Randomized double-blind, placebo-controlled trial of oral atenolol in patients with unexplained syncope and positive upright tilt table test results

A higher peak heart rate during head-up tilt test predicts the therapeutic efficacy of metoprolol in vasovagal syncope

BACKGROUND

Although beta blockers, such as metoprolol, have been widely used in the management of vasovagal syncope (VVS), their efficacy remains debated, with larger studies showing limited benefit. Identifying patient-specific characteristics that predict a positive response to metoprolol could optimize its use. This study aims to investigate the key factors that may determine which VVS patients are suitable candidates for metoprolol treatment.

METHODS

This retrospective study was conducted at a single center. Patients diagnosed with VVS and treated with metoprolol for a minimum of three months were included. A 50% reduction in syncope symptom score (SS) after three months of metoprolol treatment was used to define metoprolol responders, while those who did not achieve this reduction were classified as non-responders. After a three-month follow-up, patients were divided into two groups: responders and non-responders. Baseline data-including age, gender, comorbidities, laboratory tests, and the type of VVS-were analyzed for each patient. Changes in heart rate (HR) and blood pressure during the head-up tilt test (HUTT) were also evaluated between the two groups. Logistic regression analysis was performed to identify potential predictors of metoprolol response, and receiver operating characteristic (ROC) curve analysis was used to assess the value of these predictors in selecting potential responders.

RESULTS

A total of 168 VVS patients were enrolled between January 2016 and December 2020. Of these, 100 patients responded positively to metoprolol, while 68 did not. No significant differences in baseline characteristics or HUTT results were observed between the two groups (p > 0.05). However, responders exhibited a significantly higher peak HR compared to non-responders during the HUTT (120.13 ± 19.33 vs. 106.60 ± 22.32, p < 0.001). The increase in HR was also more pronounced in responders (0.60 ± 0.23 vs. 0.41 ± 0.25, p < 0.001). Additionally, HR variability was significantly greater in responders than in non-responders (16.18 ± 5.51 vs. 12.61 ± 5.50, p < 0.001).

CONCLUSION

Higher peak HR, larger increases in HR, and greater HR variability during the HUTT may serve as reliable predictors of a positive response to metoprolol in patients with VVS.

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.

Poincaré Plot Can Be a Useful Tool to Select Potential Responders to Metoprolol Therapy in Children with Vasovagal Syncope

Purpose

To explore the value of the longitudinal axis/transverse axis ratio (L/T) of Poincaré plot in selecting children with vasovagal syncope (VVS) who were suitable for metoprolol therapy.

Patients and Methods

Children with VVS hospitalized in Peking University First Hospital between January 2012 and June 2019 and treated with metoprolol were retrospectively included as the training set, and children with VVS hospitalized between July 2019 and December 2020 were included as the validation set. The sex, age at admission, height, weight, body mass index, course of disease, syncope symptom score before metoprolol treatment, treatment duration, supine heart rate (HR), supine systolic pressure, supine diastolic pressure, peak HR during the head-up tilt test (HUTT), changes of HR during HUTT, hemodynamic response during HUTT, left ventricular ejection fraction, left ventricular fractional shortening and the L/T of Poincaré plot were compared between responders and nonresponders in the training set. Logistic regression analysis was conducted to explore predictors. Receiver operating characteristic curve was utilized to determine the value of the predictors for selecting potential responders. Finally, the value of the predictors was further verified.

Results

In the training set including 105 children, the L/T in responders was distinctly higher than that in nonresponders (P < 0.001), and there was no apparent difference between the two groups in other indexes. The L/T was statistically related to the efficacy of metoprolol (P < 0.001). The L/T >2.7 yielded a sensitivity of 88.2% and a specificity of 82.8% for indicating responders to metoprolol. Taking L/T >2.7 to select potential responders in another 43 children with VVS in the validation set, the sensitivity was 96.6%, specificity 71.4%, and accuracy 88.4%.

Conclusion

The L/T of Poincaré plot >2.7 can be a useful tool to select potential responders to metoprolol therapy in children with VVS.

Midodrine treatment in children with recurrent vasovagal syncope

BACKGROUND

Vasovagal syncope is the most common cause of syncope in childhood and its treatment is not at a satisfactory level yet. We aimed to investigate patients who were diagnosed with vasovagal syncope, did not benefit from conventional treatment, received midodrine treatment, and to evaluate their response to midodrine treatment.

METHODS

Files of 24 patients who were diagnosed with recurrent vasovagal syncope, did not benefit from non-pharmacological treatments, and received midodrine treatment during June 2017-October 2019 were retrospectively analysed.

RESULTS

In total, 24 patients received a treatment dose of midodrine at 5 mg/day (2.5 mg BID) included in the study. The mean number of syncope was 5.75 ± 2.67 prior to treatment. Following treatment, the mean number of syncope was 0.42 ± 0.89. It was observed that syncope episodes did not recur in 17 patients, but it recurred in 4 out of 7 patients in the first 3 months of the treatment and did not recur in the following months. The episodes improved in two patients with an increase in the treatment dose, but the syncope episodes continued in only one patient.

CONCLUSION

It was concluded that midodrine treatment was effective and safe in adolescents with recurrent vasovagal syncope.

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.

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.

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.

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.

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.

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.

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.

Hypotensive bradycardic events during shoulder arthroscopic surgery under interscalene brachial plexus blocks

Sudden, profound hypotensive and bradycardic events (HBEs) have been reported in more than 20% of patients undergoing shoulder arthroscopy in the sitting position. Although HBEs may be associated with the adverse effects of interscalene brachial plexus block (ISBPB) in the sitting position, the underlying mechanisms responsible for HBEs during the course of shoulder surgery are not well understood. The basic mechanisms of HBEs may be associated with the underlying mechanisms responsible for vasovagal syncope, carotid sinus hypersensitivity or orthostatic syncope. In this review, we discussed the possible mechanisms of HBEs during shoulder arthroscopic surgery, in the sitting position, under ISBPB. In particular, we focused on the relationship between HBEs and various types of syncopal reactions, the relationship between HBEs and the Bezold-Jarisch reflex, and the new contributing factors for the occurrence of HBEs, such as stellate ganglion block or the intraoperative administration of intravenous fentanyl.

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.

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.

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.

alpha-Adrenoceptor agonists for the treatment of vasovagal syncope: a meta-analysis of worldwide published data

AIM

The present study was aimed at evaluating present randomized controlled trials (RCTs) regarding the effect of alpha-adrenoceptor agonists on vasovagal syncope (VVS).

METHODS

According to inclusion and exclusion criteria, articles were selected from medical electronic databases. RCTs were then assessed based on the Juni assessment, and meta-analysis was completed using the Review Manager 4.2 software. Indication to further evaluate effects was the recurrence of syncope during follow-up treatment or a response in the head-up tilt test (HUT) after treatment. The results were stated as odd ratio (OR), with a 95% confidence interval (CI) and a p < 0.05 significant level.

RESULTS

In total, six RCTs were selected. Funnel plot analysis showed possible publication bias. Meta-analysis of the six RCTs, including all 165 patients in the treatment group and 164 patients in the control group, indicated that alpha-adrenoceptor agonists were more effective than placebos in treating VVS (OR = 0.21, 95% CI: 0.06-0.77, p = 0.02). The further, weighted independent t-test disclosed that the weighted mean percentage of responders for midodrine (76.3%+/- 7.7%) was significantly higher than that for etilefrine (65.5%+/- 15.4%) (t = 5.863, p < 0.001).

CONCLUSION

The currently published RCTs support that alpha-adrenoceptor agonists might be effective for VVS. Midodrine can be regarded as a better choice compared with etilefrine.

Neurological aspects of syncope and orthostatic intolerance

Sudden falling with loss of consciousness from syncope and symptoms of orthostatic intolerance are common, dramatic clinical problems of diverse cause, but cerebral hypoperfusion is the ultimate mechanism in most. Cardiac, reflex, and orthostatic hypotension are important forms to consider. Syncope must be differentiated from seizures, psychiatric events, drop attacks, and other mimics. However, factors such as syncopal induced movements, ictal bradycardia, and insufficient clinical information can confound accurate diagnosis and hamper appropriate treatment. Progress in the diagnosis, treatment, and understanding of underlying mechanisms is continually advancing.

Evaluation and Management of Syncope

Context

Syncope is a commonly encountered by primary care physicians and cardiologists. Etiology is frequently not apparent, and patients may undergo unnecessary tests. Treatment must be tailored to the likely etiology. Complexities of diagnosis and treatment often warrant referral to a specialist.

Objective

To highlight the evolving recommendations for managing syncope in a clinically and cost effective manner.

Evidence Acquisition

An electronic literature search was undertaken of the Medline database from January 1996 to April 2006, using the Medical Subject Heading syncope, defibrillators, pacemakers, echocardiogram, cardiomyopathy, long QT syndrome, Arrhythmogenic right ventricular dysplasia, and Brugada syndrome. Abstracts and titles were reviewed to identify English-language trials. Bibliographies from the references as well as scientific statements from the Heart Rhythm Society, American Heart Association, and American College of Cardiology were reviewed.

Evidence Synthesis

A methodical approach to syncope can improve diagnosis, limit testing, and identify patients at risk of fatal outcome. A thorough history, physical exam and electrocardiogram are critical to the initial diagnosis. Presence of heart disease determines the extent of work-up and treatment. A trans-thoracic echocardiogram should be performed in patients with an unclear diagnosis and a positive cardiac history or an abnormal ECG. Ventricular arrhythmias are the most common cause of syncope in patients with structural heart disease. Patients with an ejection fraction less than 30 percent should receive an implantable defibrillator with few exceptions. An electrophysiology study may assist risk stratification in syncopal patients with borderline ventricular function. In patients without structural heart disease, the presence of a well defined arrhythmia syndrome consistent with a genetically determined risk of sudden death must be sought. The 12-lead electrocardiogram, family history and clinical presentation will identify most high-risk patients. Patients without structural heart disease can often be managed conservatively with well defined strategies for preventing neurocardiogenic syncope.

Conclusions

Managing syncope requires a methodical approach. An understanding of the limitations of the diagnostic tools and treatments is important. Lethal causes of syncope make it imperative to recognize the appropriate timing of referring patients to specialists.

Current treatment of recurrent vasovagal syncope: between evidence-based therapy and common sense

Vasovagal syncope is very frequent and benign and the vast majority of subjects do not need any specific treatment, but only reassurance and education. An unknown but small percentage of patients require specific treatment when syncope is very frequent or is responsible for major trauma. For these patients, there are some evidence-based therapies available and some first-line treatments appear to be established. The therapeutic choice mainly depends on the presence and duration of prodromal symptoms. In subjects aged < 70 years with well recognizable prodromes, the first-line treatment is counterpressure manoeuvres. In patients with no or minimal prodromes, but with tilt testing and carotid sinus massage (CSM) both positive, cardiac pacing appear to be the first-line therapy. However, an area of uncertainty remains, represented by patients with no or minimal prodromes and negative CSM. For these patients, appropriate treatment (drugs, tilt training, cardiac pacing, relaxation-based treatment) can be chosen by considering the clinical context, the risk of trauma and possible comorbidities, in addition to utilizing the little or controversial knowledge available, as well as common sense.

The dizzy athlete

Dizziness is a common complaint both in athletes and their nonathletic counterparts. The diagnosis and treatment of dizziness is not significantly different between the two groups. The first step in evaluation involves defining dizziness as either presyncope, vertigo, disequilibrium, or nonspecific dizziness. Once the symptoms are better defined, the evaluation should then proceed with a careful history, physical examination, and appropriate diagnostic tests as indicated. Treatment strategies can be targeted at the underlying cause with the goal of diminishing or resolving the symptoms as well as preventing their recurrence. This article focuses on the diagnosis of dizziness and subsequent treatment regimens with particular attention paid to presyncope and vertigo.

The Second Prevention of Syncope Trial (POST II)--a randomized clinical trial of fludrocortisone for the prevention of neurally mediated syncope: rationale and study design

BACKGROUND

Neurally mediated syncope is a common and frequently distressing problem. It is associated with a poor quality of life, which improves when the frequency of syncope is reduced. Few therapies for neurally mediated syncope have been proven effective. Fludrocortisone is commonly used to prevent recurrences of syncope but with little evidence to support its use. A placebo-controlled clinical trial of fludrocortisone for the prevention of neurally mediated syncope is needed.

STRUCTURE OF STUDY

POST II is a multicenter, international, randomized, placebo-controlled study of fludrocortisone in the prevention of neurally mediated syncope. The primary end point is the time to first recurrence of syncope. Patients will be randomized 1:1 to receive fludrocortisone 0.05 to 0.2 mg or matching placebo and followed for 1 year. Secondary end points include syncope frequency, presyncope, and quality of life. Primary analysis will be performed with an intention-to-treat approach, with a secondary on-treatment analysis.

POWER CALCULATIONS

Assuming a 40% risk of syncope in the control arm, a relative reduction of 40% by fludrocortisone, and a dropout rate of 20%, the enrollment of 310 patients will give an 80% power of reaching a positive conclusion about fludrocortisone therapy, with P = .05.

REGISTRATION

POST II is registered with both (ISRCTN 51802652) and (NCT00118482).

IMPLICATIONS

This study will be the first adequately powered trial to determine whether fludrocortisone is effective in preventing neurally mediated syncope. If it is effective, then fludrocortisone may become the first-line medical therapy for this condition.

Neurocardiogenic syncope: latest pharmacological therapies

Neurocardiogenic syncope is a neurally mediated disorder and is a common cause of syncope. The goal of treatment is to prevent recurrences with the aim of improving quality of life and reducing morbidity. Reassurance, in some cases, may suffice. In others, augmenting central blood volume by increasing fluid and/or salt intake is effective. The role of non-pharmacological physical manoeuvres is increasingly recognised, given the increasing clinical trial data supporting their efficacy. This review summarises the clinical evidence for a variety of pharmacological agents. Of these, midodrine appears to have yielded the most consistent favourable outcome. Its use, however, should be reserved for patients with recurrent and refractory syncope.

Prevention of Syncope Trial (POST): a randomized, placebo-controlled study of metoprolol in the prevention of vasovagal syncope

BACKGROUND

Previous studies that assessed the effects of beta-blockers in preventing vasovagal syncope provided mixed results. Our goal was to determine whether treatment with metoprolol reduces the risk of syncope in patients with vasovagal syncope.

METHODS AND RESULTS

The multicenter Prevention of Syncope Trial (POST) was a randomized, placebo-controlled, double-blind, trial designed to assess the effects of metoprolol in vasovagal syncope over a 1-year treatment period. Two prespecified analyses included the relationships of age and initial tilt-test results to any benefit from metoprolol. All patients had >2 syncopal spells and a positive tilt test. Randomization was stratified according to ages <42 and > or =42 years. Patients received either metoprolol or matching placebo at highest-tolerated doses from 25 to 200 mg daily. The main outcome measure was the first recurrence of syncope. A total of 208 patients (mean age 42+/-18 years) with a median of 9 syncopal spells over a median of 11 years were randomized, 108 to receive metoprolol and 100 to the placebo group. There were 75 patients with > or =1 recurrence of syncope. The likelihood of recurrent syncope was not significantly different between groups. Neither the age of the patient nor the need for isoproterenol to produce a positive tilt test predicted subsequent significant benefit from metoprolol.

CONCLUSIONS

Metoprolol was not effective in preventing vasovagal syncope in the study population.

Fluoxetine vs. propranolol in the treatment of vasovagal syncope: a prospective, randomized, placebo-controlled study

AIMS

To compare the therapeutic efficacy of placebo, propranolol, and fluoxetine in patients with vasovagal syncope (VVS).

METHODS AND RESULTS

Ninety-six consecutive patients with VVS were randomized to treatment with placebo, propranolol, or fluoxetine and followed-up for 6 months. Before and during treatment, they reported their syncopal and presyncopal episodes and graded their well-being, expressed as the general evaluation of life, general activities, and everyday activities (each scaled from 1 = very good to 5 = very bad). Two patients refused follow-up. Among the remaining 94, no difference between groups was observed regarding the distribution of time of vasovagal events (syncopes or presyncopes) during follow-up (log-rank test). No difference was also observed when syncopes and presyncopes were assessed separately. Eighteen patients discontinued therapy. Among the remaining 76 ('on-treatment' analysis), the mean time to a vasovagal episode (syncope or presyncope) was significantly longer in the fluoxetine group when compared with the two other groups (log-rank test, P < 0.05). A significant difference in favour of fluoxetine was also observed regarding presyncopes. The difference between groups regarding the syncope-free period was not significant. During therapy, patients' well-being was improved (decreased) only in the fluoxetine-group (13.4 +/- 0.7 vs. 15.4 +/- 0.9 before treatment, P < 0.01).

CONCLUSION

Fluoxetine seems to be equivalent to propranolol and placebo in the treatment of VVS. However, it improves patients' well-being and might be more effective in reducing presyncopes and total vasovagal events in some patients with recurrent VVS.

Seizure versus syncope

One of the most common but difficult management problems in medicine is that of patients who present with a paroxysmal loss of consciousness. All too often the underlying diagnosis remains elusive. This has a cost both in terms of mortality and ongoing morbidity and in terms of the financial burden associated with hospitalisation and repeated investigations. We describe a practical approach to this clinical dilemma, which is rooted in adherence to basic principles of history taking and examination, formulation of a reasonable differential diagnosis, followed by an intelligent use of specific investigations and selection of an appropriate treatment. We also discuss the effect of sudden unexpected death in epilepsy and sudden cardiac death. Despite a careful and thorough approach to the patient with a "seizure versus syncope" problem, many will require repeated assessment before a diagnosis is made.

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.

Usefulness of pindolol for treatment of neurocardiogenic syncope

This study evaluated the efficacy of pindolol, a noncardioselective beta blocker with intrinsic sympathetic activity, on neurocardiogenic syncope using a head-up tilt-table test in 66 patients. Pindolol was equally effective in men and women and the 2 age groups (>60 and <60 years) of the study cohort. The earliest benefit was seen </=3 days after initiating treatment. Side effects were better tolerated in younger patients (age <60 years).

Pharmacological treatment of reflex syncope

Patient education, identification of possible triggers of syncope and reassurance are a central feature of the management of patients with reflex syncope. Patients should be advised as to the importance of adequate hydration and taught physical countermaneuvers to enhance cardiac venous return. These maneuvers are sufficient for most patients, however, for a small number of patients who continue to have recurrent syncopal events, pharmacological intervention may be considered. Volume expansion can be enhanced with salt and fludrocortisone. Agents from diverse pharmacological classes have been used to attenuate the reflex response, enhance vasoconstriction and attenuate vagal outflow. Alpha adrenoreceptor agonists, anticholinergic agents, theophylline, beta adrenoreceptor antagonists, serotonin reuptake inhibitors and disopyramide are the most widely studied. None of these agents has shown a consistent therapeutic benefit in clinical trials.

Current Management of Syncope: Treatment Alternatives

Syncope, defined as a transient loss of consciousness and postural tone with spontaneous recovery and no neurologic sequelae, is among one of the most common causes of consultation with a physician. The diagnostic workup is complex but can be simplified if focused on the underlying condition. Prognosis is highly dependent on the presence or absence of structural heart disease, primarily the presence of cardiomyopathy regardless of etiology, particularly if the left ventricular (LV) function is less than 35%. The diagnostic approach to the patient with recurrent syncope and no structural heart disease is targeted to rule out neurally mediated causes. This approach usually includes a tilt table test (ie, head-up tilt), carotid sinus massage in patients older than 55 years, and an adenosine challenge test in patients who remain with unexplained syncope. Unexplained syncope in patients with reduced LV function (< 35%) may be potentially life-threatening. Infrequent causes of syncope should be sought in younger patients with a family history of sudden cardiac death. Channelopathies such as the long QT syndrome, Brugada syndrome, and catecholaminergic polymorphic ventricular tachycardia are among this variety. Therapy should address the potential mechanism of syncope. In neurally mediated causes, restoration of orthostatic tolerance, primarily by increasing volume during orthostatic stress, is recommended. Physiologic countermaneuvers and increase in salt and water intake are usually the initial therapy. With syncope in patients with an LV dysfunction (< 35%), an ICD is frequently recommended after ruling out common causes of syncope. Syncope in the elderly is usually multifactorial and therapy should include reassessment of multiple medications, which can promote neurally mediated syncope as well as searching for bradycardic causes. Empiric pacing may be used in this complex group of patients.

New approaches to the treatment and prevention of neurally mediated reflex (neurocardiogenic) syncope

Neurally mediated reflex syncope (sometimes referred to as neurocardiogenic syncope), encompasses a group of disorders of which the best known and most frequently occurring forms are the vasovagal (or common) faint, and carotid sinus syndrome. Postmicturition syncope, defecation syncope, cough syncope, and other situational reflex faints are also included among these conditions. With the exception of carotid sinus syndrome in which cardiac pacing is effective, treatment of most neurally mediated reflex faints is shifting from reliance on various drugs to greater emphasis on education and nonpharmacologic therapy. Initial management should include counseling of patients regarding recognition of early warning symptoms, and avoidance of precipitating factors. Volume expansion with salt tablets or electrolyte-containing beverages and patient education on how to perform isometric arm contractions and/or leg crossing in order to abort impending syncope are also important. Thereafter, tilt-training has demonstrated benefit in several clinical studies. When symptoms remain despite the above-noted interventions, pharmacologic therapy with midodrine or a nonselective b-blocker can be considered. In the case of most neurally mediated reflex faints, permanent cardiac pacing should be reserved only for those older patients with significant bradycardia or asystole at time of syncope when all other interventions have failed.

Response to treatment during medium-term follow-up in a series of patients with neurocardiogenic syncope

BACKGROUND

Syncope is a common symptom that has different recurrence ratios. We hypothesized that an individualized treatment regimen including pharmacologic and nonpharmacologic measures considering kind of neurocardiogenic syncope (NCS) and basal characteristics of each patient could allow optimized therapy to avoid recurrences.

METHODS

We conducted a prospective study to evaluate performance of diverse accepted treatments for NCS. Each patient received specific treatment including general measures such as an increase in salt and water intake, tilt training, specific pharmacologic treatment according to head-up tilt table test (HUTT) result, and patient basal blood pressure and heart rate measurements.

RESULTS

We followed a group of 127 patients during a main period of 20.8 +/- 9 months (range, 6-38 months). Mean age was 47.8 +/- 19.2 years and 66.9% were females. We had six (4.7%) patients with recurrence of symptoms 4 +/- 0.9 months after diagnostic HUTT. Medications used were atenolol in 20 patients, pindolol in 17, dysopiramide in 50, and fluoxetine in 25. Two patients received fludrocortisone. Tilt training was not indicated initially for patients with recurrences but was indicated later; to date, these patients have not experienced further episodes.

CONCLUSIONS

Increase in water and salt intake, as well as tilt training, showed great value in prevention of syncope recurrences in this specific set of patients. Pharmacologic treatment has an important role, but there is no single medication associated with significant improvement in symptom control.

Drug treatment of orthostatic hypotension because of autonomic failure or neurocardiogenic syncope

Orthostatic hypotension either because of autonomic failure or neurocardiogenic syncope can be very incapacitating and should be treated accordingly. Drug therapy is frequently needed to alleviate orthostatic symptoms. The physiopathological basis of neurocardiogenic syncope and of autonomic failure is completely different and their treatment should be distinct. In the past 5 years, many randomized, placebo-controlled trials have shed light on the efficacy of specific pressor drugs. In patients with orthostatic hypotension because of autonomic failure, alpha-adrenoceptor agonists, and midodrine in particular, have been shown to increase standing blood pressure and decrease orthostatic symptoms. Other drugs such as octreotide, indomethacin or ergotamine have also been shown to elevate standing blood pressure and/or orthostatic tolerance. Fludrocortisone is a well known and frequently used pressor drug but randomized controlled studies are needed to measure its efficacy. In patients with orthostatic hypotension associated with neurocardiogenic syncope, clinical trials have demonstrated that beta-blockers, especially beta(1)-selective agents without intrinsic sympathomimetic activity such as atenolol, midodrine and paroxetine can decrease recurrence of syncope. Treatment algorithms, such as those presented in this review, should always be interpreted in the light of individual patient characteristics. Many of the drugs used for orthostatic hypotension have multiple indications and contraindications that should influence therapeutic decisions. Little is known about the effectiveness and tolerability of specific combinations of pressor drugs. Consequently, sound clinical judgment and close follow-up of patients should always guide combination therapy.

Long-term outcome of patients with recurrent syncope of unknown cause in the absence of organic heart disease and relation to results of baseline tilt table testing

Among 123 patients with unexplained syncope in the absence of heart disease who were followed up for 24 +/- 7 months, syncope recurred in a similar minority of them regardless of baseline tilt table testing results. An initially unsuspected cardiac or neuropsychiatric disorder was uncovered in 17 patients later on follow-up examination.