title: Eligibility of Pacemaker Patients for Subcutaneous Implantable Cardioverter Defibrillators.
abstract: BACKGROUND
  The subcutaneous implantable cardioverter defibrillator (ICD) has emerged as a viable therapeutic option for patients who are deemed high risk for sudden cardiac death. Previous studies have shown that 7-15% of patients are not candidates for the S-ICD based on their intrinsic QRS/T-wave morphology. Presently, it is not known if the S-ICD can be considered as supplementary therapy in patients who are ventricularly paced. We sought to determine the proportion of ventricularly paced patients who would qualify for an S-ICD.
  
  
  RESULTS
  We evaluated 100 patients with transvenous pacemakers/ICDs, including 25 biventricular devices to determine S-ICD candidacy during right ventricular (RV) pacing and biventricular pacing based on the recommended QRS:T-wave ratio screening template. Fifty-eight percent of patients qualified for an S-ICD based on their QRS morphology during ventricular pacing. More patients during biventricular pacing met criteria compared to during RV pacing alone (80% vs. 46%, P <0.01). Patients that were paced from the RV septum were more likely to qualify compared to those paced from the RV apex (67% vs. 37%, respectively, P <0.01).
  
  
  CONCLUSIONS
  While S-ICD implantation may be considered as supplemental therapy in select patients with preexisting transvenous devices, relatively fewer candidates who are paced from the RV apex qualify. QRS morphologies generated from biventricular pacing as well as from septal RV pacing are more likely to screen in based on the recommended S-ICD template.
authors.affiliation: Department of Medicine, Division of Cardiology, Cornell University Medical Center, New York, USA.
authors.forename: James E
authors.initials: JE
authors.lastname: Ip
authors.affiliation: Department of Medicine, Division of Cardiology, Cornell University Medical Center, New York, USA.
authors.forename: Michael S
authors.initials: MS
authors.lastname: Wu
authors.affiliation: Department of Medicine, Division of Cardiology, Cornell University Medical Center, New York, USA.
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Kennel
authors.affiliation: Department of Medicine, Division of Cardiology, Cornell University Medical Center, New York, USA.
authors.forename: George
authors.initials: G
authors.lastname: Thomas
authors.affiliation: Department of Medicine, Division of Cardiology, Cornell University Medical Center, New York, USA.
authors.forename: Christopher F
authors.initials: CF
authors.lastname: Liu
authors.affiliation: Department of Medicine, Division of Cardiology, Cornell University Medical Center, New York, USA.
authors.forename: Jim W
authors.initials: JW
authors.lastname: Cheung
authors.affiliation: Department of Medicine, Division of Cardiology, Cornell University Medical Center, New York, USA.
authors.forename: Steven M
authors.initials: SM
authors.lastname: Markowitz
authors.affiliation: Department of Medicine, Division of Cardiology, Cornell University Medical Center, New York, USA.
authors.forename: Bruce B
authors.initials: BB
authors.lastname: Lerman
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D001145:Arrhythmias, Cardiac / Q000175:diagnosis / Q000401:mortality / Q000503:physiopathology / Q000628:therapy*; D002304:Cardiac Pacing, Artificial / Q000379:methods; D058406:Cardiac Resynchronization Therapy; D058409:Cardiac Resynchronization Therapy Devices; D000066491:Clinical Decision-Making; D016757:Death, Sudden, Cardiac / Q000209:etiology / Q000517:prevention & control*; D017147:Defibrillators, Implantable; D004554:Electric Countershock / Q000295:instrumentation*; D004562:Electrocardiography; D004608:Eligibility Determination; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010138:Pacemaker, Artificial; D018579:Patient Selection; D011237:Predictive Value of Tests; D016277:Ventricular Function, Left; D016278:Ventricular Function, Right
keywords: T-wave oversensing; defibrillator screening; implantable cardioverter-defibrillator; inappropriate shocks; pacemakers; subcutaneous implantable cardioverter defibrillator