title: Mechanism of syncope in patients with isolated syncope and in patients with tilt-positive syncope.
abstract: BACKGROUND
  Because of its episodic behavior, the correlation of spontaneous syncope with an abnormal finding can be considered a reference standard.
  
  
  RESULTS
  We inserted an implantable loop recorder in 111 patients with syncope, absence of significant structural heart disease, and a normal ECG; tilt-testing was negative in 82 (isolated syncope) and positive in 29 (tilt-positive). The patients had had >/=3 episodes of syncope in the previous 2 years and were followed up for 3 to 15 months. Results were similar in the isolated syncope group and the tilt-positive group: syncope recurred in 28 (34%) and 10 patients (34%), respectively, and electrocardiographic correlation was found in 24 (23%) and 8 (28%) patients, respectively. The most frequent finding, which was recorded in 46% and 62% of patients, respectively, was one or more prolonged asystolic pauses, mainly due to sinus arrest, preceded for a few minutes by progressive bradycardia or progressive tachycardia-bradycardia. Bradycardia without pauses was observed in 8% and 12% of cases, respectively. The remaining patients had normal sinus rhythm or sinus tachycardia, except for one, who had ectopic atrial tachycardia. In the tilt-positive group, an asystolic syncope was also recorded when the type of response to tilt-testing was vasodepressor or mixed. Presyncopal episodes were never characterized by asystolic pauses; normal sinus rhythm was the most frequent finding.
  
  
  CONCLUSIONS
  Homogeneous findings were observed during syncope. In most patients, the likely cause was neurally-mediated, and the most frequent mechanism was a bradycardic reflex. In the other cases, a normal sinus rhythm was frequently recorded. Presyncope was not an accurate surrogate for syncope in establishing a diagnosis.
authors.affiliation: Departments of Cardiology of Hospital Vall d'Hebron, Barcelona, Spain.
authors.forename: A
authors.initials: A
authors.lastname: Moya
authors.forename: M
authors.initials: M
authors.lastname: Brignole
authors.forename: C
authors.initials: C
authors.lastname: Menozzi
authors.forename: R
authors.initials: R
authors.lastname: Garcia-Civera
authors.forename: S
authors.initials: S
authors.lastname: Tognarini
authors.forename: L
authors.initials: L
authors.lastname: Mont
authors.forename: G
authors.initials: G
authors.lastname: Botto
authors.forename: F
authors.initials: F
authors.lastname: Giada
authors.forename: D
authors.initials: D
authors.lastname: Cornacchia
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001919:Bradycardia / Q000503:physiopathology; D002304:Cardiac Pacing, Artificial; D004562:Electrocardiography; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D012008:Recurrence; D013575:Syncope / Q000503:physiopathology* / Q000628:therapy; D013610:Tachycardia / Q000503:physiopathology; D018667:Tilt-Table Test