Table of Contents

 

1. Abstract
2. Case Presentations
3. Introduction
4. Critical Appraisal of the Literature
5. Etiology And Pathophysiology
   1. Pathophysiology Of Neurocardiogenic (Vasovagal) Syncope
6. Differential Diagnosis
   1. Cardiogenic Etiologies Of Syncope
      1. Hypertrophic Cardiomyopathy
      2. Supraventricular Tachycardia
      3. Other Cardiogenic Etiologies
   2. Noncardiac Etiologies Of Syncope That Require Further Evaluation
      1. Pregnancy And Ectopic Pregnancy
      2. Hypoglycemia
      3. Other Noncardiac Etiologies
   3. Noncardiac, Non–Life-Threatening Etiologies Of Syncope
      1. Neurocardiogenic Syncope
      2. Seizure
      3. Breath-Holding Spells
      4. Postural Orthostatic Tachycardia Syndrome
      5. Psychogenic Pseudosyncope
7. Prehospital Care
8. Emergency Department Evaluation
   1. Initial Management
   2. History
9. Diagnostic Studies
   1. Evidence Against Routine Testing
      1. Head-Up Tilt-Table Test
      2. Orthostatic Vital Sign Measurements
      3. Electroencephalogram And Computed Tomography
      4. Cardiac Enzymes
10. Treatment
11. Special Populations
    1. Patients With Known Cardiac Disease
12. Controversies And Cutting Edge
13. Disposition
14. Summary
15. Risk Management Pitfalls In Pediatric Patients With Syncope
16. Time- And Cost-Effective Strategies
17. Case Conclusions
18. Clinical Pathway For The Management Of Pediatric Patients With Syncope
19. Tables and Figures
    1. Table 1. Etiologies Of Syncope
    2. Table 2. Medications That Prolong The QT Interval
    3. Table 3. - Red Flags - And - Green Lights - In Patients With Syncope
    4. Table 4. Management Of Various Etiologies Of Syncope Cardiac & Non Cardiac
    5. Figure 1. Hypertrophic Cardiomyopathy On Electrocardiogram
    6. Figure 2. Long QT Syndrome On Electrocardiogram
    7. Figure 3. Delta Waves On Electrocardiogram Consistent With Wolff-Parkinson-White Syndrome
    8. Figure 4. Atrioventricular Re-Entrant Tachycardia In Wolff-Parkinson-White Syndrome
    9. Figure 5. Types Of Heart Block On Electrocardiogram
    10. Figure 6. Brugada Syndrome Patterns On Electrocardiogram
20. References

Abstract

Syncope is a condition that is often seen in the emergency department. Most syncope is benign, but it can be a symptom of a life-threatening condition. While syncope often requires an extensive workup in adults, in the pediatric population, critical questioning and simple, noninvasive testing is usually sufficient to exclude significant or life-threatening causes. For low-risk patients, resource-intensive workups are rarely diagnostic, and add significant cost to medical care. This issue will highlight critical diseases that cause syncope, identify high-risk “red flags,” and enable the emergency clinician to develop a cost-effective, minimally invasive algorithm for the diagnosis and treatment of pediatric syncope.

Case Presentations

A 10-year-old previously healthy boy presents after “passing out” and experiencing chest pain while playing basketball with friends earlier that evening. The patient reports occasional chest pain with exertion. Today, he also had chest pain while running, collapsed, and had a loss of consciousness for 4 to 5 seconds. He then returned to baseline. He has no prior history of syncope and no recent infections. He denies drug use. On physical examination, there is no evidence of acute distress, and he has normal pulmonary and cardiac examinations. You immediately order an ECG. Do you also need to obtain troponins, D-dimer, or coagulation studies? Does he also need an echocardiogram? You want the patient to see a cardiologist, but does this need to happen in the middle of the night?

A 16-year-old previously healthy adolescent girl presents with multiple episodes of syncope over the last 24 hours. Her preceding symptoms include the sensation that her heart was racing, seeing spots in her visual fields, and feeling short of breath. She had been feeling unwell for 4 days with a dry cough, but no other cold-like symptoms. The first episode of syncope occurred the previous night after getting up from seated position and walking. Her second episode of syncope was this morning, again, after getting up and walking. She had her third episode of syncope today while seated on a couch. This episode was witnessed by friends who state she was unconscious for a few seconds. She denies any pain with these episodes. She currently has no chest pain, but feels short of breath. She has no risk factors for pulmonary embolism and no family history of early cardiac death or clotting disorders. Her last menstrual period was 2 weeks ago. As you order an ECG and a pregnancy test, you think about what else you need to do for this patient.

An 18-year-old previously healthy adolescent girl presents after fainting. She was standing and waiting for the subway when she "felt the room closing in” and the “world going dark.” The next thing she remembers is lying on the ground with people looking down at her. The patient reports recent cold symptoms and decreased appetite. She denies the use of drugs or alcohol. She denies pregnancy. This has happened one other time, several years ago. Now she feels she has returned to her baseline. What diagnostic testing is helpful in the diagnosis of this patient? What further evaluation does she need, if any? How should she be managed? Does she need admission?

Introduction

Syncope is defined as a transient loss of consciousness and postural tone due to an alteration in cerebral perfusion, usually associated with spontaneous recovery. In pediatric patients, syncope is most often a brief episode with complete recovery, without sequelae. These typical episodes, however, must be differentiated from those with rare, life-threatening etiologies. Syncope is most common in teenagers, with the incidence peaking in patients aged between 15 and 19 years. Fifty percent of people report an episode of syncope during adolescence.¹ Syncope accounts for 1% to 3% of emergency department (ED) visits, with an overall incidence in the pediatric population of 0.1% to 0.5%.^2,3 Syncope must be distinguished from all other causes of loss of consciousness, such as seizures, head trauma, and psychiatric causes.

There are many ways to classify syncope, but the simplest is to divide the causes of syncope into 2 groups: cardiac and noncardiac etiologies. While cardiac causes represent the minority of syncope cases, they should not be missed,¹ as they can result in sudden death.⁴ As many as 1% to 5% of syncopal events may be related to underlying cardiac disease.⁵ This issue of Pediatric Emergency Medicine Practice will help emergency clinicians develop a broad differential diagnosis, use a classification scheme to identify the causes of syncope, and determine appropriate evaluation of the patient. Most importantly, this issue will help emergency clinicians identify the red flags for etiologies that must not be missed in the evaluation of pediatric syncope in the ED.

Critical Appraisal Of The Literature

A literature search was performed in PubMed using the terms syncope, fainting, blackout, and vasovagal. The search was limited to articles published since 1960 that involved patients aged 0 to 18 years. The term emergency department was also included in a subsequent search. This search was limited by age, English language, and human subjects. These searches identified several thousand articles that were screened by title, which resulted in approximately 150 articles that were considered for inclusion. The Cochrane Database of Systematic Reviews, Evidence-Based Medicine Reviews: Best Evidence (American College of Physicians), Database of Abstracts of Reviews of Effectiveness (DARE), and the National Guideline Clearinghouse were all queried for articles related to syncope in adults or children. The results of these queries produced more than 130 articles that were reviewed in full.

Risk Management Pitfalls In Pediatric Patients With Syncope

1. “The teenage patient assured me that she couldnot be pregnant, so I did not order an HCG test.”

Ensuring that adolescent patients have a chance to speak with providers without their parents present is an expected part of adolescent medicine and often allows capture of sensitive information. The emergency clinician must verify that teenage girls who report no sexual intercourse are really not pregnant. Results should be provided in a confidential manner based upon individual state law.

2. “It was such a classic story for neurocardiogenic syncope, except for the family history of sudden death, that I did not perform an ECG.”

Cardiac abnormalities can easily be overlooked. Most of the rules regarding limiting extensive testing presume a normal ECG. A family history of sudden death could suggest a genetically inherited cause of cardiac syncope.

3. “I asked if there were any medical problems that run in the family, but the patient didn’t tell me that her sister is deaf.”

Many families do not recognize deafness as a reportable medical problem, so this must be asked specifically. This is also true for sudden unexplained deaths in the family. Patients may not offer this information unless it is explicitly asked.

4. “The coach, parents, and patient all told me he was just overexerted while running. They think he can play in the state championship game tomorrow.”

Don’t be swayed by elite athletes, coaches, or family members minimizing symptoms. The primary goal is to ensure the safety of the patient. If syncope occurred during activity, then the patient should refrain from strenuous activity until cleared by cardiology.

5. “The patient had a history and physical examination consistent with neurocardiogenic syncope without any evidence of injury. The mother was very concerned about a brain tumor, so I obtained a CT scan to reassure her.”

Sometimes the path of least resistance can do more harm than good. Do not unnecessarily irradiate pediatric patients, as this exposes them to radiation that increases their long-term risk of cancer.

6. “I looked at the ECG quickly to check for ischemic changes as I do for my adult patients and was reassured by the ECG.”

Remember ECG analysis in pediatric patients is not primarily to assess for myocardial infarctions, and emergency clinicians must change their point of reference and concentrate on cardiac abnormalities that can cause syncope in children (eg, prolonged QT, Wolff-Parkinson- White syndrome, Brugada syndrome, or myocarditis/pericarditis).

7. “The nurse checked orthostatic vitals. I knew the patient could not be volume depleted, so we discharged her without fluid resuscitation.”

Orthostatic vitals have been shown to be neither sensitive nor specific for volume depletion. Patients who are orthostatic by symptom description should be hydrated and reassessed prior to discharge.

8. “The patient had known congenital cardiac disease, but the episode sounded neurocardiogenic so I sent him home.”

Children with underlying cardiac disease warrant consultation with pediatric cardiology prior to discharge to ensure that the syncope is not related to their underlying condition.

9. “A pediatrician referred this patient with classic syncope to the ED. His ECG was normal, but the primary care physician wanted him admitted for overnight observation.”

Routine admission for a patient who has returned to baseline, has no cardiac risk factors, and has a normal ECG is unnecessary and not cost-effective. To date, there are no data that show that routine admission after a syncopal event alters morbidity or mortality, and admission increases healthcare costs and may expose patients to additional risks.⁸⁴

10. “I know the patient had no cardiac risk factors, but I wanted to be thorough, so I ordered electrolytes, an EEG, an echo, and head-up tilttable testing.”

Extensive testing in low-risk groups rarelyimproves diagnostic yield and results

Tables and Figures

References

Evidence-based medicine requires a critical appraisal of the literature based upon study methodology and number of subjects. Not all references are equally robust. The findings of a large, prospective, randomized, and blinded trial should carry more weight than a case report.

To help the reader judge the strength of each reference, pertinent information about the study, such as the type of study and the number of patients in the study is included in bold type following the references, where available. The most informative references cited in this paper, as determined by the authors, are noted by an asterisk (*) next to the number of the reference.

1. Driscoll DJ, Jacobsen SJ, Porter CJ, et al. Syncope in children and adolescents. J Am Coll Cardiol. 1997;29(5):1039-1045. (Retrospective population-based analysis)
2. * Anderson JB, Czosek RJ, Cnota J, et al. Pediatric syncope: National Hospital Ambulatory Medical Care survey results. J Emerg Med. 2012;43(4):575-583. (Retrospective cohort; 627,489 ED visits)
3. Fischer JW, Cho CS. Pediatric syncope: cases from the emergency department. Emerg Med Clin North Am. 2010;28(3):501-516. (Review article)
4. Liberthson RR. Sudden death from cardiac causes in children and young adults. N Engl J Med. 1996;334(16):1039-1044. (Retrospective cohort)
5. Moodley M. Clinical approach to syncope in children. Semin Pediatr Neurol. 2013;20(1):12-17. (Review article)
6. * Fu Q, Levine BD. Pathophysiology of neurally mediated syncope: role of cardiac output and total peripheral resistance. Auton Neurosci. 2014;184:24-26. (Review article)
7. Mastrangelo M, Mariani R, Ursitti F, et al. Neurocardiogenic syncope and epilepsy in pediatric age: the diagnostic value of electroencephalogram-electrocardiogram holter. Pediatr Emerg Care. 2011;27(1):36-39. (Case reports; 3 case reports)
8. Medow MS, Stewart JM, Sanyal S, et al. Pathophysiology, diagnosis, and treatment of orthostatic hypotension and vasovagal syncope. Cardiol Rev. 2008;16(1):4-20. (Review article)
9. Massin MM, Bourguignont A, Coremans C, et al. Syncope in pediatric patients presenting to an emergency department. J Pediatr. 2004;145(2):223-228. (Prospective cohort; 226 patients)
10. Zhang Q, Du J, Wang C, et al. The diagnostic protocol in children and adolescents with syncope: a multi-centre prospective study. Acta Paediatr. 2009;98(5):879-884. (Prospective cohort; 474 patients)
11. * Steinberg L, Knilans TK. Syncope in children: diagnostic tests have a high cost and low yield. Pediatrics. 2005;146(3):355-358. (Retrospective cohort; 169 patients)
12. Drezner JA, Fudge J, Harmon KG, et al. Warning symptoms and family history in children and young adults with sudden cardiac arrest. J Am Board Fam Med. 2012;25(4):408-415. (Retrospective cohort; 87 families)
13. Maskatia SA. Hypertrophic cardiomyopathy: infants, children, and adolescents. Congenit Heart Dis. 2012;7(1):84-92. (Review article)
14. Maron BJ, Maron MS. Hypertrophic cardiomyopathy. Lancet. 2013;381(9862):242-255. (Review article)
15. Maron BJ, Doerer JJ, Haas TS, et al. Sudden deaths in young competitive athletes: analysis of 1866 deaths in the United States, 1980-2006. Circulation. 2009;119(8):1085-1092. (Retrospective cohort; 1866 patients)
16. Marzuillo P, Benettoni A, Germani C, et al. Acquired long QT syndrome: a focus for the general pediatrician. Pediatr Emerg Care. 2014;30(4):257-261. (Review article)
17. Miller MD, Porter C, Ackerman MJ. Diagnostic accuracy of screening electrocardiograms in long QT syndrome I. Pediatrics. 2001;108(1):8-12. (Prospective cohort; 23 family members)
18. Schwartz PJ, Moss AJ, Vincent GM, et al. Diagnostic criteria for the long QT syndrome. An update. Circulation. 1993;88(2):782-784. (Review article)
19. Reardon M, Malik M. QT interval change with age in an overtly healthy older population. Clin Cardiol. 1996;19(12):949-952. (Prospective cohort; 96 healthy subjects)
20. Vincent GM. The molecular genetics of the long QT syndrome: genes causing fainting and sudden death. Annu Rev Med. 1998;49:263-274. (Review article)
21. Moss AJ, Schwartz PJ, Crampton RS, et al. The long QT syndrome: a prospective international study. Circulation. 1985;71(1):17-21. (Prospective cohort; 196 patients)
22. Moss AJ. Prolonged QT-interval syndromes. JAMA. 1986;256(21):2985-2987. (Review article)
23. Schwartz PJ, Periti M, Malliani A. The long Q-T syndrome. Am Heart J. 1975;89(3):378-390. (Review article)
24. Kulig J, Koplan BA. Cardiology patient page. Wolff-Parkinson-White syndrome and accessory pathways. Circulation. 2010;122(15):e480-e483. (Review article)
25. Cain N, Irving C, Webber S, et al. Natural history of Wolff-Parkinson-White syndrome diagnosed in childhood. Am J Cardiol. 2013;112(7):961-965. (Propective cohort; 446 patients)
26. Fengler BT, Brady WJ, Plautz CU. Atrial fibrillation in the Wolff-Parkinson-White syndrome: ECG recognition and treatment in the ED. Am J Emerg Med. 2007;25(5):576-583. (Case reports, review article)
27. Santinelli V, Radinovic A, Manguso F, et al. The natural history of asymptomatic ventricular pre-excitation a long-term prospective follow-up study of 184 asymptomatic children. J Am Coll Cardiol. 2009;53(3):275-280. (Prospective study; 184 children)
28. Campbell RM, Strieper MJ, Frias PA, et al. Survey of current practice of pediatric electrophysiologists for asymptomatic Wolff-Parkinson-White syndrome. Pediatrics. 2003;111(3):e245-e247. (Survey, retrospective; 66 pediatric electrophysiologists)
29. Comsumer reports. The buzz on energy-drink caffeine. 2012; December 2012. Available at: http://www.consumerreports.org/cro/magazine/2012/12/the-buzz-on-energy-drink-caffeine/index.htm. (Magazine atricle)
30. Gewitz MH, Woolf PK. Textbook of Pediatric Emergency Medicine. In: Fleisher GR, Ludwig, S. eds. 6th ed. Philadelphia: Wolters Kluwer/Lippencott Williams & Wilkins Health; 2010:701-706. (Textbook chapter)
31. Caughey RW, Humphrey JM, Thomas PE. High-degree atrioventricular block in a child with acute myocarditis. Ochsner J. 2014;14(2):244-247. (Case report; 1 patient)
32. Probst V, Denjoy I, Meregalli PG, et al. Clinical aspects and prognosis of Brugada syndrome in children. Circulation. 2007;115(15):2042-2048. (Retrospective cohort; 30 children)
33. Rossenbacker T, Priori SG. The Brugada syndrome. Curr Opin Cardiol. 2007;22(3):163-170. (Review article)
34. Zaidi AN. An unusual case of Brugada syndrome in a 10-year-old child with fevers. Congenit Heart Dis. 2010;5(6):594-598. (Case report; 1 patient)
35. De Marco S, Giannini C, Chiavaroli V, et al. Brugada syndrome unmasked by febrile illness in an asymptomatic child. J Pediatr. 2012;161(4):769-769.e1. (Case report; 1 child)
36. Skinner JR, Chung SK, Nel CA, et al. Brugada syndrome masquerading as febrile seizures. Pediatrics. 2007;119(5):e1206-e1211. (Case report; 1 patient)
37. Hermida JS, Jandaud S, Lemoine JL, et al. Prevalence of drug-induced electrocardiographic pattern of the Brugada syndrome in a healthy population. Am J Cardiol. 2004;94(2):230-233. (Prospective cohort; 1000 patients)
38. Belhassen B, Glick A, Viskin S. Efficacy of quinidine in high-risk patients with Brugada syndrome. Circulation. 2004;110(13):1731-1737. (Prospective cohort; 25 patients)
39. Timm NL, McAneney C, Alpern E, et al. Is pediatric emergency department utilization by pregnant adolescents on the rise? Pediatr Emerg Care. 2012;28(4):307-309. (Retrospective cross-sectional study; 15,190 pregnancy-related ED visits)
40. Yarlagadda S, Poma PA, Green LS, et al. Syncope during pregnancy. Obstet Gynecol. 2010;115(2 Pt 1):377-380. (Review article)
41. Tenore JL. Ectopic pregnancy. Am Fam Physician. 2000;61(4):1080-1088. (Review article)
42. World Health Organization. Antiretroviral Therapy for HIV Infection in Infants and Children: Towards Universal Access: Recommendations for a Public Health Approach: 2010 Revision. Geneva2010. (Consensus guidelines)
43. Lagi A, Cencetti S, Lagi F. Incidence of hypoglycaemia associated with transient loss of consciousness. A retrospective cohort study. Int J Clin Pract. 2014;68(8):1029-1033. (Retrospective cohort; 133,285 patients, 3964 with transient loss of consciousness, 39 with transient hypoglycemia)
44. Lagi A. Syncope and hypoglycemia. Int J of Clin Med. 2011;2:129-132. (Review article)
45. Salins PC, Kuriakose M, Sharma SM, et al. Hypoglycemia as a possible factor in the induction of vasovagal syncope. Oral Surg Oral Med Oral Pathol. 1992;74(5):544-549. (Prospective study; 16 patients)
46. * Goble MM, Benitez C, Baumgardner M, et al. ED management of pediatric syncope: searching for a rationale. Am J Emerg Med. 2008;26(1):66-70. (Retrospective cohort; 140 patients)
47. * Tretter JT, Kavey RE. Distinguishing cardiac syncope from vasovagal syncope in a referral population. J Pediatr. 2013;163(6):1618-1623.e1. (Retrospective cohort; 106 patients)
48. Johnson ER, Etheridge SP, Minich LL, et al. Practice variation and resource use in the evaluation of pediatric vasovagal syncope: are pediatric cardiologists over-testing? Pediatr Cardiol. 2014;35(5):753-758. (Retrospective cohort; 617 patients)
49. Daoud AS, Batieha A, al-Sheyyab M, et al. Effectiveness of iron therapy on breath-holding spells. J Pediatr. 1997;130(4):547-550. (Randomized controlled study; 67 children)
50. Jarjour IT. Postural tachycardia syndrome in children and adolescents. Semin Pediatr Neurol. 2013;20(1):18-26. (Review article)
51. Low PA, Sandroni P, Joyner M, et al. Postural tachycardia syndrome (POTS). J Cardiovasc Electrophysiol. 2009;20(3):352-358. (Review article)
52. Raj V, Rowe AA, Fleisch SB, et al. Psychogenic pseudosyncope: diagnosis and management. Auton Neurosci. 2014;184:66-72. (Review article)
53. Chen L, Zhang Q, Ingrid S, et al. Aetiologic and clinical characteristics of syncope in Chinese children. Acta Paediatr. 2007;96(10):1505-1510. (Retrospective cohort; 154 children)
54. Sayre MR, Berg RA, Cave DM, et al. Hands-only (compression-only) cardiopulmonary resuscitation: a call to action for bystander response to adults who experience out-of-hospital sudden cardiac arrest: a science advisory for the public from the American Heart Association Emergency Cardiovascular Care Committee. Circulation. 2008;117(16):2162-2167. (Consensus guidelines)
55. Kern KB. Cardiopulmonary resuscitation without ventilation. Crit Care Med. 2000;28(11 Suppl):N186-N189. (Review article)
56. Hupfl M, Selig HF, Nagele P. Chest-compression-only versus standard cardiopulmonary resuscitation: a meta-analysis. Lancet. 2010;376(9752):1552-1557. (Meta-analysis; 3 randomized trials)
57. Bobrow BJ, Spaite DW, Berg RA, et al. Chest compression-only CPR by lay rescuers and survival from out-of-hospital cardiac arrest. JAMA. 2010;304(13):1447-1454. (Prospective observational cohort study; 5272 patients)
58. Kitamura T, Iwami T, Kawamura T, et al. Bystander-initiated rescue breathing for out-of-hospital cardiac arrests of noncardiac origin. Circulation. 2010;122(3):293-299. (Prospective study; 43,246 bystander-witnessed out-of-hospital cardiac arrests)
59. Kitamura T, Iwami T, Kawamura T, et al. Conventional and chest-compression-only cardiopulmonary resuscitation by bystanders for children who have out-of-hospital cardiac arrests: a prospective, nationwide, population-based cohort study. Lancet. 2010;375(9723):1347-1354. (Prospective cohort; 5170 children)
60. Drezner JA, Rao AL, Heistand J, et al. Effectiveness of emergency response planning for sudden cardiac arrest in United States high schools with automated external defibrillators. Circulation. 2009;120(6):518-525. (Retrospective cohort; 1710 schools, 36 sudden cardiac arrest victims)
61. Kovach J, Berger S. Automated external defibrillators and secondary prevention of sudden cardiac death among children and adolescents. Pediatr Cardiol. 2012;33(3):402-406. (Review article)
62. Ramaraj R, Ewy GA. Rationale for continuous chest compression cardiopulmonary resuscitation. Heart. 2009;95(24):1978-1982. (Review article)
63. Marcdante K, Kliegman R. Syncope. Nelson Essentials of Pediatrics. 7th ed: Saunders; 2015:486-487. (Book chapter)
64. Ritter S, Tani LY, Etheridge SP, et al. What is the yield of screening echocardiography in pediatric syncope? Pediatrics. 2000;105(5):E58. (Retrospective cohort; 480 patients)
65. Delgado C. Syncope. In: Fleisher, ed. Textbook of Pediatric Emergency Medicine. 6th ed.2010:593. (Textbook)
66. Brignole M, Ungar A, Bartoletti A, et al. Standardized-care pathway vs. usual management of syncope patients presenting as emergencies at general hospitals. Europace. 2006;8(8):644-650. (Prospective controlled multicenter study; 1674 patients)
67. * Raucci U, Scateni S, Tozzi AE, et al. The availability and the adherence to pediatric guidelines for the management of syncope in the emergency department. J Pediatr. 2014;165(5):967-972.e1. (Retrospective cohort; 1073 patients)
68. Kessler C, Tristano JM, De Lorenzo R. The emergency department approach to syncope: evidence-based guidelines and prediction rules. Emerg Med Clin North Am. 2010;28(3):487-500. (Review article)
69. Ikiz MA, Cetin, II, Ekici F, et al. Pediatric syncope: is detailed medical history the key point for differential diagnosis? Pediatr Emerg Care. 2014;30(5):331-334. (Prospective cohort; 268 children)
70. Kaufmann H. Consensus statement on the definition of orthostatic hypotension, pure autonomic failure and multiple system atrophy. Clin Auton Res. 1996;6(2):125-126. (Consensus guidelines)
71. Tanaka H, Thulesius O, Borres M, et al. Blood pressure responses in Japanese and Swedish children in the supine and standing position. Eur Heart J. 1994;15(8):1011-1019. (Prospective cohort; 131 children)
72. Koziol-McLain J, Lowenstein SR, Fuller B. Orthostatic vital signs in emergency department patients. Ann Emerg Med. 1991;20(6):606-610. (Prospective cohort; 132 patients)
73. Stewart JM. Transient orthostatic hypotension is common in adolescents. J Pediatr. 2002;140(4):418-424. (Prospective cohort; 23 healthy adolescents)
74. McGee S, Abernethy WB 3rd, Simel DL. The rational clinical examination. Is this patient hypovolemic? JAMA. 1999;281(11):1022-1029. (Meta-analysis; 14 studies)
75. Pilmer CM, Kirsh JA, Hildebrandt D, et al. Sudden cardiac death in children and adolescents between 1 and 19 years of age. Heart Rhythm. 2014;11(2):239-245. (Retrospective cohort; 116 cases of sudden cardiac death)
76. Wathen JE, Rewers AB, Yetman AT, et al. Accuracy of ECG interpretation in the pediatric emergency department. Ann Emerg Med. 2005;46(6):507-511. (Prospective analysis; 1653 ECGs, 1501 patients)
77. Hue V, Noizet-Yvernaux O, Vaksmann G, et al. ED management of pediatric syncope. Am J Emerg Med. 2008;26(9):1059-1060. (Prospective cohort)
78. Salen P, Nadkarni V. Congenital long-QT syndrome: a case report illustrating diagnostic pitfalls. J Emerg Med. 1999;17(5):859-864. (Case report; 1 patient)
79. Maron BJ, Chaitman BR, Ackerman MJ, et al. Recommendations for physical activity and recreational sports participation for young patients with genetic cardiovascular diseases. Circulation. 2004;109(22):2807-2816. (Review article)
80. Schwartz PJ. Idiopathic long QT syndrome: progress and questions. Am Heart J. 1985;109(2):399-411. (Review article)
81. Marelli AJ, Ionescu-Ittu R, Mackie AS, et al. Lifetime prevalence of congenital heart disease in the general population from 2000 to 2010. Circulation. 2014;130(9):749-756. (Retrospective cohort; 107,559 patients)
82. Salim MA, Di Sessa TG. Effectiveness of fludrocortisone and salt in preventing syncope recurrence in children: a double-blind, placebo-controlled, randomized trial. J Am Coll Cardiol. 2005;45(4):484-488. (Double-blind randomized controlled trial; 33 children)
83. Qingyou Z, Junbao D, Chaoshu T. The efficacy of midodrine hydrochloride in the treatment of children with vasovagal syncope. J Pediatr. 2006;149(6):777-780. (Randomized controlled trial; 26 children)
84. Morag RM, Murdock LF, Khan ZA, et al. Do patients with a negative emergency department evaluation for syncope require hospital admission? J Emerg Med. 2004;27(4):339-343. (Prospective cohort; 45 patients)