Central serotonergic responsiveness in neurocardiogenic syncope: a clomipramine test challenge

Role of serotonin and serotonergic-related metabolites in the pathogenesis of vasovagal syncope

BACKGROUND

Serotonin is an important neurohormone that regulates vascular tone and autonomic reflexes, though its pathophysiological role in vasovagal syncope (VVS) remains uncertain.

OBJECTIVE

This study sought to explore the involvement of serotonin and serotonergic-related metabolites in the pathogenesis of VVS.

METHODS

Sixty-six patients [mean age 45.6±17.0 years; 33 women (50%)] with recurrent VVS underwent a head-up tilt test (HUTT). Blood samples were collected from all patients in a resting supine position, with an additional sample obtained from HUTT-positive patients during syncope. Plasma and platelet serotonin levels and plasma concentrations of serotonergic-related metabolites-including serotonin's precursor 5-hydroxytryptophan (5-HTP), major metabolite 5-hydroxyindoleacetic acid, and synthesis source tryptophan-were measured using the liquid chromatography tandem mass spectrometry method.

RESULTS

HUTT was positive in 45 (68.2%) patients and negative in 21 (21.8%) patients. Significant differences were observed in plasma 5-HTP and 5-hydroxyindoleacetic acid levels between HUTT-positive and HUTT-negative patients (P<.001 and P=.040, respectively) as well as before and after syncope (P<.001 for all), whereas no significant changes were found in serotonin and tryptophan levels. Notably, plasma serotonin levels significantly increased during syncope in patients with drug-free VVS (P=.037), and a greater change in serotonin correlated with a shorter time to syncope (R2=0.38; P=.015). Furthermore, certain serotonergic-related metabolites exhibited significant correlations with hemodynamic changes during VVS episodes, with 5-HTP demonstrating the highest sensitivity.

CONCLUSION

Despite the unchanged plasma and platelet serotonin levels, certain serotonergic-related metabolites significantly changed and correlated with hemodynamic parameters during VVS episodes, suggesting the potential involvement of an altered serotonergic metabolic pathway in VVS.

Serotonin and vasovagal syncope

PURPOSE

The goal of this manuscript was to review the biological and clinical evidence that serotonin neurotransmission might play an important role in the  physiology and treatment of vasovagal syncope.

METHODS

The authors reviewed PubMed and handsearches of secondary sources for papers related to the Bezold-Jarisch reflex and serotonin, the plausible involvement of the Bezold-Jarisch reflex in vasovagal syncope, and three lines of clinical evidence involving serotonin and the syncope.

RESULTS

The Bezold-Jarisch reflex was first described following the infusion of veratrum alkaloids into animals in the 19th century. The reflex is triggered by serotonin stimulation chemoreceptors and mechanoreceptors in the the left ventricle. The afferent component of the reflex is carried by unmyelinated type C vagal nerve fibers, which results in parasympathetic efferent stimulation that causes bradycardia. The similarity of the combination of hypotension and bradycardia in the Bezold-Jarisch reflex and in vasovagal syncope led to the suggestion that the reflex was the cause of the syndrome.  Three lines of evidence implicate the serotonin 5HT3 receptors in the heart in the reflex. There is genetic and physiologic evidence for the serotonin 5HT1A and 5HT3 receptors and the serotonin reuptake transporter (SERT). Acute blockade of SERT induces vasovagal syncope in humans undergoing head-up tilt table testing, and SERT inhibition reduces hypotension and bradycardia during spinal anaesthesia. Finally, three randomized clinical trials of SERT inhibitors uniformly reported that they significantly reduce the likelihood of vasovagal syncope recurrences.

CONCLUSION

Multiple lines of evidence implicate serotonin neurotransmission in the cause of vasovagal syncope.

Serotonin reuptake inhibition for the prevention of vasovagal syncope: a systematic review and meta-analysis

PURPOSE

Vasovagal syncope is a common clinical condition that lacks effective medical therapies despite being associated with significant morbidity. Current guidelines suggest that serotonin-specific reuptake inhibitors might suppress vasovagal syncope but supporting studies have been small and heterogenous. The purpose of this study was to evaluate the efficacy of serotonin-specific reuptake inhibitors to prevent syncope in patients with recurrent vasovagal syncope by conducting a systematic review and meta-analysis of published studies.

METHODS

Relevant randomized controlled trials were identified from the MEDLINE and Embase databases without language restriction from inception to August 2022, and ClinicalTrials.gov. All studies were conducted in clinical syncope populations and compared the benefit of serotonin versus placebo. Weighted relative risks were estimated using random effects meta-analysis techniques.

RESULTS

Three studies (n = 204) met inclusion criteria. Patients were 42 ± 13 years of age and 51% female. Serotonin-specific reuptake inhibitors were found to substantially reduce the likelihood of a patient having at least one recurrence of vasovagal syncope [relative risk (RR) 0.34 (0.20-0.60), p < 0.01] with minimal between-study heterogeneity (I2 = 0%, p = 0.67). Serotonin-specific reuptake inhibitors in two reports provided significant protection against clinical presyncope [RR 0.43 (0.24-0.77), p < 0.01], with minimal between-study heterogeneity (I2 = 0%, p = 0.80).

CONCLUSIONS

Serotonin-specific reuptake inhibitors may be effective in preventing syncope induced by head-up tilt testing and in syncope in the community in randomized, double-blinded clinical trials.

Vasovagal syncope: An overview of pathophysiological mechanisms

Syncope is a short-term transient loss of consciousness, characterized by rapid onset and complete spontaneous recovery. According to the 2018 European Society of Cardiology guidelines, three different types of syncope have been identified. However, all forms of syncope share a common final pathophysiological event, global cerebral hypoperfusion, which results from the inability of the circulatory system to maintain blood pressure at the level required to efficiently supply blood to the brain. The vasovagal syncope (VVS) is the most common form of syncope. Although, VVS is generally harmless, its frequent occurrence can negatively affect quality of life and increase the risk of adverse events. The pathophysiological mechanisms underlying VVS remain obscure. The multifaceted nature of VVS presents a veritable challenge to understanding this condition and developing preventative strategies. Thus, the aim of this review was to discuss the factors contributing to the pathogenesis of VVS and provide guidance for future research.

Genetic markers of vasovagal syncope

Vasovagal syncope may have a genetic predisposition. It has a high prevalence in some families, and children of a fainting parent are more likely to faint than those without a parent who faints. Having two fainting parents or a fainting twin increases the likelihood even further. Several genotypes appear to associate with the phenotype of positive tilt tests, but the control subjects are usually those who faint and have negative tilt tests. Twin studies, highly focused genome-wide association studies, and copy number variation studies all suggest there are loci in the genome that associate with vasovagal syncope, although the specific genes, pathways, and proteins are unknown. A recent multigenerational kindred candidate gene study identified 3 genes that associate with vasovagal syncope. The best evidence to date is for central signaling genes involving serotonin and dopamine. Genome-wide association studies to date have not yet been helpful. Our understanding of the genetic correlates of vasovagal syncope leaves ample opportunity for future work.

Vasovagal reactions following venepuncture result in aberrant stress-induced cortisol levels

Venepuncture is recognized as a potent stressor and, by activating the hypothalamic-pituitary-adrenal (HPA) axis, can interfere with measuring subsequent HPA axis indices such as cortisol. A resting period of 110 min is recommended between venepuncture and the commencement of psychosocial stress induction or cortisol measurement to allow cortisol levels to return to baseline first. In experiment 1 (n = 65), in which stress induction occurred 120 min after venepuncture, we observed three cortisol stress response patterns: conventional response ("responders", 77%), conventional non-response ("non-responders", 6.15%), and aberrant non-response characterized by high baseline (pre-stress) cortisol levels ("high-baseliners", 16.9%). Based on subjective clinical observation, the aberrant non-response was exclusively present in those who experienced vasovagal reactions during venepuncture, ranging from nervousness, lightheadedness, nausea, feeling of being extremely hot or cold, confusion, slight inability to speak, weakness and visual disturbances, to loss of consciousness (syncope). In experiment 2 (n = 79), we showed that allowing 210 min between venepuncture and stress induction permits the return of cortisol levels back to baseline even in participants who experience vasovagal reactions, thereby allowing for the exhibition of a conventional cortisol stress response. In sum, while 110 min may be sufficient to circumvent the usual effects of venepuncture on cortisol levels, 210 min are needed to effectively adjust for the effects of venepuncture-induced vasovagal reactions and the subsequent sustained rise in cortisol. Allowing sufficient time between venepuncture and stress induction or cortisol measurement should also prevent misclassification of participants who show aberrant responses as non-responders or anticipatory responders.

The Search for the Genes of Vasovagal Syncope

Only humans faint, and not all do so. Syncope tends to recur, and the predisposition to syncope can persist over many decades. Observations such as these have suggested that there may be a genetic predisposition to vasovagal syncope. It seems to have a high prevalence in some families; having a parent who faints increases the likelihood of an offspring fainting, and this is increased even further if both biological parents faint. Numerous studies have correlated a number of genotypes with positive tilt tests. However, the control subjects are usually those who faint, but have negative tilt tests, making the conclusions about association with the clinical phenotype less certain. Twin studies, highly focused genome-wide association studies, and gene duplicate studies all suggest there are sites in the genome that associate with vasovagal syncope, although the specific genes, pathways, and proteins are unknown. A recent large, candidate gene study of kindreds with high, multigenerational prevalence of the vasovagal syncope identified 3 genes that associate with vasovagal syncope. Our understanding of the genetic correlates of vasovagal syncope is in its infancy, with much to be understood.

Pubertal Hormonal Changes and the Autonomic Nervous System: Potential Role in Pediatric Orthostatic Intolerance

Puberty is initiated by hormonal changes in the adolescent body that trigger physical and behavioral changes to reach adult maturation. As these changes occur, some adolescents experience concerning pubertal symptoms that are associated with dysfunction of the autonomic nervous system (ANS). Vasovagal syncope (VVS) and Postural Orthostatic Tachycardia Syndrome (POTS) are common disorders of the ANS associated with puberty that are related to orthostatic intolerance and share similar symptoms. Compared to young males, young females have decreased orthostatic tolerance and a higher incidence of VVS and POTS. As puberty is linked to changes in specific sex and non-sex hormones, and hormonal therapy sometimes improves orthostatic symptoms in female VVS patients, it is possible that pubertal hormones play a role in the increased susceptibility of young females to autonomic dysfunction. The purpose of this paper is to review the key hormonal changes associated with female puberty, their effects on the ANS, and their potential role in predisposing some adolescent females to cardiovascular autonomic dysfunctions such as VVS and POTS. Increases in pubertal hormones such as estrogen, thyroid hormones, growth hormone, insulin, and insulin-like growth factor-1 promote vasodilatation and decrease blood volume. This may be exacerbated by higher levels of progesterone, which suppresses catecholamine secretion and sympathetic outflow. Abnormal heart rate increases in POTS patients may be exacerbated by pubertal increases in leptin, insulin, and thyroid hormones acting to increase sympathetic nervous system activity and/or catecholamine levels. Given the coincidental timing of female pubertal hormone surges and adolescent onset of VVS and POTS in young women, coupled with the known roles of these hormones in modulating cardiovascular homeostasis, it is likely that female pubertal hormones play a role in predisposing females to VVS and POTS during puberty. Further research is necessary to confirm the effects of female pubertal hormones on autonomic function, and their role in pubertal autonomic disorders such as VVS and POTS, in order to inform the treatment and management of these debilitating disorders.

Genetic Association Study in Multigenerational Kindreds With Vasovagal Syncope: Evidence for Involvement of Sex-Specific Serotonin Signaling

BACKGROUND

Several studies suggest that vasovagal syncope has a genetic origin, but this is unclear. We assessed whether plausible gene variants associate with vasovagal syncope.

METHODS

We studied 160 subjects in 9 kindreds comprising 82 fainters and 78 controls. The diagnosis was ascertained with the Calgary Syncope Score. Common genetic variants were genotyped for 12 genes for vascular signaling, potassium channels, the HTR1A(serotonin 5-HT1A receptor), SLC6A4(serotonin reuptake transporter), and COMT(catecholamine O-methyltransferase). Sex-specific associations between genotypes and phenotypes were tested.

RESULTS

In 9 out of 12 variants, there was no significant association between genotype and phenotype. However, the HTR1A(-1019) G alleles associated with syncope in males, but not in females ( P=0.005). CC and GG males had 9% versus 77% likelihoods of syncope. The SLC6A4 promoter L alleles associated with decreased syncope in males but increased in females ( P=0.059). The LL and SS males had 25% and 47% syncope likelihoods, whereas females had 75% and 50% syncope likelihoods. The COMT c.472 A alleles associated with decreased syncope in males but increased in females ( P=0.017). The GG and AA males had 50% and 15% syncope likelihoods, whereas females had 52% and 73% syncope likelihoods.

CONCLUSIONS

There is a sex-dependent effect of alleles of serotonin signaling and vasovagal syncope, supporting the serotonin hypothesis of the physiology of vasovagal syncope.

Vasovagal syncope is associated with poor prognosis in patients with left ventricular dysfunction

Vasovagal syncope (VVS) is known to have a benign prognosis and be associated with enhanced contraction and activation of the left ventricular (LV) mechanoreceptors. However, a little is known about VVS in patients with LV dysfunction. The present study aimed to investigate the prevalence and prognosis of VVS in patients with LV dysfunction. We enrolled 368 patients with unexplained syncope. In 7 of these patients, LV ejection fraction was lower than 40%. The results of a head-up tilt test (HUT) and the recurrence of syncope were compared between these 7 patients with LV dysfunction and the remaining patients. Positive HUT was obtained in the 6 patients (86%) with LV dysfunction; this rate tended to be higher as compared with normal cardiac function (192/361, 53%, P = 0.069). In patients with LV dysfunction, response in HUT was mostly vasodepressor type (62%); however, most of HUT responses were mixed type in patients with normal LV function (67%). Among patients with positive HUT, the recurrent rate of syncope after HUT was higher in those with LV dysfunction than in those with normal LV function (67 vs. 21%, P = 0.008). VVS in patients with LV dysfunction may be refractory to treatment and could be associated with poor prognosis.

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.

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.

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.

Neurocardiogenic mechanisms of unexplained syncope in idiopathic dilated cardiomyopathy

Syncope in patients with advanced heart failure is a sign of poor prognosis. The cause of syncope in patients with dilated cardiomyopathy (DC) is not fully recognized and may remain elusive even after standardized evaluation. The purpose of the present study was to examine the implication of neurally mediated mechanisms in the pathophysiology of syncopal episodes in patients with DC. Twenty-six patients (21 men, 5 women; mean age 59 +/- 2 years, range 38 to 79) with DC and left ventricular ejection fractions <or=40% were included in the study. Thirteen patients with unexplained syncope or presyncope and a control group of 13 patients without unexplained syncope underwent head-up tilt tests with clomipramine challenge. The 2 groups were matched with regard to age, gender, and left ventricular ejection fractions, and there were no major differences in terms of medication. Heart rate variability analysis and plethysmography of forearm flow were performed during the tilt tests. Blood samples were also drawn for catecholamine measurements. In the group with histories of unexplained syncope, the head-up tilt test results were positive in 11 patients (84.6%). Sympathetic and parasympathetic heart rate indexes were markedly stimulated, while catecholamine concentrations and blood flow changes indicated sympathetic withdrawal during tilting. In the control group, the head-up tilt test results were negative in 12 patients (92.3%). In conclusion, neurally mediated mechanisms seem to be implicated in the pathophysiology of syncope in patients with DC and should therefore be considered in the differential diagnosis of syncopal episodes of unexplained origin.

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.

Central serotoninergic response to orthostatic challenge in patients with neurocardiogenic syncope

AIMS

To determine whether central serotoninergic system activity is impaired by orthostatic challenge in patients with neurocardiogenic syncope (NCS).

METHODS AND RESULTS

Thirty-five [mean age: 24 (SD): 6 years] patients with a clinical history of NCS and positive head-up tilt test and 35 age-matched healthy volunteers (CON = 25+/-5 years) with negative response were studied. Overnight dexamethasone suppression test (DST) (1.5 mg given at 11 p.m.) was performed to assess the sensitivity of the hypothalamic-pituitary-adrenal axis by measuring next day cortisol (microg/dL) at 8 a.m. and 4 p.m. Cardiac autonomic function, cortisol, and prolactin (ng/dL) were also determined at baseline supine (BAS) and after 5, 10, and 15 min of orthostatic stress (OS) at 60 degrees . No significant differences were observed in cortisol plasma levels after the DST: CON = 0.6+/-0.6 microg/dL vs. NCS = 0.6+/-0.5; P = 0.7. Cardiac autonomic function, cortisol, and prolactin responses were similar in both study groups (CON vs. NCS; P > 0.05) during BAS: cortisol = 8.6+/-4 vs.8.7+/-4 microg/dL and prolactin = 16.8+/-9 vs. 16.8+/-9 ng/dL; OS-5: cortisol = 8.7+/-5 vs. 8.5+/-4 microg/dL and prolactin = 16.9+/-9 vs. 15.8+/-9 ng/dL; OS-10: cortisol = 8.5+/-5 vs. 8.1+/-3 microg/dL; prolactin = 16.2+/-9 vs. 15.8+/-9 ng/dL, and OS-15: cortisol = 9.0+/-5 vs. 8.4+/-4 microg/dL; prolactin = 17.1+/-9 vs. 15.5+/-9 ng/dL.

CONCLUSION

Central serotoninergic response during orthostatic challenge was not impaired in patients with recurrent NCS. These findings suggest that the activation of the hypothalamic-pituitary-adrenal axis is not altered in patients with recurrent NCS.

Clinical recognition of neurally mediated syncope

BACKGROUND

Most cases of syncope are due to hypotension, with a vasovagal response the commonest single mechanism. Neurally mediated syncope (NMS) is a vasovagal response evoked by common physical or psychological stress factors in susceptible individuals. Although upright tilt table testing (TTT) has been developed to diagnose this condition, the clinical recognition of this common syndrome in the general community remains poor.

AIMS

To evaluate the clinical presentation of patients with NMS and pre-syncope, proven by TTT, and compare them to patients with syncope that have a low probability of having NMS (e.g. older patients with cardiac disease and negative TTT).

METHODS

Prospective evaluation by questionnaire at the time of TTT, including documentation of presenting symptoms and signs, and provoking factors in consecutive patients. Comparisons between patient groups analyzed using chi-squared tests and logistic regression.

RESULTS

Neurally mediated syncope patients were more likely to present with both syncope and pre-syncope, often with prolonged histories of pre-syncope. Certain provoking stress factors were more common in NMS, with multiple factors often present. Most NMS patients had a hypotensive prodrome before syncope, whereas control patients had a higher incidence of syncope without warning.

CONCLUSION

Neurally mediated syncope patients present with situational syncope that is not only stereotypical for the individual, but shares common features with other similar patients. While none of the clinical observations is unique to NMS, a carefully detailed history can elicit a convincing diagnostic pattern that can often obviate the need for extensive and expensive investigation, and in younger patients a TTT may not be required to make the diagnosis.

Situational Syncope:. Response to Head-Up Tilt Testing and Follow-Up: Comparison with Vasovagal Syncope

Among sequential patients with neurally-mediated syncope, we studied the response to head-up tilt test (HUTT) in patients with situational syncope (SS) and their follow-up. Our findings were compared to those in patients with vasovagal syncope (VVS). The response to HUTT in patients with SS has not to date been fully investigated. Additionally, the prognosis of SS patients has not been systematically studied. We studied 162 consecutive patients with recurrent SS or VVS, all free of structural heart disease. Before study inclusion, they underwent an HUTT and were followed up for 12 months. Patients with SS were advised to avoid the trigger event. Patients with VVS were treated with propranolol or fluoxetine. For each patient we compared the number of syncopal spells during the last 12 months before study inclusion with that during follow-up. Among the 162 patients, 36 had SS and 126 had VVS. The response to HUTT and the number of syncopes before and during follow-up were similar in both groups. Among patients with SS, 10 (28%) had also experienced occasional episodes of VVS; however, they had a similar response to HUTT and prognosis to the remaining 26 SS patients without VVS attacks. Patients with SS have a similar response to HUTT and similarly benign clinical course to patients with VVS. The coexistence of occasional VVS episodes in patients with SS is not associated with a higher rate of positive HUTT or worse prognosis.

Plasma galanin response to head-up tilt in normal subjects and patients with recurrent vasovagal syncope

Neurohumoral factors may contribute to cardiovascular changes associated with vasovagal syncope (VVS). Galanin (GAL) is a neuropeptide, widely distributed in the central and peripheral nervous systems, that interacts with both sympathetic and vagal systems as well as with neurotransmitters, such as serotonin. We investigated the changes in plasma GAL and catecholamine levels during head-up tilt (HUT) test in patients with recurrent VVS. Twenty-two patients (11 women, aged 33.1 +/- 4.2 years) with a history of VVS and 10 healthy subjects (5 women, aged 38.0 +/- 5.8 years) underwent HUT test (60 degrees, 45 minutes). GAL and catecholamine plasma levels were measured in the supine position, during HUT and, in patients with positive response, at presyncope, syncope, and after recovery of consciousness. Thirteen patients developed syncope during HUT, whereas no healthy subjects had a positive response. In healthy subjects, GAL did not change during HUT. By contrast, in patients with a history of VVS and a negative response to tilting (no syncope), GAL significantly (P <.001) increased in response to tilting (supine, 10.2 +/- 0.6 pmol/L; tilting, 18.1 +/- 1.1 pmol/L at 45 minutes) and correlated positively with the increases in blood pressure (BP) and heart rate (HR). In patients with a positive response, GAL did not change either before the loss of consciousness or during syncope. In patients with a positive response, norepinephrine (NE) significantly (P <.001) increased during tilting and then remained practically unchanged during syncope, whereas epinephrine (E) significantly (P <.001) increased during tilting and then showed further significant increases at presyncope and syncope. In conclusion, this study shows that circulating GAL levels progressively increase in correlation with the cardiovascular parameters during a negative HUT in patients with a history of VVS, whereas they remain unchanged in healthy subjects. Moreover, in the patients with tilting-induced syncope GAL does not change either before or during loss of consciousness. These data suggest a role for endogenous GAL in the adaptive responses to acute orthostatic stress preventing syncope in susceptible individuals.

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

OBJECTIVES

We sought to assess the relative therapeutic efficacy of propranolol, nadolol and placebo in recurrent vasovagal syncope (VVS).

BACKGROUND

Central and peripheral mechanisms have been implicated in the pathogenesis of VVS. Propranolol, nadolol and placebo have different sites of action on central and/or peripheral mechanisms. It has not yet been clarified whether one of the aforementioned treatments is more efficient than the others in reducing clinical episodes and exerting a beneficial effect on patients' well-being.

METHODS

We studied 30 consecutive patients with recurrent VVS and a positive head-up tilt test. All were serially and randomly assigned to propranolol, nadolol or placebo. Therapy with each drug lasted three months. On the day of drug crossover, patients reported the total number of syncopal and presyncopal attacks during the previous period. They also gave a general assessment of their quality of life, taking into account: 1) symptom recurrence; 2) drug side effects; and 3) their personal well-being during therapy (scale 0 to 4: 0 = very bad/discontinuation; 1 = bad; 2 = good; 3 = very good; 4 = excellent). At the end of the nine-month follow-up period, they reported whether they preferred a specific treatment over the others.

RESULTS

Spontaneous syncopal and presyncopal episode recurrence during each three-month follow-up period was reduced by all drugs tested (analysis of variance [ANOVA]: chi-square = 67.4, p < 0.0001 for syncopal attacks; chi-square = 60.1, p < 0.0001 for presyncopal attacks) No differences were observed in the recurrence of syncope and presyncope among the three drugs. All drugs improved the patients' well-being (ANOVA: chi-square = 61.9, p < 0.0001).

CONCLUSIONS

Propranolol, nadolol and placebo are equally effective treatments in VVS, as demonstrated by a reduction in the recurrence of syncope and presyncope, as well as an improvement in the patients' well-being.

The collapsed athlete

Athletic collapse is rare, but personnel caring for athletes at sporting events must be prepared for it. Most cases are nonfatal and, with proper management, can have good outcomes. Medical personnel should expect the typical causes of athletic collapse that occur at the events they are covering, but rare causes should also be anticipated.

Neurocardiogenic syncope: aetiology and management

Neurocardiogenic syncope is the most common cause of syncope presenting in the outpatient setting. It is usually encountered among individuals without an underlying heart disease, but not uncommonly participates in the syncope mechanism of patients with an obstructive or an arrhythmic cardiac cause for syncope as well. The vasovagal event is caused by a transient profound hypotensive reaction most commonly associated with inappropriate bradycardia resulting from activation of a complex autonomic reflex. The pathophysiology of neurocardiogenic syncope has been elucidated by tilt table testing, a noninvasive and well-tolerated method for reproducing the event in susceptible individuals. Although the majority of people with vasovagal fainting need no specific treatment, treatment is required for those presenting with problematic features such as frequent events accompanied by trauma or accidents, and occasionally by a severe cardioinhibitory pattern response. A number of different drugs have been proposed to favourably act on different aspects of the neurocardiogenic reflex but only a few randomised, placebo-controlled, drug-specific trials are currently available. Alternatively, cardiac pacing has also been introduced for patients who have symptoms that are drug-refractory or for those with a severe cardioinhibitory hypotensive response. The selection of the appropriate treatment plan should be individualised after consideration of patient history, clinical characteristics and preference, results of the baseline tilting study, and the existing evidence from the few randomised, controlled studies performed so far.

Provocation of neurocardiogenic syncope by clomipramine administration during the head-up tilt test in vasovagal syndrome

OBJECTIVES

We sought to test the hypothesis that activation of the serotonergic system in patients with vasovagal syndrome during the head-up tilt test provokes syncope.

BACKGROUND

Central serotonergic activation participates in the pathogenesis of neurocardiogenic syncope. Drugs increasing serotonin (5-HT) in the central nervous system have not been tested as drug challenges during the head-up tilt test with clomipramine (Clom-HUT).

METHODS

The serotonergic re-uptake inhibitor clomipramine was infused (5 mg in 5 min) at the start of Clom-HUT in 55 patients (mean age 40 +/- 17 years) with a positive history of recurrent neurocardiogenic syncope and in 22 healthy control subjects (mean age 46 +/- 15 years). Blood samples were taken at 0, 5, 10 and 20 min for estimation of plasma prolactin and cortisol as neuroendocrine indicators of central serotonergic responsivity. All subjects had been previously tested with a basic 60 degrees head-up tilt test (B-HUT) for 30 min, and if negative, isoproterenol infusion was given at the end of the test.

RESULTS

Twenty-nine (53%) of the 55 patients and none of the 22 control subjects had a positive result in the B-HUT. With Clom-HUT, the proportion of patients who experienced a positive response increased to 80% (n = 44), although this happened to only one control subject. Prolactin and cortisol plasma levels increased significantly in the positive Clom-HUT patient group only.

CONCLUSIONS

The results indicate an increased responsivity of the central serotonergic neural system in subjects with vasovagal syndrome, the activation of which leads to sympathetic withdrawal. The use of clomipramine infusion with the tilt test seems to considerably improve its diagnostic value.

An association between anxiety and neurocardiogenic syncope during head-up tilt table testing

To study the association between anxiety and neurocardiogenic syncope as determined by head-up tilt table testing (HUT) in men and women with presyncope or syncope, patients with unexplained syncope or presyncope undergoing HUT were asked to complete the Burns Anxiety Inventory (BAI), a validated inventory of 33 questions with responses graded from 0 to 3. HUT consisted of a 30-minute tilt to 60 degrees, which if negative, was repeated with an isoproterenol infusion. A positive HUT was defined as symptomatic hypotension and/or bradycardia. Of the 66 patients who completed the BAI and underwent HUT, 33 were men and 33 were women. The mean age was 57 +/- 18 years (17-91 years). Patients with a positive HUT had a higher BAI score than those with a negative HUT (22 +/- 12 vs 14 +/- 13, P = 0.017). This association was stronger in women with a BAI score of 24 +/- 11 in those with a positive HUT versus 13 +/- 8 in those with a negative HUT (P = 0.005). In contrast, the mean BAI score for men with a positive HUT was 19 +/- 13, as compared to 15 +/- 16 for a negative HUT (P = 0.5). In conclusion, the present study demonstrates a statistical association between anxiety (as determined by BAI) and HUT result. Gender-based analysis revealed a more statistically significant relationship between anxiety and HUT outcome for women as compared to men.