title: Treatment of unexplained syncope: a multicenter, randomized trial of cardiac pacing guided by adenosine 5'-triphosphate testing.
abstract: BACKGROUND
  The origin of 40% of syncope cases remains unknown even after a complete diagnostic workup. Previous studies have suggested that ATP testing has value in selecting successful therapy. This patient-blinded, multicenter, randomized superiority trial tested whether, in patients with syncope of unknown origin, selecting cardiac pacing in those with a positive ATP test leads to fewer recurrences than those who do not receive pacing.
  
  
  RESULTS
  From 2000 to 2005, 80 consenting patients (mean age, 75.9±7.7 years; 81% women; 56% without diagnosed structural heart disease) with syncope of unknown origin and atrioventricular or sinoatrial block lasting >10 seconds (average, 17.9±6.8 seconds) under ATP administration (20-mg IV bolus) were recruited from 10 hospitals, implanted with programmable pacemakers, and randomized to either active pacing (dual-chamber pacing at 70 bpm) or backup pacing (atrial pacing at 30 bpm). Patients were followed up regularly for up to 5 years for any syncope recurrence, the primary outcome. Mean follow-up was 16 months. Syncope recurred in 8 of 39 patients (21%) randomized to active pacing and in 27 of 41 (66%) randomized to backup pacing (control), yielding a hazard ratio of 0.25 (95% confidence interval, 0.12-0.56). After recurrence, the 27 recurrent control patients were reprogrammed to active pacing, and only 1 reported subsequent syncope.
  
  
  CONCLUSIONS
  This study suggests that, in elderly patients with syncope of unknown origin and positive ATP tests, active dual-chamber pacing reduces syncope recurrence risk by 75% (95% confidence interval, 44-88).
  
  
  BACKGROUND
  URL: http://www.controlled-trials.com/ISRCTN00029383. Unique identifier: ISRCTN00029383.
authors.affiliation: Health Studies Section, Division of Environmental Health Sciences, School of Public Health, University of Minnesota, 350 McNamara Alumni Center, 200 Oak St SE, Minneapolis, MN 55455-2008, USA.
authors.forename: Daniel
authors.initials: D
authors.lastname: Flammang
authors.forename: Timothy R
authors.initials: TR
authors.lastname: Church
authors.forename: Luc
authors.initials: L
authors.lastname: De Roy
authors.forename: Jean-Jacques
authors.initials: JJ
authors.lastname: Blanc
authors.forename: Jean
authors.initials: J
authors.lastname: Leroy
authors.forename: Georges H
authors.initials: GH
authors.lastname: Mairesse
authors.forename: Akli
authors.initials: A
authors.lastname: Otmani
authors.forename: Pierre J
authors.initials: PJ
authors.lastname: Graux
authors.forename: Robert
authors.initials: R
authors.lastname: Frank
authors.forename: Philippe
authors.initials: P
authors.lastname: Purnode
mesh_terms: D000255:Adenosine Triphosphate; D000368:Aged; D000369:Aged, 80 and over; D002304:Cardiac Pacing, Artificial / Q000379:methods*; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D016037:Single-Blind Method; D013575:Syncope / Q000175:diagnosis* / Q000503:physiopathology / Q000628:therapy*; D016896:Treatment Outcome
chemical_list: D000255:Adenosine Triphosphate