OBJECTIVE

To study the clinical efficacy of B(1) selective blockers compared to placebo in the treatment of neurocardiogenic syncope.

METHODS

Four placebo controlled randomized studies were identified after search of existing English language literature. Review Manager (RevMan version 5, Oxford, England) was used for statistical calculations. Both random and fixed effects models were used for analysis.

RESULTS

There was no demonstrable efficacy of B(1) blockers compared to placebo even after a pre-specified sensitivity analysis. There was a trend towards more adverse events in the beta blocker group compared to placebo (OR = 2.03 CI = 0.83-3.95, p = 0.12).

CONCLUSION

There is no clinical evidence for justifying the use of B(1) selective blockers in the treatment of adult neurocardiogenic syncope. These agents may in fact lead to a higher rate of adverse events compared to placebo.

Pathophysiology, diagnosis, and treatment of orthostatic hypotension and vasovagal syncope

Orthostatic hypotension (OH) occurs in 0.5% of individuals and as many as 7-17% of patients in acute care settings. Moreover, OH may be more prevalent in the elderly due to the increased use of vasoactive medications and the concomitant decrease in physiologic function, such as baroreceptor sensitivity. OH may result in the genesis of a presyncopal state or result in syncope. OH is defined as a reduction of systolic blood pressure (SBP) of at least 20 mm Hg or diastolic blood pressure (DBP) of at least 10 mm Hg within 3 minutes of standing. A review of symptoms, and measurement of supine and standing BP with appropriate clinical tests should narrow the differential diagnosis and the cause of OH. The fall in BP seen in OH results from the inability of the autonomic nervous system (ANS) to achieve adequate venous return and appropriate vasoconstriction sufficient to maintain BP. An evaluation of patients with OH should consider hypovolemia, removal of offending medications, primary autonomic disorders, secondary autonomic disorders, and vasovagal syncope, the most common cause of syncope. Although further research is necessary to rectify the disease process responsible for OH, patients suffering from this disorder can effectively be treated with a combination of nonpharmacologic treatment, pharmacologic treatment, and patient education. Agents such as fludrocortisone, midodrine, and selective serotonin reuptake inhibitors have shown promising results. Treatment for recurrent vasovagal syncope includes increased salt and water intake and various drug treatments, most of which are still under investigation.