title: Alternans of the Ventricular Electrogram in Patients with an Implanted Cardioverter-Defibrillator.
abstract: BACKGROUND
  The occurrence and significance of alternans of the ventricular electrogram (VEGM) in patients with an implanted cardioverter-defibrillator (ICD) has been rarely reported.
  
  
  OBJECTIVE
  This report describes our observations of VEGM alternans documented in nine patients with an ICD (seven new cases and two previously published cases for comparison).
  
  
  RESULTS
  We found seven new cases of near-field VEGM alternans and added two of our previously reported examples. Catecholaminergic polymorphic ventricular tachycardia (CPVT) was diagnosed in one patient based on ICD recordings. Alternans occurred during ventricular tachycardia (VT) in eight patients. A fast sinus tachycardia could not be ruled out in one patient. Stable cycle length alternans was found in five patients. QRS alternans of the left ventricular (LV) electrogram (EGM) was recorded in all five patients who had a device for cardiac resynchronization therapy capable of sensing by the LV channel. These five cases exhibited corresponding alternans of the right ventricular (RV) EGM in three cases, none in one patient, and a questionable recording in another. Alternans of the far-field (FF) VEGM occurred simultaneously with RV EGM alternans in all four patients whose device provided an FF tracing.
  
  
  CONCLUSIONS
  Ventricular alternans may be more common than realized in ICD patients with VT. The correlation of VEGM alternans with the surface electrocardiogram remains unknown. Although QRS alternans itself as an electrical pattern is generally benign, its cause may not be, as illustrated in our patient with CPVT. Furthermore, associated cycle length alternans or undersensing of the smaller alternans component may complicate ICD therapy.
authors.affiliation: Department of Medicine, University of Rochester School of Medicine and Dentistry, Rochester, New York.
authors.forename: S Serge
authors.initials: SS
authors.lastname: Barold
authors.affiliation: Biotronik, Berlin, Germany.
authors.forename: Andreas
authors.initials: A
authors.lastname: Kucher
authors.affiliation: Department of Cardiology, Jolimont Hospital, Haine St. Paul, Belgium.
authors.forename: Antoine
authors.initials: A
authors.lastname: de Meester
authors.affiliation: Ghent University Hospital, Heart Centre, Ghent, Belgium.
authors.forename: Roland X
authors.initials: RX
authors.lastname: Stroobandt
mesh_terms: D017147:Defibrillators, Implantable; D022062:Electrophysiologic Techniques, Cardiac / Q000379:methods*; D006333:Heart Failure / Q000150:complications* / Q000517:prevention & control*; D006801:Humans; D017180:Tachycardia, Ventricular / Q000150:complications* / Q000175:diagnosis*
keywords: bidirectional ventricular tachycardia; catecholaminergic polymorphic ventricular tachycardia; cycle length alternans; electrical alternans; implantable cardioverter-defibrillator; ventricular tachycardia