Syncope in Children and Adolescents: What Are the Peculiar Features?

Transcription

1 Syncope in Children and Adolescents: What Are the Peculiar Features? W. WIELING 1,N.VAN DIJK 1, K.S. GANZEBOOM 1,J.P.SAUL 2 Epidemiology Syncope can be defined as a temporary loss of consciousness and postural tone secondary to lack of adequate cerebral blood perfusion. The incidence of syncope coming to medical attention is increased in two age groups, the old and the young (Fig. 1). An incidence peak occurs around the age of 15 years, with the incidence in females being more than twice that in males [1, 2]. A lower peak occurs in older infants and toddlers, most commonly referred to as breath-holding spells [3]. The incidence of syncope in young subjects coming to medical attention varies between approximately 0.5 and 3 cases per 1000 ( %) [2]. Syncopal events which do not reach medical attention occur much more frequently. In a survey of students averaging 20 years of age, 20% of male and 50% of female students report having experienced at least one syncopal episode [4]. By comparison, the prevalence of seizures in a similar age group is about 5 per 1000 (0.5%) [5]. Cardiac syncope is even less common. The most common cause of syncope in young subjects is reflex syncope and in particular a vasovagal faint [2 4], which is diagnosed in about 80% of the paediatric patients presenting with syncope [6]. Clinical Characteristics of Reflex Syncope The term reflex syncope is used to label a heterogeneous group of disorders characterised by episodic vasodilation and/or bradycardia resulting in a transient 1 Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands; 2 Medical University of South Carolina, Charlston, SC, USA

2 634 W. Wieling et al. Fig. 1. Frequency of fainting as a reason for encounter in general practice in the Netherlands.Data obtained from the general practitioners transition project in an analysis of patient-years. Arrow indicates that a small peak occurs between 6 and 18 months of age (breath-holding spells) failure of blood pressure (BP) control [7]. The circumstances surrounding reflex syncopal events often include a change in posture, but may be associated with a wide variety of common situations (Table 1) and physical factors. The more common forms of reflex syncope seen in young subjects are described below [1]. Table 1. Typical reflex syncope triggers Prolonged standing, especially in combination with warm temperature, confined spaces, or crowding ( church syncope ) Emotional circumstances, pain (e.g. venipuncture, sight of blood) Fasting, lack of sleep, fatigue, menstruation, illness with fever Micturition Directly after intense exercise Hyperventilation and straining (self-induced syncope) Stretching, coughing Standing quickly, arising from squat Rapid weight loss Certain medications, alcohol, and illegal drugs (must be distinguished from intoxication)

3 Syncope in Children and Adolescents: What Are the Peculiar Features? 635 Vasovagal Syncope A combination of peripheral arterial and venous vasodilation followed closely by relative bradycardia is the most common physiological scenario observed during syncope in young subjects [7]. Two clinical scenarios in particular are known to provoke vasovagal faints in the young. First are situations that increase pooling of venous blood, such as standing motionless. The second are situations of intense emotion or pain. The clinical presentation of vasovagal syncope varies widely both within and among young patients. They often, but not always, experience prodromal symptoms (Table 2). Episodes may occur without an identifiable trigger, even in patients who are sitting or going about normal daily exercise. Events that occur in these patients while supine in the absence of an emotional stimulus are unlikely to be vasovagal [1]. Table 2.Typical premonitory symptoms of reflex syncope Lightheadedness, dizziness Palpitations Weakness Dimming or blurred vision Nausea, epigastric distress Feeling warm or cold Facial pallor Sweating, dilated pupils Initial Orthostatic Hypotension (Pre)syncope upon standing is observed much more commonly in the young than in adults. Almost all teenagers and adolescents are familiar with feelings of lightheadedness within a few seconds of standing up quickly, which typically resolves spontaneously within 30 s [8]. The transient fall in pressure is caused by vasodilatation in active muscles during standing up, and is not seen upon a passive head-up tilt (Fig. 2). Patients with severe complaints tend to be tall with an asthenic habitus and poorly developed musculature. The mechanism underlying the excessive fall in pressure in these patients remains to be established.

4 636 W. Wieling et al. Fig. 2. Changes in HR and BP in a patient with a history of 10 years of almost daily nearsyncope and occasional syncope upon standing up. Note the marked initial fall in finger BP with lightheadedness on standing and right panel after head-up tilt, but not with passive head-up tilt Postural Orthostatic Tachycardia Syndrome Postural orthostatic tachycardia syndrome (POTS) is defined by symptoms of cerebral and retinal hypoperfusion and an excessive increase in heart rate (HR) in the upright posture with a low normal arterial BP [9]. Reduced cerebral blood perfusion has been documented. In the average adolescent, an increase in HR of more than 35 bpm or a rise to more than 120 bpm after 2 min of standing can be considered excessive [10]. POTS is more common in females, with a ratio of about 4:1. Actual loss of consciousness occurs in a minority of the subjects. The prevalence of POTS in the general population is probably low. Fainting Larks Hyperventilation decreases CO 2, causing cerebral vasoconstriction and presyncope. Straining impedes venous return and also decreases cerebral bloodflow. These adjunctive influences, in combination with orthostatic stress, have been applied by young subjects for self-induced fainting as entertain-

5 Syncope in Children and Adolescents: What Are the Peculiar Features? 637 ment or for avoiding an undesirable task, such as a school examination ( fainting lark ) [1]. Autonomic Failure Primary global autonomic neuropathy as a cause of syncope is extremely rare in young subjects. It has been reported in association with a variety of syndromes [11] and may also occur in the setting of chronic diseases, or in patients using vasoactive medications. Breath-Holding Spells Syncope may occur in toddlers during crying [2, 3, 7]. The spells have been described in two varieties: pallid, which seems to be the result of sudden transient asystole, typically after a short cry, and cyanotic after a more prolonged cry, which mechanism most likely is similar to the fainting lark, as the hyperventilation of crying is combined with the straining of a prolonged silent cry. The onset is typically between 6 months and 2 years of age, and the spells are generally self-resolving by the age of 3 4 years. Though frightening, these spells have not been associated with serious outcomes such as sudden infant death. Associated Syndromes Psychogenic (Pseudo-syncope) A conversion reaction is a rare cause of transient loss of consciousness, but may occur in adolescents, especially females. The diagnosis should be considered when the number of events is high (up to several times a day) and there is no associated physical injury. The duration of the unconsciousness is often prolonged (10 30 min) despite a supine posture. During an episode, the eyes may be tightly closed with a lid flutter, while during true syncope or epilepsy the eyes are often open and deviated. An unusual posture may be assumed. Passive lifting and dropping of an extremity rarely demonstrates limpness or unawareness of pain [12]. When BP is monitored, it is normal or elevated. Typically, patients use the events to (un)consciously avoid an unpleasant emotional situation. Illicit substance abuse, in particular alcohol and cocaine, are also associated with unexplained episodes of syncope. Migraine When related to the basilar artery, migraines can be a cause of syncope [12]. Although specific cerebral flow deficits have not been documented, prodromal symptoms can suggest brainstem or cerebellar ischaemia. Attacks may

6 638 W. Wieling et al. start with bilateral visual symptoms, dysarthria, vertigo, diplopia, nystagmus, and/or ataxia, may progress to syncope, and may be followed by a more typical migraine headache (not always present). Arterial pressure is typically normal or mildly elevated. A (family) history of migraines is common both in patients with syncope and in those with basilar migraine. Diagnostic Evaluation Basic Assessment Reflex syncopal disorders have an excellent prognosis, but may have a dramatic impact on quality of life. Diagnosing these disorders, therefore, is of great importance. A detailed patient and family history is the most crucial part of the initial work-up. In young patients without known heart disease, a typical history (Tables 1-3) combined with a normal physical examination and ECG can be used to diagnose reflex syncope and to determine whether the episode might be due to a non-syncopal condition or has a potentially malignant aetiology. Physical exam should focus on the heart and BP. HR and BP should be assessed with the patient in supine position and again after 3 minutes standing. Extended Assessment History and physical examination should be used to guide the subsequent diagnostic work-up. Otherwise, most tests are unlikely to produce diagnostic results [13]. Ambulatory (loop) ECG recorders should be used in patients with palpitations associated with syncope. Echocardiography should be obtained when a heart murmur is present. When syncope occurs during physical exertion, echocardiography and an exercise test should be performed. Syncope occurring in the cool-down phase after exercise is likely to be neurally mediated, but should also be treated with suspicion. Electroencephalography may be indicated for patients showing prolonged loss of consciousness, seizure activity, or a significant post-ictal phase of lethargy and confusion. Electrophysiological study has a minor role in paediatric patients with syncope, but may be warranted if there is a high suspicion of a tachyarrhythmia. Tilt Testing In patients with recurrent atypical vasovagal or unexplained syncope, tilt table testing can be helpful. Drawbacks of head-up tilt testing are the high false positive and false negative rates. Tilt testing is therefore not the most

7 Syncope in Children and Adolescents: What Are the Peculiar Features? 639 appropriate tool for diagnosing patients with vasovagal syncope, but may be reassuring and instructive to the patient. In patients with conversion reactions, loss of consciousness may occur with no significant decreases in HR, BP, or cerebral blood flow. Distinguishing Syncope from Epilepsy Myoclonic jerks mimicking a seizure may occur during syncope [14]. Typically, prolonged asystole of about 10 s is needed in adults before myoclonic jerks occur. In young persons the anoxic threshold is reported to be lower, and it is lowest in early childhood. Clinical features by which seizure may be distinguished from syncope are summarised in Table 3. Table 3. Features distinguishing syncope from seizures Syncope Jerks begin after falling Typically pale LOC usually < 1 2 min Incontinence less common No tongue biting Post-syncopal confusion typically mild or absent, but prolonged fatigue is common Difficult in standing until recovery is complete Seizure Jerks begin while standing May be cyanotic LOC often > 5 min Incontinence more common Tongue biting in about 25% of cases Post-ictal confusion universal and often prolonged Standing often possible early in recovery Therapy of Reflex Syncope The treatment of reflex syncope is subject of ongoing research [15, 1] Aborting the Acute Episode For acute management of an episode, recognition of pre-syncopal symptoms and applying physical manoeuvres, such as lying down, is usually sufficient to avoid loss of consciousness. More subtle manoeuvres have also demonstrated effectiveness without drawing as much attention to the patient an important point for many adolescents. Leg crossing and muscle tensing are easily taught and highly effective in young patients. Squatting is even more effective, and can be used as an emergency measure when symptoms develop more rapidly.

8 640 W. Wieling et al. Preventing (Pre-)syncopal Events The most important therapy is education and reassurance. Patients should be informed that the risk of sudden death is virtually non-existent, but that physical injury is of some concern. Initial advice should include early recognition of warning symptoms and avoidance of triggering events. Non-Pharmacological. A low-salt diet should be avoided and hydration status optimised. Manoeuvres can be used as a preventive measure. In highly motivated patients with recurrent symptoms, tilt training may reduce recurrences. Patient compliance may, however, limit its use in young subjects. In patients with blood phobia, psychological deconditioning is the first choice of therapy. Pharmacological. Pharmacological therapy should be reserved for patients whose symptoms recur despite non-pharmacological treatment, since undesirable side effects often outweigh any positive effects. β-blockers are commonly prescribed, but have been demonstrated in most trials to be ineffective and frequently have side effects. The mineralocorticoid fludrocortisone is used in combination with high salt and fluid intake to increase blood volume. Mild fluid retention and occasional hypertension are generally the only significant side effects, making it the best tolerated agent in paediatric patients. Of other medications, including β-agonists, the side effects are often intolerable. An unresolved issue is how long prophylactic therapy should be advised. Pacing. Even in the instance of cardioinhibitory syncope with prolonged asystoles, pacemaker therapy should be avoided whenever possible. Conventional therapy is almost always possible and clearly preferable in young patients. Breath-holding spells. Most patients can be dealt with through reassurance and instructions to maintain the child in a supine position rather than upright during a spell. When asystole is documented, the muscarinic blocker glycopyrollate may be helpful. Only in rare cases is pacing required. Acknowledgements This article has been revised from ref. [1], with permission from the BMJ Publishing Group. References 1. Wieling W, Ganzeboom KS, Saul JP (2004) Reflex syncope in children and adolescents. Heart 90: Driscoll DJ, Jacobsen SJ, Porter CJ et al (1997) Syncope in children and adolescents. J Am Coll Cardiol 29:

9 Syncope in Children and Adolescents: What Are the Peculiar Features? Lombroso CT, Lerman P (1967) Breathholding spells (cyanotic and pallid infantile syncope). Pediatrics 39: Ganzeboom KS, Colman N, Reitsma JB et al (2003) Prevalence and triggers of syncope in medical students. Am J Cardiol 91: Wallace H, Shorvon S, Tallis R (1998) Age-specific incidence and prevalence rates of treated epilepsy in an unselected population of and age-specific fertility rates of women with epilepsy. Lancet 352: Massin MM, Bourguignont A, Coremans C et al (2004) Syncope in pediatric patients presenting to an emergency department. J Pediatr 145: Saul JP (1999) Syncope: etiology, management, and when to refer. J S C Med Assoc 95: Dambrink JH, Imholz BP, Karemaker JM et al (1991) Postural dizziness and transient hypotension in two healthy teenagers. Clin Auton Res 1: Low PA, Sandroni P, Singer W et al (2002) Postural tachycardia syndrome an update. Clin Auton Res 12: Wieling W, Karemaker JM (1999) Non-invasive continuous recording of heart rate and blood pressure in the evaluation of neurovascular control. In: Mathias CJ, Bannister R (eds) Autonomic failure: a textbook of clinical disorders of the autonomic nervous system. Oxford University Press, Oxford 11. Axelrod F (2002) Genetic autonomic disorders. Clin Auton Res 12(suppl 1): van Dijk JG (2003) Conditions which mimic syncope. In: Benditt DG, Blanc JJ, Brignole M, Sutton R (eds) The evaluation and treatment of syncope: a handbook for clinical practice. Blackwell/Futura, New York 13. Steinberg LA, Knilans TK (2005) Syncope in children: diagnostic tests have a high cost and low yield. J Pediatr 146: Hoefnagels WA, Padberg GW, Overweg J et al (1991) Transient loss of consciousness: the value of the history for distinguishing seizure from syncope. J Neurol 238: Brignole M, Alboni P, Benditt DG et al (2004) Guidelines on management (diagnosis and treatment) of syncope update Europace 6: