title: A novel pacing method to suppress repolarization alternans in vivo: implications for arrhythmia prevention.
abstract: BACKGROUND
  Repolarization alternans (RA), a pattern of ventricular repolarization that repeats on an every other beat basis, has been closely linked with the substrate associated with ventricular tachycardia/ventricular fibrillation.
  
  
  OBJECTIVE
  To evaluate a novel method to suppress RA.
  
  
  METHODS
  We have developed a novel method to dynamically (on R-wave detection) trigger pacing pulses during the absolute refractory period. We have tested the ability of this method to control RA in a structurally normal swine heart in vivo.
  
  
  RESULTS
  RA induced by triggered pacing can be measured from both intracardiac and body surface leads and the amplitude of R-wave triggered pacing-induced alternans can be locally modulated by varying the amplitude and width of the pacing pulse. We have estimated that to induce a 1 μV change in alternans voltage on the body surface, coronary sinus, and left ventricle leads, a triggered pacing pulse delivered in the right ventricle of 0.04±0.02, 0.05±0.025, and 0.06±0.033 μC, respectively, is required. Similarly, to induce a 1 unit change in Kscore (ratio of alternans peak to noise), a pacing stimulus of 0.93±0.73, 0.32±0.29, and 0.33±0.37 μC, respectively, is required. We have been able to demonstrate that RA can be suppressed by R-wave triggered pacing from a site that is within or across ventricles. Lastly, we have demonstrated that the proposed method can be used to suppress spontaneously occurring alternans in the diseased heart.
  
  
  CONCLUSIONS
  We have developed a novel method to suppress RA in vivo.
authors.affiliation: Harvard-MIT Division of Health Sciences and Technology, Massachusetts Institute of Technology, Cambridge, Massachusetts; Division of Cardiology, Massachusetts General Hospital, Harvard Medical School, Boston, MA 02129, USA. aarmoundas@partners.org
authors.forename: Antonis A
authors.initials: AA
authors.lastname: Armoundas
authors.forename: Eric H
authors.initials: EH
authors.lastname: Weiss
authors.forename: Omid
authors.initials: O
authors.lastname: Sayadi
authors.forename: Shawna
authors.initials: S
authors.lastname: Laferriere
authors.forename: Naveen
authors.initials: N
authors.lastname: Sajja
authors.forename: Theofanie
authors.initials: T
authors.lastname: Mela
authors.forename: Jagmeet P
authors.initials: JP
authors.lastname: Singh
authors.forename: Conor D
authors.initials: CD
authors.lastname: Barrett
authors.forename: E
authors.initials: E
authors.lastname: Kevin Heist
authors.forename: Faisal M
authors.initials: FM
authors.lastname: Merchant
mesh_terms: D000818:Animals; D018780:Body Surface Potential Mapping / Q000379:methods*; D002304:Cardiac Pacing, Artificial / Q000379:methods*; D058406:Cardiac Resynchronization Therapy / Q000379:methods; D004195:Disease Models, Animal; D004562:Electrocardiography / Q000379:methods; D006329:Heart Conduction System / Q000503:physiopathology; D008297:Male; D011897:Random Allocation; D012016:Reference Values; D012680:Sensitivity and Specificity; D013552:Swine; D017180:Tachycardia, Ventricular / Q000175:diagnosis / Q000517:prevention & control*; D018487:Ventricular Dysfunction, Left / Q000175:diagnosis / Q000628:therapy; D014693:Ventricular Fibrillation / Q000175:diagnosis / Q000517:prevention & control*