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

Canadian Cardiovascular Society and Canadian Pediatric Cardiology Association Position Statement on the Approach to Syncope in the Pediatric Patient

Pediatric syncope is a common problem that peaks in adolescence, for which there are few data or evidence-based consensus on investigation and management. This document offers guidance for practical evaluation/management of pediatric patients (age < 19 years) with syncope encountered in the acute or primary care setting. The writing committee used the Grading of Recommendations, Assessment, Development, and Evaluation (GRADE) methodology. Most syncope is vasovagal, which is benign and does not require extensive investigation. This Position Statement presents recommendations to encourage an efficient and cost-effective disposition for the many patients with a benign cause of syncope, and highlights atypical or concerning clinical findings associated with other causes of transient loss of consciousness. The prodrome and the circumstances around which the event occurred are the most important aspects of the history. Syncope occurring midexertion suggests a cardiac etiology. A family history, which includes sudden death in the young or from unknown causes or causes that might be suspected to be other than natural can be a red flag. The electrocardiogram is the most frequently ordered test, but the yield is low and the test is not cost-effective when applied broadly to a population of patients with syncope. We recommend an electrocardiogram when the history is not suggestive of vasovagal syncope and there are features suggestive of a cardiac cause like absence of a prodrome, midexertional event, family history of early-life sudden death or heart disease, abnormal physical examination, or new medication with potential cardiotoxicity. For most patients with syncope, medical testing is not required and lifestyle modifications without medications suffice to prevent recurrences.

Tilt table test today - state of the art

A tilt table test (TTT) is an inexpensive, noninvasive tool for the differential diagnosis of syncope and orthostatic intolerance and has good diagnostic yield. The autonomic system malfunction which underlines the reflex syncope is manifested as either hypotension or bradycardia, while an orthostatic challenge is applied. The timing of the response to the orthostatic challenge, as well as the predominant component of the response help to differentiate between various forms of neurocardiogenic syncope, orthostatic hypotension and non-cardiovascular conditions (e.g., pseudosyncope). Medications, such as isoproterenol and nitrates, may increase TTT sensitivity. Sublingual nitrates are easiest to administer without the need of venous access. TTT can be combined with carotid sinus massage to evaluate carotid sinus hypersensitivity, which may not be present in supine position. TTT is not useful to access the response to treatment. Recently, implantable loop recorders (ILR) have been used to document cardioinhibitory reflex syncope, because pacemakers are beneficial in many of these patients, especially those over 45 years of age. The stepwise use of both TTT and ILR is a promising approach in these patients. Recently, TTT has been used for indications other than syncope, such as assessment of autonomic function in Parkinson's disease and its differentiation from multiple system atrophy.

Exercise-induced syncope in a sedentary woman

Vasovagal (neurocardiogenic) syncope, a subtype of reflex syncope, has many well-known triggers. However, we found no previous report of vasovagal exercise-induced syncope in a sedentary person. We present the case of a 35-year-old sedentary woman who experienced vasovagal syncope as she underwent an exercise stress test. Results of evaluations, including resting and stress electrocardiography and echocardiography, were normal. Her presentation is highly unusual: syncope has typically not been associated with exercise except in young athletes, people with structural heart abnormalities, or people with a prolonged QT syndrome. To our knowledge, this is the first report of vasovagal syncope associated with exercise in a sedentary patient who had normal cardiac and electrophysiologic function. We suggest possible physiologic mechanisms and diagnostic strategies.

Minimally invasive approach to the child with palpitations

Palpitations are a common reason for referral to a pediatric cardiologist. Although generally benign, palpitations are a significant cause for concern in the individual and their family. Similarly, palpitations may be the initial presentation of significant heart disease, resulting in heightened concern in the referring physician. Although emphasis is usually placed on excluding arrhythmia as the cause for palpitations, there are a variety of noncardiac causes for palpitations. The patient history and physical examination are the key components of the evaluation and guide subsequent investigations. In many cases, an immediate diagnosis cannot be made and additional testing may be required; this often includes further monitoring for episodes, cardiac imaging and ambulatory monitoring. Current technologies for ambulatory monitoring during symptoms include Holter monitoring and a variety of patient-activated event recorders, including implantable loop recorders. Each presents its own unique advantages and disadvantages to aid diagnosis in the management of a child with palpitations. The primary focus for the clinician is to determine whether the etiology is benign in nature or whether there is underlying heart disease that may carry a more serious prognosis.

Blood pressure regulation X: what happens when the muscle pump is lost? Post-exercise hypotension and syncope

Syncope which occurs suddenly in the setting of recovery from exercise, known as post-exercise syncope, represents a failure of integrative physiology during recovery from exercise. We estimate that between 50 and 80% of healthy individuals will develop pre-syncopal signs and symptoms if subjected to a 15-min head-up tilt following exercise. Post-exercise syncope is most often neurally mediated syncope during recovery from exercise, with a combination of factors associated with post-exercise hypotension and loss of the muscle pump contributing to the onset of the event. One can consider the initiating reduction in blood pressure as the tip of the proverbial iceberg. What is needed is a clear model of what lies under the surface; a model that puts the observational variations in context and provides a rational framework for developing strategic physical or pharmacological countermeasures to ultimately protect cerebral perfusion and avert loss of consciousness. This review summarizes the current mechanistic understanding of post-exercise syncope and attempts to categorize the variation of the physiological processes that arise in multiple exercise settings. Newer investigations into the basic integrative physiology of recovery from exercise provide insight into the mechanisms and potential interventions that could be developed as countermeasures against post-exercise syncope. While physical counter maneuvers designed to engage the muscle pump and augment venous return are often found to be beneficial in preventing a significant drop in blood pressure after exercise, countermeasures that target the respiratory pump and pharmacological countermeasures based on the involvement of histamine receptors show promise.

Postexercise syncope: Wingate syncope test and effective countermeasure

Altered systemic haemodynamics following exercise can compromise cerebral perfusion and result in syncope. As the Wingate anaerobic test often induces presyncope, we hypothesized that a modified Wingate test could form the basis of a novel model for the study of postexercise syncope and a test bed for potential countermeasures. Along these lines, breathing through an impedance threshold device has been shown to increase tolerance to hypovolaemia, and could prove beneficial in the setting of postexercise syncope. Therefore, we hypothesized that a modified Wingate test followed by head-up tilt would produce postexercise syncope, and that breathing through an impedance threshold device (countermeasure) would prevent postexercise syncope in healthy individuals. Nineteen recreationally active men and women underwent a 60 deg head-up tilt during recovery from the Wingate test while arterial pressure, heart rate, end-tidal CO2 and cerebral tissue oxygenation were measured on a control day and a countermeasure day. The duration of tolerable tilt was increased by a median time of 3 min 48 s with countermeasure in comparison to the control (P < 0.05), and completion of the tilt test increased from 42 to 67% with the countermeasure. During the tilt, mean arterial pressure was greater (108.0 ± 4.1 versus 100.4 ± 2.4 mmHg; P < 0.05) with the countermeasure in comparison to the control. These data suggest that the Wingate syncope test produces a high incidence of presyncope, which is sensitive to countermeasures such as inspiratory impedance.

Characterization of presbyequilibrium among institutionalized elderly persons

OBJECTIVE

The aim was to characterize dizziness, vertigo, poor maintenance of posture, and sudden instabilities (called presbyequilibrium) among institutionalized elderly to model and identify possible treatable causes.

METHODS

A questionnaire based study focusing on symptoms among 72 elderly persons from a single residential facility and followed them for 3 years.

RESULTS

Dizziness, vertigo, poor maintenance of posture, and black-outs were reported by 68% of the 72 elderly and make them at risk for falls, and reduced quality of life. The most common complaint was postural instability, with a tendency to fall. "Spinning" vertigo and "floating" sensation had a strong inter-correlation and correlated with habitual falls. The various dizziness symptoms often occurred in combinations. Attacks of self-experienced syncope never occurred alone but always in combination with "spinning vertigo" or "tendency to fall". In factorial analysis, presbyequilibrium could be divided into six categories. Two of these categories correlated with falls.

CONCLUSIONS

Among elderly, presbyequilibrium is commonly characterized by a combination of phenomena involving perceptual, orientation, postural, and autonomic manifestations. It is often difficult to obtain an accurate history from the elderly and the presence of vestibular symptoms is frequently overlooked. Taking a careful history and utilizing the classification of symptoms that emerged from the factorial analysis may give a deeper understanding of the etiology of presbyequilibrium, thereby facilitating appropriate rehabilitation.

Practical management: a systematic approach to the evaluation of exercise-related syncope in athletes

Syncope and presyncope are relatively common presentations among athletes. The distinction between post-exercise and during-exercise syncope is critically important. While the great majority of these episodes occur just after exercise and are benign, syncope can be an indication of serious underlying cardiovascular disease if it occurs during exercise. Syncope presents a challenging differential diagnosis, as well as a daunting array of diagnostic tests and advanced imaging strategies. Sequencing a proper evaluation, and deciding who requires consultation and restriction, can be difficult for the medical provider. We present a systematic approach that assists the sports physician in arriving at a diagnosis and organizing an initial management strategy.

The challenge of diagnosing arrhythmogenic right ventricular cardiomyopathy in the young

We report two cases of arrhythmogenic right ventricular cardiomyopathy (ARVC) in the pediatric age group. In both cases, the diagnosis was considered and pursued but would not be made utilizing Task Force Criteria. The diagnosis was made based on the morphology of a single beat during exercise testing. We illustrate the difficulty of diagnosing ARVC in the young even with a heightened index of suspicion.

Relation of clinical presentation of syncope to the age of patients

The aim of the study was to evaluate the effect of patient age on the clinical presentation of syncope and to establish the diagnostic value of clinical history in older patients. A total of 485 consecutive patients with unexplained syncope referred to secondary and tertiary hospitals were divided into 2 predefined age groups: 224 patients <65 years and 261 patients > or =65 years. The diagnostic criteria for the cause of syncope were developed before the beginning of the study. The clinical features of syncope were analyzed using a standard 46-item form. A cardiac cause of syncope was established in 27 younger (12%) and 89 older (34%) patients. A neurally mediated cause was established in 154 younger (68%) and 142 older (54%) patients. In patients > or =65 years, the clinical features of cardiac and neurally mediated syncope were very similar. The diagnosis of the cause of syncope was possible on the basis of the history alone in 26% younger and 5% older patients (p <0.0001). Myoclonic movements, effort syncope, and supine position during loss of consciousness were the most specific (97%, 99%, and 99%, respectively) diagnostic criteria for a cardiac cause of syncope in older patients, but, all together, they accounted for only 14% of patients. In conclusion, compared with younger patients, the medical history has a limited value in the diagnosis of the cause of syncope in older patients. The specificity of some features is high but these can be observed in only a minority of patients.

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.

Exertional dizziness and autonomic dysregulation

OBJECTIVES

To define the clinical characteristics and treatment of dizziness induced by physical exertion and to investigate autonomic nervous system function in exertional dizziness.

STUDY DESIGN

Retrospective case series from a review of 1400 patients evaluated for dizziness at a neurotology referral center, identifying those with predominantly exertional symptoms.

METHODS

Records of patients with exertional dizziness were screened to eliminate those with known vestibular deficits, cardiopulmonary illnesses, and psychiatric disorders. The clinical characteristics, evaluation results, and treatment of nine patients with purely exertional dizziness were described.

RESULTS

The cohort included 4 male and 5 female patients (age range, 13-53 y) with symptoms for 1 to 8 years. Only one patient had a history of autonomic symptoms: phlebotomy-induced syncope in childhood. No patient was taking medications that caused dizziness or orthostasis. All patients experienced "spacey" or "foggy" head sensations without vertigo during exertion. Provocative activities ranged from standing upright for extended periods to running and swimming. On examination, voluntary hyperventilation provoked moderate symptoms in all patients (without nystagmus or anxiety), although no patient had spontaneously occurring, hyperventilation-related complaints. Seven patients underwent autonomic testing. Tilt table tests (n = 5) produced severe symptoms in one patient and mild symptoms in two patients. Sodium lactate infusions (n = 6) provoked marked symptoms in four patients and moderate symptoms in one patient. All were treated for autonomic dysregulation. Seven patients improved substantially and resumed all of their premorbid activities. Two improved slightly.

CONCLUSIONS

In nine patients with exertional dizziness, autonomic challenges were provocative, and medications for autonomic dysregulation were effective. Exertional dizziness may be a clinical manifestation of autonomic nervous system dysregulation.