title: Electrocardiographic predictors of bradycardia-induced torsades de pointes in patients with acquired atrioventricular block.
abstract: BACKGROUND
  Predictors of torsades de pointes (TdP) in bradyarrhythmia-induced acquired long QT syndrome are not well defined.
  
  
  OBJECTIVE
  The purpose of this study was to search for electrocardiographic (ECG) TdP predictors in patients with acquired atrioventricular block (AVB) and QT prolongation.
  
  
  METHODS
  We analyzed 12-lead ECGs from 20 patients (15 females, age 65.9 ± 15.6 years) with TdP episodes from among 898 AVB patients (2.2%) in 3 tertiary hospitals. The ECG repolarization parameters in TdP patients were compared with those of 80 age- and sex-matched control AVB patients with no TdP episodes.
  
  
  RESULTS
  TdP was initiated by premature ventricular complexes with a long-short sequence of activation. The average cycle length of the long sequence was 1289.9 ± 228.9 ms and was 2.3 ± 0.6 times longer than the cycle length of the short sequence. TdP patients had a significantly longer mean QT interval (716.4 ± 98.9 ms vs 523.2 ± 91.3 ms, P = .001), mean T peak to end interval (334.2 ± 59.1 ms vs 144.0 ± 73.7 ms, P = .001) and a higher T peak to end interval/QT ratio (0.49 ± 0.09 vs 0.27 ± 0.11, P = .001) compared with non-TdP controls. TdP patients showed a higher prevalence of notched T waves in which T2 was at least 3 mm taller than T1 (45.0% vs 1.3%, P = .001), triphasic T waves (30.0% vs 1.3%, P = .001), reversed asymmetry (20.0% vs 0%, P = .001), and T-wave alternans (35.0% vs 0%, P = .001). An algorithm combining these morphologic parameters was able to differentiate TdP patients from non-TdP patients with high sensitivity (85.0%) and specificity (97.5%).
  
  
  CONCLUSIONS
  An algorithm combining specific T-wave morphologies was useful for identifying patients with AVB who are at risk for developing TdP.
authors.affiliation: Heart Institute, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.
authors.forename: Min Soo
authors.initials: MS
authors.lastname: Cho
authors.affiliation: Heart Institute, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea. Electronic address: gbnam@amc.seoul.kr.
authors.forename: Gi-Byoung
authors.initials: GB
authors.lastname: Nam
authors.affiliation: Heart Institute, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.
authors.forename: Yong-Guin
authors.initials: YG
authors.lastname: Kim
authors.affiliation: Heart Institute, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.
authors.forename: Ki-Won
authors.initials: KW
authors.lastname: Hwang
authors.affiliation: Heart Institute, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.
authors.forename: Yoo Ri
authors.initials: YR
authors.lastname: Kim
authors.affiliation: Heart Institute, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.
authors.forename: HyungOh
authors.initials: H
authors.lastname: Choi
authors.affiliation: Heart Institute, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.
authors.forename: Sung-Hwan
authors.initials: SH
authors.lastname: Kim
authors.affiliation: Division of Cardiology, Department of Internal Medicine, Chonbuk National University Hospital, Chonbuk National University, Chonju, Korea.
authors.forename: Kyoung-Suk
authors.initials: KS
authors.lastname: Rhee
authors.affiliation: Department of Cardiology, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea.
authors.forename: Nam-Joon
authors.initials: NJ
authors.lastname: Kim
authors.affiliation: Department of Cardiology, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea.
authors.forename: June Soo
authors.initials: JS
authors.lastname: Kim
authors.affiliation: Heart Institute, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.
authors.forename: Jun
authors.initials: J
authors.lastname: Kim
authors.affiliation: Heart Institute, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.
authors.forename: Kee-Joon
authors.initials: KJ
authors.lastname: Choi
authors.affiliation: Heart Institute, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.
authors.forename: You-Ho
authors.initials: YH
authors.lastname: Kim
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000465:Algorithms; D054537:Atrioventricular Block / Q000150:complications* / Q000503:physiopathology; D016022:Case-Control Studies; D004562:Electrocardiography / Q000379:methods*; D005260:Female; D006801:Humans; D008133:Long QT Syndrome / Q000150:complications* / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D012307:Risk Factors; D012680:Sensitivity and Specificity; D016171:Torsades de Pointes / Q000175:diagnosis* / Q000209:etiology / Q000503:physiopathology
keywords: Atrioventricular block; Bradycardia; Long QT syndrome; T waves; Torsades de pointes