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

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

W. W

IELING¹

, N.

VAN

D

IJK¹

, K.S. G

ANZEBOOM¹

, J. P. S

AUL²

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 (0.05–0.3%) [2].

Syncopal events which do not reach medical attention occur much more fre- quently. 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

1Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands;

2Medical University of South Carolina, Charlston, SC, USA

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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 com- mon forms of reflex syncope seen in young subjects are described below [1].

Fig. 1.Frequency of fainting as a reason for encounter in general practice in the Nether- lands. Data obtained from the general practitioners’ transition project in an analysis of 93 297 patient-years. Arrow indicates that a small peak occurs between 6 and 18 months of age (breath-holding spells)

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)

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Vasovagal Syncope

A combination of peripheral arterial and venous vasodilation followed close- ly by relative bradycardia is the most common physiological scenario observed during syncope in young subjects [7]. Two clinical scenarios in par- ticular are known to provoke vasovagal faints in the young. First are situa- tions 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].

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 feel- ings of lightheadedness within a few seconds of standing up quickly, which typically resolves spontaneously within 30 s [8]. The transient fall in pres- sure 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.

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

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

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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 cere- bral 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 pre-

syncope. Straining impedes venous return and also decreases cerebral blood-

flow. These adjunctive influences, in combination with orthostatic stress,

have been applied by young subjects for self-induced fainting as entertain-

Fig. 2.Changes in HR and BP in a patient with a history of 10 years of almost daily near- syncope 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

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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 pro- longed 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 frighten- ing, these spells have not been associated with serious outcomes such as sud- den 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 con- sidered 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, prodro-

mal symptoms can suggest brainstem or cerebellar ischaemia. Attacks may

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start with bilateral visual symptoms, dysarthria, vertigo, diplopia, nystag- mus, 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 dra- matic 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 per- formed. Syncope occurring in the cool-down phase after exercise is likely to be neurally mediated, but should also b e t reated w ith 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 pae- diatric patients with syncope, but may be warranted if there is a high suspi- cion 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

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appropriate tool for diagnosing patients with vasovagal syncope, but may be reassuring and instructive to the patient. In patients with conversion reac- tions, 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.

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 demon- strated 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.

Table 3.Features distinguishing syncope from seizures

Syncope Seizure

Jerks begin after falling Jerks begin while standing

Typically pale May be cyanotic

LOC usually < 1–2 min LOC often > 5 min

Incontinence less common Incontinence more common

No tongue biting Tongue biting in about 25% of cases

Post-syncopal confusion typically mild Post-ictal confusion universal and or absent, but prolonged fatigue is common often prolonged

Difficult in standing until recovery Standing often possible early in

is complete recovery

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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 recog- nition 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 recur- rences. 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 fludrocor- tisone is used in combination with high salt and fluid intake to increase blood volume. Mild fluid retention and occasional hypertension are general- ly the only significant side effects, making it the best tolerated agent in pae- diatric 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 reassur- ance 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.

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