title: Long-term outcomes of pediatric sinus bradycardia.
abstract: OBJECTIVE
  To delineate the long-term outcomes and mechanisms of pediatric sinus bradycardia.
  
  
  METHODS
  Participants with sinus bradycardia who were identified from a survey of 432,166 elementary and high school students, were enrolled 10 years after the survey. The clinical course, heart rate variability, and hyperpolarization-activated cyclic nucleotide-gated potassium channel 4 (HCN4) gene were assessed.
  
  
  RESULTS
  A total of 104 (male:female was 60:44; prevalence, 0.025%) participants were observed to have sinus bradycardia at age 15.5 ± 0.2 years with a mean heart rate of 48.4 ± 0.4 beats per minute; 86 study participants (83%) responded to clinical assessment and 37 (36%) underwent laboratory assessment. Athletes composed 37.8% of the study participants. During the extended 10-year follow-up, 15 (17%) of the participants had self-limited syncopal episodes, but none had experienced life-threatening events. According to Holter recordings, none of the participants had heart rate <30 beats per minute or a pause longer than 3 seconds. Compared with 67 age- and sex-matched controls, the variables of heart rate based on the spectral and time domain analysis of the participants with sinus bradycardia were all significantly higher, indicating higher parasympathetic activity. The results of mutation analysis were negative in the HCN4 gene in all of our participants.
  
  
  CONCLUSIONS
  The long-term outcomes of the children and adolescents with sinus bradycardia identified using school electrocardiographic survey are favorable. Parasympathetic hyperactivity, instead of HCN4 gene mutation, is responsible for the occurrence of sinus bradycardia.
authors.affiliation: Department of Pediatrics, National Taiwan University Hospital and Medical College, National Taiwan University, Taipei, Taiwan.
authors.forename: Shuenn-Nan
authors.initials: SN
authors.lastname: Chiu
authors.forename: Lian-Yu
authors.initials: LY
authors.lastname: Lin
authors.forename: Jou-Kou
authors.initials: JK
authors.lastname: Wang
authors.forename: Chun-Wei
authors.initials: CW
authors.lastname: Lu
authors.forename: Chi-Wei
authors.initials: CW
authors.lastname: Chang
authors.forename: Ming-Tai
authors.initials: MT
authors.lastname: Lin
authors.forename: Yu Chuan
authors.initials: YC
authors.lastname: Hua
authors.forename: Hung-Chi
authors.initials: HC
authors.lastname: Lue
authors.forename: Mei-Hwan
authors.initials: MH
authors.lastname: Wu
mesh_terms: D000293:Adolescent; D000328:Adult; D001919:Bradycardia / Q000175:diagnosis* / Q000235:genetics / Q000503:physiopathology; D016022:Case-Control Studies; D002648:Child; D054815:Cyclic Nucleotide-Gated Cation Channels / Q000235:genetics; D004562:Electrocardiography; D005260:Female; D005500:Follow-Up Studies; D005819:Genetic Markers; D006306:Health Surveys; D006339:Heart Rate / Q000502:physiology; D006801:Humans; D064428:Hyperpolarization-Activated Cyclic Nucleotide-Gated Channels; D008297:Male; D009124:Muscle Proteins / Q000235:genetics; D009154:Mutation; D015221:Potassium Channels; D011379:Prognosis; D012189:Retrospective Studies; D013624:Taiwan; D055815:Young Adult
chemical_list: D054815:Cyclic Nucleotide-Gated Cation Channels; D005819:Genetic Markers; C119587:HCN4 protein, human; D064428:Hyperpolarization-Activated Cyclic Nucleotide-Gated Channels; D009124:Muscle Proteins; D015221:Potassium Channels
keywords: Beats per minute; ECG; Electrocardiographic; HCN4; HF; HRV; Heart rate variability; High frequency; Hyperpolarization-activated cyclic nucleotide-gated potassium channel 4; LF; Low frequency; N-N; Normal-to-normal; Pro-brain natriuretic peptide; SD of heart rate; SDNN; bpm; pro-BNP