Recent Advances and Future Directions in Syncope Management: A Comprehensive Narrative Review

Syncope is a highly prevalent clinical condition characterized by a rapid, complete, and brief loss of consciousness, followed by full recovery caused by cerebral hypoperfusion. This symptom carries significance, as its potential underlying causes may involve the heart, blood pressure, or brain, leading to a spectrum of consequences, from sudden death to compromised quality of life. Various factors contribute to syncope, and adhering to a precise diagnostic pathway can enhance diagnostic accuracy and treatment effectiveness. A standardized initial assessment, risk stratification, and appropriate test identification facilitate determining the underlying cause in the majority of cases. New technologies, including artificial intelligence and smart devices, may have the potential to reshape syncope management into a proactive, personalized, and data-centric model, ultimately enhancing patient outcomes and quality of life. This review addresses key aspects of syncope management, including pathogenesis, current diagnostic testing options, treatments, and considerations in the geriatric population.

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.

Tilt testing remains a valuable asset

Head-up tilt test (TT) has been used for >50 years to study heart rate/blood pressure adaptation to positional changes, to model responses to haemorrhage, to assess orthostatic hypotension, and to evaluate haemodynamic and neuroendocrine responses in congestive heart failure, autonomic dysfunction, and hypertension. During these studies, some subjects experienced syncope due to vasovagal reflex. As a result, tilt testing was incorporated into clinical assessment of syncope when the origin was unknown. Subsequently, clinical experience supports the diagnostic value of TT. This is highlighted in evidence-based professional practice guidelines, which provide advice for TT methodology and interpretation, while concurrently identifying its limitations. Thus, TT remains a valuable clinical asset, one that has added importantly to the appreciation of pathophysiology of syncope/collapse and, thereby, has improved care of syncopal patients.

Are women really more affected by vasovagal syncope than men?

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

Recurrent seizures in a young woman: when video-EEG diagnoses a cardiac cause: a case report

Background

While transient loss of consciousness is a frequent presenting symptom, differential diagnosis between syncope and epilepsy can be challenging. Misdiagnosis of epilepsy leads to important psychosocial consequences and eliminates the opportunity to treat patient’s true condition.

Case summary

A 39-year-old woman presenting with recurrent seizures since her childhood was referred to neurological consultation. Electroencephalograms (EEGs) and magnetic resonance imaging previously performed were normal. A sleep-deprived video-EEG was performed and highlighted after 12 h of sleep deprivation a progressive dropping of the heart rate followed by a complete heart block without ventricular escape rhythm and asystole for about 30 s. Her EEG recording later showed diffuse slow waves traducing a global cerebral dysfunction and suffering. The diagnosis of vaso-vagal syncope with predominant cardioinhibitory response was made and a dual-chamber pacemaker with rate-drop response algorithm was implanted. After a 2 years of follow-up, the patient remained free of syncope.

Discussion

Patients presenting with loss of consciousness and convulsion are often diagnosed with epilepsy despite normal EEGs. In patients presenting with recurrent seizures with unclear diagnosis of epilepsy or in a situation of drug-resistant epilepsy, syncope diagnosis should always be considered and a risk stratification is necessary. The benefit of pacemaker implantation in patients with recurrent vaso-vagal syncope is still very controversial. Only patients presenting with spontaneous asystole should be considered for pacemaker implantation in case of recurrent vaso-vagal syncope.

[Management of syncope in clinical practice : What has changed according to the new ESC guidelines 2018?]

Syncope is a common problem in clinical practice, which affects approximately 1% of patients admitted to European emergency departments. The clinical practice guidelines for the diagnosis and management of syncope published by the European Society of Cardiology (ESC) are based on the newest scientific data in the field and have provided clinical cardiologists with a structured therapeutic approach for affected patients over many years. The previous ESC guidelines on syncope were published in 2009 and are compared to the most recent edition, which was published in 2018. This review summarizes the most important innovations with respect to the diagnostic principles and treatment of syncope. The initial assessment of the patient and the risk stratification in the emergency department are the focus of the review. Another important topic that is adequately covered in the current guidelines is the rising significance of implantable loop recorders for the evaluation of unexplained syncope and the assessment of potential indications for a definitive treatment with a pacemaker or implantable cardioverter defibrillator (ICD). Additional changes involve the evidence level with respect to the use of other diagnostic (ECG monitoring, tilt testing) and therapeutic measures (indications for pacemaker implantation, catheter ablation of tachycardiac rhythm disorders).

Cardiovascular and Cerebral Hemodynamics in Asymptomatic Healthy Subjects With/Without Abnormal Head-up Tilt Test Versus Recurrent Fainters

PURPOSE

The aim of this study was to compare hemodynamic and autonomic responses during head-up tilt test (HUTT) between healthy volunteers and patients with a history of fainting and confirmed vasovagal syncope. We hypothesize that the autonomic and hemodynamic physiologic responses remain intact during orthostatic stress in people without previous fainting and negative HUTT, but deteriorate similarly in patients with recurrent vasovagal syncope and in asymptomatic healthy subjects who develop a vasovagal response during HUTT.

METHODS

The study included 57 asymptomatic healthy volunteers (42% women, mean age 23.7 ± 3.6 years) categorized as negative HUTT (n = 41) and positive HUTT (n = 16). They were compared with 14 patients (50% women, mean age 24.2 ± 6.1 years) with previous spontaneous recurrent syncope and inducible vasovagal response during HUTT. Cerebral and cardiovascular hemodynamic variables were assessed noninvasively during the HUTT in each participant.

RESULTS

In all patients with recurrent syncope, tilt was positive after a mean delay of 15.6 ± 8.6 minutes and did not differ from the time to syncope observed after 19.6 ± 6.9 minutes in asymptomatic healthy subjects with a positive test. A significant decrease throughout the tilting was observed in the blood pressure, peripheral resistances, cerebral blood flow, and vascular efferent sympathetic regulation in both groups of subjects with a positive test.

CONCLUSIONS

This study shows that there are subjects, without a history of syncope, who have a positive HUTT with hemodynamic and autonomic responses alike to patients with confirmed vasovagal syncope, precluding them to be selected as controls in vasovagal syncope studies.

Role of head-up tilt table testing in patients with syncope or transient loss of consciousness

The tilt table test (TTT) is a useful method for the management of reflex syncope. However, the TTT is incomplete and has several problems. The indications for this test are established using guidelines. The TTT is not suitable for all syncopal patients. It is currently unclear (1) When should the TTT be used, (2) for which types of patients TTT should be performed, and (3) does the TTT provide useful information to guide indication for pacing therapy for reflex syncope. The answers to these questions appear in recent reports from two guidelines published by the European Society of Cardiology and the Japan Circulation Society. The indications for TTT do not apply to all syncopal patients, but selected patients. For patients with low risks and rare syncopal events, the TTT is not necessary, even when diagnoses are unconfirmed. The TTT is used not only for diagnosis of reflex syncope, but also for many clinical management of several conditions (i.e., exclusion of cardiac syncope). Positive TTT results cannot predict the effects of pacing therapy for reflex syncope. The decision to use pacing therapy should be based on documented electrocardiograms and other findings, including TTT results.

The pathophysiologic mechanisms associated with hypotensive susceptibility

INTRODUCTION

Patients with vasovagal syncope (VVS) and positive tilt table test (TTT) were not found to benefit from pacing in the ISSUE-3 trial despite the presence of spontaneous asystole during monitoring. "Hypotensive susceptibility" unmasked by TTT was reported as a possible explanation. The purpose of this study was to assess the pathophysiologic mechanisms associated with hypotensive susceptibility.

METHODS

366 consecutive patients with the diagnosis of VVS who also had TTT were identified. Baroreflex gain (BRG) in addition to blood pressure (BP) and heart rate (HR) responses during the first 20 min of TTT were analyzed and compared between patients with positive TTT (n = 275, 75 %) and negative TTT (n = 91, 25 %).

RESULTS

The mean BRG was similar between the groups (12.5 ± 6.3 versus 12.4 ± 6.3 ms/mmHg, p = 0.72); however, an age-dependent decrease was noted (17.6 ± 4.8, 15.0 ± 6.0, 10.6 ± 4.2, 10.3 ± 6.4 and 9.9 ± 8.5 ms/mmHg for patients <21, 21-40, 41-60, 61-80 and >80 years old, respectively; p < 0.001). In addition, we saw a main effect of age on the type of response with a greater prevalence of a vasodepressor response in older subjects (p < 0.001). During the first 20 min of TTT, BP was similar in patients with tilt-positive VVS when compared with patients with tilt-negative VVS; however, HR was significantly lower.

CONCLUSION

BRG is similar in tilt-positive VVS patients when compared with tilt-negative VVS patients. An age-dependent decrease in BRG was noted with a higher prevalence of a vasodepressor response seen in older patients. The clinical significance of the blunted HR response in tilt-positive VVS remains to be determined.

Randomized Prospective Comparison of Two Protocols for Head-up Tilt Testing in Patients with Normal Heart and Recurrent Unexplained Syncope

BACKGROUND

This randomized study was aimed to compare the diagnostic value of two head-up tilt testing protocols using sublingual nitroglycerin for provocation in patients with recurrent unexplained syncope and normal heart.

METHODS

The patients with normal findings in physical examination, electrocardiography and echocardiography were randomly submitted to one of upright tilt test protocols. The only difference between two protocols was that nitroglycerin was administered after a five minute resting phase in supine position during protocol B. We also considered eighty normal persons as the control group.

RESULTS

Out of 290 patients that underwent tilt testing, 132 patients were in group A versus 158 patients in group B. Both groups had an identical distribution of clinical characteristics. Tilt test was positive in 79 patients in group A (25 in passive phase, 54 in active phase) versus 96 patients in group B (43 in passive phase, 53 in active phase). There was no significant difference between results in two groups (P value= 0.127). Forty cases were tested with protocol A and forty underwent tilt testing with protocol B. Tilt test was positive in 4 cases with protocol A versus 3 cases in protocol B. The positive rates of tilt testing with protocol A was 60% while it was 61% in protocol B. The specificity of testing with protocol A was 90% and it was 92.5% in protocol B.

CONCLUSIONS

According to our data, adding a period of rest and returning to supine position before nitroglycerin administration had no additional diagnostic yield.

Depressive symptoms and neurocardiogenic syncope in children: a 2-year prospective study

OBJECTIVE

To evaluate prospectively the relationship between neurocardiogenic syncope (NCS) and depressive symptoms in pediatric patients.

METHODS

Forty-five patients (aged 12.3 ± 2.9 years) with NCS (diagnosed as ≥ 1 syncopal episodes with typical symptoms, reproduced by tilt-table testing, in the absence of structural or primary electrical heart disease) were compared with 45 age- and gender-matched control subjects. Assessment was performed at baseline and 2 years thereafter. Depressive symptoms and self-perception profile of participants were evaluated, along with their parents' psychological distress, defensive profile and hostility. Family cohesion and adaptability, as well as the opinion of parents and teachers on children's strengths and difficulties, were also examined.

RESULTS

At baseline, patients showed more (P = .008) depressive symptoms than controls, correlating with the number of syncopal episodes, impaired relationship with parents and poor family cohesion. A conservative management strategy of NCS was adopted and psychological counseling was offered, focusing on patients with clinically significant depressive symptoms and their families. During follow-up, depressive symptoms decreased in patients (P < .001), but remained stable in controls. Child-parent relationship, family cohesion and family adaptability improved at follow-up in patients. No recurrent syncope was noted during follow-up and this along with improvement in child-parent relationship were associated with depressive symptoms improvement.

CONCLUSIONS

Depressive symptomatology is common in pediatric patients with NCS. Our findings call for additional investigation in larger controlled clinical interventional studies that will enhance understanding of the possible pathophysiological association between depressive symptomatology and NCS in pediatric populations.

Head-up tilt testing for diagnosing vasovagal syncope: a meta-analysis

BACKGROUND

A systematic evaluation focused on sensitivity and specificity of head-up tilt testing (HUT) for diagnosing vasovagal syncope has not been previously performed. We conducted a meta-analysis of studies comparing HUT outcome between patients with syncope of unknown origin and control subjects without previous syncope.

METHODS

We searched Pubmed and Embase databases for all English-only articles concerning case-control studies estimating the diagnostic yield of HUT, and selected 55 articles, published before March 2012, including 4361 patients and 1791 controls. The influence of age, test duration, tilt angle, and nitroglycerine or isoproterenol stimulation on tilt testing outcome was analyzed.

RESULTS

Head-up tilt testing demonstrated to have a good overall ability to discriminate between symptomatic patients and asymptomatic controls with an area under the summary receiver-operating characteristics curve of 0.84 and an adjusted diagnostic odds ratio of 12.15 (p<0.001). A significant inverse relationship between sensitivity and specificity of tilt testing for each study was observed (p<0.001). At multivariate analysis, advancing age and a 60° tilt angle showed a significant effect in reducing sensitivity and increasing specificity of the test. Nitroglycerine significantly raised tilt testing sensitivity by maintaining a similar specificity in comparison to isoproterenol.

CONCLUSIONS

The results from this meta-analysis show the high overall performance of HUT for diagnosing vasovagal syncope. Our findings provide useful information for evaluating clinical and instrumental parameters together with pharmacological stressors influencing HUT accuracy. This could allow the drawing of tilt testing protocols tailored on the diagnostic needs of each patient with unexplained 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.

Head Up Tilt Testing: An Appraisal of Its Current Role in the Management of Patients with Syncope

Head up tilt testing (HTT) is now commonly used to investigate otherwise unexplained syncope and presyncope. This test has been used for over 20 years primarily to diagnose neurally mediated syncope, but HTT's exact role in the diagnostic process remains uncertain. Recognized limitations include poor reproducibility, lack of prognostic role, and insufficient randomized studies to guide therapeutic choice. In this review, we describe the indications and methods recommended by present guidelines on utilizing HTT. In addition, present criticisms and limitations of this test, along with future perspectives, are outlined.

Effect of clinical triggers on positive responses to tilt-table testing potentiated with nitroglycerin or clomipramine

The effect of clinical triggers on tilt-table testing (TTT) responses has not been systematically evaluated. In the present study, we evaluated the effect of clinical triggers on positive responses to TTT potentiated with nitroglycerin (which acts mainly through peripheral dilation) or clomipramine (which acts mainly through a central serotoninergic mechanism). We enrolled 380 consecutive adult patients. In 66 patients, syncope was triggered by emotional distress (central trigger), in 161 by specific situations or prolonged standing (peripheral trigger), and in 153 syncope occurred in the absence of any detectable trigger. Nitroglycerin TTT, performed in 252 patients, consisted of a passive phase of 20 minutes followed, if negative, by sublingual administration of 400 μg nitroglycerin spray and continuation of tilting for 15 minutes. Clomipramine TTT, performed in 128 patients, consisted of 20 minutes of tilting with intravenous administration of 5 mg clomipramine during the first 5 minutes. The positivity of nitroglycerin TTT was greater in patients with clinical triggers (71% central and 75% peripheral) than in those without (36%). With clomipramine TTT, the positivity rate was greater in patients with central triggers (92%) than in those with peripheral triggers (45%) or no triggers (30%). The cardioinhibitory form was more frequent in patients with a central trigger than in the other 2 groups (34% vs 12% and 7%) and with clomipramine TTT than with nitroglycerin TTT (19% vs 11%, respectively). In contrast, mixed or vasodepressor forms were more frequently induced by nitroglycerin TTT (41% vs 24%). In conclusion, the presence of clinical triggers increased the positivity of TTT and influenced the type of response. We found some specificity of nitroglycerin and clomipramine for peripheral and central mechanisms.

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.