title: Undersensing of VF in a patient with optimal R wave sensing during sinus rhythm.
abstract: We describe a case of potentially fatal undersensing of VF by a third generation ICD with predetermined automatic gain control. In this patient, ventricular sensing was optimal, as R wave amplitudes during sinus rhythm were at least 16 mV. Cyclical, high amplitude signals during VF elevated the sensing floor to such an extent that complete undersensing of subsequent lower amplitude local electrograms occurred. This led to bradypacing and complete ICD therapy failure. Therefore, high R wave amplitudes during sinus rhythm do not warrant flawless sensing during VF.
authors.affiliation: Department of Cardiology, Academic Medical Center, Amsterdam, The Netherlands. L.R.Dekker@amc.uva.nl
authors.forename: Lukas R C
authors.initials: LR
authors.lastname: Dekker
authors.forename: Tim A M
authors.initials: TA
authors.lastname: Schrama
authors.forename: Frans H L
authors.initials: FH
authors.lastname: Steinmetz
authors.forename: Raymond
authors.initials: R
authors.lastname: Tukkie
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D017147:Defibrillators, Implantable; D004562:Electrocardiography; D019544:Equipment Failure Analysis; D006339:Heart Rate / Q000502:physiology; D006801:Humans; D008297:Male; D008838:Microcomputers; D012680:Sensitivity and Specificity; D012984:Software; D014693:Ventricular Fibrillation / Q000175:diagnosis / Q000503:physiopathology / Q000628:therapy*