Abstract 14398: Prospective Evaluation of Defibrillation Threshold and Post-shock Rhythm in Young ICD Recipients: High-energy Defibrillation and Post-shock Pacing May Not be Necessary
Introduction: Adaptation of transvenous or entirely subcutaneous ICD systems to the needs of pediatric and congenital heart patients is problematic due to constraints of vascular and thoracic anatomy. These problems could be addressed by eliminating cardiac pacing and/or reducing ICD generator size via lowering max shock energy. We describe the first prospective evaluation of defibrillation threshold (DFT) and post-shock rhythm in this population. These data may guide development of an ICD designed specifically for children.
Hypothesis: High-energy devices and obligatory post-shock pacing may not be required for effective pediatric ICD therapy.
Methods: We prospectively studied patients weighing ≤60 kg at time of clinically necessary ICD intervention. DFTs were obtained using a binary search protocol with 3 VF inductions, beginning at 9J. Post-shock pacing was tested in patients with normal AV conduction. Post-shock pacing was programmed using a predetermined, stepwise protocol, lowering the rate prior to each VF induction. For each post-shock event, post-shock pacing was considered necessary if there were ≥7 ventricular-paced beats or asystole >4 seconds in the first 20 seconds after defibrillation.
Results: Twenty patients (pts) were enrolled (11 had channelopathy, 5 congenital heart disease, and 4 cardiomyopathy). The median age was 16 yrs, with a median weight of 48 kg. Twelve pts had a transvenous high-voltage coil; 8 had pericardial +/- subcutaneous coil(s). Using our protocol, median DFT was 7J (range 3-31J). 19/20 pts had a DFT of ≤15J, and all pts <25kg had DFT ≤9J (n=6). There was no significant difference in DFT between pts with transvenous vs. pericardial +/- subcutaneous coils (median 7J vs. 6J, P=0.59). No pt with normal AV conduction prior to defibrillation required post-shock pacing (n=16). There were no adverse events.
Conclusions:These data suggest that most pediatric ICD patients have low DFTs and adequate post-shock escape rhythm. There may be a subset of patients with smaller body size in whom a lower energy device may be sufficient. This may help determine appropriate parameters for future design of smaller, pediatric-specific ICDs.
- © 2010 by American Heart Association, Inc.