title: Effect of atropine and isoproterenol on tachycardia induction in asymptomatic patients with Wolff-Parkinson-White electrocardiographic pattern.
abstract: OBJECTIVE
  To determine if pharmacological interventions aimed at altering autonomic tone would allow induction of orthodromic atrioventricular reentrant tachycardia in asymptomatic patients with the Wolff-Parkinson-White electrocardiographic pattern.
  
  
  METHODS
  Prospective interventional protocol in consecutive eligible patients.
  
  
  METHODS
  University hospital.
  
  
  METHODS
  Eighteen asymptomatic patients (13 male and five female) with the Wolff-Parkinson-White electrocardiographic pattern without inducible tachycardia in the drug-free state.
  
  
  METHODS
  Electrophysiological assessment was performed at baseline, after intravenous administration of atropine (0.03 mg/kg) and during isoproterenol infusion (0.5 to 2 micrograms/min).
  
  
  RESULTS
  Orthodromic reciprocating tachycardia was not inducible at baseline because of absent retrograde accessory pathway conduction in seven patients. In five patients, orthodromic atrial echo beats could be induced (which blocked retrogradely in the accessory pathway in three patients and anterogradely in the atrioventricular node in two). In the remaining six patients, neither orthodromic echo beats nor reciprocating tachycardia could be induced despite intact retrograde accessory pathway conduction. Following atropine administration (mean dose 1.9 +/- 0.3 mg), anterograde and retrograde accessory pathway effective refractory periods decreased from 360 +/- 172 to 284 +/- 62 ms and from 340 +/- 38 to 296 +/- 32 ms, respectively (both P < 0.05 versus control). Orthodromic reciprocating tachycardia was induced in two patients (nonsustained in one). During isoproterenol infusion (mean dose 1.0 +/- 0.3 micrograms/min), anterograde and retrograde accessory pathway effective refractory periods decreased further to 243 +/- 23 and 248 +/- 22 ms, respectively (both P < 0.05 versus after atropine); two further patients had inducible orthodromic reciprocating tachycardia (nonsustained in one). No patient with absent retrograde accessory pathway conduction developed retrograde accessory pathway conduction or reciprocating tachycardia with isoproterenol and/or atropine.
  
  
  CONCLUSIONS
  Isoproterenol and/or atropine allowed tachycardia induction in four of 18 asymptomatic patients with the Wolff-Parkinson-White electrocardiographic pattern. In the majority of these patients, tachycardia is not inducible because of deficient retrograde accessory pathway conduction which does not improve with autonomic facilitation.
authors.affiliation: Department of Medicine, University of Western Ontario, London.
authors.forename: Y H
authors.initials: YH
authors.lastname: Kim
authors.forename: J W
authors.initials: JW
authors.lastname: Leitch
authors.forename: G J
authors.initials: GJ
authors.lastname: Klein
authors.forename: R
authors.initials: R
authors.lastname: Yee
authors.forename: R A
authors.initials: RA
authors.lastname: Leather
mesh_terms: D000293:Adolescent; D000328:Adult; D001285:Atropine / Q000494:pharmacology*; D004562:Electrocardiography / Q000187:drug effects*; D005260:Female; D006329:Heart Conduction System / Q000187:drug effects*; D006339:Heart Rate / Q000187:drug effects; D006801:Humans; D007545:Isoproterenol / Q000494:pharmacology*; D008297:Male; D008875:Middle Aged; D011379:Prognosis; D011446:Prospective Studies; D013610:Tachycardia / Q000139:chemically induced*; D014927:Wolff-Parkinson-White Syndrome / Q000188:drug therapy* / Q000503:physiopathology
chemical_list: D001285:Atropine; D007545:Isoproterenol