title: Syncope due to idiopathic paroxysmal atrioventricular block: long-term follow-up of a distinct form of atrioventricular block.
abstract: OBJECTIVE
  We present data on patients with syncope due to paroxysmal atrioventricular (AV) block unexplainable in terms of currently known mechanisms.
  
  
  BACKGROUND
  Paroxysmal AV block is known to be due to intrinsic AV conduction disease or to heightened vagal tone.
  
  
  METHODS
  We evaluated 18 patients presenting with unexplained syncope who had: 1) normal baseline standard electrocardiogram (ECG); 2) absence of structural heart disease; and 3) documentation, by means of prolonged ECG monitoring at the time of syncopal relapse, of paroxysmal third-degree AV block with abrupt onset and absence of other rhythm disturbances before or during the block.
  
  
  RESULTS
  The study group consisted of 9 men and 9 women, mean age 55 ± 19 years, who had recurrent unexplained syncope for 8 ± 7 years and were subsequently followed up for as long as 14 years (4 ± 4 years on average). The patients had no structural heart disease, standard ECG was normal, and electrophysiological study was negative. In all patients, prolonged ECG monitoring documented paroxysmal complete AV block with 1 or multiple consecutive pauses (mean longest pause: 9 ± 7 s at the time of syncope); AV block occurred without P-P cycle lengthening or PR interval prolongation. During the observation time, no patient had permanent AV block; on permanent cardiac pacing, no patient had further syncopal recurrences.
  
  
  CONCLUSIONS
  Common clinical and electrophysiological features define a distinct form of syncope due to idiopathic paroxysmal AV block characterized by a long history of recurrent syncope, absence of progression to persistent forms of AV block, and efficacy of cardiac pacing therapy.
authors.affiliation: Department of Cardiology, Arrhythmologic Centre, Ospedali del Tigullio, Lavagna, Italy. mbrignole@ASL4.liguria.it
authors.forename: Michele
authors.initials: M
authors.lastname: Brignole
authors.forename: Jean-Claude
authors.initials: JC
authors.lastname: Deharo
authors.forename: Luc
authors.initials: L
authors.lastname: De Roy
authors.forename: Carlo
authors.initials: C
authors.lastname: Menozzi
authors.forename: Dominique
authors.initials: D
authors.lastname: Blommaert
authors.forename: Lara
authors.initials: L
authors.lastname: Dabiri
authors.forename: Jean
authors.initials: J
authors.lastname: Ruf
authors.forename: Regis
authors.initials: R
authors.lastname: Guieu
mesh_terms: D000241:Adenosine / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000378:metabolism; D000328:Adult; D000368:Aged; D054537:Atrioventricular Block / Q000150:complications*; D004562:Electrocardiography / Q000379:methods; D004594:Electrophysiology; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D012008:Recurrence; D013575:Syncope / Q000503:physiopathology*; D013997:Time Factors
chemical_list: D000255:Adenosine Triphosphate; D000241:Adenosine