title: Improving SVT discrimination in single-chamber ICDs: a new electrogram morphology-based algorithm.
abstract: BACKGROUND
  Wide-spread adoption of ICD therapy has focused efforts on improving the quality of life for patients by reducing "inappropriate" shock therapies. To this end, distinguishing supraventricular tachycardia from ventricular tachycardia remains a major challenge for ICDs. More sophisticated discrimination algorithms based on ventricular electrogram morphology have been made practicable by the increased computational ability of modern ICDs.
  
  
  RESULTS
  We report results from a large prospective study (1,122 pts) of a new ventricular electrogram morphology tachycardia discrimination algorithm (Wavelet Dynamic Discrimination, Medtronic, Minneapolis, MN, USA) operating at minimal algorithm setting (RV coil-can electrogram, match threshold of 70%). This is a nonrandomized cohort study of ICD patients using the morphology discrimination of the Wavelet algorithm to distinguish SVT and VT/VF. The Wavelet criterion was required ON in all patients and all other supraventricular tachycardia discriminators were required to be OFF. Spontaneous episodes (N = 2,235) eligible for ICD therapy were adjudicated for detection algorithm performance. The generalized estimating equations method was used to remove bias introduced when an individual patient contributes multiple episodes. Inappropriate therapies for supraventricular tachycardia were reduced by 78% (90% CI: 72.8-82.9%) for episodes within the range of rates where Wavelet was programmed to discriminate. Sensitivity for sustained ventricular tachycardia was 98.6% (90% CI: 97-99.3%) without the use of high-rate time out.
  
  
  CONCLUSIONS
  Results from this prospective study of the Wavelet electrogram morphology discrimination algorithm operating as the sole discriminator in the ON mode demonstrate that inappropriate therapy for supraventricular tachycardia in a single-chamber ICD can be dramatically reduced compared to rate detection alone.
authors.affiliation: University of Western Ontario, London, Ontario, Canada. gklein@uwo.ca
authors.forename: George J
authors.initials: GJ
authors.lastname: Klein
authors.forename: Jeffrey M
authors.initials: JM
authors.lastname: Gillberg
authors.forename: Anthony
authors.initials: A
authors.lastname: Tang
authors.forename: Shmuel
authors.initials: S
authors.lastname: Inbar
authors.forename: Arjun
authors.initials: A
authors.lastname: Sharma
authors.forename: Christina
authors.initials: C
authors.lastname: Unterberg-Buchwald
authors.forename: Paul
authors.initials: P
authors.lastname: Dorian
authors.forename: Hans
authors.initials: H
authors.lastname: Moore
authors.forename: Firat
authors.initials: F
authors.lastname: Duru
authors.forename: Ethan
authors.initials: E
authors.lastname: Rooney
authors.forename: Daniel
authors.initials: D
authors.lastname: Becker
authors.forename: Katie
authors.initials: K
authors.lastname: Schaaf
authors.forename: David
authors.initials: D
authors.lastname: Benditt
mesh_terms: D000465:Algorithms; D015331:Cohort Studies; D017147:Defibrillators, Implantable; D003936:Diagnosis, Computer-Assisted / Q000379:methods*; D003937:Diagnosis, Differential; D016002:Discriminant Analysis; D004554:Electric Countershock / Q000379:methods; D004562:Electrocardiography / Q000379:methods*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013617:Tachycardia, Supraventricular / Q000175:diagnosis* / Q000517:prevention & control; D017180:Tachycardia, Ventricular / Q000175:diagnosis* / Q000517:prevention & control; D013813:Therapy, Computer-Assisted / Q000379:methods*