title: Fetal tachycardia: mechanisms and predictors of hydrops fetalis.
abstract: OBJECTIVE
  This study had three objectives: 1) to determine the electrophysiologic mechanisms of fetal supraventricular tachycardia at presentation and postnatally; 2) to identify the clinical and electrophysiologic predictors of hydrops fetalis; and 3) to describe the medium-term follow-up (1 to 7 years) of patients with fetal supraventricular tachycardia.
  
  
  BACKGROUND
  Fetal supraventricular tachycardia causes significant fetal and neonatal morbidity and mortality. Prenatal analysis and postnatal confirmation of fetal supraventricular tachycardia mechanisms have been limited.
  
  
  METHODS
  Supraventricular tachycardia mechanisms were evaluated by prenatal Doppler/M-mode echocardiography, immediate neonatal surface electrocardiography and postnatal transesophageal electrophysiologic procedures in 30 consecutive patients presenting with fetal supraventricular tachycardia (17 managed prenatally, 13 first managed postnatally).
  
  
  RESULTS
  The fetal supraventricular tachycardia mechanism was 1:1 atrioventricular conduction in 22 patients and supraventricular tachycardia with atrioventricular block (atrial flutter) in 8. At the postnatal transesophageal electrophysiologic procedure, tachycardia was induced in 27 of 30 patients; atrioventricular reentrant tachycardia in 25 (93%) of 27 and intraatrial reentrant tachycardia in only 2 (7%) of 27. Hydrops was present in 12 of 30 fetuses. Sustained supraventricular tachycardia (> 12 h) and lower gestation at presentation correlated with hydrops (p < 0.02, p < 0.05), but mechanism of tachycardia and heart rate did not. Gestational age at delivery was significantly greater in those who received intrauterine management (39 +/- 1.3 vs. 37 +/- 2.9 weeks, p = 0.04) despite earlier presentation (32.6 vs. 37.1 weeks). Cesarean section deliveries were reduced in the same group (3 of 17 vs. 11 of 13, p = 0.0006).
  
  
  CONCLUSIONS
  Atrioventricular reentrant tachycardia was the predominant mechanism of supraventricular tachycardia in the fetus. There was a high association of supraventricular tachycardia with atrioventricular block in utero and accessory atrioventricular connections. Outcome at 1 to 7 years was excellent regardless of severity of illness at clinical presentation.
authors.affiliation: Department of Pediatrics, Children's Memorial Hospital, Chicago, Illinois 60614, USA.
authors.forename: Z J
authors.initials: ZJ
authors.lastname: Naheed
authors.forename: J F
authors.initials: JF
authors.lastname: Strasburger
authors.forename: B J
authors.initials: BJ
authors.lastname: Deal
authors.forename: D W
authors.initials: DW
authors.lastname: Benson
authors.forename: S S
authors.initials: SS
authors.lastname: Gidding
mesh_terms: D015150:Echocardiography, Doppler; D004562:Electrocardiography; D005260:Female; D005315:Fetal Diseases / Q000000981:diagnostic imaging / Q000503:physiopathology; D006801:Humans; D015160:Hydrops Fetalis / Q000209:etiology* / Q000503:physiopathology; D007231:Infant, Newborn; D011247:Pregnancy; D012189:Retrospective Studies; D013617:Tachycardia, Supraventricular / Q000150:complications* / Q000000981:diagnostic imaging / Q000503:physiopathology; D016216:Ultrasonography, Prenatal