title: Classification and mechanism of Torsade de Pointes initiation in patients with congenital long QT syndrome.
abstract: OBJECTIVE
  To examine the initiating mode of Torsade de Pointes (TdP) in patients with congenital long QT syndrome (LQTS).
  
  
  RESULTS
  We evaluated 111 episodes of TdP recorded on the electrocardiograms of 24 patients with congenital LQTS, and clarified the initiating mode, the three consecutive preceding RR intervals defined as C(2), C(1), and C(0), the timing of initiating premature ventricular contraction (PVC) and the cycle length (CL) of TdP. Three different initiating patterns were observed: (1) a "short-long-short" sequence (SLS) pattern (23 patients, 72 TdP, 65%) defined as one or more short-long cardiac cycles followed by an initiating short-coupled PVC (C(1)>C(2) and C(0)), (2) an "increased sinus rate" (ISR) pattern (8 patients, 28 TdP, 25%) defined as a gradual increase in sinus rate with or without T-wave alternans (C(2)>/=C(1)>/=C(0)), and (3) a "changed depolarization" (CD) pattern (5 patients, 11 TdP, 10%) defined as a sudden long-coupled PVC or fusion beat followed by short-coupled PVC. The C(0) was shorter in ISR than SLS and CD (mean C(0): 488 vs. 587 and 603 ms, respectively; P<0.05). Therefore, the initiating PVC appeared near the T-wave peak of the last beat before onset in ISR, while it occurred after the T-wave peak in SLS and CD. The CL of TdP was shorter in ISR than in SLS (256 vs. 295 ms, P<0.05).
  
  
  CONCLUSIONS
  Our data show the existence of three predominant initiating modes of TdP in patients with congenital LQTS and suggests a differential mechanism of initiation of TdP for each mode.
authors.affiliation: Division of Cardiology, Department of Internal Medicine, National Cardiovascular Center, 5-7-1 Fujishiro-dai, Suita 565-8565, Japan.
authors.forename: Takashi
authors.initials: T
authors.lastname: Noda
authors.forename: Wataru
authors.initials: W
authors.lastname: Shimizu
authors.forename: Kazuhiro
authors.initials: K
authors.lastname: Satomi
authors.forename: Kazuhiro
authors.initials: K
authors.lastname: Suyama
authors.forename: Takashi
authors.initials: T
authors.lastname: Kurita
authors.forename: Naohiko
authors.initials: N
authors.lastname: Aihara
authors.forename: Shiro
authors.initials: S
authors.lastname: Kamakura
mesh_terms: D000293:Adolescent; D000328:Adult; D002648:Child; D002675:Child, Preschool; D004562:Electrocardiography / Q000379:methods; D005260:Female; D006801:Humans; D007223:Infant; D008133:Long QT Syndrome / Q000150:complications / Q000151:congenital* / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D016171:Torsades de Pointes / Q000209:etiology* / Q000503:physiopathology; D018879:Ventricular Premature Complexes / Q000209:etiology* / Q000503:physiopathology