title: Intermittent versus Persistent Wolff-Parkinson-White Syndrome in Children: Electrophysiologic Properties and Clinical Outcomes.
abstract: BACKGROUND
  Intermittent Wolff-Parkinson-White (WPW) syndrome is considered to have a lower risk of sudden death. Fewer data exist regarding electrophysiologic (EP) characteristics and the natural history of intermittent WPW in children.
  
  
  METHODS
  All patients with WPW age 1-18 years at a single institution (1996-2013) were reviewed. Patients with intermittent preexcitation were compared to those with loss of preexcitation on Holter/exercise testing and those with persistent preexcitation. High-risk accessory pathway (AP) was defined as AP effective refractory period (APERP), block cycle length, or shortest preexcited RR interval during atrial fibrillation ≤250 ms.
  
  
  RESULTS
  A total of 295 patients were included: 226 (76.6%) persistent, 39 (13.2%) intermittent, and 30 (10.2%) loss of preexcitation Holter/exercise. There were no differences in symptoms between groups. Median interquartile range APERP was significantly longer in intermittent WPW (380 [320, 488] ms vs 320 [300, 350] ms persistent, 310 [290, 330] ms loss of preexcitation Holter/exercise; P = 0.0008). At baseline, there was no difference between groups in frequency of high-risk pathways. However, when isoproterenol values were included, high-risk pathways were more frequent among patients with loss of preexcitation on Holter/exercise (54% vs 16% persistent, 11% intermittent; P = 0.005). There was one death in a patient with loss of preexcitation on exercise testing, no EP study, and prior drug use. A second patient with persistent WPW and APERP 270 ms required resuscitation following a methadone overdose.
  
  
  CONCLUSIONS
  Intermittent preexcitation in children does not connote a lower risk AP by EP criteria or reduced symptoms. The low number of pediatric WPW patients who develop preexcited atrial fibrillation or sudden death warrants larger studies to investigate these outcomes.
authors.affiliation: Department of Pediatrics, University of Colorado, Denver, Colorado.
authors.forename: Michelle E
authors.initials: ME
authors.lastname: Kiger
authors.affiliation: Division of Cardiology, Children's Hospital Colorado, Aurora, Colorado.
authors.forename: Anthony C
authors.initials: AC
authors.lastname: McCanta
authors.affiliation: Department of Biostatistics, University of Colorado, Denver, Colorado.
authors.forename: Suhong
authors.initials: S
authors.lastname: Tong
authors.affiliation: Division of Cardiology, Children's Hospital Colorado, Aurora, Colorado.
authors.forename: Michael
authors.initials: M
authors.lastname: Schaffer
authors.affiliation: Division of Cardiology, Children's Hospital Colorado, Aurora, Colorado.
authors.forename: Martin
authors.initials: M
authors.lastname: Runciman
authors.affiliation: Division of Cardiology, Children's Hospital Colorado, Aurora, Colorado.
authors.forename: Kathryn K
authors.initials: KK
authors.lastname: Collins
mesh_terms: D058606:Accessory Atrioventricular Bundle / Q000175:diagnosis / Q000401:mortality; D000293:Adolescent; D017677:Age Distribution; D015984:Causality; D002648:Child; D002675:Child, Preschool; D002908:Chronic Disease; D015897:Comorbidity; D004562:Electrocardiography / Q000706:statistics & numerical data*; D005260:Female; D006801:Humans; D007223:Infant; D008297:Male; D011226:Pre-Excitation Syndromes / Q000175:diagnosis* / Q000401:mortality*; D015995:Prevalence; D011379:Prognosis; D012008:Recurrence; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D017678:Sex Distribution; D015996:Survival Rate; D014927:Wolff-Parkinson-White Syndrome / Q000175:diagnosis* / Q000401:mortality*
keywords: Wolff-Parkinson-White syndrome; children; intermittent preexcitation; risk stratification; ventricular preexcitation