title: Prevalence of Microvolt T-Wave Alternans in Patients With Long QT Syndrome and Its Association With Torsade de Pointes.
abstract: BACKGROUND
  Prevalence of microvolt T-wave alternans (TWA) and the strength of its association with torsade de pointes (TdP) history have not been fully investigated in patients with long QT syndrome (LQTS).
  
  
  RESULTS
  Twenty-four-hour continuous 12-lead ECGs were recorded in 10 healthy subjects (5 men; median age, 21.5 years) and 32 patients (13 men; median age, 13 years) with LQTS types 1 (n=18), 2 (n=4), 3 (n=4), and unidentified (n=6). Peak TWA was determined by the Modified Moving Average method. None of the healthy subjects had TWA ≥42 µV. All 8 (100%) LQTS patients with a history of TdP exhibited TWA ≥42 µV, whereas only 14 (58.3%) of the 24 LQTS patients without TdP history reached ≥42 µV (p=0.04). Thus, the 42-µV cut point provided 100% sensitivity and 41.7% specificity for an association with TdP history. In the 22 (68.8%) LQTS patients with TWA ≥42 µV, only 2 (median; interquartile range, 1-3) leads exhibited TWA ≥42 µV. Highest TWA levels were recorded in precordial leads (V1-V6) in 30 (93.8%) patients, most frequently in lead V2 (43.8%). A single ECG lead detected only ≤63.6% of TWA ≥42 µV episodes, whereas the combined leads V2 to V5 detected 100% of TWA ≥42 µV.
  
  
  CONCLUSIONS
  Microvolt TWA is far more prevalent in LQTS patients than previously reported and is strongly associated with TdP history. TWA should be monitored from precordial leads in LQTS patients. The use of a limited set of ECG leads in conventional monitoring has led to underestimation of TWA and its association with TdP.
authors.affiliation: From the Gifu University Hospital, Gifu, Japan (N.T., T.K., H.T., T.N., M.K., K.N., S.M.); Gifu Prefectural General Medical Center, Gifu, Japan (H.G., T.K.); Matsunami General Hospital, Gifu, Japan (M.T.); and Department of Medicine, Harvard Medical School, Beth Israel Deaconess Medical Center, Boston, MA (R.L.V.). sunanezumi417@yahoo.co.jp.
authors.forename: Nobuhiro
authors.initials: N
authors.lastname: Takasugi
authors.affiliation: From the Gifu University Hospital, Gifu, Japan (N.T., T.K., H.T., T.N., M.K., K.N., S.M.); Gifu Prefectural General Medical Center, Gifu, Japan (H.G., T.K.); Matsunami General Hospital, Gifu, Japan (M.T.); and Department of Medicine, Harvard Medical School, Beth Israel Deaconess Medical Center, Boston, MA (R.L.V.).
authors.forename: Hiroko
authors.initials: H
authors.lastname: Goto
authors.affiliation: From the Gifu University Hospital, Gifu, Japan (N.T., T.K., H.T., T.N., M.K., K.N., S.M.); Gifu Prefectural General Medical Center, Gifu, Japan (H.G., T.K.); Matsunami General Hospital, Gifu, Japan (M.T.); and Department of Medicine, Harvard Medical School, Beth Israel Deaconess Medical Center, Boston, MA (R.L.V.).
authors.forename: Mieko
authors.initials: M
authors.lastname: Takasugi
authors.affiliation: From the Gifu University Hospital, Gifu, Japan (N.T., T.K., H.T., T.N., M.K., K.N., S.M.); Gifu Prefectural General Medical Center, Gifu, Japan (H.G., T.K.); Matsunami General Hospital, Gifu, Japan (M.T.); and Department of Medicine, Harvard Medical School, Beth Israel Deaconess Medical Center, Boston, MA (R.L.V.).
authors.forename: Richard L
authors.initials: RL
authors.lastname: Verrier
authors.affiliation: From the Gifu University Hospital, Gifu, Japan (N.T., T.K., H.T., T.N., M.K., K.N., S.M.); Gifu Prefectural General Medical Center, Gifu, Japan (H.G., T.K.); Matsunami General Hospital, Gifu, Japan (M.T.); and Department of Medicine, Harvard Medical School, Beth Israel Deaconess Medical Center, Boston, MA (R.L.V.).
authors.forename: Takashi
authors.initials: T
authors.lastname: Kuwahara
authors.affiliation: From the Gifu University Hospital, Gifu, Japan (N.T., T.K., H.T., T.N., M.K., K.N., S.M.); Gifu Prefectural General Medical Center, Gifu, Japan (H.G., T.K.); Matsunami General Hospital, Gifu, Japan (M.T.); and Department of Medicine, Harvard Medical School, Beth Israel Deaconess Medical Center, Boston, MA (R.L.V.).
authors.forename: Tomoki
authors.initials: T
authors.lastname: Kubota
authors.affiliation: From the Gifu University Hospital, Gifu, Japan (N.T., T.K., H.T., T.N., M.K., K.N., S.M.); Gifu Prefectural General Medical Center, Gifu, Japan (H.G., T.K.); Matsunami General Hospital, Gifu, Japan (M.T.); and Department of Medicine, Harvard Medical School, Beth Israel Deaconess Medical Center, Boston, MA (R.L.V.).
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Toyoshi
authors.affiliation: From the Gifu University Hospital, Gifu, Japan (N.T., T.K., H.T., T.N., M.K., K.N., S.M.); Gifu Prefectural General Medical Center, Gifu, Japan (H.G., T.K.); Matsunami General Hospital, Gifu, Japan (M.T.); and Department of Medicine, Harvard Medical School, Beth Israel Deaconess Medical Center, Boston, MA (R.L.V.).
authors.forename: Takashi
authors.initials: T
authors.lastname: Nakashima
authors.affiliation: From the Gifu University Hospital, Gifu, Japan (N.T., T.K., H.T., T.N., M.K., K.N., S.M.); Gifu Prefectural General Medical Center, Gifu, Japan (H.G., T.K.); Matsunami General Hospital, Gifu, Japan (M.T.); and Department of Medicine, Harvard Medical School, Beth Israel Deaconess Medical Center, Boston, MA (R.L.V.).
authors.forename: Masanori
authors.initials: M
authors.lastname: Kawasaki
authors.affiliation: From the Gifu University Hospital, Gifu, Japan (N.T., T.K., H.T., T.N., M.K., K.N., S.M.); Gifu Prefectural General Medical Center, Gifu, Japan (H.G., T.K.); Matsunami General Hospital, Gifu, Japan (M.T.); and Department of Medicine, Harvard Medical School, Beth Israel Deaconess Medical Center, Boston, MA (R.L.V.).
authors.forename: Kazuhiko
authors.initials: K
authors.lastname: Nishigaki
authors.affiliation: From the Gifu University Hospital, Gifu, Japan (N.T., T.K., H.T., T.N., M.K., K.N., S.M.); Gifu Prefectural General Medical Center, Gifu, Japan (H.G., T.K.); Matsunami General Hospital, Gifu, Japan (M.T.); and Department of Medicine, Harvard Medical School, Beth Israel Deaconess Medical Center, Boston, MA (R.L.V.).
authors.forename: Shinya
authors.initials: S
authors.lastname: Minatoguchi
mesh_terms: D000200:Action Potentials; D000293:Adolescent; D016022:Case-Control Studies; D002648:Child; D015716:Electrocardiography, Ambulatory; D005260:Female; D006329:Heart Conduction System / Q000503:physiopathology*; D006339:Heart Rate; D006801:Humans; D007564:Japan / Q000453:epidemiology; D008133:Long QT Syndrome / Q000175:diagnosis / Q000453:epidemiology / Q000503:physiopathology*; D008297:Male; D015995:Prevalence; D012307:Risk Factors; D013997:Time Factors; D016171:Torsades de Pointes / Q000175:diagnosis / Q000453:epidemiology / Q000503:physiopathology*; D055815:Young Adult
keywords: T-wave alternans; arrhythmias, cardiac; electrocardiography; heart conduction system; long QT syndrome; torsade de pointes