Definition (Pediatr Rev 2000;21:384; Pediatr Rev 2000;21:201)
• Sudden, often brief loss of consciousness and postural tone 2/2 ↓ cerebral blood flow
• Presyncope is the feeling one is about to pass out
Etiology
• Breath-holding spells: Incidence of 4.6% and primarily 1–5 yr of age, strong FHx
• Provoked by pain, anger, or frustration; normal physical and neuro exam
• Cyanotic type (80%): Peaks at 2 yo and resolves by 5 yo
• Characterized by a prodromal period of crying then forced expiration and apnea
• Involuntary Valsalva → ↑ intrathoracic pressure → ↓ cardiac output → ↓ cerebral blood flow, LOC, and loss of muscle tone
• May be assoc w/ generalized clonic jerks, opisthotonos, and bradycardia
• Pallid type (20%): Preceded by frustration, pain, sudden startle, or minor trauma
• Initial quieting and breath holding → pallor → LOC and loss of muscle tone
• Abnormal slowing of HR w/ ocular compression seen in >50%
• Ocular compression test w/ at least 3 sec of asystole, followed by pallid syncope, and no epileptiform discharges on EEG confirms dx
• Neurocardiogenic (vasovagal): ∼75% syncope in kids. 2/2 autonomic dysfxn; often +FHx
• Usually in adolescents after prolonged standing in a crowded, warm environment
• Characteristically preceded by nausea, diaphoresis, light-headedness, or yawning
• Cardiac syncope
• Arrhythmogenic: Prolonged QT, WPW, heart block, sick sinus syndrome, SVT
• Recent study of QTc in children presenting to ED; 1/3 w/ QTc ≥440 ms (borderline prolonged); of these 31% w/ f/u and 62.5% w/ significant normalization of QTc in follow-up (Pediatrics 2011;128: e1395)
• Structural: HOCM, severe aortic/pulmonic stenosis, pHTN, anom L coronary
• POTS (postural orthostatic tachycardia syndrome)
• Myxomas
• Neuropsychiatric
• Seizures/drop attacks
• Hyperventilation syndrome/panic attacks
• Hypoglycemia: Gradual onset w/ weakness, hunger, sweating, agitation, confusion
• Migraines assoc w/ vertebrobasilar vascular spasm: HA persists after awakening
• Benign paroxysmal vertigo: Sudden falling attacks w/ dizziness in pts <6 yo
• Cough syncope: Most common in children w/ asthma
• Recovery w/i seconds, and consciousness restored w/i minutes
Clinical Manifestations
• Hx most important in selecting dx studies and guiding Rx
• Should include the time of day, time of last meal, and details of preceding activities
• Syncope at rest/recumbent suggests sz or arrhythmias
• Syncope w/ exercise suggests HOCM
• Syncope while standing suggests vasovagal
• Syncope w/o warning suggests primary cardiac
• Medication Hx including prescribed, OTC, and illicit drugs
• FHx: Sudden unexplained death, deafness, arrhythmias, congenital heart disease, sz, metabolic diseases, or MI at young age
Physical Exam
• Cardiac exam: Pulse, BP, orthostatics, murmurs, clicks; detailed neuro exam
Diagnostic Studies: Guided by History and Physical Exam
• Measurement of serum glucose & lytes rarely of value unless an acute episode
• EKG: Assess rhythm, conduction, premature beats, delta waves, chamber enlargement, PR, QRS, and QTc; further testing w/ exercise tests or 24-hr Holter if needed
• Toxicology screen
• Echocardiography w/ Doppler studies
• Tilt-table testing for positional syncope
• EEG: In pt w/ prolonged LOC, suspected sz; postictal, drowsiness or confusion
• Cardiology c/s indicated for pathologic heart murmur, CP preceding syncope, arrhythmia, ↑QTc, Q waves, RV strain (suggestive of pHTN), or LVH on EKG, or w/ FHx of cardiomyopathy or sudden death
Treatment
• Breath-holding spells: Reassurance and explanation of pathophysiology most important
• Iron therapy has been shown to decrease incidence in cyanotic type
• Consider anticholinergics in pallid type if they become severe or frequent
• Neurocardiogenic: (H&P negative for other causes and EKG nml; trial of fluid therapy w/ 1 8 oz glass liquid q2–4h and 2 8 oz glasses prior to athletic participation. 90% will respond w/o need for further referral. Non-responders referred to Cardiology, may need PO salt suppl +/− fludrocortisone (Pediatr Rev 2003;24:269)
• Cardiac: Include drug therapy, radiofrequency ablation, or pacemaker placement
• Pts w/ long QT should not receive macrolides or cisapride
• Seizures: Appropriate anticonvulsants