title: Unexplained syncope evaluated by electrophysiologic studies and head-up tilt testing.
abstract: OBJECTIVE
  To determine the clinical characteristics of subgroups of patients with unexplained syncope having electrophysiologic studies and head-up tilt testing and to assess the efficacy of various therapies.
  
  
  METHODS
  Retrospective study.
  
  
  METHODS
  Inpatient services of a tertiary referral center.
  
  
  METHODS
  Eighty-six consecutively referred patients with unexplained syncope.
  
  
  METHODS
  All patients had electrophysiologic examinations. Patients with negative results subsequently had head-up tilt testing.
  
  
  RESULTS
  Twenty-nine (34%) patients (group 1) had abnormal electrophysiologic results, with sustained monomorphic ventricular tachycardia induced in 72%. Thirty-four (40%) patients (group 2) had syncope provoked by head-up tilt testing. The cause of syncope remained unexplained in 23 (26%) patients (group 3). Structural heart disease was present in 76%, 6%, and 30% of groups 1, 2, and 3, respectively. In group 1, pharmacologic or nonpharmacologic therapy was recommended based on electrophysiologic evaluation. All group 2 patients had negative results on head-up tilt testing while receiving oral beta blockers (27 patients) or disopyramide (7 patients). Group 3 patients did not receive any specific therapy. During a median follow-up period of 18.5 months, syncope recurred in 9 (10%) patients.
  
  
  CONCLUSIONS
  The combination of electrophysiologic evaluation and head-up tilt testing can identify the underlying cause of syncope in as many as 74% of patients presenting with unexplained syncope. Therapeutic strategies formulated according to the results of these diagnostic tests appear to prevent syncope effectively in most patients.
authors.affiliation: Sinai Samaritan Medical Center, Milwaukee, Wisconsin.
authors.forename: J S
authors.initials: JS
authors.lastname: Sra
authors.forename: A J
authors.initials: AJ
authors.lastname: Anderson
authors.forename: S H
authors.initials: SH
authors.lastname: Sheikh
authors.forename: B
authors.initials: B
authors.lastname: Avitall
authors.forename: P J
authors.initials: PJ
authors.lastname: Tchou
authors.forename: P J
authors.initials: PJ
authors.lastname: Troup
authors.forename: C J
authors.initials: CJ
authors.lastname: Gilbert
authors.forename: M
authors.initials: M
authors.lastname: Akhtar
authors.forename: M R
authors.initials: MR
authors.lastname: Jazayeri
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001145:Arrhythmias, Cardiac / Q000150:complications / Q000175:diagnosis*; D001919:Bradycardia / Q000175:diagnosis; D002648:Child; D004568:Electrodiagnosis / Q000379:methods*; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007545:Isoproterenol; D008297:Male; D008875:Middle Aged; D011187:Posture; D013575:Syncope / Q000209:etiology*; D013610:Tachycardia / Q000175:diagnosis; D013617:Tachycardia, Supraventricular / Q000175:diagnosis
chemical_list: D007545:Isoproterenol