Clinical presentation and long-term follow-up of athletes with exercise-induced vasodepressor syncope

2024 HRS expert consensus statement on arrhythmias in the athlete: Evaluation, treatment, and return to play

Youth and adult participation in sports continues to increase, and athletes may be diagnosed with potentially arrhythmogenic cardiac conditions. This international multidisciplinary document is intended to guide electrophysiologists, sports cardiologists, and associated health care team members in the diagnosis, treatment, and management of arrhythmic conditions in the athlete with the goal of facilitating return to sport and avoiding the harm caused by restriction. Expert, disease-specific risk assessment in the context of athlete symptoms and diagnoses is emphasized throughout the document. After appropriate risk assessment, management of arrhythmias geared toward return to play when possible is addressed. Other topics include shared decision-making and emergency action planning. The goal of this document is to provide evidence-based recommendations impacting all areas in the care of athletes with arrhythmic conditions. Areas in need of further study are also discussed.

Recommendations for participation in leisure-time physical activity and competitive sports in patients with arrhythmias and potentially arrhythmogenic conditions: Part 1: Supraventricular arrhythmias. A position statement of the Section of Sports Cardiology and Exercise from the European Association of Preventive Cardiology (EAPC) and the European Heart Rhythm Association (EHRA), both associations of the European Society of Cardiology

Symptoms attributable to arrhythmias are frequently encountered in clinical practice. Cardiologists and sport physicians are required to identify high-risk individuals harbouring such conditions and provide appropriate advice regarding participation in regular exercise programmes and competitive sport. The three aspects that need to be considered are: (a) the risk of life-threatening arrhythmias by participating in sports; (b) control of symptoms due to arrhythmias that are not life-threatening but may hamper performance and/or reduce the quality of life; and (c) the impact of sports on the natural progression of the underlying arrhythmogenic condition. In many cases, there is no unequivocal answer to each aspect and therefore an open discussion with the athlete is necessary, in order to reach a balanced decision. In 2006 the Sports Cardiology and Exercise Section of the European Association of Preventive Cardiology published recommendations for participation in leisure-time physical activity and competitive sport in individuals with arrhythmias and potentially arrhythmogenic conditions. More than a decade on, these recommendations are partly obsolete given the evolving knowledge of the diagnosis, management and treatment of these conditions. The present document presents a combined effort by the Sports Cardiology and Exercise Section of the European Association of Preventive Cardiology and the European Heart Rhythm Association to offer a comprehensive overview of the most updated recommendations for practising cardiologists and sport physicians managing athletes with supraventricular arrhythmias, and provides pragmatic advice for safe participation in recreational physical activities, as well as competitive sport at amateur and professional level. A companion text on recommendations in athletes with ventricular arrhythmias, inherited arrhythmogenic conditions, pacemakers and implantable defibrillators is published as Part 2 in Europace.

Pathophysiology of Noncardiac Syncope in Athletes

The most frequent cause of syncope in young athletes is noncardiac etiology. The mechanism of noncardiac syncope (NCS) in young athletes is neurally-mediated (reflex). NCS in athletes usually occurs either as orthostasis-induced, due to a gravity-mediated reduced venous return to the heart, or in the context of exercise. Exercise-related NCS typically occurs after the cessation of an exercise bout, while syncope occurring during exercise is highly indicative of the existence of a cardiac disorder. Postexercise NCS appears to result from hypotension due to impaired postexercise vasoconstriction, as well as from hypocapnia. The mechanisms of postexercise hypotension can be divided into obligatory (which are always present and include sympathoinhibition, histaminergic vasodilation, and downregulation of cardiovagal baroreflex) and situational (which include dehydration, hyperthermia and gravitational stress). Regarding postexercise hypocapnia, both hyperventilation during recovery from exercise and orthostasis-induced hypocapnia when recovery occurs in an upright posture can produce postexercise cerebral vasoconstriction. Athletes have been shown to exhibit differential orthostatic responses compared with nonathletes, involving augmented stroke volume and increased peripheral vasodilation in the former, with possibly lower propensity to orthostatic intolerance.

Syncope in Children and Adolescents

In the pediatric age group, most cases of syncope represent benign, neutrally-mediated alterations in vasomotor tone. Due to the global cerebral hypoperfusion, syncope is defined as a transient loss of consciousness followed by spontaneous recovery and/or a state of presyncope, including dizziness, lightheadedness, pallor, diaphoresis and palpitations which may precede the loss of consciousness. These symptoms could be a sign of a life-threatening event in a small subset of patients, even though most causes of syncope in childhood are benign, and life-threatening causes of syncope generally have cardiac etiology. In all these cases, routine evaluation includes history, physical examination and a 12-lead standard electrocardiogram which should be performed. Further investigation is indicated by worrying features which include syncope that occurs without warning, syncope during exercise, history of familial sudden death, and abnormalities on clinical exam or electrocardiography. The fact is that syncope generates great fear of injury or sudden death among parents and doctors, and the main aim of the present paper is to help the physician involved in the care of children to differentiate the life-threatening causes of syncope from the common, more benign neutrally-mediated syncope.

A new test for diagnosing vasovagal syncope: Standing after treadmill test with sublingual nitrate administration

Introduction

Increased adrenergic tone might be an additional trigger of orthostatic stress of vasovagal syncope (VVS). Exercise before standing might provide increased sensitivity compared to standing using a sublingual nitroglycerines protocol during tilt table testing. The aim of this study was to evaluate the diagnostic value of treadmill testing before standing with nitroglycerin administration.

Methods and results

A total of 36 patients with syncope or presyncope were enrolled for the test. VVS was confirmed in 29 patients according to the Calgary Score (≥ -2), including 20 patients who were likely to have typical (classical) VVS. All 36 subjects were subjected to a novel provocation test consisting of treadmill test using the Bruce protocol followed by standing with administration of 300 μg sublingual nitroglycerin. Consequently, syncope or presyncope occurred in 22 patients of the 36 patients. The sensitivity and a specificity of the test for Calgary score based VVS was 82.7% and 85.75%, respectively. Reproducibility rate for typical VVS was 90% (18 of 20). In all symptomatic patients, systolic blood pressure dropped to < 90 mmHg and symptom occurred a mean of 6.7 ± 2.3 minutes after the nitroglycerine administration. No patient required anticholinergics injection to restore vital signs.

Conclusions

Treadmill test with administration of sublingual nitroglycerines might be safely used to reproduce syncope in patients with VVS. More clinical experience and confirmation are needed to validate this protocol.

Recommendations for participation in leisure-time physical activity and competitive sports in patients with arrhythmias and potentially arrhythmogenic conditions Part I: Supraventricular arrhythmias and pacemakers

This document by the Study Group on Sports Cardiology of the European Society of Cardiology extends on previous recommendations for sports participation for competitive athletes by also incorporating guidelines for those who want to perform recreational physical activity. For different supraventricular arrhythmias and arrhythmogenic conditions, a description of the relationship between the condition and physical activity is given, stressing how arrhythmias can be influenced by exertion or can be a reflection of the (patho)physiological cardiac adaptation to sports participation itself. The following topics are covered in this text: sinus bradycardia; atrioventricular nodal conduction disturbances; pacemakers; atrial premature beats; paroxysmal supraventricular tachycardia without pre-excitation; pre-excitation, asymptomatic or with associated arrhythmias (i.e. Wolff-Parkinson-White syndrome); atrial fibrillation; and atrial flutter. A related document discusses ventricular arrhythmias, channelopathies and implantable cardioverter defibrillators.

Cerebellar hemorrhagic injury in premature infants occurs during a vulnerable developmental period and is associated with wider neuropathology

BACKGROUND

Cerebellar hemorrhagic injury (CHI) is being recognized more frequently in premature infants. However, much of what we know about CHI neuropathology is from autopsy studies that date back to a prior era of neonatal intensive care. To update and expand our knowledge of CHI we reviewed autopsy materials and medical records of all live-born preterm infants (<37 weeks gestation) autopsied at our institution from 1999-2010 who had destructive hemorrhagic injury to cerebellar parenchyma (n = 19) and compared them to matched non-CHI controls (n = 26).

RESULTS

CHI occurred at a mean gestational age of 25 weeks and involved the ventral aspect of the posterior lobe in almost all cases. CHI arose as a large hemorrhage or as multiple smaller hemorrhages in the emerging internal granule cell layer of the developing cortex or in the nearby white matter. Supratentorial germinal matrix hemorrhage occurred in 95% (18/19) of CHI cases compared to 54% (14/26) of control cases (p = 0.003). The cerebellar cortex frequently showed focal neuronal loss and gliosis (both 15/19, 79%) in CHI cases compared to control cases (both 1/26, 4% p < 0.0001). The cerebellar dentate had more neuronal loss (8/15, 53%) and gliosis (9/15, 60%) in CHI cases than controls (both 0/23, 0%; p < 0.0001). The inferior olivary nuclei showed significantly more neuronal loss in CHI (10/17, 59%) than in control cases (5/26, 19%) (p = 0.0077). All other gray matter sites examined showed no significant difference in the incidence of neuronal loss or gliosis between CHI and controls.

CONCLUSIONS

We favor the possibility that CHI represents a primary hemorrhage arising due to the effects of impaired autoregulation in a delicate vascular bed. The incidences of neuronal loss and gliosis in the inferior olivary and dentate nuclei, critical cerebellar input and output structures, respectively were higher in CHI compared to control cases and may represent a transsynpatic degenerative process. CHI occurs during a critical developmental period and may render the cerebellum vulnerable to additional deficits if cerebellar growth and neuronal connectivity are not established as expected. Therefore, CHI has the potential to significantly impact neurodevelopmental outcome in survivors.

Syncope in children and adolescents: Evaluation and treatment

Syncope in children is most often neurally mediated and usually has a natural history of spontaneous resolution or improvement. Syncope is defined as the temporary loss of consciousness resulting from a reversible disturbance of cerebral function. It is characterized by a loss of consciousness due to a lack of cerebral blood flow, rapid or sudden onset, falling of the patient, if not supported, and transiency of the attack. In children, it is most often benign, but may sometimes herald a more serious, potentially life-threatening cause. The main purpose of the present paper is to propose an evaluation scheme that will allow the physician involved in the care of children to differentiate the life-threatening causes of syncope with potential for injury or sudden death from the common, more benign neurally mediated syncope. Secondarily, the present article facilitates the identification of the patient with neurally mediated syncope who may benefit from medical therapy and distinguishes syncope from the more frequent noncardiac 'spells' of childhood.

Late gestation cerebellar growth is rapid and impeded by premature birth

OBJECTIVE

Cognitive impairments and academic failure are commonly reported in survivors of preterm birth. Recent studies suggest an important role for the cerebellum in the development of cognitive and social functions. The objective of this study was to examine the impact of prematurity itself, as well as prematurity-related brain injuries, on early postnatal cerebellar growth with quantitative MRI.

METHODS

Advanced 3-dimensional volumetric MRI was performed and cerebellar volumes were obtained by manual outlining in preterm (<37 weeks) and healthy term-born infants. Intracranial and total brain volumes were also calculated.

RESULTS

A total of 169 preterm and 20 healthy full-term infants were studied; 145 had preterm MRI (pMRI), 75 had term MRI (tMRI), and 51 underwent both pMRI and tMRI. From 28 weeks' postconceptional age to term, mean cerebellar volume (177%) in preterm infants increased at a much faster rate than did mean intracranial (110%) or mean brain (107%) volumes. Smaller cerebellar volume was significantly related to lower gestational age at birth and to intracranial and total brain volumes. Mean cerebellar volume of preterm infants at tMRI was significantly smaller than the volumes of term-born infants. Cerebellar growth impairment was correlated strongly with associated brain injuries, even in the absence of direct cerebellar injury.

CONCLUSIONS

Our data suggest that the growth of the immature cerebellum is particularly rapid during late gestation. However, this accelerated growth seems to be impeded by premature birth and associated brain injury. The long-term neurodevelopmental disabilities seen in survivors of premature birth may be attributable in part to impaired cerebellar development.

Exercise related syncope, when it's not the heart

Syncope or pre-syncope in association with physical exercise may be the first indication of a dangerous underlying cardiovascular condition. Thus, the diagnostic workup of patients presenting with exercise-related syncope must include assessment of the risk for acute cardiac death. When potentially lethal conditions have been ruled out, several hypotensive syndromes that are associated with exercise should be considered. This review aims to give a concise overview of several forms of exercise- related functional hypotensive syndromes causing syncope, including the physiology of post-exercise hypotension. The focus is on underlying mechanisms, clinical considerations, and outlining treatment strategies for these syndromes.

Responses to Tilt test in young and elderly patients with syncope of unknown origin

The aim of the present study was to assess the cardiovascular autonomic function and responses to tilt test in young and elderly patients with syncope of unknown origin. We evaluated two groups of patients with previous unexplained syncope: 192 older subjects (112 males, 80 females, mean age 67.2 +/- 6.8 years) and 188 young subjects (102 males, 86 females, mean age 25 +/- 9 years). All patients underwent ambulatory electrocardiogram (ECG) monitoring, to evaluate time domain indices of heart rate variability (HRV), and head-up tilt test in the morning after an overnight fast. The responses of positive tilt test were classified using the VAsovagal Syncope International Study (VASIS) criteria: mixed (VASIS-1), cardioinhibition (VASIS-2A), severe cardioinhibition/asystole (VASIS-2B), pure vasodepression (VASIS-3). All the time-domain HRV indexes were lower in the older than in young subjects. The rate of positive responses was not different in the two groups. In elderly group the positive head-up tilt test responses showed: a pure vasodepressive response (VASIS 3) in 126 patients (65%), a mixed (VASIS-1) response in 25 patients (13%), a cardioinhibitory (VASIS-2A) response in 13 patients (7%). Only 28 (14.6%) of elderly group patients had negative head-up tilt test response. In contrast, in young group the positive head-up tilt test responses showed: 114 patients (61.2%) a mixed (VASIS-1) vasovagal response, 40 patients (22.3%) a cardioinhibitory (VASIS-2A) response, four (2.1%) patients a severe cardioinhibitory (VASIS-2B) and four (2.1%) patients a pure vasodepression (VASIS-3) response, respectively. The tilt test was negative in response in 26 young patients (12.2%). Our results confirm that the head-up tilt test may be useful in assessing unexplained syncope, since it is seen to be positive in 85% of elderly patients and 86% in young patients. In our subjects, vasodepressive response was the most frequent cause of syncope in older subjects, while vasovagal response is the commonest cause of syncope of young patients. This different behaviour in the elderly may be is explained with physiological aging, which is associated with a reduction of sympathetic-parasympathetic control on the cardiac rhythm, demonstrated by reduction in all the time domain HRV indices.

Exercise-induced syncope associated with QT prolongation and ephedra-free Xenadrine

The Food and Drug Administration recently banned the sale of ephedra alkaloids because of their association with arrhythmic sudden death, myocardial infarction, and stroke. This has resulted in the emergence of formulations marketed for weight loss and performance enhancement that are "ephedra free" but contain other sympathomimetic substances, the safety of which has not been established. We report a case of exercise-induced syncope in a healthy 22-year-old woman that occurred 1 hour after she took the second dose of Xenadrine EFX, an ephedra-free weight-loss supplement. Electrocardiography revealed prolongation of the QT interval (corrected QT, 516 milliseconds); this resolved in 24 hours. Results of echocardiography and exercise stress testing were normal. Nine months of monitoring with an implanted loop recorder revealed no arrhythmias in the absence of Xenadrine EFX. Although this product contains a number of compounds whose pharmacologic effect is poorly characterized, notable quantities of phenylephrine are present, and the proarrhythmic potential of this compound in the setting of exercise is discussed.

MRI measurements of the pons and cerebellum in children born preterm; associations with the severity of periventricular leukomalacia and perinatal risk factors

Our purpose was to measure the size of the pons and cerebellum in preterm babies with periventricular leukomalacia (PVL), and to study their relationship with the severity of PVL and with perinatal risk factors. We examined 33 premature children, mean gestational age 31 weeks, range 26-36 weeks with PVL on MRI, and 27 full-term controls. On MRI at 0.4-5.5 years (mean 1.4 years) we measured the area of the corpus callosum and vermis, the anteroposterior diameter of the pons and the volume of the cerebellum. The area of the corpus callosum was used as a marker of white matter loss and PVL severity. All regional brain measurements except that of the vermis were significantly lower in patients than controls: corpus callosum (mm(2)): 239.6+/-92.5 vs 434.8+/-126.8, P <0.01; pons (mm): 14.8+/-3.0 vs 17.9+/-1.4, P <0.01]; cerebellum (cm(3)): 68.2+/-31.6 vs 100.6+/-28.3, P <0.01; vermis (mm(2)): 808.1+/-292.2 vs 942.2+/-246.2, NS. Significant reduction in the area of the vermis: 411.3+/-203.3 vs 935+/-252.6 mm(2); cerebellar volume: 16.3+/-12.5 vs 96.6+/-20.2 mm(3); and the diameter of the pons: 10.1+/-2.2 vs 17.5+/-1.3 mm ( P<0.01) were observed in seven children with gestational age < or =28 weeks, severe hypotension and large patent ductus arteriosus (PDA). There was a significant correlation between the duration of mechanical ventilation and the size of the vermis, pons and cerebellum (R=-0.65, -0.57 and -0.73, respectively, P <0.01).

Cardiac risk factors and participation guidelines for youth sports

Accurate assessment of the cardiac system in pediatric and adolescent youth is important. The hemodynamic demands associated with exercise, training, and sport participation are usually positive and beneficial; however, when an underlying cardiac problem exists, it is imperative that such cardiac problems be identified. Safe sport-related cardiac participation guidelines should be provided for young athletes and their families and coaches. This chapter provides a physician perspective on the recognition and current cardiac management considerations for young athletes participating in both static and dynamic types of sports. The most recent guidelines for hypertension in youth are also provided.

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.

Syncope

Successful treatment of patients with syncope depends on the accuracy of the diagnosis, because syncope is a symptom, not a disease; diagnosis of the cause for syncope therefore creates a blueprint for treatment. Most experienced practitioners can diagnose the cause of syncope for less than half of their patients. Excessive and repeat testing is expensive and may not improve the chance of a correct diagnosis. Patient history is the key to the diagnosis. Treatment may vary from a lifestyle change to open heart surgery. The great challenge of treating patients with syncope is to provide cost-effective, safe therapy to those with a benign course and still provide needed treatment for those whose syncope is life threatening.

Costs and utility of tests in the evaluation of the pediatric patients with syncope

New diagnostic tests have markedly improved the ability to establish a cause of syncope in pediatric patients, but at a substantial cost. The goal of syncope evaluation should be to diagnose treatable causes and identify patients at high risk for sudden death. The diagnostic utility of commonly used tests is reviewed. Although there are limited data on the application of specific diagnostic tests in the child with syncope, most tests have a low yield in unselected patients. A more directed approach to testing, based on the results of history, physical examination and the electrocardiogram is likely to result in significant cost reduction while still identifying patients with life threatening disorders. Validation of such an approach awaits prospective evaluation.

Evaluation and treatment of pediatric patients with neurocardiogenic syncope

Neurocardiogenic syncope is the most common form of syncope in children. The most widely accepted mechanism of its etiology is a vigorous contraction of the heart due to relative hypovolemia leading to stimulation of C-fibers and sympathetic withdrawal. Episodes usually occur with an upright position and are preceded by a typical prodrome. A classic history is paramount to the diagnosis. Tilt testing aids in the diagnosis in certain cases. The cornerstone of therapy is maintaining adequate hydration and avoiding situations that may lead to harm with syncopal events. Beta blockers, fludrocortisone, alpha adrenergic agents and disopyramide are commonly used to prevent syncope. Seratonin reuptake inhibitors, pacing with rate drop algorithms and tilt training are relatively new in the armamentarium of therapy.

Differences between cerebral and cerebellar autoregulation during progressive hypotension in rats

Autoregulation in the brain is essential to the maintenance of perfusion and hence to the normal functioning of the organism in the face of various hemodynamic challenges. The existence of prodromal symptoms preceding fainting suggests that cerebellar autoregulation could be altered earlier than cerebral autoregulation during the development of hypotension. The purpose of this study was to compare cerebral and cerebellar autoregulatory responses to hypotension induced by two rates of hemorrhage 1.5 and 2.0 ml/min. Cortical blood flows were measured simultaneously using laser Doppler flowmetry in rats. With increasing rate of hemorrhage, the kinetics of autoregulation were maintained in the cerebrum, whereas it caused a progressive loss in the efficacy of autoregulation in the cerebellum.

Exercise-induced neurocardiogenic syncope: clinical data, pathophysiological aspects, and potential role of tilt table testing

The evaluation of syncope occurring during exercise or occurring spontaneously in highly trained individuals presents a unique diagnostic challenge. It is of critical importance to exclude potential life-threatening disorders such as hypertrophic cardiomyopathy, long QT syndrome, right ventricular dysplasia, anomalous coronary artery distribution, valvular heart disease, myocarditis, or exercise-induced arrhythmia. This review is not directed towards identifying, treating, or determining athletic eligibility of individuals with such disorders. Rather, we endeavour to discuss the pathophysiology of exercise-induced neurocardiogenic syncope and to address the role of head upright tilt testing in evaluating syncope in athletic individuals in whom proper evaluation has excluded the presence of ischaemic heart disease or primary structural or electrical heart disease.

Management of vasovagal syncope

Vasovagal syncope is a common disorder of autonomic cardiovascular regulation that can be very disabling and result in a significant level of psychosocial and physical limitations. The optimal approach to treatment of patients with vasovagal syncope remains uncertain. Although many different types of treatment have been proposed and appear effective based largely on small nonrandomized studies and clinical series, there is a remarkable absence of data from large prospective clinical trials. However, based on currently available data, the pharmacologic agents most likely to be effective in the treatment of patients with vasovagal syncope include beta blockers, fludrocortisone, and alpha-adrenergic agonists. In this article, we provide a summary of the various therapeutic options that have been proposed for vasovagal syncope and review the clinical studies that form the basis of present therapy for this relatively common entity.

Role of adenosine receptors in the paradoxic bradycardia response of rats to inferior vena cava occlusion during an infusion of isoproterenol

BACKGROUND

In susceptible humans, vasodepressor reactions are induced by restriction of venous return (upright tilting) and administration of isoproterenol. Because paradoxic bradycardia is a major manifestation of vasodepressor reactions, and allowing for extrapolation between paradoxic bradycardia in rats and vasodepressor reactions, we examined whether adenosine receptors mediate the paradoxic bradycardia reaction.

METHODS AND RESULTS

Paradoxic bradycardia was induced in rats by inferior vena cava occlusion during an isoproterenol infusion. We studied whether dipyridamole, an adenosine transport inhibitor, and aminophylline (nonselective) or DPCPX (selective) A1 antagonists augmented or inhibited paradoxic bradycardia, respectively, during inferior vena cava occlusion. The maximum changes in R-R during 60 seconds of inferior vena cava occlusion were that (1) in control, the rate accelerated (DeltaR-R, -9.7+/-0.8 ms, P<0.001); (2) during isoproterenol (0.8 microg . min-1), paradoxic bradycardia occurred (DeltaR-R, +92.0+/-32.0 ms, P<0.001); (3) during isoproterenol but after dipyridamole, paradoxic bradycardia occurred at a much lower dose of isoproterenol (0.2 microg . min-1), and the magnitude was increased at all doses (at 0.8 microg . min-1 isoproterenol, DeltaR-R, +195.6+/-27.6 ms, P<0.001 versus isoproterenol alone, DeltaR-R, +92.0+/-32 ms); (4) during isoproterenol and dipyridamole, atropine did not block paradoxic bradycardia, but cervical vagotomy inhibited paradoxic bradycardia (DeltaR-R, +5.6+/-1.8 ms, P<0.001 compared with isoproterenol and dipyridamole alone); and (5) during isoproterenol alone, aminophylline or DPCPX blocked paradoxic bradycardia (DeltaR-R, -5.4+/-1.0 ms, and DeltaR-R, -2.6+/-0.5 ms, respectively, each P<0.001 compared with isoproterenol alone).

CONCLUSIONS

The adenosine A1 receptor mediates the paradoxic bradycardia reflex during inferior vena cava occlusion in the face of isoproterenol via vagal afferents.

Exercise-induced vasovagal syncope: limiting the risks

Syncopal episodes in an athlete require a thorough evaluation because some of the possible causes are life-threatening. Two case studies demonstrate the diagnostic work-up, which typically involves electrocardiography, echocardiography, and exercise testing. Tilt-table testing can be used to confirm a diagnosis of vasovagal syncope, but only after structural heart disease has been ruled out. Treatment of vasovagal syncope includes avoiding dehydration and using one or a combination of medications shown to be useful for this condition. Care must be exercised in choosing medications; some are prohibited in organized athletics, and some can hurt performance.

Syncope in the pediatric patient

Syncope in the pediatric patient is a common and usually benign event that frequently causes concern and anxiety. This article describes three general categories of syncope in children and adolescents: cardiac, noncardiac, and neurocardiogenic. The discussion includes specific pediatric issues and dissimilarities when compared to adult patients with syncope. In addition, a focused approach to the diagnostic evaluation of syncope in childhood is described.

Clinical approach to diagnosis of syncope. An Overview

Effective management of the syncope patient is critically dependent on excluding conditions in which altered consciousness is not due to syncope (e.g., seizure and sleep disorders) then establishing the basis for syncopal symptoms. The initial diagnostic step in syncope patients is differentiation of those individuals with normal cardiovascular status from those with structural heart disease. In the former, tilt-table testing and related studies of autonomic nervous system function are usually the most productive direction in which to proceed. In patients with structural heart disease, a functional assessment of the suspected structural disturbance (i.e., hemodynamic, angiographic, imaging as appropriate) and evaluation for susceptibility to symptomatic arrhythmias by monitoring or conventional electrophysiologic testing is appropriate. Autonomic function testing should follow if the diagnosis remains unclear. In only a few instances should specialized neurologic studies be undertaken as an initial step. The ultimate objective is always to obtain a sufficiently strong correlation between syncopal symptoms and detected abnormalities to feel confident in the diagnosis, permit an accurate assessment of prognosis, and develop an appropriate treatment plan.

Neurally mediated syncopal syndromes: pathophysiological concepts and clinical evaluation

The neurally mediated syncopal syndromes encompass a number of apparently related disturbances of reflex cardiovascular control characterized by transient inappropriate bradycardia and/or vasodilation of various arterial and venous beds. Certain of these syndromes (e.g., carotid sinus syndrome, postmicturition syncope) are encountered occasionally in clinical practice, whereas others are quite rare (e.g., swallow syncope). On the other hand, vasovagal syncope occurs so frequently, that as a group, the neurally mediated syncopal syndromes are among the most important causes of syncope. The pathophysiology of the neurally mediated syncopal syndromes is incompletely understood, but can be considered in terms of four basic elements: (1) the afferent limb; (2) central nervous system (CNS) processing; (3) the efferent limb; (4) feedback loops. The afferent limb consists of several peripheral and CNS trigger sites and the associated connections to medullary cardiovascular centers. CNS processing and efferent signals result in both bradycardia, which may be marked or relative, and vasodilatation. Failure of baroreceptor feedback controls to prevent hypotension is important in facilitating development of symptomatic hypotension. Head-up tilt table testing has become the diagnostic technique of choice for clinically assessing susceptibility to neurally mediated syncope, particularly of the vasovagal type. Most studies suggest that such testing discriminates relatively well between symptomatic patients and asymptomatic control subjects, of whom 10%-15% have a false-positive test results. Sensitivity of tilt table testing is more difficult to evaluate because there is no accepted diagnostic gold standard. However, sensitivity (measured against a classic presentation) has been estimated to range from 32%-85%, with most reports favoring the higher end of this range. Treatment strategies for neurally mediated syncope remain controversial. Many single episodes do not warrant treatment unless physical injury has occurred, or a high risk occupation or avocation is involved. Tilt test exposure alone may prove beneficial in educating patients with recurrent syncope to recognize warning signs of an imminent faint. Large controlled clinical studies have not been performed to test the efficacy of pharmacological therapy (e.g., beta-adrenergic blockers, disopyramide, serotonin reuptake blockers, vasoconstrictors) or pacing therapy. Such studies may be difficult to undertake due to the variable frequency of spontaneous symptoms and apparent long periods of remission. Nonetheless, many investigators and clinicians have come to rely on these agents, and on tilt testing to guide treatment decisions. Studies employing careful correlation of long-term clinical follow-up with results of early and perhaps later repeat tilt studies are still needed.