Treatment of neurally mediated reflex syncope

The Role of the Autonomic Nervous System in Vasovagal Syncope

The mechanism of vasovagal syncope (VVS) is multifaceted and involves a delicate balance within the autonomic nervous system (ANS). This review delves into the complex interplay between the ANS and VVS, elucidating the pivotal role that autonomic imbalance plays in the pathophysiology of this condition. Through a comprehensive exploration of the sympathetic and parasympathetic branches of the ANS, this review provides insights into the mechanisms that underlie VVS. In addition, this article discusses established and emerging research on the management of VVS.

Postural Tachycardia Syndrome and Neurally Mediated Syncope

PURPOSE OF REVIEW

This article reviews the diagnosis and management of the most common disorders of orthostatic intolerance: postural tachycardia syndrome (POTS) and neurally mediated syncope.

RECENT FINDINGS

POTS is a heterogeneous syndrome caused by several pathophysiologic mechanisms that may coexist (limited autonomic neuropathy, hyperadrenergic state, hypovolemia, venous pooling, joint hypermobility, deconditioning). Neurally mediated syncope occurs despite intact autonomic reflexes. Management of orthostatic intolerance aims to increase functional capacity, including standing time, performance of daily activities, and exercise tolerance. Nonpharmacologic strategies (fluid and salt loading, physical countermaneuvers, compression garments, exercise training) are fundamental for patients with POTS, occasionally complemented by medications to raise blood pressure or slow heart rate. Neurally mediated syncope is best managed by recognition and avoidance of triggers.

SUMMARY

Significant negative effects on quality of life occur in patients with POTS and in patients with recurrent neurally mediated syncope, which can be mitigated through targeted evaluation and thoughtful management.

Fluoxetine vs. placebo for the treatment of recurrent vasovagal syncope with anxiety sensitivity

AIMS

The optimal medical therapy of patients with vasovagal syncope (VVS) remains controversial. Fluoxetine is effective against anxiety and panic disorders, while its use has shown promising results for VVS. Anxiety sensitivity is a personality trait observed in a considerable proportion of patients with VVS, associated with predisposition to anxiety and panic disorders. Our aim was to examine whether fluoxetine exerts beneficial effects regarding VVS prevention in the subset of patients with anxiety sensitivity.

METHODS AND RESULTS

We assessed 106 patients with typical history of recurrent VVS, without other comorbidities, and a diagnostic, positive head-up tilt test. A psychiatric examination ruled out clinical psychiatric disease. Their psychological, stress-related profile was assessed by the Anxiety Sensitivity Index (ASI) questionnaire, a 16-item questionnaire, assessing fear of anxiety-related sensations, previously studied in VVS. Patients scoring positive for ASI (n = 60, 57% of the population) were randomized in a 2:1 fashion to receive either 10-40 mg fluoxetine daily (n = 40) or placebo (n = 20), and were followed-up for 1 year. A significant difference was observed between patients receiving fluoxetine and those with placebo, regarding the distribution of syncope-free time during the study (P < 0.05). A significant difference was also observed between the two groups regarding presyncopal events and the total number of patients who experienced syncope or presyncope during follow-up.

CONCLUSION

Sensitivity to anxiety is a common personality trait in recurrent VVS. Fluoxetine is superior to placebo against syncope in these patients. This drug may be a first-line pharmacological treatment for this difficult-to-treat group.

Alteration of gene expression profiling including GPR174 and GNG2 is associated with vasovagal syncope

Vasovagal syncope (VVS) causes accidental harm for susceptible patients. However, pathophysiology of this disorder remains largely unknown. In an effort to understanding of molecular mechanism for VVS, genome-wide gene expression profiling analyses were performed on VVS patients at syncope state. A total of 66 Type 1 VVS child patients and the same number healthy controls were enrolled in this study. Peripheral blood RNAs were isolated from all subjects, of which 10 RNA samples were randomly selected from each groups for gene expression profile analysis using Gene ST 1.0 arrays (Affymetrix). The results revealed that 103 genes were differently expressed between the patients and controls. Significantly, two G-proteins related genes, GPR174 and GNG2 that have not been related to VVS were among the differently expressed genes. The microarray results were confirmed by qRT-PCR in all the tested individuals. Ingenuity pathway analysis and gene ontology annotation study showed that the differently expressed genes are associated with stress response and apoptosis, suggesting that the alteration of some gene expression including G-proteins related genes is associated with VVS. This study provides new insight into the molecular mechanism of VVS and would be helpful to further identify new molecular biomarkers for the disease.

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.

A clinical manifestation-based prediction of haemodynamic patterns of orthostatic intolerance in children: a multi-centre study

OBJECTIVE

At present, the haemodynamic diagnosis of orthostatic intolerance is based mainly on the head-up tilt table test, which is sometimes risky for patients. Thus, it is important to find objective and safe methods to differentiate haemodynamic patterns of orthostatic intolerance cases.

METHODS

In all, 629 children with orthostatic intolerance, either vasovagal syncope or postural orthostatic tachycardia syndrome, were included in the multi-centre clinical study. We analysed the association between the clinical manifestation and haemodynamic patterns of the patients.

RESULTS

Syncope after motion with a prodrome of chest distress or palpitations and the concomitant symptom(s) after a syncopal attack, with debilitation, dizziness or headache, were the most important variables in predicting the diagnosis of vasovagal syncope. The overall diagnostic accuracy was 71.5%.

CONCLUSION

Complaint of syncope after motion with prodromal chest distress or palpitation and the concomitant symptom after a syncopal attack, with subsequent debilitation, dizziness or headache, were the most important variables in the diagnosis of vasovagal syncope in children with orthostatic intolerance.

A teenage fainter (dizziness, syncope, postural orthostatic tachycardia syndrome)

This article informs the general pediatrician about the diagnosis, evaluation, and treatment of teenage patients with presyncope and loss of consciousness. The focus is on distinguishing noncardiac fainting from life-threatening syncope. Current treatment strategies of vasovagal syncope and postural orthostatic tachycardia syndrome are also outlined.