Pediatric Annals

The Diagnosis and Management of Syncope in Children and Adolescents

David S Braden, MD, FAAP, FACC; Charles H Gaymes, MD, FAAP, FACC

Abstract

From the Greek synkoptein, meaning "to cut short," syncope is defined as the temporary loss of consciousness resulting from a reversible disturbance of cerebral function. Most of the causes for syncope are benign, although some are potentially life-threatening. Syncope is characterized by a sudden onset causing falling, if the patient is not supported, from a disruption of postural tone and transience of rhe attack.1 It is not an uncommon problem, accounting for up to 6% of all hospital admissions.2 Syncope occurs predominantly in teenagers and older adults. It is estimated that up to 20% of all children will experience at least one episode of fainting before the end of adolescence.2 Although syncope in the pediatric and adolescent age groups is usually benign, it often raises the issue of sudden death in patients, parents, and physicians. These concerns may in turn limit the adolescent's educational and employment opportunities. Until recently, most patients have often undergone extensive cardiac and neurologic evaluation without finding a cause.

Syncope is often in the differential diagnosis of a number of other "spells" in children, including seizures, breath-holding spells, and apnea. Taking a careful history of the event will usually allow the physician to sort out the most likely problem. The pediatrician is often the first physician seen and the one most suited to make the diagnosis and to manage most problems. It is important to recognize potentially life-threatening events, especially syncope related to heart disease, and to make appropriate referrals.

Table

Referral to a cardiologist is indicated for patients who have atypical syncope, abnormal cardiovascular physical findings, or an abnormal electrocardiographic result. Those at high risk for cardiogenic syncope should also be referred. An echocardiogram is routinely obtained to rule out obstructive lesions, cardiomyopathies, tumors, and mitral valve prolapse. A 24-hour ambulatory electrocardiogram monitor is usually indicated to rule out occult dysrhythmias. If there is a suggestion of dysrhythmia on electrocardiogram or Holtet or by history, a loop event recorder is obtained. Occasionally, an electrophysiologic study (EPS) is necessary, especially in competitive athletes with exercise-related episodes. In any patients with exercise-related episodes, an exercise stress test is mandatory to look for ST-T changes associated with coronary insufficiency and to look for catecholaminesensitive dysrhythmias. Coronary angiography may also be needed if any doubt remains about the coronary arteries, especially in competitive athletes.

For patients with recurrent syncope, competitive athletes, and patients in whom the distinctions between NMS and other conditions is unclear, upright tilt testing is performed.9,10,11 Intravenous access is obtained and the patient's electrocardiographic results and blood pressure are monitored. The test is performed in a quiet room with a variable period of supine rest. Following this, the patient U tilted upright to an angle of 60° to 80°, with slight increases in sensitivity and slight decreases in specificity at higher tilt angles. The time upright varies from 20 to 60 minutes. Normal patients exhibit a slight increase in heart rate and a small but transient fall in blood pressures. A positive test result identifies neuromuscular syncope and is characterized by syncopal or near-syncopal symptoms associated with a vasodepressor, cardioinhibitory, or mixed response.8 A borderline result is one that causes unusually high swings in blood pressure (>15 mm Hg) and heart rate (>15 beats/min), results in only dizziness, and/or fails to induce signs of a vasovagal reaction.

If symptoms cannot be induced, the patient is returned to a supine position and an isoproterenol infusion is begun at 1.0 µm/min and increased until the resting heart rate increases by 20% to 30%. Upright tilting is repeated, and the test is terminated on the induction of syncope or…

From the Greek synkoptein, meaning "to cut short," syncope is defined as the temporary loss of consciousness resulting from a reversible disturbance of cerebral function. Most of the causes for syncope are benign, although some are potentially life-threatening. Syncope is characterized by a sudden onset causing falling, if the patient is not supported, from a disruption of postural tone and transience of rhe attack.1 It is not an uncommon problem, accounting for up to 6% of all hospital admissions.2 Syncope occurs predominantly in teenagers and older adults. It is estimated that up to 20% of all children will experience at least one episode of fainting before the end of adolescence.2 Although syncope in the pediatric and adolescent age groups is usually benign, it often raises the issue of sudden death in patients, parents, and physicians. These concerns may in turn limit the adolescent's educational and employment opportunities. Until recently, most patients have often undergone extensive cardiac and neurologic evaluation without finding a cause.

Syncope is often in the differential diagnosis of a number of other "spells" in children, including seizures, breath-holding spells, and apnea. Taking a careful history of the event will usually allow the physician to sort out the most likely problem. The pediatrician is often the first physician seen and the one most suited to make the diagnosis and to manage most problems. It is important to recognize potentially life-threatening events, especially syncope related to heart disease, and to make appropriate referrals.

Table

TABLE 1Classification of Syncope in Children

TABLE 1

Classification of Syncope in Children

PATHOPHYSIOLOGY

Cardiac output (CO) is determined by the product of the heart rate (HR) and the stroke volume (SV). Blood pressure (BP) is determined by the product of the cardiac output and the total peripheral resistance (TPR). Therefore, blood pressure, which ultimately determines cerebral perfusion, can be represented by the equation: BP = HR × SV × TPR. Alterations in any of these factors can precipitate syncope. Syncope can be caused by a decrease or loss of intrinsic cerebral circulation, a decrease in cardiac output, a decrease in systemic arterial pressure to pressures inadequate to perfuse the brain, or an inadequate supply of energy substrates in the blood supplied to the brain.1

CLASSIFICATION

Syncope can be classified into two groups: neurally mediated vasopressor syncope and cardiovascular syncope from intrinsic disease of the cardiovascular system (Table 1). The most common cause of syncope in the pediatric age group is vasodepressor syncope, or the common faint, also referred to as neurally mediated syncope (NMS) or neurocardiogenic syncope? It accounts for 50% of syncope in children and adolescents. NMS is characterized by a sudden fall in blood pressure associated with dizziness, lightheadedness, or loss of consciousness, and is accompanied by prominent symptoms of autonomic activity, ie, pallor, diaphoresis, nausea, and hyperventilation. NMS is often initiated by environmental stimuli, for example, having blood drawn or even the sight of blood can elicit syncope in some patients. Venous pooling in the lower extremities causes a decrease in ventricular preload with a compensatory increase in heart rate and ventricular contractility. This in turn stimulates unmyelinated C-fiber receptors in the atria, ventricles, and the pulmonary artery. These fibers communicate to the dorsovagal nucleus of the brainstem. The efferent arc of this vasovagal reflex is not completely understood, but it causes at least three different responses: bradycardia, hypotension, or both bradycardia and hypotension. Paradoxical cerebral vasoconstriction, rather than the expected vasodilation in the face of hypotension, may also be part of the efferent response, as may be abnormal subcutaneous microvascular blood flow.4

Simple fainting spells are typically self-limited, with patients on the floor less than 1 minute followed by gradual return of cerebral perfusion and awakening. However, syncope or near-syncope can reoccur if the child sits or stands too soon. NMS is much more common in adolescents than younger children. However, the pallid breath-holding spell in infants can be considered as NMS in that age group. Interestingly, the sight of blood does not evoke breath-holding spells in infants as it so often does in older children and adults. This fact suggests that some learned component precipitates NMS for that cause. Breath-holding spells are discussed elsewhere in this issue of Pediatric Annals.

Fortunately, cardiac syncope occurs much less frequently than NMS. Cardiac syncope does not follow the stimuli typical for NMS. Clinical features that suggest an underlying cardiac problem are listed in Table 2. Cardiac syncope may be primary, resulting from a structural defect that causes obstruction to ventricular outflow, or secondary to a dysrhythmia. Hypercyanotic spells, usually associated with tetralogy of Fallot, can occur with any heart defect with the potential of intracardiac right-to-left shunting (eg, tricuspid atresia, transposition with pulmonic stenosis, or Eisenmenger syndrome). An increase in obstruction to pulmonary blood flow and/or a fall in systemic vascular resistance can precipitate such a spell. Syncope secondary to decreased cardiac output can occur from outflow obstruction on either the right or left side of the heart, coronary anomalies, and abnormalities or intrinsic cardiac muscle disease.

Dysrhythmias more often cause syncope in structurally abnormal hearts, but can occur in hearts that are structurally normal as a result of bradydysrhythmias or tachydysrhythmias. Of particular importance is the prolonged QT syndrome, which may be congenital or acquired (Table 3). Prolonged QT syndrome often presents as syncope on exercise or exertion and can also masquerade as a seizure. It is associated with a particular type of ventricular tachycardia referred to as "torsades de pointes." Although the cause of congenital prolonged QT syndrome is probably multifactorial, the traditional explanation is an imbalance between the influences of the right and left stellate ganglia. Initial treatment is beta-adrenergic-blocking medications. Left stellate ganglianectomy is reserved for cases resistant to pharmacologic management.

Table

TABLE 2Risk Factors That Favor a Diagnosis of Cardiac Syncope

TABLE 2

Risk Factors That Favor a Diagnosis of Cardiac Syncope

Vascular syncope can be either orthostatic or cerebrovascular in etiology. Orthostatic syncope is the result of the failure of normal compensatory and reflex mechanisms. It is similar to vasodepressor syncope but with fewer premonitory symptoms and a longer time course. Neurogenic causes include peripheral neuropathies, spinal cord or ganglia damage, and syringomyelia. Other predisposing factors include prolonged bed rest, prolonged standing, bleeding, dehydration, pregnancy, adrenal insufficiency, and drugs (eg, vasodilators, diuretics, and phenothiazines). Cerebrovascular syncope can be embolic in nature (endocarditis, surgical complications, or prosthetic cardiac valves), secondary to an intracardiac thrombus or tumor, or associated with arm exercise as in the subclavian steal syndrome. Other, less common forms of vascular syncope include vasovagal syncope (secondary to severe vagally mediated bradycardia), carotid sinus syncope, cough syncope, postmicturition syncope, swallowing syncope,5 glossopharyngeal neuralgia, and hair-grooming syncope.6 Table 4 outlines conditions that may mimic syncope and their distinguishing characteristics.

EVALUATION

The goals of evaluating the syncopal child or adolescent are to identify those conditions that are associated with a risk of injury or sudden death, to identify those patients with NMS who might benefit from long-term medical treatment, and to distinguish between syncope and other "spells" of childhood (Table 4). The initial evaluation in the emergency room or practitioner's office is centered around a thorough history and physical examination.8 The patient and family should be questioned about preceding activities and symptoms such as chest pain, palpitations, vertigo, or headaches. If there was loss of consciousness, its progression and duration should be ascertained. Brief clonic activity or incontinence associated with syncope is not uncommon, referred to as a syncopal seizure. A prolonged generalized motor seizure is most likely epilepsy as is repeated, brief episodes of atonia in small children ("drop attacks").The past medical history for congenital heart disease, seizures, or use of prescription drugs is important. When taking the family history, the pediatrician should explore for syncope, deafness, seizures, or premature sudden death.

Table

TABLE 3Causes of Prolonged QT Syndrome

TABLE 3

Causes of Prolonged QT Syndrome

The physical examination must include complete vital signs, including heart rate and blood pressure measurements in both the supine and upright positions. Special attention should be paid to the cardiovascular system, noting murmurs, differential pulses and blood pressure, accentuated pulmonic closure sounds, and mid-systolic clicks.

For patients with an isolated typical fainting spell and a normal examination result, laboratory evaluation may be unnecessary. Patients with histories compatible with seizures or those with abnormal neurologic examination findings should have an electroencephalogram and perhaps a neurologic consultation. For other patients with syncope, the initial laboratory evaluation is usually guided by the results of the history and physical examination, but this usually includes a complete blood count, chemistries, and urinalysis and urine drug screen (in adolescents), and pregnancy tests for girls. An electrocardiogram should be obtained to look for evidence of chamber enlargement, ST'T wave abnormalities, arteriovenous block, bradycardia, ectopic beats, and Wolff-ParkinsonWhite syndrome. The QT interval should be measured in lead II and corrected for heart rate using Bazett's formula: QT corrected = QT measured/square root of the preceding RR interval (normal <0.450).

Table

TABLE 4"Spells" That Mimic Syncope

TABLE 4

"Spells" That Mimic Syncope

Table

TABLE 5Medications for the Treatment of Neurally Mediated Syncope

TABLE 5

Medications for the Treatment of Neurally Mediated Syncope

Referral to a cardiologist is indicated for patients who have atypical syncope, abnormal cardiovascular physical findings, or an abnormal electrocardiographic result. Those at high risk for cardiogenic syncope should also be referred. An echocardiogram is routinely obtained to rule out obstructive lesions, cardiomyopathies, tumors, and mitral valve prolapse. A 24-hour ambulatory electrocardiogram monitor is usually indicated to rule out occult dysrhythmias. If there is a suggestion of dysrhythmia on electrocardiogram or Holtet or by history, a loop event recorder is obtained. Occasionally, an electrophysiologic study (EPS) is necessary, especially in competitive athletes with exercise-related episodes. In any patients with exercise-related episodes, an exercise stress test is mandatory to look for ST-T changes associated with coronary insufficiency and to look for catecholaminesensitive dysrhythmias. Coronary angiography may also be needed if any doubt remains about the coronary arteries, especially in competitive athletes.

For patients with recurrent syncope, competitive athletes, and patients in whom the distinctions between NMS and other conditions is unclear, upright tilt testing is performed.9,10,11 Intravenous access is obtained and the patient's electrocardiographic results and blood pressure are monitored. The test is performed in a quiet room with a variable period of supine rest. Following this, the patient U tilted upright to an angle of 60° to 80°, with slight increases in sensitivity and slight decreases in specificity at higher tilt angles. The time upright varies from 20 to 60 minutes. Normal patients exhibit a slight increase in heart rate and a small but transient fall in blood pressures. A positive test result identifies neuromuscular syncope and is characterized by syncopal or near-syncopal symptoms associated with a vasodepressor, cardioinhibitory, or mixed response.8 A borderline result is one that causes unusually high swings in blood pressure (>15 mm Hg) and heart rate (>15 beats/min), results in only dizziness, and/or fails to induce signs of a vasovagal reaction.

If symptoms cannot be induced, the patient is returned to a supine position and an isoproterenol infusion is begun at 1.0 µm/min and increased until the resting heart rate increases by 20% to 30%. Upright tilting is repeated, and the test is terminated on the induction of syncope or near-syncope, if the heart rate increases to over 150 to 170 beats/min, or if there is intolerance of isoproterenol (headache, nausea, or chest pain). Normal saline infusion followed by upright tilting can also be used to predict patient response to mineralocorticoid and salt therapy. Intravenous or oral beta-adrenergic blockade can be used to predict response to chronic oral beta-adrenergic blockade.13

TREATMENT

Reassurance alone is indicated for the child with an isolated episode of typical vasodepressor syncope and a normal evaluation result. For the child who occasionally passes out under similar circumstances, avoidance therapy may be all that is needed, eg, adequate fluids, rising slowly, avoidance of overheating, or thromboembolic support stockings. For the child with recurrent vasodepressor syncope or near-syncope, pharmacologic prophylaxis may be needed. Table 5 summarizes medications used in the management of pediatric syncope, including doses, proposed mechanisms of action, and potential side effects. Flucocortisone is a mineralocorticoid that, when given at a dose of 0.1 to 0.3 mg daily with salt tablets, augments preload and prevents triggering of the efferent limb of the syncopal response.7,8 Beta-adrenergicblocking agents such as atenolol or long-acting propanolol decrease adrenergic stimulation.14 Pseudoephrine has also been found to be successful by causing venoconstriction and augmenting blood pressure. Other medications used occasionally include scopolamine patches, disopyramide,15 theophylline, and verapamil. More recently, sertraline has been shown to be successful in decreasing the frequency of syncope.16 If the initial agent is unsuccessful, a second agent may be added. Patients who respond are continued on medications for 9 to 12 months. On cessation of medication, many patients remain asymptomatic or minimally symptomatic. Medication can be continued for a longer period with minimal, if any, risk.

The prognosis is related to the underlying cause of the syncope, but is generally very good, especially in those with NMS. Most children will undergo a decrease in frequency and/or severity of episodes with maturity.

REFERENCES

1. O'Laughlin MP, McNamara DG. Syncope. In: Carton A, Bricker JX McNamara DG, eds. TV Science and Practice of Pediatric Cardiology. Philadelphia, Pa: Lea and Febiger, 1990:1229-124«.

2. Manolis AS, Evaluation of patients with syncope: focus of age-relared differences. American College of Cardiology Current Journal Review. 1994:3:13-18.

3. Koeinski D]i Wolfe DA, Grubb BP. Neurocardiogenic syncope: a review of pathophysiology, diagnosis and treatment. Cardiovascular Reports & Reviews. 1993;June:22-29.

4. Benditi DG, Chen M, Hansen R, et al. Characterization of subcutaneous microvascular blood flow during tilt table-induced neurally-mediated syncope. J Am Coil Cardiol. 1995;25:70-75.

5. Woody RC. Keil EA. Swallowing syncope in a child. Pediatrics. 1986;78:507-509.

6. Lewis DW, Frank LM. Hair-grooming syncope seizures. Pediatrics. 1993;91:836-837.

7. Krongrad E- Syncope and sudden death. In: Emmanoilides CC, Riemenschneider TA, Allen HD. Gutgesell HP, eds. Heart Disease m infants, Children and Adolescents. Baltimore, Md: Williams & Wilkins; 1995:1604-1619.

8. Balaji S, Gillette PC. Evaluation and management of syncope in children. American College cf Cardiology Current Journal Review. 1994;3:45-47.

9. Benditi DG, Ferguson DW, Grubb BP, et aL Tilt cable testing for assessing syncope. J Am Coll Cardiol. 1996;286:263-275.

10. Thilenius OG, Quiñones JA, Husayi TS, Novale J. Tilt test for diagnosis of unexplained syncope in pediatric patients. Pediatrics. 1991;87:334-338.

11. Strieper MJ, AuId DO, Hube JE, Campbell RM. Evaluation of recurrent pediatric syncope: role of tilt table testing. Pediatrics. 1994;93:660-662.

12. Ross BA, Hughes S, Anderson E, Gi lette PC. Abnormal responses to orthostatic testing in children and adolescents with recurrent unexplained syncope. Am Heart J. 1991;122:748-754.

14. Strieper MJ. Campbell RM. Efficacy of alpha-adrenergic agonist therapy for prevention of pediatric neurocaidiogenic syncope. J Am Coll Cardiol. 1993;22:497-597.

15. Morillo CA, Leitch JW, Yee R, et al. A placebo-controlled trial of intravenous and oral disopyromide for prevention of neuraily mediated syncope induced by head-up tilt. JAmCoU Cardiol. 1993;22:1843-1 848.

16. Grubb BP. Samoil D, Kosinski D. Use of sertaline hydrochloride in the treatment of refractory neurocardiogenic syncope and adolescents. J Am CoC Cardiol. 1994:24:490-494.

TABLE 1

Classification of Syncope in Children

TABLE 2

Risk Factors That Favor a Diagnosis of Cardiac Syncope

TABLE 3

Causes of Prolonged QT Syndrome

TABLE 4

"Spells" That Mimic Syncope

TABLE 5

Medications for the Treatment of Neurally Mediated Syncope

10.3928/0090-4481-19970701-08

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