Undersensing by an ICD due to alternans of the ventricular electrogram.
Alternans of the ventricular electrogram (VEGM) during ventricular tachycardia (VT) is a rare cause of ventricular undersensing by an implantable cardioverter-defibrillator (ICD). This report describes a patient with a St. Jude ICD who exhibited sustained monomorphic VT associated with surface QRS alternans, alternating cycle lengths, alternans of the VEGM causing intermittent undersensing of the smaller component, and intermittent 2:1 counting of ventricular intervals during 1:1 sensing in response to the ICD detection algorithm. VEGM undersensing was corrected noninvasively simply by programming the threshold start from 62.5% to 50% which increased the sensitivity based on the amplitude of the VEGM. This maneuver did not affect the satisfactory and stable defibrillation threshold.
Heart Center, University Hospital Ghent, Ghent, Belgium. frederic.vanheuverswyn@uzgent.be
Frederic E
FE
Van Heuverswyn
Liesbeth
L
Timmers
Roland X
RX
Stroobandt
S Serge
SS
Barold
D017147:Defibrillators, Implantable; D004562:Electrocardiography; D006801:Humans; D008297:Male; D008875:Middle Aged; D017180:Tachycardia, Ventricular / Q000503:physiopathology* / Q000628:therapy*