Prospective Evaluation of Defibrillation Threshold and Postshock Rhythm in Young ICD Recipients


  • Institution of all authors at the time of study was Department of Cardiology, Children's Hospital Boston, Harvard Medical School, Boston, MA

  • Financial support: Supported in part by the John R. Grey IV Cardiology Fellowship Fund at Children's Hospital, Department of Cardiology, Children's Hospital Boston. None of the authors have any relevant financial relationships to disclose.

Address for reprints: Andrew E. Radbill, M.D., 2200 Children's Way, Suite 5230/Nashville, TN 37232-9119. Fax 615-322-2210; e-mail:


Background: Adaptation of implantable cardioverter defibrillator (ICD) systems to the needs of pediatric and congenital heart patients is problematic due to constraints of vascular and thoracic anatomy. An improved understanding of the defibrillation energy and postshock pacing requirements in such patients may help direct more tailored ICD therapy. We describe the first prospective evaluation of defibrillation threshold (DFT) and postshock rhythm in this population.

Methods: We prospectively studied patients ≤60 kg at time of ICD intervention. DFTs were obtained using a binary search protocol with three VF inductions. Postshock pacing was programmed using a stepwise protocol, lowering the rate prior to each VF induction.

Results: Twenty patients were enrolled: 11 had channelopathy, five congenital heart disease, and four cardiomyopathy. The median age was 16 years, median weight 48 kg. Twelve patients had a transvenous high-voltage coil; eight had pericardial +/− subcutaneous coil(s). Median DFT was 7 J (range 3–31 J); 19/20 patients had DFT ≤15 J and all patients <25 kg had DFT ≤9 J (n = 6). There was no difference in DFT between patients with transvenous versus pericardial +/− subcutaneous coils (median 7 J vs 6 J, P = 0.59). No patient with normal atrioventricular conduction prior to defibrillation required postshock pacing (n = 16). There were no adverse events.

Conclusions: These data suggest that many pediatric ICD patients have low DFTs and adequate postshock escape rhythm. This may help determine appropriate parameters for future design of pediatric-specific ICDs. (PACE 2012;35:1487–1493)