title: Intracardiac electrogram T-wave alternans/variability increases before spontaneous ventricular tachyarrhythmias in implantable cardioverter-defibrillator patients: a prospective, multi-center study.
abstract: BACKGROUND
  T-wave alternans (TWA) increases before ventricular tachycardia (VT) or fibrillation (VF), suggesting that it may warn of VT/VF in implantable cardioverter-defibrillator patients. Recently, we described a method for measuring alternans and nonalternans variability (TWA/V) from electrograms (EGMs) stored in implantable cardioverter-defibrillators before VT/VF. The goal of this prospective, multicenter study was to determine whether EGM TWA/V was greater before VT/VF than at baseline.
  
  
  RESULTS
  We enrolled 63 implantable cardioverter-defibrillator patients. TWA/V was computed from stored EGMs before spontaneous VT/VF and from sequential windows of 8 pairs of beats using 4 different control recordings: baseline rhythm, rapid pacing at 105 bpm, segments of ambulatory Holter EGMs matched to the time of VT/VF episodes, and EGMs before spontaneous supraventricular tachycardia. During follow-up, 28 patients had 166 episodes of VT/VF. TWA/V was greater before VT/VF (62.9 ± 3.1 μV; n = 28) than during baseline rhythm (12.8 ± 1.8 μV; P < 0.0001; n = 62), during rapid pacing (14.5 ± 2.0 μV; P < 0.0001; n = 52), before supraventricular tachycardia (27.5 ± 6.1 μV; P < 0.0001; n = 9), or during time-matched ambulatory controls (12.3 ± 3.5 μV; P < 0.0001; n = 16). By logistic regression, the odds of VT/VF increased by a factor of 2.2 for each 10-μV increment in TWA/V (P < 0.0001).
  
  
  CONCLUSIONS
  In implantable cardioverter-defibrillator patients, EGM TWA/V is greater before spontaneous VT/VF than in control recordings. Future implantable cardioverter-defibrillators that measure EGM TWA/V continuously may warn patients and initiate pacing therapies to prevent VT/VF.
authors.affiliation: Cedars-Sinai Medical Towers, 8635 W Third St, Ste 1190-W, Los Angeles, CA 90048. swerdlow@ucla.edu.
authors.forename: Charles
authors.initials: C
authors.lastname: Swerdlow
authors.forename: Theodore
authors.initials: T
authors.lastname: Chow
authors.forename: Mithilesh
authors.initials: M
authors.lastname: Das
authors.forename: Anne M
authors.initials: AM
authors.lastname: Gillis
authors.forename: Xiaohong
authors.initials: X
authors.lastname: Zhou
authors.forename: Athula
authors.initials: A
authors.lastname: Abeyratne
authors.forename: Raja N
authors.initials: RN
authors.lastname: Ghanem
mesh_terms: D000368:Aged; D017147:Defibrillators, Implantable; D022062:Electrophysiologic Techniques, Cardiac / Q000379:methods*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D013617:Tachycardia, Supraventricular / Q000503:physiopathology*; D017180:Tachycardia, Ventricular / Q000175:diagnosis / Q000503:physiopathology*