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

Abstract

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)

Placement of implantable cardioverter‐defibrillators in paediatric and congenital heart defect patients: a pipeline for model generation and simulation prediction of optimal configurations

“…Large DFT and CVT differences were observed between ICD configurations, underlining the importance of choosing the optimal ICD configuration. Furthermore, clinical data evaluating the DFTs of different ICD configurations in paediatric and CHD patients are scarce (Radbill et al 2012), so physicians cannot currently rely on published reports when deciding which ICD configuration to use in a patient of this cohort. The pipeline and methodology developed in this study presents a novel approach to predicting the optimal ICD configurations before device implantation, a tool particularly important for paediatric and CHD patients who often have contraindications for transvenous lead ICD implantation.…”

“…The choice of lead placement options was based on Stephenson et al (2006), and enabled the exploration of both epicardial and subcutaneous lead locations and multiple electric field vectors. ICD lead dimensions were 5 × 0.2 × 0.2 cm 3 , roughly the size of the RV coil of a typical transvenous ICD lead, as this type of lead is commonly used ‘off‐label’ for non‐transvenous lead placement in the paediatric and CHD populations (Stephenson et al 2006; Radbill et al 2012). From the chosen ICD can and lead locations, 11 ICD configurations were assembled so that the shock vector would be across the ventricles for each configuration, and so that configurations with epicardial leads and with single and multiple subcutaneous leads could be tested.…”

Inherited Arrhythmias in the Pediatric Population: An Updated Overview

“…Two aspects that must be considered with ICDs in young patients are reserving an extra lead length forming a loop in the right atrium in order to follow the child's growth and avoiding dislodgment in case of a transvenous ICD; programming the ICD with the VT and VF zone set very high (>220 bpm), having a long detection interval (>30 s), and the activation of SVT discriminators, avoiding inappropriate shock for sinus tachycardia. Every ICD must be tested in the operating room with 10 J shocks in patients <25 kg and 15 J shocks for those >25 kg [223]. AF episodes in children are usually self-limiting [224], and they can be regarded as hints for BrS [196].…”

Appropriate Parameters for Pediatric‐Specific Implantable Cardioverter‐Defibrillators

“…Radbill et al tried to determine “appropriate parameters for future design of pediatric‐specific implantable cardioverter‐defibrillators (ICDs)” in their “prospective evaluation of defibrillation threshold and postshock rhythm in young ICD recipients.” Their prospective trial used a binary search algorithm for determining the energy threshold in steps of between 33% and 116% increase. Surprisingly the subpopulation of six patients with a weight below 25 kg had an average defibrillation threshold of 6 J, whereas the other patients with weight above 40 kg possessed an average of 9 J (without one runaway value of 31 J is still higher with 7.4 J).…”

“…Unfortunately, there was no description of the ICD models used in the paper so that a relationship between model and its output capacitance cannot be established. A table giving information on stored energy threshold, manufacture and model, output capacitance, and impedance measured of each patient would help to calculate a regression between energy and time constant that would certainly confirm a tendency in accordance with theory.…”