title: Effects of sotalol on the signal-averaged electrocardiogram in patients with sustained ventricular tachycardia: relation to suppression of inducibility and changes in tachycardia cycle length.
abstract: OBJECTIVE
  This study examines the effects of sotalol on the signal-averaged electrocardiogram (ECG) in patients with spontaneous and inducible sustained ventricular tachycardia and correlates these findings with the effect of sotalol on tachycardia inducibility and tachycardia rate.
  
  
  BACKGROUND
  Standard electrocardiography generally does not detect any change in the duration of the QRS complex resulting from sotalol therapy. However, the signal-averaged ECG is more sensitive than the standard ECG for detecting changes in QRS duration induced by antiarrhythmic drugs and can also detect changes in late potential duration.
  
  
  METHODS
  Signal-averaged electrocardiography was performed before therapy in 30 patients with spontaneous and inducible ventricular tachycardia, and both electrophysiologic study and a signal-averaged ECG were repeated during therapy with d,l-sotalol.
  
  
  RESULTS
  During sotalol therapy the signal-averaged QRS duration decreased by 2.6 +/- 6.6 ms in the 11 patients with no inducible tachycardia during therapy, whereas it increased by 3.8 +/- 5.8 ms (p = 0.01) in the 19 patients with inducible tachycardia during therapy. In the latter group there was a significant positive correlation between prolongation of tachycardia cycle length and prolongation of late potential duration by sotalol (r = 0.56, p = 0.01).
  
  
  CONCLUSIONS
  Sotalol can alter QRS and late potential duration as measured by the signal-averaged ECG. Prolongation of QRS duration or late potential duration may reflect a slowing of conduction by sotalol that may interfere with this agent's antiarrhythmic efficacy and slow ventricular tachycardia.
authors.affiliation: Department of Internal Medicine, University of Utah Medical Center, Salt Lake City 84132.
authors.forename: R A
authors.initials: RA
authors.lastname: Freedman
authors.forename: L A
authors.initials: LA
authors.lastname: Karagounis
authors.forename: J S
authors.initials: JS
authors.lastname: Steinberg
mesh_terms: D002214:Capsules; D002304:Cardiac Pacing, Artificial / Q000379:methods; D004562:Electrocardiography / Q000187:drug effects* / Q000295:instrumentation / Q000379:methods / Q000706:statistics & numerical data; D006339:Heart Rate / Q000187:drug effects; D006801:Humans; D013015:Sotalol / Q000008:administration & dosage*; D017180:Tachycardia, Ventricular / Q000175:diagnosis / Q000188:drug therapy* / Q000503:physiopathology
chemical_list: D002214:Capsules; D013015:Sotalol