title: Reduction of ICD shock burden by eliminating back-up pacing induced ventricular tachyarrhythmias.
abstract: BACKGROUND
  Implantable cardioverter defibrillators (ICD) may have the capacity to provoke or worsen ventricular tachyarrhythmias (VT). It has been reported that ICD shocks by itself can increase mortality. This study aimed to determine the role of back-up pacing-induced VT (PIT) in the overall ICD shock burden by avoiding pause-related ventricular back-up pacing.
  
  
  RESULTS
  A population of 550 single-chamber ICD patients was studied. Of them, 17 (3%, 69 ± 16 years, 14 male) patients had documented episodes of PIT. A total of 431 VT episodes were documented including 89 (21%) due to PIT. In 3 patients, VT events were exclusively PITs. After ≥2 documented PITs, the pacing output for VVI pacing was set to a subthreshold level resulting in noncapturable ventricular back-up pacing. All other device parameters remained unchanged to prove a potential proarrhythmic effect of pause related back-up pacing. During a follow-up of 99 ± 39 months after reducing the pacing output to a subthreshold level, no further episodes of PIT were observed (P < 0.001). Moreover, with the prevention of PITs, the ICD shock burden decreased significantly (pre: 150 vs. post: 18, P < 0.001). However, a single event of pause-induced VT occurred due to missing back-up pacing.
  
  
  CONCLUSIONS
  PIT is a frequent mechanism of VTs in ICD patients resulting in a substantially increased shock burden. Elimination of pause-related back-up pacing by subthreshold pacing output effectively abolishes PIT and thus significantly reduces ICD shock burden.
authors.affiliation: II. Medical Clinic, Department of Electrophysiology, University Medical Center, Johannes Gutenberg-University, Mainz, Germany.
authors.forename: Cathrin
authors.initials: C
authors.lastname: Theis
authors.affiliation: II. Medical Clinic, Department of Electrophysiology, University Medical Center, Johannes Gutenberg-University, Mainz, Germany.
authors.forename: Hanke
authors.initials: H
authors.lastname: Mollnau
authors.affiliation: II. Medical Clinic, Department of Electrophysiology, University Medical Center, Johannes Gutenberg-University, Mainz, Germany.
authors.forename: Sebastian
authors.initials: S
authors.lastname: Sonnenschein
authors.affiliation: II. Medical Clinic, Department of Electrophysiology, University Medical Center, Johannes Gutenberg-University, Mainz, Germany.
authors.forename: Torsten
authors.initials: T
authors.lastname: Konrad
authors.affiliation: II. Medical Clinic, Department of Electrophysiology, University Medical Center, Johannes Gutenberg-University, Mainz, Germany.
authors.forename: Ewald
authors.initials: E
authors.lastname: Himmrich
authors.affiliation: II. Medical Clinic, Department of Electrophysiology, University Medical Center, Johannes Gutenberg-University, Mainz, Germany.
authors.forename: Karsten
authors.initials: K
authors.lastname: Bock
authors.affiliation: II. Medical Clinic, Department of Electrophysiology, University Medical Center, Johannes Gutenberg-University, Mainz, Germany.
authors.forename: Eberhard
authors.initials: E
authors.lastname: Schulz
authors.affiliation: II. Medical Clinic, Department of Electrophysiology, University Medical Center, Johannes Gutenberg-University, Mainz, Germany.
authors.forename: Denise
authors.initials: D
authors.lastname: Kämpfner
authors.affiliation: II. Medical Clinic, Department of Electrophysiology, University Medical Center, Johannes Gutenberg-University, Mainz, Germany.
authors.forename: Simon
authors.initials: S
authors.lastname: Gerhardt
authors.affiliation: II. Medical Clinic, Department of Electrophysiology, University Medical Center, Johannes Gutenberg-University, Mainz, Germany.
authors.forename: Blanca
authors.initials: B
authors.lastname: Quesada Ocete
authors.affiliation: II. Medical Clinic, Department of Electrophysiology, University Medical Center, Johannes Gutenberg-University, Mainz, Germany.
authors.forename: Thomas
authors.initials: T
authors.lastname: Münzel
authors.affiliation: II. Medical Clinic, Department of Electrophysiology, University Medical Center, Johannes Gutenberg-University, Mainz, Germany.
authors.forename: Thomas
authors.initials: T
authors.lastname: Rostock
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D002304:Cardiac Pacing, Artificial / Q000009:adverse effects; D017147:Defibrillators, Implantable; D004554:Electric Countershock / Q000009:adverse effects / Q000295:instrumentation*; D022062:Electrophysiologic Techniques, Cardiac; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010138:Pacemaker, Artificial; D011237:Predictive Value of Tests; D011474:Prosthesis Design; D011475:Prosthesis Failure; D012307:Risk Factors; D017180:Tachycardia, Ventricular / Q000175:diagnosis / Q000209:etiology* / Q000503:physiopathology / Q000628:therapy; D013997:Time Factors; D016896:Treatment Outcome
keywords: ICD shocks; implantable cardioverter-defibrillator; pacemaker-induced ventricular tachycardia; proarrhythmia; sudden death; ventricular tachycardia