title: Microvolt T-wave alternans as a predictor of ventricular tachyarrhythmias: a prospective study using atrial pacing.
abstract: BACKGROUND
  Microvolt T-wave alternans (TWA) is reported to be closely associated with sudden cardiac death (SCD) and ventricular tachycardia (VT). Animal experiments revealed that microvolt TWA is highly dependent on heart rate. The purpose of this study was to determine whether patients with TWA at relatively low heart rates have increased vulnerability to ventricular tachyarrhythmias.
  
  
  RESULTS
  Subjects were 248 consecutive patients (158 men, 90 women; mean age, 59+/-17 years) who underwent electrophysiological study from 1997 to 2000. TWA recording was made in sinus rhythm and at atrial pacing rates of 90, 100, 110, and 120 bpm with the Cambridge Heart CH2000 system. Alternans voltage (V(alt)) was measured when the alternans ratio was >3 for a period of >1 minute in VM, X, Y, Z, or 2 adjacent precordial leads. Study end point was the first appearance of VT, ventricular fibrillation (VF), appropriate implantable cardioverter-defibrillator therapy with pacing or shocks, or SCD. During the 37+/-12-month follow-up period, 22 patients had sustained VT, and 5 patients died of SCD. In patients with >1.9-microV V(alt) at rates of 90, 100, and 110 bpm, the incidence of VT/VF/SCD was 56%, 28%, and 18%, respectively. V(alt) of >2.9 microV at a heart rate of 90 bpm had a 70% positive predictive value for VT/VF/SCD. However, when V(alt) was <0.9 microV at a rate of 120 bpm, negative predictive value was 100%.
  
  
  CONCLUSIONS
  Patients with TWA at relatively low heart rates are susceptible to ventricular tachyarrhythmias.
authors.affiliation: Third Department of Internal Medicine, Showa University, 1-5-8 Hatanodai, Shinagawa-ku, Tokyo 142-8666, Japan. k-tanno@p02.itscom.ne
authors.forename: Kaoru
authors.initials: K
authors.lastname: Tanno
authors.forename: Syunsho
authors.initials: S
authors.lastname: Ryu
authors.forename: Norikazu
authors.initials: N
authors.lastname: Watanabe
authors.forename: Yoshino
authors.initials: Y
authors.lastname: Minoura
authors.forename: Mitsuharu
authors.initials: M
authors.lastname: Kawamura
authors.forename: Taku
authors.initials: T
authors.lastname: Asano
authors.forename: Youichi
authors.initials: Y
authors.lastname: Kobayashi
authors.forename: Takashi
authors.initials: T
authors.lastname: Katagiri
mesh_terms: D002304:Cardiac Pacing, Artificial; D016757:Death, Sudden, Cardiac / Q000453:epidemiology; D018572:Disease-Free Survival; D004562:Electrocardiography / Q000379:methods*; D005260:Female; D005500:Follow-Up Studies; D006325:Heart Atria / Q000503:physiopathology; D006339:Heart Rate; D006801:Humans; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D012680:Sensitivity and Specificity; D017180:Tachycardia, Ventricular / Q000175:diagnosis* / Q000453:epidemiology / Q000503:physiopathology; D014693:Ventricular Fibrillation / Q000453:epidemiology