title: The intravenous adenosine test: a new test for the identification of bradycardia pacing indications? A pilot study in subjects with bradycardia pacing indications, vasovagal syncope and controls.
abstract: BACKGROUND
  Intravenous adenosine has recently been used in the diagnosis of unexplained syncope, but there is no consensus as to the meaning of a 'positive' test. The objective is to determine the sensitivity and specificity of intravenous adenosine testing in the diagnosis of bradycardia-pacing indications [sinus node dysfunction(SND), atrio-ventricular block (AVB) and cardio-inhibitory carotid sinus syndrome (CSS)].
  
  
  METHODS
  Pilot cohort study.
  
  
  METHODS
  Patients-(i) Bradycardia-pacing group: Consecutive patients referred for pacing for SND, AVB and CSS; (ii) Consecutive head-up tilt (HUT)-positive VVS patients. Controls-(i) Simple controls (S-Con: normal examination/ECG) and (ii) Electrophysiology controls (EP-Con: consecutive subjects referred for accessory pathway ablation). Pacing referrals and EP-Con had electrophysiology studies to confirm referral diagnosis and exclude others. All subjects had bolus injection of 20 mg intravenous adenosine during continuous ECG and blood pressure monitoring (positive test: >or=6 s asystole, >or=10 s high-degree AVB post-injection). Sensitivity, specificity, safety and tolerability of the test were measured.
  
  
  RESULTS
  Of 264 potential participants (4 SND, 8 AVB, 7 CSS, 10 VVS, 10 EP-Con and 11 S-Con) 50 were studied. All (100%) of the bradycardia-pacing group were adenosine test-positive, as were 6 (60%) VVS. None (0%) and 3 (27%) of the EP- and S-Con groups were positive. Adenosine testing was 100% sensitive and 86% specific for bradycardia-pacing indications, and 100% specific using the diagnostically 'clean' EP-Con results. There were no significant adverse or side effects.
  
  
  CONCLUSIONS
  Adenosine testing reliably identified patients with definitive bradycardia-pacing indications in whom alternative diagnoses were excluded. Further work is needed to evaluate the role of this test in the diagnosis of unexplained syncope.
authors.affiliation: Falls and Syncope Service, Institute for Ageing and Health, Newcastle University, Royal Victoria Infirmary, Newcastle upon Tyne, UK. swparry@hotmail.com
authors.forename: S W
authors.initials: SW
authors.lastname: Parry
authors.forename: T
authors.initials: T
authors.lastname: Chadwick
authors.forename: J C
authors.initials: JC
authors.lastname: Gray
authors.forename: R S
authors.initials: RS
authors.lastname: Bexton
authors.forename: M
authors.initials: M
authors.lastname: Tynan
authors.forename: J P
authors.initials: JP
authors.lastname: Bourke
authors.forename: S
authors.initials: S
authors.lastname: Nath
mesh_terms: D000241:Adenosine; D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000889:Anti-Arrhythmia Agents; D001145:Arrhythmias, Cardiac / Q000150:complications; D054537:Atrioventricular Block / Q000175:diagnosis*; D001919:Bradycardia / Q000150:complications / Q000175:diagnosis* / Q000628:therapy; D002304:Cardiac Pacing, Artificial; D016022:Case-Control Studies; D004812:Epidemiologic Methods; D005260:Female; D006801:Humans; D007262:Infusions, Intravenous; D008297:Male; D008875:Middle Aged; D019462:Syncope, Vasovagal / Q000175:diagnosis*; D018667:Tilt-Table Test; D055815:Young Adult
chemical_list: D000889:Anti-Arrhythmia Agents; D000241:Adenosine