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Author: Anjali Subbaswamy, MD
Syncope/Long QT. Syncope is a loss of consciousness related to decreased cerebralperfusiontotheareasofthebrainnecessaryforconsciousness,which include the brainstem, reticular activating system, and the bilateral cerebral cortices. International incidence was reported in 126 of the 100,000 children monitored, with peak incidence between the ages 15 to 19. Neurocardiogenic syncope and neurologic disorders were the most common etiologies, representing 80% and 9%, respectively. Other causes included psychological, cardiac, respiratory, toxicologic, and metabolic problems (Table 118.1 ). Neurocardiogenic and disease-related syncope were easily identified or suspected by history and physical examination.
Vasovagal syncope may be characterized by the sudden loss of vasomotor tone with resultant systemic hypotension (the vasodepressor response), accompanied by significant bradycardia or asystole, known as the cardioinhibitory response. Most episodes occur when the patient is in the upright position, either during a prolonged period of standing (such as in church, gym/military drill), or during the rapid change from supine or sitting positiontostanding.Theremaybeanemotionalcomponentandsymptomsoften occur in the setting of fatigue, hunger, concurrent illness, and dehydration. The loss of consciousness typically lasts <1 to 2 minutes.
Table 118.1 Causes of Syncope in Children
Autonomic
Vasovagal (fainting): Most common cause in children
Excessive vagal tone: Athletes, adolescents
Reflex:
Situational: Cough, micturition, hair grooming
Pallid breath holding
Orthostatic: Dehydration, blood loss
Cardiac:
Obstructive lesions: Aortic stenosis, hypertrophic obstructive cardiomyopathy, primary pulmonary hypertension
Arrhythmia: Supraventricular tachycardia, ventricular tachycardia, heart block
Hypercyanosis: Tetralogy of Fallot spells
Miscellaneous: Pump dysfunction, myocardial infarction, anomalous coronary anatomy
Noncardiac:
Neurologic: Seizures, migraine
Metabolic: Hypoglycemia
Hyperventilation
Hysterical: Audience, complete absence of trauma
Vascular: Cervical anomalies, vertebrobasilar insufficiency
Syncope during exercise or physical activity should always raise the question of a cardiac abnormality in which the patient is unable to maintain cardiac output to meet increased demands. A family history of syncope, seizures, or unexplained sudden death may also identify those at risk for long QT syndrome (LQTS), hypertrophic obstructive cardiomyopathy, Wolf-Parkinson-White syndrome, or arrhythmogenic right ventricular dysplasia. Those with LQTS may demonstrate prolongation of the QT interval during physical exercise, intense emotion (e.g., fright, anger, or pain), or by a startling noise. The classic example is of a child who jumps into a pool, and the sudden cold triggers the arrhythmia. This can lead to syncope and in some instances drowning. This may be the initial presentation of the arrhythmia. Clues for the suspicion of LQTS include a corrected QT interval (QTc) >0.44 seconds, unexplained syncope, seizures, or cardiac arrest preceded byemotion or exercise or family history of LQTS. It is important to calculate the QTc (beginning of QRS complex to end of the T wave) by hand and not rely on the autocalculation by the electrocardiographic machine. The average age of first syncopal episode in LQTS is 14 years. The 1-year mortality after first syncopal episode is 20%, emphasizing the need for a high index of suspicion. There is a rare, autosomal recessive disorder of congenital sensory deafness associated with a prolonged QT interval called the Jervell and Lange-Nielsen syndrome.
GarsonAJr,DickM2nd,FournierA,etal.ThelongQTsyndromeinchildren.Aninternational
study of 287 patients. Circulation. 1993;87:1866–1872.
Massin MM, Bourguignont A, Coremans C, et al. Syncope in pediatric patients presenting to
an emergency department. J Pediatr. 2004;145(2):223–228.
Prodinger RJ, Reisdorff EJ. Syncope in children. Emerg Med Clin North Am. 1998;16(3):617–
626.
Read excerpts from these other book chapters related to Syncope:
Copyright Details: Avoiding Common Pediatric Errors, Copyright © 2008 Williams & Wilkins.
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More About This Book:
Title: Avoiding Common Pediatric Errors Authors: Anthony D Slonim MD, DrPH; Lisa Marcucci MD Publisher: Lippincott Williams & Wilkins Copyright: 2008 ISBN: 0-7817-7489-6 
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