title: Age-related arrhythmogenesis on ascent and descent: "autonomic conflicts" on hypoxia/reoxygenation at high altitude?
abstract: OBJECTIVE
  To discern whether arrhythmogenesis at high-altitude (HA) may differ depending on ascent or descent, as well as on age.
  
  
  METHODS
  Male subjects (37.9±12.0 SD y, n=33) were separated into a young (Y) group (29.6±5.73 SD y, n=18) and an older (O) one (47.9±9.83 SD y, n=15). All subjects were monitored by Holter electrocardiography while successively ascending (41.2±7.51 SD min) and descending (38.7±6.68 SD min) between 2950 and 5050 m as car passengers on a 25 km road in Northern Chile. Arrhythmic events (AE) ensued when the difference between two consecutive RR intervals exceeded 0.16 sec.
  
  
  RESULTS
  From 311 AE registered, 29% occurred on ascent and 71% on descent, the sinusal type predominating in both age groups. AE incidence, RR interval duration, and heart rate variability (HRV) in the time domain (RMSSD) increased during descent, as compared to ascent, in the Y group (p<0.05), but not in the O one. Independently of age, AE incidence along descent associates with the time previously spent at 5050 m (p<0.001).
  
  
  CONCLUSIONS
  Rapid transitions at HA favor arrhythmogenesis, the latter becoming evident particularly in the Y group on descent. Age-dependent changes of autonomic activity appear to be involved in arrhythmogenesis on transitions at HA.
authors.affiliation: 1 Facultad de Medicina, ICBM, Universidad de Chile , Santiago, Chile .
authors.forename: Claus
authors.initials: C
authors.lastname: Behn
authors.forename: Gustavo A
authors.initials: GA
authors.lastname: Dinamarca
authors.forename: Nicole F
authors.initials: NF
authors.lastname: De Gregorio
authors.forename: Viviana
authors.initials: V
authors.lastname: Lips
authors.forename: Ennio A
authors.initials: EA
authors.lastname: Vivaldi
authors.forename: Daniel
authors.initials: D
authors.lastname: Soza
authors.forename: Manuel A
authors.initials: MA
authors.lastname: Guerra
authors.forename: Raúl F
authors.initials: RF
authors.lastname: Jiménez
authors.forename: Eduardo A
authors.initials: EA
authors.lastname: Lecannelier
authors.forename: Héctor
authors.initials: H
authors.lastname: Varela
authors.forename: Juan A
authors.initials: JA
authors.lastname: Silva-Urra
mesh_terms: D000328:Adult; D000367:Age Factors; D000531:Altitude; D001145:Arrhythmias, Cardiac / Q000209:etiology* / Q000503:physiopathology; D001334:Automobile Driving; D001341:Autonomic Nervous System / Q000502:physiology*; D002677:Chile; D006801:Humans; D000860:Hypoxia / Q000209:etiology / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged
keywords: arrhythmogenesis; descent vs. ascent; high-altitude; “autonomic conflicts”