Precise Measurement of Pediatric Defibrillation Thresholds

Defibrillation Thresholds in a Pediatric Cohort Using Binary Search Protocol

Patients who receive an implantable cardioverter-defibrillator (ICD) usually undergo testing at the end of the ICD procedure to measure the amount of energy able to successfully defibrillate the heart (defibrillation threshold testing, or DFT). This study proposes to perform that measurement in pediatric patients already undergoing clinically necessary ICD procedures, with the measurement performed using a binary search method that has been previously validated in adult cohorts. We hypothesize that pediatric DFTs, when precisely measured, may be lower than previously assumed from extrapolation of adult data.

Study Overview

• Status: Completed
• Conditions: Pediatrics; Defibrillators, Implantable
• Intervention / Treatment: Diagnostic test: Defibrillator threshold testing; Other: Observation of post-shock intrinsic cardiac rhythm

• Study Type: Observational
• Enrollment (Actual): 20

Contacts and Locations

Study Locations

• United States
  • Massachusetts
    • Boston, Massachusetts, United States, 02115
      • Children's Hospital Boston

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Child; Adult; Older Adult
• Accepts Healthy Volunteers: No
• Genders Eligible for Study: All

• Sampling Method: Non-Probability Sample

Study Population

All patients seen by the electrophysiology service at Children's Hospital Boston who are identified to be at very high risk of sudden cardiac death and in need of an ICD

Description

Inclusion Criteria:

• Current follow-up at Children's Hospital Boston
• Children with current or planned ICDs who are scheduled by their primary electrophysiologist for clinically necessary assessment/re-assessment of defibrillation threshold
• If the patient has an ICD system with a non-transvenous shock coil: weight ≤35kg at time of initial implant, with current weight <50kg
• If the patient has an ICD system with a conventional transvenous shock coil: current weight ≤60kg

Exclusion Criteria:

• Clinical failure of any system component not able to be addressed by hardware repair or exchange
• Hemodynamic instability that in the judgment of the primary electrophysiologist warrants abbreviation of DFT assessment
• Unsuccessful induction of fibrillation during DFT testing

Study Plan

How is the study designed?

Number of groups / cohorts

1

Cohorts and Interventions

Group / Cohort

Intervention / Treatment

Pediatric ICD pts; Inclusion criteria for study participants included: 1) weight ≤60 kg, 2) new or existing ICD system, and 3) clinically necessary assessment of the defibrillation efficacy of the ICD system. Transvenous systems utilized a high-voltage ICD coil with active-fixation lead attached to the right ventricular endocardial surface, whereas non-transvenous systems depended upon a high-voltage shocking coil placed within the pericardial, subcutaneous or pleural space. To be included in the post-shock pacing portion of the study, adequate sinus and AV node function had to be present at baseline. Exclusion criteria included 1) tenuous hemodynamic status felt to warrant abbreviation of the defibrillation efficacy testing or 2) inability to induce fibrillation during defibrillation threshold testing (DFT).

Diagnostic test: Defibrillator threshold testing; Measurement of the defibrillation threshold was performed using a modified binary search protocol. This protocol specified three distinct inductions of ventricular fibrillation (VF) for all subjects, with a 3-5 minute observation/waiting period between inductions. The initial shock energy was programmed at 9 joules (J) for all patients, with internal rescue shocks at 31J followed by device-specific maximum deliverable energy. The outcome of the initial induction determined the programmed energies for both the initial and internal rescue shocks for the second induction, and likewise for the third induction. All shocks were biphasic and delivered at manufacturers' default tilt, polarity and duration, and all final programmed shock vectors included an active can. External defibrillation pads were in place for delivery of external rescue shock should the internal shocks fail.; Other: Observation of post-shock intrinsic cardiac rhythm; Prior to each of the three ventricular fibrillation inductions performed as part of the binary search protocol, post-shock pacing was re-programmed using a pre-determined, stepwise protocol that progressively decreased the lower rate limit. For the purpose of this protocol, post-shock pacing was considered necessary if 1) ≥7 ventricular-paced beats or 2) asystole >4 seconds was observed in the first 20 seconds after defibrillation, or if the systolic blood pressure demonstrated a >10% decrease from pre-induction baseline at follow-up measurement 1 minute post-defibrillation. Rescue ventricular pacing via the programmer was available for all subjects.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Defibrillation Threshold	The defibrillation threshold is a measure of the minimum amount of energy (in Joules) that is able to successfully defibrillate an episode of ventricular fibrillation. This measurement is specific to each individual patient with his/her specific defibrillator configuration. There are several different strategies to measuring this in an individual patient; this study utilized the binary search protocol.	During clinical ICD procedure, as a single event

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Do DFTs Vary by Type of ICD Systems Implanted?	The defibrillation threshold (as measured in Joules as already described in the details regarding the primary outcome) will be compared between patients with two distinct general types of implanted defibrillator systems: 1) transvenous ICD systems (defibrillator leads located inside the vein and attached to the endocardial surface of the heart) and 2) non-transvenous ICD systems (including all other types of debrillation systems).	During clinical ICD procedure, as a single event
Intrinsic Heart Rate in the Immediate Post-defibrillation Period	A patient will be considered to have an intrinsic slow heart rate in the period of time immediately following defibrillation (20 seconds) if any of the following are observed: >7 paced beats, asystole >4 seconds, or experienced >10% decrease in systolic blood pressure.	During clinical ICD procedure, as a single event

Collaborators and Investigators

• Sponsor: Boston Children's Hospital
• Investigators: Principal Investigator: Andrew E Radbill, MD, Boston Children's Hospital

Study record dates

Study Major Dates

• Study Start (Actual): June 4, 2009
• Primary Completion (Actual): May 26, 2010
• Study Completion (Actual): May 10, 2012

Study Registration Dates

• First Submitted: January 6, 2010
• First Submitted That Met QC Criteria: January 6, 2010
• First Posted (Estimate): January 7, 2010

Study Record Updates

• Last Update Posted (Actual): February 5, 2018
• Last Update Submitted That Met QC Criteria: July 24, 2017
• Last Verified: July 1, 2017

More Information

Terms related to this study

• Other Study ID Numbers: 09-04-0209

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: NO

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No