title: A novel lead configuration for optimal spatio-temporal detection of intracardiac repolarization alternans.
abstract: BACKGROUND
  Electric alternans is a pattern of variation in the shape of ECG waveform that occurs every other beat. In humans, alternation in ventricular repolarization, known as repolarization alternans (RA), has been associated with increased vulnerability to ventricular tachycardia/fibrillation and sudden cardiac death.
  
  
  RESULTS
  This study investigates the spatio-temporal variability of intracardiac RA and its relationship to body surface RA in an acute myocardial ischemia model in swine. We developed a real-time multichannel repolarization signal acquisition, display, and analysis system to record ECG signals from catheters in the right ventricle, coronary sinus, left ventricle, and epicardial surface before and after circumflex coronary artery balloon occlusion. We found that RA is detectable within 4 minutes after the onset ischemia and is most prominently seen during the first half of the repolarization interval. Ischemia-induced RA was detectable on unipolar and bipolar leads (both in near- and far-field configurations) and on body surface leads. Far-field bipolar intracardiac leads were more sensitive for RA detection than body surface leads, with the probability of body surface RA detection increasing as the number of intracardiac leads detecting RA increased, approaching 100% when at least three intracardiac leads detected RA. We developed a novel, clinically applicable intracardiac lead system based on a triangular arrangement of leads spanning the right ventricular and coronary sinus catheters, which provided the highest sensitivity for intracardiac RA detection when compared with any other far-field bipolar sensing configurations.
  
  
  CONCLUSIONS
  In conclusion, intracardiac alternans, a complex spatio-temporal phenomenon associated with arrhythmia susceptibility and sudden cardiac death, can be reliably detected through a novel triangular right ventricular-coronary sinus lead configuration.
authors.affiliation: Harvard-MIT Division of Health Sciences and Technology, Massachusetts Institute of Technology, Cambridge, USA.
authors.forename: Eric H
authors.initials: EH
authors.lastname: Weiss
authors.forename: Faisal M
authors.initials: FM
authors.lastname: Merchant
authors.forename: Andre
authors.initials: A
authors.lastname: d'Avila
authors.forename: Lori
authors.initials: L
authors.lastname: Foley
authors.forename: Vivek Y
authors.initials: VY
authors.lastname: Reddy
authors.forename: Jagmeet P
authors.initials: JP
authors.lastname: Singh
authors.forename: Theofanie
authors.initials: T
authors.lastname: Mela
authors.forename: Jeremy N
authors.initials: JN
authors.lastname: Ruskin
authors.forename: Antonis A
authors.initials: AA
authors.lastname: Armoundas
mesh_terms: D000818:Animals; D018780:Body Surface Potential Mapping / Q000379:methods*; D016757:Death, Sudden, Cardiac / Q000209:etiology* / Q000517:prevention & control; D017147:Defibrillators, Implantable; D004195:Disease Models, Animal; D006321:Heart / Q000503:physiopathology*; D006329:Heart Conduction System / Q000503:physiopathology*; D008297:Male; D013552:Swine; D017180:Tachycardia, Ventricular / Q000150:complications / Q000175:diagnosis* / Q000628:therapy