DESCRIPTION

• Syncope is defined as a sudden transient loss of consciousness and postural tone with recovery of sensory perception shortly thereafter (<1 min).
• Associated physical trauma to the affected patient as a result of the episode is common.
• Consciousness usually returns with assumption of the supine position.
• Episode reflects a transient decrease in cerebral perfusion pressure.
• Rarely life-threatening in children and adolescents
• System(s) affected: Cardiovascular, Neurologic, Musculoskeletal
• Synonym(s): For neurocardiogenic syncope, vasovagal, common faint, neurally mediated, and benign syncope

EPIDEMIOLOGY

• Represents 3% of emergency room visits and 6% of hospitalizations for adults in the U.S.
• Far less frequent in childhood
• Predominant age: Uncommon in children; increasing frequency through adolescence
• Predominant sex: Male = Female

Incidence

• ~20% of children will have a syncopal episode by age 15.
• Larger percentage will have presyncopal sensations.

Prevalence

Not well described in children

RISK FACTORS

• For neurocardiogenic syncope: Prolonged recumbency, physical exhaustion, and pregnancy
• Breath-holding spells in infancy are usually neurocardiogenic in nature.
• For other forms of syncope: Presence of Wolff-Parkinson-White (WPW) syndrome on resting EKG, arrhythmogenic RV dysplasia (ARVD), prolongation of the QT interval on EKG or family history of such, family history of catecholaminergic polymorphic ventricular tachycardia (CPVT), presence of massive ventricular hypertrophy or family history of sudden death in hypertrophic cardiomyopathy (HCM), or serious electrolyte abnormalities

Pregnancy Considerations

Represents a risk factor for neurocardiogenic syncope in adults

Genetics

Variable depending on etiology

GENERAL PREVENTION

For patients with neurocardiogenic syncope, recognition of signs and symptoms preceding a syncopal episode will often allow prevention of such episodes.

PATHOPHYSIOLOGY

Common pathway for all forms of neurocardiogenic syncope is stimulation of the medullary vasodepressor region via the Bezold-Jarisch reflex.

ETIOLOGY

• Most common etiology is neurocardiogenic (23–93% of all childhood syncope)
• Major forms of neurocardiogenic form include vasodepressor, cardioinhibitory, and mixed response.
• Other potential etiologies include bradycardias (sinus bradycardia or atrioventricular block), serious ventricular arrhythmias (eg, long QT syndrome, CPVT, ARVD), supraventricular arrhythmias, or congenital lesions associated with reduced antegrade flow such as aortic stenosis, cardiomyopathy, coronary arterial anomalies, severe pulmonary stenosis, and cardiac tumors.

Outline

• Description
• Epidemiology
  • Incidence
  • Prevalence
• Risk Factors
  • Pregnancy Considerations
  • Genetics
• General Prevention
• Pathophysiology
• Etiology

Most common signs and symptoms:

• Light-headedness or visual changes are often noted prior to loss of consciousness (neurocardiogenic).
• When neurocardiogenic in etiology, consciousness usually returns rapidly with assumption of supine position.
• When syncope is due to arrhythmogenic mechanism (eg, long QT syndrome (LQTS), supraventricular tachycardia, and ventricular arrhythmias), often preceded by palpitations or rapid or irregular heart beat; length of syncopal period may be longer than neurocardiogenic.
• For patients with syncope due to arrhythmia, EKG/Holter monitoring may offer clues to etiology such as presence of WPW, ventricular or atrial ectopy, or prolongation of the QT interval.

History

• Neurocardiogenic (vasovagal, neurally mediated, common faint)
• Commonly seen on hot/humid day, on rapidly arising from supine or seated position, in setting of poor nutrition or hydration
• Standing upright for long periods with venous pooling in lower extremities
• History of light-headedness with arising from supine position
• Positive family history of neurocardiogenic syncope often present
• Syncope with exercise is atypical for neurocardiogenic syncope and demands further testing beyond physical exam and history.

Physical Exam

• For patients with neurocardiogenic syncope, presence of orthostatic changes should be assessed, with this exception: Physical exam is often not useful in diagnosis.
• Patients with congenital heart defects can have multiple findings on auscultation (see topics on specific heart defects).

DIAGNOSTIC TESTS & INTERPRETATION

• EKG:
  • Atrial and ventricular ectopy may be noted.
  • Presence of ventricular preexcitation (eg, WPW) should be assessed.
  • Atrioventricular conduction should be reviewed (PR interval).
  • Assessment of precordial voltages and ST-T wave changes in assessing for hypertrophic cardiomyopathy should be made (may be more sensitive than even ECG for this diagnosis).
  • QTc interval should be measured in all cases.
  • 24-hr ambulatory Holter should be screened for ectopy or intermittent preexcitation.
  • Home event recording can be useful to detect infrequent arrhythmic events.
• Echo:
  • Should be considered in many syncopal children, particularly with a history suggesting a cardiac etiology, an abnormal physical exam, family history of congenital heart disease (eg, HCM, aortic stenosis) or abnormal EKG.
• Head-up tilt-table test:
  • Rarely performed in cases where history and etiology are not clear. Test can be repeated with isoprenaline infusion, although specificity decreases with this addition.
• Electrophysiologic study:
  • Performed in all patients with syncope and WPW to assess risk characteristics of accessory pathway; otherwise, performed when the etiology is unclear and arrhythmia is suspected either by history or common association (eg, tetralogy of Fallot)
• Exercise stress study:
  • Should be performed in all patients with exercise-induced syncope, as well as in patients with activity-related arrhythmias; often used to assess ventricular ectopy response to high-catechol state in patients with ventricular arrhythmias

Lab

• CBC and electrolytes (including magnesium, calcium, and glucose); blood and urine for toxicology in cases of potential ingestion or illicit drug use
• Genetic testing is successful in identifying ~75% of patients with LQTS; all genetic mutations have not, however, been identified thus far. Genetic testing for CPVT, HCM, and ARVD is also available all patients with these conditions will not be identified.

Imaging

Echo:

• Used primarily to rule out congenital heart disease, cardiomyopathies and pulmonary HTN; also useful to assess ventricular function

Diagnostic Procedures/Surgery

• Cardiac catheterization:
  • May be necessary to diagnose congenital heart disease
  • RV angiography may help in diagnosis of arrhythmogenic RV dysplasia (although not very sensitive); biopsy also may be useful to make this diagnosis.
• Cardiac MRI:
  • Demonstrated relatively sensitive for diagnosis of ARVD and increasingly helpful in quantitative follow-up of patients with cardiomyopathies.

Pathological Findings

For various congenital heart lesions, refer to specific AHA Cardiac Consult Book topics.

DIFFERENTIAL DIAGNOSIS

Neurologic disorders (eg, seizure disorder, neuropathies, brain arteriovenous malformations), metabolic disorders (eg, diabetic ketoacidosis), anemia or ingestions/illicit drug usage

Outline

• Information
• History
• Physical Exam
• Diagnostic Tests & Interpretation
  • Lab
  • Imaging
  • Diagnostic Procedures/Surgery
  • Pathological Findings
• Differential Diagnosis

• Drug therapy is not usually required for neurocardiogenic syncope. For those cases in which it is required, the following are occasionally prescribed:
  • Mineralocorticoid steroid therapy (eg, fludrocortisone) may be useful in certain patients to increase intravascular volume and reduce episodes.
  • -Blockade may be efficacious in some patients with this disorder.
  • Methylxanthines have been advocated as treatment for patients with more cardioinhibitory symptomatology.
  • Disopyramide has anticholinergic and negative inotropic effects that have been demonstrated efficacious in certain tilt-table studies.
  • -Adrenergic stimulation (eg, midodrine) has been effective in the rare patients that continue to have syncope despite efforts to increase intravascular volume; careful attention to BP is warranted when these agents are used.
• For patients with arrhythmic etiologies, antiarrhythmic therapy (tailored to the individual arrhythmic substrate) is indicated.
• -Blockers; LQTS patients should all be treated with -blockers as this has been definitively demonstrated to reduce syncope and death via arrhythmia in all series in children and adults. Efficacy of -blockade in LQTS type 3 is controversial.
• Contraindications:
  • For patients with WPW, use of digoxin and verapamil is not recommended in patients <1 yr of age and absolutely contraindicated in patients >1 yr of age.
• Precautions:
  • Refer to manufacturer’s profile of each drug.

ADDITIONAL TREATMENT

General Measures

• For neurocardiogenic syncope, care is most often outpatient. For most other forms, hospitalization for evaluation/observation or intervention may be necessary.
• Self-awareness of symptoms prior to fainting (prodrome) is important to prevention of neurocardiogenic episodes:
  • When symptoms are felt, patients should either sit or assume a supine position.
• Adequate hydration is important to prevent episodes:
  • When patients are adequately drinking, the urine is clear (and thus not concentrated).
• When the previously noted measures are carefully followed, they are 95% effective in prevention of further neurocardiogenic syncopal episodes.

SURGERY

• Pacemaker implantation is indicated in cases of bradycardia and may be indicated in rare cases of neurocardiogenic syncope with a predominant cardioinhibitory component.
• Also demonstrated effective in prevention of ventricular arrhythmias in certain forms of LQTS
• Automatic internal cardioverter–defibrillator (AICD) implantation is indicated in patients with documented ventricular arrhythmias unresponsive to or unprotected by medication.
• The role of ICD implantation in children with high-risk diseases, such as hypertrophic cardiomyopathy or LQTS, is still controversial and not fully yet elucidated, but their use in this population is growing with improved ease of implantation.
• Stellate gangliectomy has been demonstrated efficacious in certain forms of LQTS in some series and may be effective therapy for CPVT.
• Surgical treatment of associated congenital lesions may be indicated.

Outline

• Additional Treatment
  • General Measures
• Surgery

FOLLOW-UP RECOMMENDATIONS

• Close regular visits for assessment of symptoms and change in such with therapy is indicated.
• Follow-up for various other conditions causing syncope other than neurocardiogenic are reviewed in individual topics on separate conditions.

Patient Monitoring

Close regular visits for assessment of symptoms and change in such with therapy is indicated.

DIET

For patients with neurocardiogenic syncope, high-salt diets with adequate hydration are indicated.

PATIENT EDUCATION

• Educate patients with neurocardiogenic syncope to appreciate and note the anticipatory feelings of light-headedness that precede syncopal episodes in order to take appropriate actions (supine position, head between knees, etc.) to avoid syncope.
• For other conditions, understanding the importance of compliance with medical regimen is critical.
• Activity:
  • For some patients, moderation of exercise may be indicated.
  • Certain LQTS patients may have episodes of torsade de pointes triggered by high catecholamine level activities, and in these patients activity that is associated with high catecholamine levels should be curtailed.
• Prevention:
  • For patients with neurocardiogenic syncope, recognition of signs and symptoms preceding a syncopal episode will often prevent such episodes.

PROGNOSIS

• For patients with neurocardiogenic syncope, symptoms usually improve as patients age, with fewer episodes in late adolescence and early adulthood. This may represent self-education at avoidance of activities that induce episodes or recognition of syncopal prodrome with subsequent appropriate preventive measures.
• Arrhythmia course is highly variable and is largely related to efficacy of drug or other (eg, catheter ablation, AICD) therapy.
• Incidence of atrial arrhythmias following Fontan or Mustard/Senning palliation for congenital heart disease increases with time from operation. Episodes or recognition of preceding symptom complexes with subsequent appropriate preventive measures.

COMPLICATIONS

• Bodily musculoskeletal injury due to falls is common.
• Brain injury due to hypoperfusion of the brain in the setting of prolonged, severe arrhythmias can occur.

Outline

• Follow-Up Recommendations
  • Patient Monitoring
• Diet
• Patient Education
• Prognosis
• Complications

CODES

ICD9

780.2 Syncope and collapse

SNOMED

271594007 syncope (disorder)

ADDITIONAL READING

• Kanter RJ. In: Gillette, Garson, eds. Syncope in clinical pediatric arrhythmias. Philadelphia: WB Saunders; 1999.
• Priori SG, Schwartz PJ, Napolitano C, et al. Risk stratification in the long-QT syndrome. N Engl J Med. 2003;348:1866–1874.
• Rickers C, Wilke NM, Jerosch-Herold M, et al. Utility of cardiac magnetic resonance imaging in the diagnosis of hypertrophic cardiomyopathy. Circulation. 2005;112:855–861.
• Tester DJ, Ackerman MJ. Cardiomyopathic and channelopathic causes of sudden unexplained death in infants and children. Annu Rev Med. 2009;60:69–84.
• Wiley TM, O’Donoghue S, Platia EV. Neurocardiogenic syncope: Evaluation and management. Cardiovasc Rev Rep. 1993;14:15–25.

Robert H. Pass

Welton M. Gersony