Permanent cardiac pacing versus medical treatment for the prevention of recurrent vasovagal syncope: a multicenter, randomized, controlled trial

Syncope: diagnosis and management

Syncope is defined as transient loss of consciousness due to global cerebral hypoperfusion. It is characterized by having a relatively rapid onset, brief duration with spontaneous and full recovery. The major challenge in the evaluation of patients with syncope is that most patients are asymptomatic at the time of their presentation. A thorough history and physical examination including orthostatic assessment are crucial for making the diagnosis. After initial evaluation, short-term risk assessment should be performed to determine the need for admission. If the short-term risk is high, inpatient evaluation is needed. If the short-term risk is low, outpatient evaluation is recommended. In patients with suspected cardiac syncope, monitoring is indicated until a diagnosis is made. In patients with suspected reflex syncope or orthostatic hypotension, outpatient evaluation with tilt-table testing is appropriate. Syncope units have been shown to improve the rate of diagnosis while reducing cost and thus are highly recommended.

Syncope

Syncope is common representing approximately 3% of ED visits and up to 6% of hospital admissions, with a cost close to 2 billion dollars per year. Diagnostic testing is often poorly sensitive and evaluations commonly lack a standardized approach. A mindful and systematic approach can increase sensitivity and improve diagnostic accuracy. A thorough history and physical exam is paramount, as conclusions drawn from the history and exam will guide further assessment. Developing a strategy for the first and, if necessary, subsequent tests will improve the accuracy of identifying the etiology of syncope and reduce cost. Although syncope has a favorable prognosis, identification of patients with structural heart disease is critical, as these patients are at greatest risk for mortality. Several risk scoring systems have been developed to help separate high risk from low risk patients.

Pathophysiology of neurally mediated syncope: Role of cardiac output and total peripheral resistance

Syncope is a common clinical condition occurring even in otherwise healthy people without underlying cardiovascular disease. Neurally mediated syncope is by far the most common cause of syncope in individuals without any structural heart disease. Based on traditional wisdom, loss of sympathetic tone with relaxation of vascular smooth muscle is the key mechanism underlying the pathophysiology of syncope, especially in patients without an acute decrease in heart rate. However, this concept has recently been challenged. Some microneurographic studies indicate that sympathetic withdrawal may not always be a prerequisite even for the development of classic "vasodepressor" forms of syncope. Conversely, a decrease in cardiac output appears to be a determinant factor for syncope in most circumstances. This article reviews the relative contribution of cardiac output versus sympathetic vasoconstriction in neurally mediated syncope in otherwise healthy individuals. It is suggested that a moderate to severe fall in cardiac output with or without vasodilatation may contribute to syncope.

Reflex vasovagal syncope--is there a benefit in pacemaker therapy?

Reflex vasovagal syncope often affects young populations and is associated with a benign prognosis in terms of mortality. However, a minority of patients have recurrent episodes, with a considerable impact on their quality of life. Pacemaker therapy has been an option in these patients since the 1990s if a conservative strategy fails. Initially, non-randomized and open-label randomized trials showed promising results, but these studies were associated with a significant placebo effect. Recently, an approach based on the use of implantable loop recorders has shown that some patients with reflex vasovagal syncope could benefit from implantation with dual-chamber pacemakers, particularly patients aged >40 years, with recurrent syncopal episodes resulting in frequent injuries, in whom a long asystole (≥3 s asystole with syncope or ≥6 s asystole without syncope) has been documented with an implantable loop recorder. The authors present a literature review on the role of cardiac pacing in reflex vasovagal syncope and propose a diagnostic and therapeutic decision flowchart for patients with syncope of probable reflex etiology.

[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.

Management of vasovagal syncope: 2004

Vasovagal syncope is a common disorder that affects at least 20% of people at some time in their lives. Probably half of these patients faint recurrently; for many this causes physical trauma, a substantial reduction in quality of life, and difficulties with driving, employment and education. The last 15 years have seen striking advances in diagnostic approaches and prognostic understanding. A number of physiological, pharmacological and electrical therapies have been developed and tested to various degrees in patients. These include counterpressure manoeuvres, salt and fluid recommendations, and attempted treatment with fludrocortisone, midodrine, beta-blockers, serotonin reuptake inhibitors, and permanent pacemakers. This review highlights the most important of these advances and suggests strategies for managing this often difficult problem.

Benefit of pacemaker therapy in patients with presumed neurally mediated syncope and documented asystole is greater when tilt test is negative: an analysis from the third International Study on Syncope of Uncertain Etiology (ISSUE-3)

BACKGROUND

In the Third International Study on Syncope of Uncertain Etiology (ISSUE-3), cardiac pacing was effective in reducing recurrence of syncope in patients with presumed neurally mediated syncope (NMS) and documented asystole but syncope still recurred in 25% of them at 2 years. We have investigated the role of tilt testing (TT) in predicting recurrences.

METHODS AND RESULTS

In 136 patients enrolled in the ISSUE-3, TT was positive in 76 and negative in 60. An asystolic response predicted a similar asystolic form during implantable loop recorder monitoring, with a positive predictive value of 86%. The corresponding values were 48% in patients with non-asystolic TT and 58% in patients with negative TT (P=0.001 versus asystolic TT). Fifty-two patients (26 TT+ and 26 TT-) with asystolic neurally mediated syncope received a pacemaker. Syncope recurred in 8 TT+ and in 1 TT- patients. At 21 months, the estimated product-limit syncope recurrence rates were 55% and 5%, respectively (P=0.004). The TT+ recurrence rate was similar to that seen in 45 untreated patients (control group), which was 64% (P=0.75). The recurrence rate was similar between 14 patients with asystolic and 12 with non-asystolic responses during TT (P=0.53).

CONCLUSIONS

Cardiac pacing was effective in neurally mediated syncope patients with documented asystolic episodes in whom TT was negative; conversely, there was insufficient evidence of efficacy from this data set in patients with a positive TT even when spontaneous asystole was documented. Present observations are unexpected and need to be confirmed by other studies. Clinical Trial Registration- URL: http://www.clinicaltrials.gov. Unique identifier: NCT01463358.

Tilt-table test: its role in modern practice

Syncope is a major healthcare problem with significant morbidity, mortality and healthcare cost. It is a common symptom with a complex pathophysiology and, therefore, several aetiologies. Tilt-table testing (TTT) is an important, yet perhaps not widely-used, test that forms part of the management of syncope. We sought to assess the utilisation of this test in our institution for the investigation of patients with syncope, to study the referral patterns and the outcomes and usefulness of the TTT in a real-life setting. We undertook a retrospective study of all the TTT that were performed in our institution between January 2009 and October 2009. Of the 69 patients in which TTT was performed, 14 (20%) presented with presyncope, 24 (35%) with a single episode of syncope and 24 (44%) with multiple episodes. The average age was 57.2 years and 64% were female. Of the total patients, 35 (51%) had an abnormal TTT. Of the patients with normal TTT, four had internal loop recorders and six were referred to other medical specialities. The remaining patients (49%) had no formal diagnosis and were referred back to their general practitioner. TTT remains a common test modality and has great value when undertaken in the correct clinical context. This underlines the importance of a detailed clinical history. The European Society of Cardiology guidelines ensure a methodical and rational approach to syncopal patients and aide in choosing the right patient for the right test.

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.

Successful implanted pacemaker for an extreme inhibitory reflex syncope evoked by post herpetic trigeminal neuralgia

Syncope is defined as a transient loss of consciousness due to cerebral hypoperfusion characterized by rapid onset, short duration, and spontaneous complete recovery. Numerous causes of syncope have been described. Vasovagal syncope is the most common with a number of precipitants. We report a case of post herpetic trigeminal neuralgia leading to neurocardiogenic syncope. These episodes were preceded by severe stabbing left frontal headaches followed by significant sinus bradycardia, asystole, and syncope requiring pacemaker implantation. To our knowledge only one previous case of post herpetic trigeminal neuralgia leading to syncope has been reported. <Learning objective: Neuralgia-associated syncope is a rare phenomenon. Failing to recognize and treat appropriately may be associated with recurring episodes of syncope with significant lifestyle limitations. Although post herpetic neuralgia is treatable, one should be prepared to insert a pacemaker if treatment fails to control symptoms that progress to cardioinhibitory syncope.>.

Pacemaker therapy in syncope

The current evidence for pacemaker therapy is reviewed in 2 different syncopal conditions: reflex syncope with cardioinhibitory response and syncope in patients with bundle branch block. Although recent trials support the use of pacemaker therapy in selected patients with reflex syncope in whom an asystole is documented during spontaneous syncope or in whom an asystole is provoked with adenosine-5'-triphosphate administration, the best strategy in these patients and in those with syncope and bundle branch block is not well established. Ongoing clinical trials will answer this question.

Key challenges in the current management of syncope

Patients commonly present with syncope at emergency departments and other facilities for urgent care. Syncope is understood by physicians to be a transient, self-terminating period of cerebral hypoperfusion that usually results from systemic hypotension, and clinical guidelines for the care of patients with presumed syncope are available. However, the diagnosis and management of such patients continue to pose important diagnostic, therapeutic, and economic challenges, which are the focus of this Review. First, we discuss how to improve symptom characterization to distinguish syncope from other forms of transient loss of consciousness and syncope mimics. Second, we compare methods of risk stratification in patients with suspected syncope, and recommend the introduction of syncope clinics with enhanced interdisciplinary collaboration to optimize patient care at reduced expense. Third, we highlight the importance of the appropriate selection of diagnostic tools and treatment strategies in these syncope clinics. Finally, we address the difficulties associated with therapy for the most-common form of syncope--vasovagal or reflex syncope.

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.

Pacemaker therapy in patients with neurally mediated syncope and documented asystole: Third International Study on Syncope of Uncertain Etiology (ISSUE-3): a randomized trial

BACKGROUND

The efficacy of cardiac pacing for prevention of syncopal recurrences in patients with neurally mediated syncope is controversial. We wanted to determine whether pacing therapy reduces syncopal recurrences in patients with severe asystolic neurally mediated syncope.

METHODS AND RESULTS

Double-blind, randomized placebo-controlled study conducted in 29 centers in the Third International Study on Syncope of Uncertain Etiology (ISSUE-3) trial. Patients were ≥40 years, had experienced ≥3 syncopal episodes in the previous 2 years. Initially, 511 patients, received an implantable loop recorder; 89 of these had documentation of syncope with ≥3 s asystole or ≥6 s asystole without syncope within 12 ± 10 months and met criteria for pacemaker implantation; 77 of 89 patients were randomly assigned to dual-chamber pacing with rate drop response or to sensing only. The data were analyzed on intention-to-treat principle. There was syncope recurrence during follow-up in 27 patients, 19 of whom had been assigned to pacemaker OFF and 8 to pacemaker ON. The 2-year estimated syncope recurrence rate was 57% (95% CI, 40-74) with pacemaker OFF and 25% (95% CI, 13-45) with pacemaker ON (log rank: P=0.039 at the threshold of statistical significance of 0.04). The risk of recurrence was reduced by 57% (95% CI, 4-81). Five patients had procedural complications: lead dislodgment in 4 requiring correction and subclavian vein thrombosis in 1 patient.

CONCLUSIONS

Dual-chamber permanent pacing is effective in reducing recurrence of syncope in patients ≥40 years with severe asystolic neurally mediated syncope. The observed 32% absolute and 57% relative reduction in syncope recurrence support this invasive treatment for the relatively benign neurally mediated syncope.

CLINICAL TRIAL REGISTRATION

URL: http://www.clinicaltrials.gov. Unique identifier: NCT00359203.

A case of swallow syncope associated with cold beverage ingestion

Swallow syncope (also known as deglutition syncope) is a relatively rare type of syncope that is treatable if diagnosed correctly. We report a case of a 39-year-old man with recurrent swallow syncope. The patient did not have structural heart disease. He developed a complete atrioventricular block upon drinking a cold beverage (Chilsung cider) while undergoing a repeated head-up tilt test. The patient was advised to avoid cold beverages and has been symptom free for 5 months.

Sleep syncope: treatment with a permanent pacemaker

Vasovagal syncope usually occurs during upright posture, but Jardine et al. have described a variant that occurs at night. During "sleep syncope" patients are awakened from sleep with nausea, abdominal cramping, or a sense of impending diarrhea; get up; and faint in the bathroom. We report on a patient with recurrent sleep syncope (with physical injury) in whom an asystolic pause was documented during one of her "sleep syncope" spells. Implantation of a dual chamber pacemaker (5-year follow-up) "cured" her of further syncope. This is a report of pacemaker use for this unusual form of reflex syncope.

Syncope in adults: systematic review and proposal of a diagnostic and therapeutic algorithm

This review aims to provide a practical and up-to-date description on the relevance and classification of syncope in adults as well as a guidance on the optimal evaluation, management and treatment of this very common clinical and socioeconomic medical problem. We have summarized recent active research and emphasized the value for physicians to adhere current guidelines. A modern management of syncope should take into account 1) use of risk stratification algorithms and implementation of syncope management units to increase the diagnostic yield and reduce costs; 2) early implantable loop recorders rather than late in the evaluation of unexplained syncope; and 3) isometric physical counter-pressure maneuvers as first-line treatment for patients with neurally-mediated reflex syncope and prodromal symptoms.

An increased endothelial-independent vasodilation is the hallmark of the neurally mediated syncope

BACKGROUND

The neurally mediated syncope (NMS) is sustained by complex cardiac and vascular reflexes, acting on and amplified by central autonomic loops, resulting in bradycardia and hypotension.

HYPOTHESIS

Our aim was to assess whether the pathophysiology of NMS is also related to an abnormal peripheral vasoreactivity.

METHODS

We evaluated by ultrasound the flow-mediated vasodilation (FMD) and the nitrate-mediated dilation (NMD) in 17 patients with NMS, induced by drug-free tilt test in 6 subjects and by nitrate-potentiated tilt test in the other 11 cases; the syncope was classified as vasodepressive (VD) in 8 cases, cardioinhibitory (CI) in 7, and mixed in 2.

RESULTS

The FMD was not different from controls (10.2 ± 4.5 vs 11.4 ± 3.9, P = ns), with normal recovery times; the NMD was greater in fainting subjects than in controls (26.7 ± 7.3 vs 19.0 ± 3.6, P < 0.05), with higher values in VD than in CI syncope (31.1 ± 7.0 vs 23.1 ± 5.0, P = ns); compared to controls, subjects with NMS showed normal recovery times after FMD but longer recovery times after nitrate administration (13.0 ± 5.6 vs 6.3 ± 0.7 minutes, P < 0.05).

CONCLUSIONS

The evaluation of endothelial function supports evidence that NMS is characterized by a marked and sustained endothelial-independent vasodilation, in the presence of a normal FMD; vascular hyperreactivity in response to nitrate administration is particularly overt in vasodepressive syncope and can explain the high rate of responses to nitrate administration during tilt test.

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.

Physiological phenomenology of neurally-mediated syncope with management implications

BACKGROUND

Due to lack of efficacy in recent trials, current guidelines for the treatment of neurally-mediated (vasovagal) syncope do not promote cardiac pacemaker implantation. However, the finding of asystole during head-up tilt -induced (pre)syncope may lead to excessive cardioinhibitory syncope diagnosis and treatment with cardiac pacemakers as blood pressure is often discontinuously measured. Furthermore, physicians may be more inclined to implant cardiac pacemakers in older patients. We hypothesized that true cardioinhibitory syncope in which the decrease in heart rate precedes the fall in blood pressure is a very rare finding which might explain the lack of efficacy of pacemakers in neurally-mediated syncope.

METHODS

We studied 173 consecutive patients referred for unexplained syncope (114 women, 59 men, 42 ± 1 years, 17 ± 2 syncopal episodes). All had experienced (pre)syncope during head-up tilt testing followed by additional lower body negative suction. We classified hemodynamic responses according to the modified Vasovagal Syncope International Study (VASIS) classification as mixed response (VASIS I), cardioinhibitory without (VASIS IIa) or with asystole (VASIS IIb), and vasodepressor (VASIS III). Then, we defined the exact temporal relationship between hypotension and bradycardia to identify patients with true cardioinhibitory syncope.

RESULTS

Of the (pre)syncopal events during tilt testing, 63% were classified as VASIS I, 6% as VASIS IIb, 2% as VASIS IIa, and 29% as VASIS III. Cardioinhibitory responses (VASIS class II) progressively decreased from the youngest to the oldest age quartile. With more detailed temporal analysis, blood pressure reduction preceded the heart-rate decrease in all but six individuals (97%) overall and in 10 out of 11 patients with asystole (VASIS IIb).

CONCLUSIONS

Hypotension precedes bradycardia onset during head-up tilt-induced (pre)syncope in the vast majority of patients, even in those classified as cardioinhibitory syncope according to the modified VASIS classification. Furthermore, cardioinhibitory syncope becomes less frequent with increasing age.

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.

The placebo effect and the autonomic nervous system: evidence for an intimate relationship

For many subjectively experienced outcomes, such as pain and depression, rather large placebo effects have been reported. However, there is increasing evidence that placebo interventions also affect end-organ functions regulated by the autonomic nervous system (ANS). After discussing three psychological models for autonomic placebo effects, this article provides an anatomical framework of the autonomic system and then critically reviews the relevant placebo studies in the field, thereby focusing on gastrointestinal, cardiovascular and pulmonary functions. The findings indicate that several autonomic organ functions can indeed be altered by verbal suggestions delivered during placebo and nocebo interventions. In addition, three experimental studies provide evidence for organ-specific effects, in agreement with the current knowledge on the central control of the ANS. It is suggested that the placebo effects on autonomic organ functions are best explained by the model of 'implicit affordance', which assumes that placebo effects are dependent on 'lived experience' rather than on the conscious representation of expected outcomes. Nevertheless, more studies will be needed to further elucidate psychological and neurobiological pathways involved in autonomic placebo effects.

GRADE guidelines: 9. Rating up the quality of evidence

The most common reason for rating up the quality of evidence is a large effect. GRADE suggests considering rating up quality of evidence one level when methodologically rigorous observational studies show at least a two-fold reduction or increase in risk, and rating up two levels for at least a five-fold reduction or increase in risk. Systematic review authors and guideline developers may also consider rating up quality of evidence when a dose-response gradient is present, and when all plausible confounders or biases would decrease an apparent treatment effect, or would create a spurious effect when results suggest no effect. Other considerations include the rapidity of the response, the underlying trajectory of the condition, and indirect evidence.

Recurrent syncope in a cancer patient: a case report and review of the literature

A 59-year-old male with invasive squamous cell carcinoma of the left preauricular region, treated with several chemotherapy regimens and radiation therapy, was admitted for recurrent syncopal episodes. He was found to be suffering from neurocardiogenic reflex-mediated syncope secondary to mechanical compression of the carotid baroreceptors and glossopharyngeal nerve by the tumor. We discuss the pathophysiology of this case and the available treatment options.

Assessment of systolic ejection time as a hemodynamic marker of incipient bradycardic vasovagal syncope. A pilot study

BACKGROUND

Detection of markers of incipient syncope in patients with vasovagal syncope (VVS), without prodromal symptom, is still an open issue. The aim of this study was to assess the behavior of heart rate (HR) and ejection time, expressed as the percentage of the corresponding cardiac cycle (ET%), in patients with bradycardic VVS with a view to providing an alarm before the event.

METHODS

In 33 patients with syncope and positive tilt testing and in 33 control patients, we collected beat-to-beat data on HR, ET%, stroke volume (SV), and blood pressure (BP). The trends of HR and ET% were analyzed. A set of combined changes of HR and ET% were tested in order to select the most appropriate algorithm for detecting the incipient syncope within the 3 minutes preceding the event.

RESULTS

In patients with positive tilt testing, BP significantly decreased at 3 minutes before and at the time of syncope (P < 0.0001). HR slowly rose at 3 minutes before syncope and then suddenly decreased at the time of syncope (P < 0.0001). The correlation between SV and ET% was r = 0.79 (P < 0.0001). SV and ET% significantly decreased throughout tilt testing (P < 0.0001). The selected setting for the algorithm provided sensitivity of 97% and specificity of 73%. The theoretical alarm was generated at least 9 and 5 seconds before syncope, respectively, in 76% and 85% of the subjects.

CONCLUSION

The combined trends in HR and ET% may provide a marker of incipient bradycardic VVS in the majority of patients.

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.

Late Recognition of Malignant Vasovagal Syncope

A 21-year-old female with a history of seizures since the age of 5 presented for long-term electroencephalographic (EEG) monitoring, but was found instead to have neurocardiogenic syncope. Is it appropriate for this patient to get a pacemaker?

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.