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

Pediatric Syncope: An Examination of Diagnostic Processes, Therapeutic Approaches and the Role of the Tilt Test: Insights from an 18-Year Single-Center Experience

Objectives: Syncope is a common cause of the transient loss of consciousness, with neurally mediated syncope (NMS) and particularly vasovagal syncope (VVS) being the most prevalent types among older children and adolescents. VVS is primarily caused by heightened parasympathetic activity triggered by emotional or postural stimuli, resulting in a temporary disruption of circulation. Although anamnesis and physical examination play key roles in diagnosing VVS, additional diagnostic methods are necessary in unclear cases. This study aims to evaluate the long-term outcomes of pediatric patients with syncope, focusing on clinical characteristics, diagnosis, and treatment approaches. Methods: A retrospective analysis was conducted on 455 pediatric patients aged 8-21 years who presented with syncope at our cardiology clinic between 2005 and 2023. Patients diagnosed with cardiac syncope, epilepsy, or postural orthostatic tachycardia syndrome (POTS) were excluded. The remaining 283 patients were categorized into two groups: those with confirmed VVS-based on a comprehensive evaluation, including medical history, physical examination, and electrocardiography-and those suspected of VVS who lack a confident diagnosis after an initial assessment requiring tilt table testing. Clinical features, diagnostic methods, and treatment outcomes were analyzed. Results: The study cohort had a mean age of 13.5 ± 1.6 years, with a female predominance of 69%. Among patients who underwent tilt table testing (TTT), 74.8% exhibited a positive response, with mixed-type syncope being the most prevalent (51%). Syncope recurrence was significantly higher in the TTT group (54%) compared to the clinically diagnosed group (15%) (p < 0.001). Relapse risk was strongly associated with the syncope subtype, particularly cardioinhibitory type 2B (OR: 2.3, 95% CI: 1.1-4, p < 0.01), and episode frequency (OR: 1.7, 95% CI: 1.3-2.5, p = 0.03). Beta-blocker therapy was selectively administered and demonstrated a reduced relapse risk in a univariate analysis. Conclusions: VVS is a significant health issue in pediatric patients and the therapeutic modalities available encompass various interventions, including modifications to lifestyle, adequate hydration, and pharmacological therapies. TTT was found to be an effective diagnostic tool for identifying high-risk patients and is recommended for appropriate cases in pediatric VVS diagnosis in accordance with the guidelines, with the objective of refining therapeutic methodologies and ultimately augmenting patient prognoses.

A contemporary review of the head-up tilt test: Utility and limitations

The Head-Up Tilt Test (HUTT) has been widely used for the past four decades as part of the overall assessment of the potential causes of collapse in patients with recurring transient loss of consciousness (TLOC) of unknown cause. The ability of a positive HUTT often to reproduce patient symptoms and illustrate to the patient that the physician is confident of the diagnosis have been major advances in clinical TLOC management. Tilt testing has been particularly important in understanding and diagnosing vasovagal syncope (VVS) and orthostatic hypotension. Despite HUTT having great clinical utility, different HUTT protocols and drug provocations result in different test yields. Limited HUTT reproducibility has led some researchers to criticize HUTT utility. As in most medical tests, limitations are part of the test. Herein, we provide a contemporary review of HUTT's utility in diagnosing and managing various TLOC disorders with intent to clarify its role in clinical practice.

Malignant vasovagal syncope in children

BACKGROUND

Malignant vasovagal syncope (VVS) is a unique form of cardioinhibitory VVS, characterized by prolonged asystole. To deepen the understanding of this distinct type of VVS in children, this article reviews advancements in the potential pathogenesis, diagnostic approaches, clinical significance, and treatment controversies of malignant VVS in pediatric patients.

DATA SOURCES

This article was developed by reviewing the literature and studies in databases including PubMed and Chinese Journal Full-text Database up to September 2024. Search terms included "malignant vasovagal syncope" AND "children" or "vasovagal syncope" AND "asystole" AND "children".

RESULTS

To date, studies focused on malignant VVS in children remain limited. Theoretically, children with malignant VVS are at risk of physical or mental impairment due to this cardiac asystole, though no definite conclusions have been reached. The mechanism underlying the significant cardiac inhibition in malignant VVS remains unclear, and the treatment strategy of malignant VVS is debatable.

CONCLUSIONS

The understanding of children with malignant VVS is insufficient. Further research is required to evaluate the clinical features and the pathogenesis of pediatric VVS with cardiac asystole and to establish effective management strategies for malignant VVS. Video Abstract.

Clinical features and response at head-up tilt test of patients with situational syncope

OBJECTIVE

The study compared clinical characteristics and response at head-up tilt test (HUTT) between situational (SS) and vasovagal syncope (VVS).

METHODS

Consecutive patients who underwent nitroglycerin-potentiated HUTT were retrospectively dichotomised into two groups: those with a history of SS and those with a history of VVS. The patients with SS were further subdivided into patients with SS alone and with SS and at least one episode of VVS.

RESULTS

1285 patients were enrolled: 246 (19.1%) had SS (SS alone in 121 and SS+VVS in 125). Patients with SS were older (48.8±20.0 vs 44.4±19.1, p=0.007) and more frequently male (57.3% vs 47.7%, p=0.001). At multivariable analysis, smoking habit (OR 2.28; p<0.0001), history of traumatic syncope (OR 2.29; p=0.0001) and ACE inhibitors/angiotensin II receptor blockers (OR 4.74; p<0.0001) were independently associated with SS. HUTT was positive in 175 (71.1%) patients with SS and in 737 (70.9%) patients with VVS (p=0.9). Patients with SS showed more mixed (42.3% vs 32.0%, p=0.002) and vasodepressor forms (10.6% vs 6.1%, p=0.01) and less cardioinhibitory responses compared with others (18.3% vs 32.8%, p<0.0001).

CONCLUSIONS

Compared with VVS, patients with SS have different clinical characteristics and a higher prevalence of hypotensive drugs leading to hypotensive susceptibility. The positivity rate of HUTT is high and similar to that of VVS, although patients with SS show a higher prevalence of hypotensive responses.

The clinical presentation of syncope influences the head-up tilt test responses

INTRODUCTION

Little is still known about the positivity rate of nitroglycerin (NTG) potentiated head-up tilt test (HUTT) according to the history-based clinical features of syncope. The study aimed to compare the HUTT positivity rate and type of responses in patients with classical and non-classical vasovagal syncope (VVS).

MATERIALS AND METHODS

We retrospectively evaluated all consecutive patients who underwent NTG-potentiated HUTT for VVS. The study population was dichotomized into classical and non-classical VVS.

RESULTS

A total of 1285 VVS patients (45± 19.1 years; 49.6% male) were enrolled: 627 (48.8%) had a history of classical VVS and 658 (51.2%) of non-classical VVS. HUTT was positive in 866 (67.4%) patients. The positivity rate was significantly higher in patients with classical compared to those with non-classical VVS (81.5% vs 54%; P< 0.0001). Cardioinhibitory response showed similar total positivity rate (27.6% vs 31%; P= 0.17), but higher relative prevalence among positive tests (57.7% vs 33.9%, P< 0.0001) in patients with non-classical VVS. At multivariable analysis, classical reflex syncope, male sex, history of traumatic syncope and use of diuretics were independent predictors of HUTT positivity.

CONCLUSION

The clinical presentation of syncope influences the overall HUTT positivity rate and the type of responses. Cardioinhibitory response and traumatic syncope are more likely in patients with non-classical VVS.

Prevalence of asystole during tilt test-induced vasovagal syncope may depend on test methodology

This review addresses tilt-testing methodology by searching the literature which reports timing of asystole and loss of consciousness (LOC). Despite the Italian protocol being the most widely adopted, its stipulations are not always followed to the letter of the European Society of Cardiology guidelines. The discrepancies permit reassessment of the incidence of asystole when tilt-down is early, impending syncope, compared with late, established LOC. Asystole is uncommon with early tilt down and diminishes with increasing age. However, if LOC is established as test-end, asystole is more common, and it is age-independent. Thus, the implications are that asystole is commonly under-diagnosed by early tilt-down. The prevalence of asystolic responses observed using the Italian protocol with a rigorous tilt down time is numerically close to that observed during spontaneous attacks by electrocardiogram loop recorder. Recently, tilt-testing has been questioned as to its validity but, in selection of pacemaker therapy in older highly symptomatic vasovagal syncope patients, the occurrence of asystole has been shown to be an effective guide for treatment. The use of head-up tilt test as an indication for cardiac pacing therapy requires pursuing the test until complete LOC. This review offers explanations for the findings and their applicability to practice. A novel interpretation is offered to explain why pacing induced earlier may combat vasodepression by raising the heart rate when sufficient blood remains in the heart.

New hemodynamic criteria to separate classical orthostatic hypotension from vasovagal syncope

OBJECTIVE

To define and evaluate hemodynamic criteria to distinguish between classical orthostatic hypotension (cOH) and vasovagal syncope (VVS) in tilt table testing (TTT).

METHODS

Inclusion criteria for VVS were a history of VVS and tilt-induced syncope defined as a blood pressure (BP) decrease and electroencephalographic changes during syncope with complaint recognition. Criteria for cOH were a history of cOH and a BP decrease meeting published criteria. Clinical diagnoses were established prior to TTT. We assessed (1) whether the decrease of systolic BP accelerated, "convex," or decelerated, "concave"; (2) the time from head-up tilt to when BP reached one-half its maximal decrease; (3) the difference between baseline heart rate (HR) and HR at BP nadir. We calculated the diagnostic yield of optimized thresholds of these features and their combinations.

RESULTS

We included 82 VVS cases (40% men, median age 44 years) and 65 cOH cases (66% men, median age 70 years). BP decrease was concave in cOH in 79% and convex in VVS in 94% (p < 0.001). The time to reach half the BP decrease was shorter in cOH (median 34 sec, interquartile range (IQR) 19-98 sec) than in VVS (median 1571 sec, IQR 1381-1775 sec, p < 0.001). Mean HR increased by 11 ± 11 bpm in cOH and decreased by 20 ± 19 bpm in VVS (p < 0.001). When all three features pointed to VVS, sensitivity for VVS was 82% and specificity was 100%. When all three pointed to cOH, sensitivity for cOH was 71% and specificity was 100%.

INTERPRETATION

These new hemodynamic criteria reliably differentiate cOH from VVS.

Head-up tilt test diagnostic yield in syncope diagnosis

BACKGROUND

The European Syncope Guidelines (ESG) recommend the use of Head-up tilt test (HUT) in case of suspicion of vasovagal syncope (VVS) or orthostatic hypotensive syncope (OHS) after an adequate initial inconclusive evaluation. We report a single center experience in the scenario of suspected VVS or OHS, who underwent HUT in patients referred to a Syncope Clinic after ruling out high-risk causes.

METHODS

We prospectively and consecutively included all syncopal patients that were referred for HUT, by their attending physician after performing a series of diagnostic tests to rule out cardiac etiology. The clinical history and diagnostic tests performed were reviewed prior to HUT. Patients were pre-classified according to the recommendations from the ESG as; VVS, OHS or Syncope of Unknown Etiology (SUE).

RESULTS

We studied 1058 patients, 558 (52.7%) males, mean age 46.5 ± 20.1 yr. There were no gender differences in age, risk factors, previous heart diseases, ECG findings or number of previous tests. Based on the ESG criteria a significant number of diagnostic tests were probably unnecessarily performed. HUT was positive in 609 patients (57.5%). The rate of positive HUT according to pre-classification was significantly different among groups: 60% VVS, 46.1% OHS and 54.3% SUE (p = 0.037). Combining ESG recommendations and HUT results of the 1058 resulted in 762 (72%) diagnosed as VVS, 89 (8.4%) as OHS and 207 (19.5%) as SUE.

CONCLUSIONS

Appropriate application of ESG recommendations combined with HUT, identified 81% of patients with non-cardiogenic syncope, potentially avoiding a significant number of unnecessary diagnostic tests.

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.

Tilt-table test: its role in modern practice

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